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sailfl
Sun 23 August 2009, 07:16
A potential client asked if I could cut a grid out of 1/8" aluminum in a diamond shape for the openings in the doors for kitchen cabinets. I told him that I could and proceeded to cut the shape out sentra using 1/8" end mill. He was concerned with how the corners would look. He didn't want them to be round off. He was happy with the results but I was unhappy with the quality of the cut.

The diamonds were cut with the longer points of the diamond on the X axis and the short points on the Y axis. The sides were not smooth but had chatter. I was concerned that I was having a problem with my pinon and set screws again.

5843

I created some larger diamond shapes and cut them out of solid surface material using 1/8", 1/4" and 1/5" bits at 35, 70 and 100 IPM. In every case, there was a cut problem. I looked over some of the other things that I have been cutting and I found a slight indication of the same problem.

I started to look for things that might be loose. I even took the motors off to check to see if I had a loose pinon and set screw but they were fine. I talked with Sean about the problem also.

Router Bracket

I decided that I might have a problem with the way my router bracket is mounted to the Z Slide. I have attached a diagram. Because I am using preground rails, I could not attach the router bracket directly to the Z Slide. I had to allow for the rails and the screws that hold the rails to the Z Slide. I used most likely to long of spacers or set offs - they were .43" wide X .75" long. I think they might be flexing or had the potential for flexing.

I decided that I wanted the eleminate the set offs completely and add the Quick Release Plate. I picked up a piece of .5" aluminum and created a plate 3.25" x 4.5", the same size as the Router Bracket Plate. I then milled the back side of the plate so that it would fit between the rails and allow for the screws. I have not added register pins because the fit is so thight.

Though I have no experience using a Bridgeport milling machine, I am very pleased with how the plate turned out and how tight it fits.

Spider and V Wheels

Some builders are reversing the eccentric bushings to set the V Wheels off of the Spider instead of using a Bearing Support Base in Drawing M120220T. I used a bushing that was 5/8" Wide x 1/2" Length. This gave me about .30" space between the back of the Z Slide Tube and the Spider. Not much space but it was enough not to cause a problem. Additional info: I am using a 3/16" bolt to hold the V Wheels.

When I added the Quick Release Plate, I created another problem. I need more space between the Z Slide Tube and the Spider to allow for the nut and washer that attaches to the 3/8" bolt that is used to secure the QR Plate. I got the additional space by adding a 1/4" X 1" X 1" piece of aluminum between the bushing and the Spider.

I don't know why I have not presented this problem before this but it is never to late.

I have the piece put together but I have not tightened the V Wheels and checked for squareness and tried cutting any thing yet.

I am looking for a reality check.

Gerald, Do I need to create a 20mm Bearing Support Base and replace my bushing and 1/4" aluminum piece? Would that be better than what I have created?

DXF 2000 file with I think the right measurements.

5842

Pictures for viewing. Sorry that the Bridgeport is sideways. Fixed


5845
5846
5847

I hope this makes sense to others besides just me!

I also created another problem for my self. With the changes to the position of the router, I have to redo my dust collection foot. Which is fine if my cut problem goes away.

Thanks

Alan_c
Sun 23 August 2009, 08:13
Nils

Do you get the same result if you cut a square with the sides parallel to the X and Y axis? If you are only getting it on the "diagonal" then it is probably because of resonance between the X and Y motors. I get the same result when I cut a circle, there are 4 areas of roughness around the perimeter interspersed with 4 perfectly smooth areas. I am hoping that the reduction belt drives will reduce this problem.

Gerald D
Sun 23 August 2009, 08:34
Nils, what you are seeing is a very regular pattern:

5848

. . . . which us guys with direct-drive motors have been battling with for years. I think you have geared motors? Anyway, we found that we could stiffen the structure of the machine, but that the marks would remain for diagonal cuts.

The facts that the marks only occur on diagonals and are regular, shows that there is an interaction between the steps/drives of the 2 axes.

The things we learnt to do:

1. Clean and grease the racks. Easy to do and has a signicant influence.

2. Check pinion gears for wear. If the pinion gear tips touch the bottom of the V in the rack, there will be backlash at that point. Is that regular pattern perhaps matching the rack profiles of X and Y racks? (tricky to determine on the diagonal - cannot just hold a rack off-cut against it)

3. Experiment with faster or slower cutting speeds. Sometimes it helps

4. Increase the resolution. We learnt that geared motors were much better than ungeared motors.

5. And then get to wondering if the backlash in the gearbox is causing it . . . . . . .

(I have moved the issue about z-slide roller support bases to its own thread here (http://www.mechmate.com/forums/showthread.php?t=2078))

sailfl
Sun 23 August 2009, 09:43
Gerald,

Yes, I have geared motors. That being the case should I be seeing the same issue?

Do you think that I might have had some movement because of the extended stand offs that I used on the router bracket or am I just wishing that was my problem?

One of the things I thought of doing for the grid pattern that I have to cut is to turn the pattern and cut it so that the lines run more on a horizontal / vertical direction.

Gerald D
Sun 23 August 2009, 10:00
Geared motors cures that problem while cutting wood, but cutting very hard stuff makes the cut quality suffer. The unknown is the backlash of the geared motor . . . .

I don't think that the stand off's can generate such a regular pattern.

Test your cutting directions in some scrap with a test pattern (star?) - there will probably be some better things to do.

sailfl
Sun 23 August 2009, 10:35
Gerald,

I think the problem is still in the wood but you don't see it because the grain is more giving. When I was testing, I cut the same pattern in wood and could hardly detect it but it was there. It will be interesting to see if the problem still exist when I finish changing things.

Thanks for your input and knowledge. I will post sooner next time.

hennie
Mon 24 August 2009, 00:14
Nils the sharpness of your cutter is also a factor.

sailfl
Mon 24 August 2009, 02:39
Hennie,

Yes, the cutter needs to be sharp but that was not a factor. I used new bits.

MattyZee
Mon 24 August 2009, 04:57
Does the pattern change with different angles?
I reckon the repeatable pattern points to the drivetrain. But given the short pattern (i'm guessing <10mm?) i don't reckon its the rack or pinion. The pinion would produce a pattern closer to 70-80mm depending on the gear (i doubt such a repeatable pattern is occuring around the pinion in a discrete integer multiple). It may be something internal to the gear motor. If the motors are 7.2:1, then a mis-shaped internal pinion may result in a pattern closer to the 10mm you are seeing.
It could be either the X ot Y motors. The easiest thing to try might be to swap the Y and Z motors. and see if that improves things. If its not the Y, then maybe swap with one of the X motors.

Gerald D
Mon 24 August 2009, 06:08
Here is a straight line drawn diagonally across my PC monitor:

5858

My pixel size is about 0.5mm, but I can create any "roughness step" length by changing the angle slightly. The pattern is created when the line has to decide which pixel is the nearest.

MattyZee
Mon 24 August 2009, 06:19
Yes, very good Gerald. But the steps in Nils photo looks to be more than the 'resolution' of his motors. I was interested in seeing if an angle closer to the X or Y axis was better. If it is the Y motor having an internal eccentricity for example, a cut almost parallel to Y axis should be worse than one almost parallel to the X axis.

sailfl
Mon 24 August 2009, 06:58
Matt,

I can not do any cutting until I get my modifications complete which I would like to finish this week if my welder has the time.

Richards
Mon 24 August 2009, 09:56
I don't think that backlash would be a factor because the motors do not reverse directions on that particular cut. Also, because both motors are energized (moving) on a diagonal cut, neither axis would go into its reduced current mode, so neither axis would be pushed by the other axis.

Gerald's post #10, showing a straight line, displayed on a diagonal shows how the problem could be caused. We're dealing with digital electronics. If there is a 10:1 ratio between the X-axis and the Y-axis, one of the axes is going to get a step pulse 1/10th of the rate of the other axis. A step is a finite movement, not a partial movement, so the slower axis may make a step at somewhat irregular intervals.

The other factor, which is probably the major factor, is the hardness of the material. The cutter bounces and giggles and wiggles as it chews through the material, after all, aluminum is not butter. It resists the cutter. That bouncing is transferred to the structure of the machine. If the harmonics are right, the structure can cause the bouncing to be amplified.

On my Shopbot, with no gearing, I had a severe chatter problem, even worse than the photo of the aluminum. With a 3:1 belt-drive and then with upgraded 7.2:1 geared motors, the problem was reduced, but not eliminated. I get chatter every time I cut aluminum or plastic. Most of the time when I cut MDF, I get chatter that can be seen but hardly felt with the fingertips.

When I complimented the owner of a 'big iron' machine that cost over $250,000 about the smoothness of his cuts, he told me that he had spent hours and hours making various trial cuts at different speeds before he finally found the proper feed speed and the proper spindle speed to eliminate most of the chatter. After listening to him, I tried various speeds on my machine and found that feed speed is a large part of the chatter problem. Large circles require a different speed than small circles. Diagonal cuts require speed compensation depending on the angle. Cuts with a straight-line portion and a curve usually require two speeds.

Because almost all of my work is with wood, I found that sanding the edge was the fastest solution on one-of-a-kind parts. When I cut aluminum or plastic for customers, I show them some worse-case samples so that they know what to expect. Usually the results are better than the samples, but at least the customer didn't expect better than he got.

isladelobos
Mon 24 August 2009, 10:34
We can test
it is possible two printer ports and two PMDX.?
1- X motors.
2- Y & Z motors.
I do not think that solves a lot.

Alan_c
Mon 24 August 2009, 16:11
What might also help if it is being caused by the cutter flexing, is to do a rough cut at a larger size and then a finishing cut on size (you CAM program should be able to do that, I use Enroute3 with that capability) that way the cutter is only taking a small "bite" and will flex a lot less. This obviously increases the cutting time but if it is a critical part or there is going to be lots of them it could save a lot of sanding.

Gerald D
Mon 24 August 2009, 21:03
This thread brings back lots of memories :) More factors:

- Small diameter bits magnify the problem, bigger bits give smoother cuts.

- V-rollers of the gantry/car/slide must be seating down firmly. The y-car in particular must have all 4 rollers seating with equal pressure. In general, everything on the mechanicals must be firm.

- Low power PCs and Mach3 together have a problem in generating a train of smoothly spaced steps for multiple simultaneous axes.......(hence the SmoothStepper)

sailfl
Tue 25 August 2009, 03:28
Some additional information:

I have a drawing of what I cut.

I made a number of test cuts using 35, 70 and 100 IPM, I used 1/8", 1/4" and 1/2" end mills. The bits were a new or almost new. I cut the pattern in solid surface material.

I saw the same results no mater what size or speed. I had the router set at 20,000.

For any one that has the time, I would be interested in see if you get the same results or what kind of results you do get.

I will be checking to see what my Mach Kernel setting is set at but I believe it is at 25,000.

sailfl
Sat 05 September 2009, 02:25
Gerald,

I thought my problems were resolved until I cut the Fleur De Lys model from my Aspire - Vectric Art 3D collection.

I sized the Model to .5" X 5" X 5.75" and cut it out of MDF. I used a .25 O Flute End Mill for Roughing out, .25 Ball Nose and .125 Ball Nose for finish cuts and a .125 End Mill to cut the model out of the material. I used an .125 End Mill to cut the model out to retain the detail.

The machine is doing a fantastic job of cutting the surface as you can see from the photo. When the .25 End Mill was roughing out, the surface cuts were absolutely smooth - the machine is cutting flat. Even the Ball Nose bits did a fantastic job except for one area that does not show up on the photo where there is a slight indent.

The problem is chatter, when I cut the model out, which appears on both sides of two leafs - there must be a name for them but I don't know it. I did use a smaller bit which I ran at 50 IPM. Maybe for this small model, that was even too fast.

I am going to recut my diamond model in solid surface material and MDF to see what the results are there.

An area of concern are the washers that I used for the Gantry V Wheels. May be there is play there. I will take a picture of that when I have light. I might have to make some bushings for that area.

I realize that the Milwaukee has some run out.

Does cutting slower on a small surface help.

These are the things I want to cut so I want to resolve this problem.

I am open to additional suggestions. I do think that the Z Slide is not the problem.

hennie
Sat 05 September 2009, 05:05
Nils did you cut it out in one pass and at what speed?.I have noticed on my MM when I do fast cutting with the smaller dia bits it does the same so maybe try cutting at a slower rate.Also when the bits start getting blunt it does the same.

sailfl
Sat 05 September 2009, 05:06
Pictures of the washers that I had to insert for the V Wheels on the Gantry / X Axis.

I think that I might have a problem here and that I need to make some bushings like I did for the spider. What do you think?

sailfl
Sat 05 September 2009, 05:09
Hennie,

The material that is being cut at this point is .20" and it was cut with one pass at 50 IPM. I did another cut this morning to test slower speed and I cut it at 28 IPM and the chatter was still there.

javeria
Sat 05 September 2009, 05:36
Ah nils I have the same problem! I cut some mdf with a 8 mm straight edge router bit nd there were chatter marks all over. the spped was 55 ipm @ 0.4 inch depth.

i suspect my spindle mounting now cause I have only one clamp holding the spindle!

Gerald D
Sat 05 September 2009, 06:22
Nils, every time I think of a reply for you, I realise that I have said it before. I have reviewed my previous posts in this thread, and they all still apply.

Changing washers behind the gantry rollers won't change anything because the rollers are pushed up by the gantry weight (on the z-axis the load oscillates).

sailfl
Sat 05 September 2009, 06:39
Gerald,

I hear you. I will recheck that the Gantry and the Y-Car to verify that they are sitting firmly on the rails. The Gantry is not so difficult, the Y-Car is a pain. I will check back with you.

I am not sure I want to move to a smooth stepper.....

Thanks

Irfan,

Yes, I would suspect that part of your problem is the way the spindle is mounted but now that I have reworded my bracket mount and the Z Slide, I don't think my problem is there.

Thanks

sailfl
Sat 05 September 2009, 07:20
Gerald,

I have disengaged the motors for the Gantry and the Y-Car.

When I twist the Y-Car, I can not detect any movement. The V Wheels seem to be firmly sitting on the rails. I also visually looked at each of the V Wheels as I moved the Y-Car back and forth along the Gantry rail. I could not detect any gaps.

I did the same with the Gantry but it is a little more difficult to twist. I also visually looked at each of the V Wheels on the Gantry as I moved it along the X axis. No gaps.

Is there any thing I have missed? Is there any thing else I can try?

Thanks

WFY
Sat 05 September 2009, 08:26
Hi Nils,
Is there a possibility that the debris in the bottom of the "v" grove is possibly lifting the wheel off the rail slightly?

Gerald D
Sat 05 September 2009, 08:55
The things we learnt to do:

1. Clean and grease the racks. Easy to do and has a signicant influence.

2. Check pinion gears for wear. If the pinion gear tips touch the bottom of the V in the rack, there will be backlash at that point. . . . .



Did you?

Doug_Ford
Sat 05 September 2009, 09:00
Nils,

Beautiful work.

I can see the facets in the edge of the workpiece but they appear to be tiny. I'm wondering if the runout in the router's spindle and the small amount of play in your V wheels are the cause. Can't the facets be easily sanded out? I mean, you're going to have to sand whatever you cut out anyway. Are you expecting to cut out objects and apply a finish without sanding them?

Leko
Sat 05 September 2009, 09:13
Nils,

Have you tried disconnecting one of your x motors and trying a cut, then disable the other one & try a cut.

Realize that either your x axis or y axis are probably doing this pulsating all the time, but it only shows on diagonal cuts. When you are cutting in straight x or straight y directions the pulse is directly in line with the cut.

I can only think of 4 things that would result in such a regular pattern; loose grub screw, bent motor shaft, bad motor, or bad Gekko. I'd recheck your pinion to motor connections again.

2cents from somebody that only has a Mechmate in my head.

sailfl
Sat 05 September 2009, 10:43
Buzz, No debris. If the V Wheel lifted up I see a change in the surface but the wheels are clean.

Gerald, I will address those issues. Thanks for mentioning.

Doug, Thanks. The cut turned out very nice. I am concerned that there still is a mechanical problem and I want to eleminate those. The chatter is more than I want to sand. My goal is not to have to sand any thing....I realize that is not a realistic goal but I can still want it. I have checked the runout and it is not good and so some of the problem can be attributed to that.

I will do some more test cuts to see if my cut has gotten worse since I modified the Z Slide which had very little chatter.

Leko, I don't have any of the problem you mentioned but I will think about the motor test.

Thanks to all.

Leko
Sat 05 September 2009, 11:55
This seems like a continuation of the problems you've had in the past (posts 269 and 303 of your thread) just not as pronounced.

Doug_Ford
Sat 05 September 2009, 14:17
On second thought, I don't see how marks like those could be the result of runout in the router spindle. Spindle runout would leave a rough random cut on the edge. The edges of your board appear more like facets.

It has to be something other than that. Gerald and Mike and some other guys talked about improving your resolution. Changing to smaller pinions will be cheaper than buying a Smoothstepper and it will improve your resolution.

Gerald D
Sat 05 September 2009, 20:34
It could be interesting to try another PC.

And then we must not forget that this particular pattern, which has ovals and uneven curves, might be built up from small irregular bits of data. . . . .

sailfl
Mon 07 September 2009, 15:48
Gerald,

I have reached a new level of frustration with my ability to fix my problem and I am about ready to order new C Channel and start over on the table.

On Saturday, I did listen to your words and I checked the V Wheels on the Gantry and I discovered that the wheels on the left side or 0,60 did not ride exactly on center. I added a .5mm washer to both the front and back. Once I did that, all wheels made excellent contact with the rails. I checked the wheels along the full length of the rails and it all looked good.

I reinstalled the motors and moved the machine to its sleeping spot but I did not cut any thing.

Sunday, I took a beach day.

Today, I went out to test my efforts.

The first thing that happened was the noise that came from the pinon gears and rack. I did not hear any noise on Saturday. So I got out the washer that I used to leve the motors to match the rack. Problem I described in another thread.

After inserting the washers, the noise went away.

I got some solid surface material and cut a diamond pattern at 70 IPM. The chatter was back. I then checked the Z Slide but it was good.

I am open to suggestions and thanks for your help.

Doug_Ford
Tue 08 September 2009, 07:39
Gerald has been able to successfully diagnose every problem everyone has had so far. The last thing he recommended was to try another PC so that's what I would do.

sailfl
Tue 08 September 2009, 08:47
Doug,

I would like to be able to try another computer but I don't have one and I don't know of any one that has one I can use.

I did run the Mach test program and it checks out okay.

I am willing to try any thing to resolve my problem and I appreciate all the help.

Greg J
Tue 08 September 2009, 18:48
Nils,

Do you access the Internet from a different PC than the one used for the MM?

If so, just for a test, use the PC in the house to run Mach.

sailfl
Tue 08 September 2009, 21:17
Greg J,

The only other PC I have is a notebook computer which will not work. Thanks for the suggestion.

jhiggins7
Wed 09 September 2009, 06:30
Nils,

I bought a used Small Form Factor PC from these guys (http://www.hcditrading.com/).

It came with XP Pro and was ready to run. In addition to the price of the machine I paid shipping and taxes (they are located in Texas) for a total of $114. It arrived a couple of days after I placed the order.

The computer is shown in this post (http://www.mechmate.com/forums/showthread.php?p=23934&postcount=102)from my build thread.

I hope you are able to solve the problem soon.

sailfl
Wed 09 September 2009, 07:29
John

Thanks for the info but I have a cheap Pentinum III which I paid about the same. We are not sure that is the problem. I have no need for an additional computer unless I it is the problem.

domino11
Wed 09 September 2009, 08:45
Nils,
I wish I was closer to you, I have a few you could try. I seem to keep getting older computers when I help a friend upgrade. :)

sailfl
Wed 09 September 2009, 09:17
Let me explain my frustration.

I am frustrated with me. I have reached the max of my mechanical ability. I am actually lost to some extent. When it comes to software and computers, I have some ability.

I have the greatest respect for Gerald's design and abilities to resolve problems that people have with their builds and I did not mean I was frustrated with Gerald. I also have respect for the other bulders on this forum and their abilities.

What I have done so far:

1) I have lubicated the X and Y Rails using Dupont's Teflon Dry Wax lubicant.

2) I have add some half washers to the motor mounts to make the pinon gears perpendicular to the rack. When I mean half washer here, I am talking about a washer that is cut in half. I am thinking of making some thing better.

3) I have rechecked that the Z Slide is perpendicular and the router bracked is level. When I cut flat things are good.

4) I did check the pinon gears for wear and it does not look like to me that there is a wear problem. I also checked to see if the pinon gear was bottoming out on the rack and it is not doing that.

5) How do I change the resolution? What resolution are you talking about?

6) How do I check for backlash with my geared motors?

I went back over this thread to check all the suggestions, I hope I have answered them all or have requested additional clarification.

I am still geting chatter when I cut at 70 IPM.

Before I added the washer to the gantry wheels, my cuts were better but I had chatter.

I don't know what to try next.

Thank you for your assistance.

jeffa
Wed 09 September 2009, 09:49
Nils,

I am by no means an expert on the Mechmate, but I've spent a lot of my life building, troubleshooting and repairing machinery. I have followed your post and I have thought that what I would do is make some longish angled cuts in the same piece of stock with varying degrees on the angle. Perhaps you could start with a straight 'X' axis cut and then make subsequently steeper cuts in 10 degree increments until you reach a straight 'Y' axis cut. This would allow you to examine, compare and contrast the quality of the cuts under differing angles using a known straight vector.

You also may want to try this twice. Once climb milling and once conventional milling.

Just a thought.

Regards,

Jeff

Doug_Ford
Wed 09 September 2009, 10:13
Jeff,

You beat me to it. I was also going to suggest the angled cuts. However, I would like to add an explanation as to why Nils should try this technique. There are a lot of us that think this is a resolution problem. Nils, since you seem to have a regular pattern, when you change the angle of the cut, depending on whether the angle is shallower or steeper, the regular pattern should lengthen or shorten. In my opinion, this will provide additional evidence that it is a resolution problem.

You asked about resolution. A short answer is your gear box ratio. You said you know about computers. Imagine a couple of curves. One curve is analog and the other is digital. The analog curve is perfectly smooth but the digital curve is composed of a series of short lines and is sort of choppy like the picture Gerald drew. If you increase your resolution by changing your gearbox from 3.6:1 to 7.2:1 or to 14.4:1, you will have a smoother curve. One of the cheapest ways to change the ratio is to use a smaller pinion gear.

Doug_Ford
Wed 09 September 2009, 10:15
Oh yeah. You can check the backlash in your gear box with a dial test indicator. Google it and I'll bet you find pictures of the set up. Harbor Freight has cheap dial indicators.

Gerald D
Wed 09 September 2009, 10:26
Nils, when I looked at your .dxf file of the diagonal in question, it appeared to be a pure 45 degree line......is that correct?

Everyone else, are any of you having issues with 45 degree diagonals? I assume not.

One of the factors that can make such a stark difference between similar machines is the performance of the PC. But Nils does not have a spare PC to test with.

However, you could try something else...........

A 45 degree diagonal means the pulse rates of X and Y are identical. For a test, program your Mach to cut a straight line at 50 IPM in the X direction. But, disconnect your y-gecko's inputs from the PMDX and connect it in parallel to one of the x-gecko's inputs. The machine will run at 70IPM on the diagonal, but Mach3 will not have the duty of synchronising the two axes.

Gerald D
Wed 09 September 2009, 10:29
For experimental purposes, you can eliminate backlash by pushing against your y-car & gantry while it is cutting.

sailfl
Wed 09 September 2009, 11:50
Gerald,

Thanks for the suggestion.

Just so I don't screw things up. I want to disconnect the three Y wires at the PMDX and connect them to the same connectors that the X wires are connected.

I am working on trying to find a PC that I can borrow.

Gerald D
Wed 09 September 2009, 12:00
Best to "park" the y-car away from the end of the gantry before swopping wires - you don't know for sure which way it will go...

You only need to move the "step" and "dir" wires onto the wires going to a x-gecko next to it (I assume they are G203V's). Leave "the" com where it is.

sailfl
Wed 09 September 2009, 12:24
Good thing I asked.

Could there be a problem with the ribbon cable that runs from the bottom of the Controller Box to the top where the PMDX is located? The ribbon cable is taped to the side of the box.

sailfl
Wed 09 September 2009, 12:56
Gerald,

I could not use the cables that run to the Gecko. They are too short so I attached a small wire and ran that to the X. It did not like it at all.

The X with the new input did not like it at all.

I also recalculated the steps for motor tuning.

30 pinons : 1.5 X Pi = 4.7124

2000 X 7.2 = 14,400

14,400 / 4.7124 = 3055.7677. The old setting was 3057. some thing

sailfl
Wed 09 September 2009, 17:43
I have verified that the ribbon cable is not a problem. I had a regular printer cable so I bypassed the ribbon cable the problem is still there.

I will have to put a file together to try Doug changing diagonal cuts.

I am still thinking of people that might have a computer I can borrow to do a test.

Greg J
Wed 09 September 2009, 20:15
Hey Nils,

From a trouble shooting point of view, frustration is the worst kind of mind set.

I can't count the number of times when I'm trying to solve a problem (with the MM also) and I'm pissed. I do more damage than good. The answer to the problem is staring you in the face and you can't see it for the blinders.

I'm always amazed when I put it away for the evening and return the next morning (or whenever) how easy the problem is to see.

Anyways, don't forget to take a break and clear the head. Now, if you have a project and customer is chomping at the bit, that's different.

You'll figure it out. :)

Gerald D
Wed 09 September 2009, 22:59
Nils, I am going to back away from this thread. I find it very frustrating to try and work with you. Example: In post #49 I ask you to test something. 20 minutes later you are onto a different course. An hour later you tell me that you have discarded my test, and that you are onto yet another course.

Helping people to build and run MechMates is not my profession, it is my hobby. Right now that hobby is too demanding and I am pushing the heavy aspects of it onto the backburner.

sailfl
Thu 10 September 2009, 03:30
Gerald,

I am sorry you feel that way. I have ADHD. So that is the way I operate. I jump from one thing to another. It frustrating for me also.

I did not reject your test. I did try it but it appeared one x motor ran one way and the other ran the opposite direction. That was after I attached the Y Dir and Step into the X with the X still connected.

I was concerned that I would damage some thing if I continued to try. So I reported back and in the mean time I tried some thing else. Maybe I did not set the test up correctly.

Thank you for your time.

isladelobos
Thu 10 September 2009, 04:27
Nils, tome precauciones antes de actuar con la electrónica.
Las recomendaciones son buenas.
Sigo este hilo con atención.
Me interesan mucho sus pruebas y los resultados obtenidos. Gracias.

The mechanics of your machine seems perfect.
You can put one fine ballpen in the router site and trace some diagonal and circular lines
in different places of the table for see the accuracy.

Doug_Ford
Thu 10 September 2009, 08:12
Good idea Ros.

Nils, if you move the car into the middle of the table with the Z axis all the way up, you shouldn't damage anything during Gerald's recommended test. Just don't cut anything at first. This step is just to confirm that things are working correctly before you try cutting.

So the first step is to move the car into the middle of your table, place the Z axis all the way up, then connect the wires like Gerald told you too. When you use the keys on your keyboard to move the X Axis in any direction, you shouldn't hit a stop for a few seconds. A few seconds will be enough time to react and remove your finger from the button. With the wires connected per Gerald's instructions, the cutting bit should move on a diagonal when you press the X Axis button.

In your last post, you wrote that the motors seemed to turn in opposite directions. Yep. The X axis motors have to since they face in opposite directions on the gantry. That's why you want to put the car in the middle of the table. Like Gerald said, you don't know which way it will move. (You could figure it out but putting the car in the middle of the table is much simpler.)

Okay, back to the test. Once you have confirmed that your X and Y axes are moving together, program your Mechmate to cut a straight line on the X Axis. It will make a diagonal cut. If the cut is smooth, this would seem to indicate that changing the computer might fix your problem. If you get the same pattern as before, this would indicate that changing the resolution might help.

I agree with Greg J too. It seems the more pissed off I get about a problem, the harder it is to solve. Relax and have a barley sandwich like Greg. :)

sailfl
Thu 10 September 2009, 08:46
Doug,

Doug thanks for helping.

This AM, I went back out and tried again. I thought that maybe I had a bad connection. So I reconnected things again according to the what I understand.

What I understand is this: Take the Dir and Step wires from the Y Gecko and connect them to one of the X Gecko Dir and Step. I left the X wires there that are already connected. So I had the X and the Y Dir and Step wires in the same X Gecko.

I was not clear. Things don't move too well. It appears that the one of the gantry with only X is moving in the positive X direction and the other end of the gantry is moving in the negative X direction. They are in conflect. It doesn't make sense to me but it does not work the way it should. Because there is a conflict, I don't keep it running. I stop it.

"connect it in parallel to one of the x-gecko's inputs" I guess I don't understand what this means.

I think I am making the connection incorrectly.

Send me you phone number by PM. May be you can walk me though it.

Thanks

domino11
Thu 10 September 2009, 13:01
Nils,
Actually you need to move the connections for the Y motor at the pmdx. You want to put it in paralell with one of the x motors pmdx outputs. This way, you are driving the y motor with the same signal as one of your x motors. The connections at the geckos remains untouched. You will have one pmdx output open and one x motor pmdx ouput coneected to one x gecko and one y gecko. The other x pmdx output remains as you had it. Hope this helps. Also see my pm. :)

sailfl
Thu 10 September 2009, 13:08
Heath,

Thanks, that is what I was going to do the first time but I misread Gerald's and thought I needed to do it at the Gecko's. Thanks

Doug_Ford
Thu 10 September 2009, 17:34
I don't know if I'll be much help Nils. This might be a case of the blind leading the blind. I'm no whiz on the electrical stuff but I'm happy to try to assist.

Sorry I didn't answer you before now but I've been working on a research paper all day long.

Thanks for adding your post too Heath.

Take your time Nils. Unless you've got the money to buy a new computer or a Smoothstepper right now, there is no point in rushing through this. You'll just make a mistake or overlook something.

What happened when you changed the wires and made the diagonal cut? Was it smoother?

I looked at a stack of objects I cut out the other day and they had a diagonal cut on them. All of them had a slight pattern. I'd never noticed it before because I always sand them down.

shaper
Thu 10 September 2009, 17:38
Nils

Sorry to but in especially since I'm not any sort of authority on any of this but it just seams to me that a couple of likely things have been skipped here. The first response to this question was that it is likely a mechanical issue, am I correct???

It would also seam to me that you have inspected the visible mechanics and particularly the bits you built yourself well therefore (by process of elimination) if it's going to be a mechanical issue it's going to be somewhere you haven't looked or can't see my first port of call here would be your gear boxes. Have you tried the test that Gerald suggested in post #47, simple fast effective but you didn't give any feedback (maybe you've done this). Also in post #16 Gerald suggested that this types of thing is accentuated with small bits (I'm assuming lower pressure against the gantry and therefore the motors), Have you re-cut at larger size to allow use of a larger bit and seen the effect?

On the PC thing (and I'm probably not telling you anything new here) all large financial institutions and large corporates rotate their computer every three years, this means that about now they are tossing the last of their P4's often these are sold to small auction houses for next to nothing and then auctioned of (either on the web or in local sales) I managed to pick one of these up recently for $20 in good nick even had a reasonable quality (though old obviously) graphics card in it, so i wouldn't just overlook the option or purchasing one.

Anyway long story short, 90% of what I have said is probably wrong but that's fine the bigger issues is that there seams to be big holes in the tests you have tried (or the feedback supplied to the group). This likely what is fustrating Gerald, to solve these things you will need to be methodical and with all these ideas flying around it's important to cover off what has and has not been tried. Perhaps now would be a good time to go back over the thread summarise the suggestions and detail which have been tried the results, which have not then you can cover off the issues that have not been addressed.

Sorry for the essay.:)

sailfl
Thu 10 September 2009, 17:38
Thanks to Heath, I was able to run Gerald's suggested test cut in post #46. I actually ran it twice but the first time I forgot to set the speed at 50 IPM.

I created a 3" horizontial line, I used a new .5" O Flute End Mill and the material was solid surface .5" thick and the speed was 50 IPM. The 45 degree cut turned out to be 4" in length. I made two cuts.

Both cuts have chatter but they are closer together and what is even stranger to me is that 2" towards the end of the cut it is smoother though you can see fine chatter lines.

Since I have chatter that rules out the computer?

Since I have made changes to the Z Slide, added the quick change plate and I modified the Gantry V Wheels to sit better and I had chatter before I did all this but not as bad, it would seems to me that I have a set up problem or a mechanical problem of some kind.

I am using 30 teeth pinon gears and others are using 30 teeth but are not experiencing chatter. What is different with my machine?

What do you think my next steps should be to resolve my issue.

I also want to thank all those that have been posting ideas to help me resolve this problem.

Thanks

Doug_Ford
Thu 10 September 2009, 18:04
Great input Jed.

Yes, Nils. It seems to me that the fact that you still have chatter would indicate that the computer is fine.

I still think it is a resolution problem. The chatter you keep writing about appears to have a pattern. It isn't random. If you had a loose mechanical connection between two pieces, you might get a random pattern. Or if your wheels weren't seated properly on the rails, you might get a random pattern. If you look back at the line Gerald drew, your pattern looks something like that. In my opinion, a smaller pinion might help somewhat and a Smoothstepper would be the best route.

I think the reason that your chatter got worse after you made those mechanical changes is because you tightened things up. Even though you have "chatter" I bet your cuts are slightly more accurate now than they were. The slop in your machine probably obscured the pattern and it simply appeared to be smoother. Just my guess.

I'm not sure that "no one else has chatter problems." Like me, maybe they hadn't noticed before because it didn't matter to them based on what they are using the machine to cut. In other words, if someone was using their Mechmate to cut out parts for a pocketwatch, the chatter you have in your machine would be a problem. However, if that individual was cutting out cabinet parts with it, the chatter wouldn't be a problem.

bradm
Thu 10 September 2009, 18:25
Hmm. I just re-read this whole thread. I think what is being stated is:

- Changing the cut speed has no effect on the chatter pattern.
- The chatter pattern got closer together when you ran the post #46 test.

If that is true, I think you just ruled _in_ the computer. To confirm this without another computer, I propose the following:

Go back to the normal gecko wiring.

Change your computer setup to use 1/2 the current gear ratio settings. Since you are at 3056, go to 1528. This should cause your machine to cut everything at 1/2 size and 1/2 speed, so make your test cut twice as long if need be to see clearly.

If the chatter stays the same, it's mechanical. If it changes (gets closer together, perhaps by 1/2), then you have computer troubles, or gcode troubles.
Note that if it's mechanical, it may be that the smaller pinion will get closer to your expectation. If it's computer, smoothstepper might get closer.

Speaking of gcode troubles, for the simple diagonal test case, can you confirm that it has only 8 (or 4) G1 lines, one for each side? If that gcode file is longer than about 20-30 lines, it points towards something funny.

Also, in any future photos, would you include a tape measure? It may help inspire thoughts in some of our visual thinkers.

chopper
Thu 10 September 2009, 21:59
I know what the problem is, I have had the same issue and resolved it,
Nills if you will put your ADD a side for a few minutes we can get you up and running with greater accuracy,
what is going on is three fold, since you have checked all the physical attributes and are sure every thing is tight, it comes to backlash in the geared motors, I was running the 7.2's and had about 5 to 8 thousands backlash in the gear heads, which is fine in wood no good in aluminum, you need to change the drives to belt drives you can see my posts about this in the Driving Mechanisms, 4 to 1 transmissions for sale? also the larger tooth (30) pinion gears magnify the problem you need to switch the pinions to 20 tooth gears, I would suggest that when going to belt drives you go as big of reduction as possible ( that is why I made the 4 to 1's) the bigger the reduction the smaller the steps the smaller the chatter marks same goes for the pinions.
the rest of the problem lies in the tool head, I believe that you are running the Milwaukee router for this application, I have the same one, you need to get rid of the run out in the tool head, to do this you will need to by new bearings for the router and replace them it is quite simple to do there are threads here an how to do this, but the key is to replace them with better bearings than you currently use, I am on my third set of bearings with about 100 hrs of time on the machine, the bearings that come in the router lasted maybe 8 hours or so, if you are running the factory bearings they are for sure junk by now... I spent more on the bearings than I did buying the router, but by doing this I cut the run out from 8-10 thousands down to 1.5 thousands if you do this you will eliminate most of the chatter and your machine will run quieter with less effort than ever before the same goes for the belt drives once you go belt you wont go back they are far superior, check out the posts good luck//chopper

sailfl
Fri 11 September 2009, 02:19
Brad,

I will try the test later Friday. I did look at the G code and there were 8 G1 moves. 4 for Z and 4 for X.

Chopper,

I am not ready to move to belt drives.

I do believe that runout is a problem. I checked the runout again just the other day. Without the router running, I have 4 thousands and I am sure that it is higher with the motor running. I have sent Chopper a PM requesting the part # for the bearings he is using.

I am sure that the bearings that Milwaukee uses are fine for hand routing. I called them earlier this year and asked them what they considered factory runout to be and they had no idea or they didn't want to share that bad number.

chopper
Fri 11 September 2009, 08:59
I sent Nils a PM with the info he requested,
but others may not know this that the bearings that come from the factory are not rated for the speed that the router will turn, I believe that the bearings in the Milwaukee were rated for 12,000RPM at best and to accomplish this they add play to the bearings to keep the heat down because the ball bearings are not machined to high tolerances,APDEC 3, by replacing the bearings to a higher APDEC rating the tighter the tolerances get which = less run out,
I am currently using APDEC 7 bearings, I have thought about and actually designed a collet system for my router to eliminate the run out, I am confident that this system will work but I have come to the conclusion that it wouldn't be cost effective, since the price of spindles has come down (Chinese)
to a reasonable price,
the single best improvement I have made to my machine is the belt drives,
the second would be the bearings
//chopper

Doug_Ford
Fri 11 September 2009, 13:55
I don't want to sound argumentative but how could run out in the spindle be responsible for creating a pattern? I don't mean chatter, I mean a uniform pattern like Nils has.

Leko
Fri 11 September 2009, 16:40
Doug,

Think harmonic resonance.

chopper
Fri 11 September 2009, 20:33
I don't want to sound argumentative but how could run out in the spindle be responsible for creating a pattern? I don't mean chatter, I mean a uniform pattern like Nils has.
I cant honestly answer this with precise information, all I know is it works,
I think most of the issue is in back lash, but I also believe that both problems magnify each other,
it is not a matter of argument Doug all opinions are welcome, hell I am no deciding factor or guru, I am just trying to share what I have learned with my cnc you can use it or not just like Nils can decide to use the info or not, all I know is since I switched to belt drives and changed the bearings, my cut quality has improved drastically, the bearings were changed since the photos were taken in the 4:1 transmission posts so the cuts are even better than the ones shown
//chopper

chopper
Fri 11 September 2009, 21:33
I have had a lot of you ask about the bearings here is the info I have;
the router that I am using is a 5625-29 Milwaukee
the lower bearing is a New Hampshire Ball Bearing
pn: R-104SS KEA7P58 (this is the good one )
www.nhbb.com
tel. 603-924-4100 this is the info off the box,
the original upper bearing is an NSK 608DW this is directly stamped it the bearing
with this info you can cross reference them..
hope this helps,
Charlie
AKA chopper

sailfl
Sat 12 September 2009, 01:05
Doug and Jed

I will try to take a picture of the results on post #63. I am responding, your post came at the same time or close to when I posted my results.

I think runout whether that is caused by the collet and / or the worn router bearings is a factor in the quality of cut. Since I am not a mechanical guy, I don't know if it can been seen as uniform pattern like what Gerald high lighted. One of the reason spindles are used over routers is that they have high level of tolerances in the bearings and collets along with the motors are designed for long running applications. Though routers work, they are not designed to be used in a CNC application and they don't have the tolerances. Thank goodness they do work because most of us can not afford the cost of a spindle.

It is possible that I am asking the Router to provide a quality of cut that it is not capable of giving. I think the MM is capable, more than capable. Since I don't have a background or experience in CNC, I want to be sure I have my machine set up correctly and that it is cutting well. That is why when I found the chatter and it seems to have gottern worse after all my modifications, I posted what I found and asked for help.

At this point, I do not believe the computer is a part of the problem.

Doug_Ford
Sat 12 September 2009, 09:41
I'm not buying the resonance argument when the runout is so small and the pattern looks like Nils' does. Sorry.

Richards
Sun 13 September 2009, 02:41
I had significant chatter with the original non-geared 1:1 motors on my Shopbot. When I installed a 3:1 belt-drive transmission, most of the chatter was eliminated, but, depending on the material, and the type of cut, there was still some chatter. Finally, I replaced the original motors with 7.2:1 geared motors (Oriental Motors ASM98 Alpha motors). I have about the same amount of chatter with the geared motors as I had with the belt-drive transmission.

Both the belt-drive transmission and the geared motors reduced the amount of chatter, but neither eliminated it.

The harder the material (plastic, solid surface material, aluminum), the more evident the chatter. Even MDF shows significantly more chatter than baltic-birch plywood.

(My machine has a Colombo spindle, so run-out is almost non-existent. Chatter "test" were run using a full sheet of MDF being held in place by a 4-zone two-vacuum (FEIN vacuums) system. None of the cuts went entirely through the material, so material movement was not a factor.)

chopper
Sun 13 September 2009, 09:51
Richards,
I do not know what is wrong with your machine or what is different about it than mine.
but I went from the 7.2:1 geared motors to the belt drives (mine are 4:1)
I cut primarily aluminum, and the chatter was almost eliminated I had significant backlash with the 7.2's there is no way that the 7.2's are as good as the belt drives at least in my case, maybe it is because your drives are made out of aluminum,plastic, mdf, or some other inferior material other than steel which will flex, or maybe your tolerances in making those drives are to loose I don't know but something is wrong, I am down to 1.5 thousands run out on my router (Milwaukee)
and it appears that is about the amount of chatter I have on my parts,
when I switch out the router for a spindle I believe that I will be close to 0
on chatter marks, currently I have a second machine set up and running the same drives He cuts mdf and is currently having 0 chatter marks while doing so with a porter cable router
I have zero chatter marks in plastic and mdf ( I do not cut much mdf)
the only material that has issue right now is the aluminum and that is my primary material, if I were you and I had a Colombo spindle and some one with a Milwaukee router was getting better or equal cuts I would be looking for what is wrong
//chopper

bradm
Sun 13 September 2009, 09:59
Chopper, I think you missed the point that Mike has a ShopBot, not an MM, despite the fact that he's one of the most valuable contributors to the forum. So he has some inherent machine differences that likely explain the difference in your experiences.

chopper
Sun 13 September 2009, 10:19
Brad,
I do not get your reply?
if Mikes machine is not the same then why are we comparing to it?
He may be one of the most valuable contributors to this site but that doesn't mean I cannot disagree with what he says, in fact I am not disagreeing I am just stating my findings with my experiences,
and comparing them to what he (Mike) has stated, now if his machine is so different then explain to me how his findings are relevant?
it seems to me you missed the point....
and some how are upset that I have come to a different conclusion,
these are not personal attacks, digs, or anything else, no disrespect intended or implied, towards you or Mike or anyone else, I came here freely to learn and to share what I have learned that is all.
//chopper

Richards
Sun 13 September 2009, 11:35
Chopper,

I know that you are trying to sell belt-drive transmissions. I have no argument with that, but lets look at the inherent weakness with any belt-drive transmission. In the fifteen different models that I designed, manufactured and installed on my Shopbot, the weak point was belt flex. A stepper motor can only have a certain amount of "overhang" or pressure/force on the motor's shaft before problems arise. Browning recommends at least 1/4" of flex in the belt when moderate thumb pressure is applied to the belt. That's the amount that I used with the 150-tooth belts that I used. The second weak spot is the hinge bolt. It has to be loose enough to allow vertical movement of the belt-drive transmission, otherwise you would have to have a perfectly "flat" rack.

Between the flex in the belt and the movement allowed by the hinge bolt, any flex in a 1/2" thick aluminum mounting plate would not be measurable.

If you look at the various photos that are posted on this forum that show chatter, you'll see the same pattern and the same severity that I had pre-belt-drive / pre-gearbox. The chatter was still visible after I added belt-drives and after I removed the belt-drives and added the gearbox equipped motors, although the depth of the chatter marks was greatly reduced.

All of the belt-drive transmissions that I tried gave the same results. There was no difference between transmissions that I prototyped using MDF, plywood, 1/2" plastic or 1/2" aluminum. That tells me that the frame is not the weak link in a belt-drive transmission.

I'm sure that you're aware that the $1,700 Alpha motors use a different gearbox than the $257 PK296A2A-SG7.2 motors, although my PK296 motors have remarkably little back-lash, much less than the tech support person at Oriental Motor told me to expect.

I freely admit that the MechMate is a much more robust machine than my PRT-Alpha Shopbot. I wish that I had one, but I only have room for one machine in my shop and I already have a Shopbot.

A CNC machine is made up of a lot of different "systems", i.e., frame, motors, router/spindle, hold-down method, etc. Any one "system", i.e. transmission/gearbox, cannot compensate completely for weaknesses in the other "systems".

chopper
Sun 13 September 2009, 12:06
Mike,
I make these statements as an observation, I put the belt drives up for sale to help others who could not or cannot make them for their selves,
I am offended that you would suggest that I am pushing this issue to sell drives,
that is not the case, if the belt drives were inferior I would say so, in fact I here by ask Gerald to remove my post from the market section, I will no longer offer them for sale, if you want to build them you are on your own....
I cannot believe that you all get so pissy when someone questions you or has a different conclusion than you, sorry I tried to offer help to someone who asked for it....
I may not be a guru of cnc, but I have been around the block a few times and I know what I know, I will put my drives where my mouth is I will put them up against the oriental 7.2's and they will and do out perform them day in day out
I have tested and proved this over and over ...on two separate machine
//chopper

smreish
Sun 13 September 2009, 13:12
....and in the spirit of troubleshooting where all of us are trying to be positive about mechanical design issues, Nils still has a challenge that is not resolved. I have seen the cut issue up close and personal and it has me stumped.

I haven't seen this kind of repeatable chatter/cutter issue ever. Not on my bridgeport, not on a Mazak, not a multicam, not on a shopbot series 1, not a shopbot PRT, not a thermwood, etc.

Nils' Mechanically sound machine has almost identical components to two other MM's here in Orlando and I cannot reproduce Nils results. Thus, I am challenged to help him resolve it.

Any positive discussion will be helpful....Pissy banter just makes it harder.

Let's try to keep it nice guys...

So, if someone would really like to resolve the perceived backlash issue as the culprit of this cutting problem, then chuck up a bit in the collet, cut some diamond shapes in solid surface or hard material about 5" in size with 45 degree sides splitting the x/y plane and publish the results. Now that would be a helpful clinical trial instead of a heated debate on who's is better and bigger!

Science, not politics.

Doug_Ford
Sun 13 September 2009, 13:39
Awwww....come on Sean. I was enjoying it. :D

Doug_Ford
Sun 13 September 2009, 13:53
As requested. This is 3/4" mdf cut with a 1/4" carbide bit at around 60 ipm in a single pass. The other side didn't have a pattern but there was a small amount of chatter. I used chalk to help highlight the pattern.

Look at Nils picture in post #1. It looks almost identical.

isladelobos
Sun 13 September 2009, 16:00
Doug Thanks. your cut is in diagonal?

You can test 30ipm 60ipm 90ipm in the same cut line and the pattern is identical betwen chatter marks?

Doug_Ford
Sun 13 September 2009, 17:14
Yes. It was cut on the diagonal. I haven't tested at those speeds but I will do so. Give me a day or two.

I'm starting to wonder if maybe one of my wheels on the car is not fully seated in a small section of the rail. The reason I say that is because this pattern is not stepped. The short sections of the pattern are slightly raised. I could easily understand if the pattern was like a set of stairs. I'm wondering if the car is getting pulled back and forth slightly as a result of the changing amount of pressure applied as the motor is given a step but then rocked back in the other direction as the router approaches the point right before it is given another step.

Unlike Nils, I'm not that worried about it. If I can fix it, I will but I'm not going to spend a lot of time tinkering with it.

The raised section of the pattern is approximately .003" and are about 1/8" long. Easily sanded out.

smreish
Sun 13 September 2009, 17:32
...Now that's what I am talking about! :D Thanks Doug! That's ozarkian help :)

Kobus_Joubert
Sun 13 September 2009, 22:41
Wow.. a 19 mm thick mdf cut with a 6 mm cutter in one pass.....???? I have never tried that before. Don't even think my little 500 W Makita router will handle it.

I always thought that you should not cut deeper than half your bit diameter...therefore if I use a 6mm cutter I will not go more than 3 mm per pass. With my little router I prefer to cut about 1.5 mm per pass on a 6 mm cutter. Takes more time to cut, but it's not so hard on the machine.

smreish
Mon 14 September 2009, 06:24
...interesting. That pattern looks familiar. Thank you Doug - very helpful!

sailfl
Mon 14 September 2009, 07:05
Doug,

Thanks for taking the time to do some test cuts.

I don't believe that I could cut 3/4" MDF with 1/4" bit in one pass. I will have to try it when I have some extra MDF. I also don't think I would have that little chatter.

I would like to see you cut the diamond pattern in a piece of solid surface material and see what kind of chatter you get. It it much harder than MDF.

I have a question. I looked over your build thread and I could not find where you listed what motors you are using. I think they are the geared PK296A2A-SG7.2 motors but I would like to verify.

Also you mentioned that you set your debounce setting to 500? You did that based on a J.R. thread. I searched his thread but could not find it mentioned there but I might have missed it. Why did you set the debounce level?

Also you changed your kernal to 35,000, Why?

Thanks for the input.

sailfl
Mon 14 September 2009, 07:26
Over the week-end, I opened a thread on the Mach forum site were I briefly described my problem and asked if there was a way to test if the computer had a problem with regards to the kernal. I did not get an answer on that.

But I did get another comment about the settings for CV (Constant Velocity). It was suggested that CV can have an effect with regards to chatter. So I did some reading. There is a separate PDF document called CV Notes that briefly deals with some of the parameters.

In Mach, if you click on the Config tab and go to General Configuration, you will see on the right side, a General Configuration area and a CV Control area.

Under General Configuration (GC), there is a "Look Ahead ___ Lines" with the default of 20.

Under CV Control Area, there is "CV Dist Tolerance ____ Units" with the default of 180.
There is also a "Stop CV on angles > _____ Degrees with the defalut of 0.

Based on my reading of the CV Notes, I made the following changes:

CV Look Ahead 200 lines.
CV Dist Tolerance 100 units
Stop CV on angles > 90 degrees.

After restarting, I cut my Diamond at both 35 and 70 IPM and the cuts were smooth. But when I cut at 100 IPM, I still had chatter.

I have since changed the CV Dist Tolerance to 50 Units. I recut the Diamond at 100 IPM and no change in chatter.

I found the results most interesting and I am going to post my results on the Mach forum site. I also wanted to share these results with you.

Doug_Ford
Mon 14 September 2009, 08:00
Nils,

Those are the motors that I'm using. I don't recall resetting the debounce nor why I would have done that. If I remember correctly, I set the kernal at that setting because my testing showed that the computer would allow it. I'd love to cut some solid surface material for you but I don't have any. I'm sure you could cut 3/4" mdf at 60 ipm in one pass since you are using the same motors and router as me. However, I can hear it slow the router motor at points in the process. I'm sure Sean will be rolling his eyes when he reads this and I know I'll probably have to replace the bearings in the router a little sooner but that's okay. Oh yeah, and that single pass cut also included a sheet of .030" aluminum.

smreish
Mon 14 September 2009, 14:36
Doug, I would never roll my eyes! LOL. With the right bit and feed rate, not a big deal. Of course, you have about a billion CFM of air rushing past your bit on the way to the cyclone to help keep the cutting area clean and cool! :D

domino11
Tue 15 September 2009, 06:54
Nils,
With the new settings in mach, do you think you are past the rough angle cutting now? Or are you still tweaking. Myabe some comparison pics of the differences?

sailfl
Tue 15 September 2009, 08:06
Heath,

I still am having a problem. This morning, I increased my router speed because I had lowered for some thing else and I cut a straight piece and things were smooth. In fact, I pulled a Doug and cut the .5" solid surface material with a .25" bit at 400 IPM and it was very smooth. Less I forget, I cut it in one pass!

I thought this is a very good sign. So I cut my Diamond pattern and the chatter was there. The Mach people are thinking that it might be bit deflection.

I am not doing any thing else until I have received and installed the new ABEC 7 bearings that I have ordered for my router. I want to see what affect that has on the results. Since I already have 4-5 thousands runout with my router. I think the new bearings will tighten things up.

I will be happy to post my results with pictures.

domino11
Tue 15 September 2009, 08:11
Thanks Nils,
I am sure your outcome will be very userfull to everyone. Have you changed the router bearing before? I am eager to hear how it goes for you.

sailfl
Tue 15 September 2009, 08:11
No, I have not change the router bearings before.

Greg J
Tue 15 September 2009, 19:15
Nils,

Paco has a great site/blog detailing bearing removal for the Milwaukee router.

http://pacosarea.blogspot.com/search/label/router

domino11
Tue 15 September 2009, 19:24
Thanks Greg,
I was just looking for that for Nils. :)

sailfl
Wed 16 September 2009, 03:36
Greg J and Heath,

Thanks for the paco site. I have seen his site before but it will come in handy when I replace my bearings.

I am replacing my bearing with a better rated bearing than with the standard factory bearing. The bearings they use are not rated as high as the highest motor setting on the router. Chopper suggested and it made sense to me to use bearings that are rated higher. The lower larger bearing, I am replacing with a ABEC 7 rated bearing and the top bearing is rated for 34,000 RPM. Which is much higher than the router can handle. It has a higher tolerance and should help with runout.

I will take some pictures and post my progress.

Thanks again for the info.

chopper
Sat 19 September 2009, 19:12
Here are some pics of the cuts I made today they are in aluminum
6061, cut at a 45 degree angle to the machine
//chopper

liaoh75
Sun 20 September 2009, 02:02
Hi Chopper, may I ask how thick that aluminum is and what were your cut parameters? Specifically, inches per minute, and depth per pass. That cut looks pretty good to me.

sailfl
Sun 20 September 2009, 02:04
Chopper,

That looks as good as a mill would cut. How about more details.

liaoh75
Sun 20 September 2009, 02:28
Hi Nils, I know a computer swap was recommended for test purposes, did you every try that? The reason I ask is because I have had a problem before and believe it or not, each machine I tried (to resolve a different problem than you are having) produced a slightly different sound on my Mechmate which indicates to me the PC does play a role in your cut quality or should I say cut "characteristics". In all, I believe I have had 5 different machines with identical settings in Mach driving my gantry and each made a noticably difference sound when jogging at the exact same speed settings - some machines were smoother and some rougher. Don't ask me why but it is definitely worth a try on your trouble shooting adventure even if that means borrowing a friend's machine - P4 vintage works best in my tests. Well worth the time and effort. One thing I've learned working on this wonderful machine is that sometimes, the solutions that don't seem logical ironically turns out to be the fix. Keep an open mind and don't throw in the towel as the solution is probably right around the corner.

Hope you can get your proble resolved.

sailfl
Sun 20 September 2009, 03:32
David,

I have not switched out computers. I don't believe my problem is with the computer but I appreciate you mentioning you results.

sailfl
Sun 20 September 2009, 06:25
Today, I finished replacing the bearings in my Milwaukee router with higher tolerance ones. My runout went from 4-5 thousands to just under 2 thousands. When you run the router it does sound like it is quieter.

But I have actually gone backwards in the quality of my cut. I was cutting smooth at 35 and 70 IPM in solid surface material and having problems at 100. Now, I am no longer smooth at 35 and 70. I did not expect that I would go backwards. I am not sure what I am going to do next because I would have thought that changing the bearings would not have made things worse.

I am begining to think the computer might be a problem.

liaoh75
Sun 20 September 2009, 06:58
Nils, if you do try a different machine, whatever you do, don't go with a modern dual core. The power saving features built into the CPU (which can't be shut off) will not give you a smooth pulse train. This was the root of my problem. If you look in the trouble shooting section of the forum, there is an entire thread dedicated to this.

I am now using a Celeron 2.4 with 512MB of ram and to this day, not a single blip on the control side. My P4 3.06 with HT worked even smoother but, that machine is dedicated to my DVR system and I'm not going to change over unless I have to. Stay with P4 era PC if you do a swap or you will most likely experience the same issues I did where the steppers lock up during a jog or cut. I hope my experience can help you avoid a few pit falls. Now, I'm battling with interference from a VFD hooking up my Chinese Spindle. Good Luck!

chopper
Sun 20 September 2009, 18:43
Hi Chopper, may I ask how thick that aluminum is and what were your cut parameters? Specifically, inches per minute, and depth per pass. That cut looks pretty good to me.

the aluminum is 6061 and .250 in thickness,
the cut parameters were .020 removed per pass at 40 inches per minute on the feed rate, with no lube, 8,000 rpm on the power head 2 flute up spiral bit
//chopper

jhiggins7
Sun 20 September 2009, 19:27
Chopper,

Thanks for sharing the cutting parameters. The cuts look very clean. It is clear that your system is very effective. I think cutting aluminum with a MechMate "on the diagonal" must be one of the most challenging jobs around. I assume that the other cuts I see on the aluminum were also made by the MechMate.

I looked back at your build pictures and I don't see the "power head." Did you end up with a spindle like you were discussing?

Any how, very nice work and thank you for sharing your results with us.

chopper
Sun 20 September 2009, 19:57
John,
no spindle, just a Milwaukee, router....
//chopper

Gerald D
Sun 20 September 2009, 21:20
I am making a quick visit to this thread, and will then stay away again.

The major marks shown on the work piece are maybe about 1/8" to 3/8" apart. There is zero chance that is caused by spindle/router bearings, gearbox backlash, spacers behind V-wheels, machine vibrations, or any mechanical defect. The fact that the pattern is repeatable and consistent indicates that the machine is being instructed to cut that pattern - in other words; the PC is telling the MM to cut the pattern.

When the PC was relieved of calculating load (paralleling the drives) the pattern changed. That proved that the PC was responsible, but somehow the opposite conclusion was reached.

Replacing the PC might not solve the issue, you may get a similar behaviour - Doug's test shows that.

When I point a finger at the PC, it includes hardware and software. I mean the "electronic pulse generating system". A PC can very easily generate disturbances onto smooth pulses if it is doing unnecessary tasks in the background. Thus, when I say to try another PC, I mean to try one that is set up differently. However, it could help to change the setup of the existing PC.

I believe that this thread has been sidetracked by focussing entirely on the mechanical aspects, and that tempers get inflamed by belt-drives vs gearboxes. I am 100% sure that a belt-drive will do zero for curing the particular problem mentioned at the start of this thread.

lumberjack_jeff
Sun 20 September 2009, 21:57
An inexpensive experiment would be to copy a good test file to a thumb drive, download the EMC live cd
http://www.linuxcnc.org/content/view/21/4/lang,en/

boot your computer with it, and run the test reference file from the thumb drive.

EMC isn't horribly difficult to configure, and you don't need to swap computers, or wipe your current one.

Windows is fundamentally not a realtime operating system. I don't know how Mach gets around this constraint. EMC is working nicely for me with a *really* rudimentary computer.

http://bbs.homeshopmachinist.net/showpost.php?p=458690&postcount=26

On edit, I read now that you can't use a thumbdrive with mach... is that true?

sailfl
Mon 21 September 2009, 06:02
Gerald,

Thanks for your input and for looking at this again.

The computer I am currently using with the machine is a Dell Pentium III. It is bare bones in that it has Windows XP Pro and Mach. I didn't add virus but I am going to check that today. I also did not add any other programs that should be running in the back ground. But I am going to look at Task Manager today to see what else is running.

I have been using my memory stick to load my GCode files and I know others do the same. I will try running from the hard drive because there could be a communication problem.

There is another MM builder that lives close to me that did not document his build. I recently visited his machine to look at his belt drives. I ran the diamond cut file on his machine at 100 IPM and he did not have a problem. I associated the smooth cut to the belt drives but it could also be the computer. He has recently offered to bring his computer over to try it on my machine. I hope that we will be able to do that on Tuesday. I will report back on the results.

Jeff, I have been trying enough things that have muddy up the water, I don't want to try another software package. I am well aware that windows is not a realtime operating system from my experience with simulators and realtime responses. But I appreciate you suggestion and for try to help me.

domino11
Mon 21 September 2009, 06:15
Nils,
Your windows installation might be stock but there will be lots of bloat that MS installs by default. These extra services have been known to cause problems with cnc activities. Also antivirus scanners can be a real problem, especially the real time scanners and when a scheduled scan starts. Your MM computer does not need to be connected to the internet so the need for antivirus is very small. You can look at Black Viper's (http://www.blackviper.com/WinXP/servicecfg.htm) windows services site to see what services can be turned off that you do not need. Look at bare bones setup for starters.

sailfl
Mon 21 September 2009, 09:13
I checked and I do not have any virus software running.

I also ran my diagonal file with the GCode file loaded on the hard drive and not on the memory stick.

I opened task manager. In the performance window, the peak was about 15% activity while mach cut the file. I then opened the process window, Mach was the only process that ran and it peaked at 15%.

I don't believe any thing else is running but I am going to try another computer to verify that there is a problem with the current computer.

I will keep you posted.

Alan_c
Mon 21 September 2009, 15:46
I have just returned from Johannesburg where I was offered a position at a very large fruniture manufacturer managing the maintenance at two plants (turned it down even though the salary offered was astranomical by my standards - all the money in the world cant justify an abusive boss!)

But to the point...at this plant they have 9 big iron CNC's, two of them massive SCM Ergons with three heads and two huge extremely fast moving tables. The cut quality coming off these (R7 million) machines in chipboard was no better than what I get with my direct drive Mechmate when driven a bit fast. If I slow down, my cut quality is a bit better. I am still going to fit belt drives as I feel it will improve things but maybe we ARE expecting a bit much from the system when we try and get milling machine quality cuts from a gantry router. The fact that chopper is getting such good cuts in ally is heartening but there are just too many variable factors in computer make up, build quality and respective machine rigidity to make comparisons on this small scale.

Try another computer or two before chasing any more suspected problems.

inventall
Mon 21 September 2009, 16:20
Allan_C, all the more reason we need a sample test board to determine how well we built our machine. :D

p.s. I agree on the boss thing, best to walk away:)

Greg J
Mon 21 September 2009, 20:30
(turned it down even though the salary offered was astranomical by my standards - all the money in the world cant justify an abusive boss!)



:):):) Sorry for the thread drift

sailfl
Wed 23 September 2009, 09:57
Today, I tried another computer that is being used on a MM that was built but not documented in the greater Orlando area.

Using the other computer we got the same cutting results on my machine. If you remember I did cut my diagonal file on his machine and it was smooth.

I thought my Z Slide was tight but he thought it was loose so I tightened things up but it did not help. On closer inspection it looks as though the Spider is flexing. I do have mamba or 3/16" Spider.

What is the best way to stiffen the spider?

Thanks

astrolavista
Wed 23 September 2009, 11:54
I "Stiffened" mine with some .375" rod top and bottom..

domino11
Wed 23 September 2009, 12:56
Dont forget to see this
Beefing up a thin spider (http://www.mechmate.com/forums/showthread.php?t=1043)

sailfl
Thu 24 September 2009, 07:52
Gerald,

I am assuming that I have a flexing Spider or do you think I am on the wrong path again?

I have looked at the two thread that I could find with regards to flexing spiders.

http://www.mechmate.com/forums/showthread.php?t=513&highlight=flexing+spider

Beefing up a thin Spider that Heath posted.

I don't believe I have the right equipment to check the flex in the spider but I believe it was flexing.

I am wondering if the larger bushing that I made, 1" diameter, .75" long, to offset the VWheels so that I could have enough space for the nut/bolt for the quick release plate and offset the Z Slide, are actually creating a more torque on the Spider.

I even replaced my new bushings with the smaller ones I had been using, .375" Diameter, .4375" long to see if it would stop the flex but it did not.

I realize that the suggestion to place bars across the back was a solution to the thinner Spider. I also saw the stay solution were you added an angle piece that went to another bolt hole.

I could easily try either solution. Then I could at least see if this fixed my problem.

Thanks

Gerald D
Tue 06 October 2009, 13:26
A random thought . . . . what would be the effect of having too little capacitance at the power supply to the geckos?

Posts relating to capacitance moved to Capacitors (http://www.mechmate.com/forums/showthread.php?p=31178&postcount=33)

chopper
Mon 12 October 2009, 20:13
Nils,
this is my last post on this subject,
I will say it was a pleasure to talk to you and try to help you with your problem,


with that said, I cannot believe how some of you trouble shoot your problems this is a simple deduction, and conclusion process.
everyone said that this was a computer problem, so a mutual friend of mine and Nils, went over to his house with his known good computer with no issues and ran Nils machine, found that the same problem existed with new computer,
so the computer was eliminated,

bearings in the router were thought to have been an issue, they were changed and problem seemed to get worse, not expected but understandable.
(since the run-out or slop in the bearings would or could dampen the back lash and when the slop was reduced it made it worse )

also the spider was thought to have flex which could multiply the back lash but I wouldn't consider it a major issue at this time, but I would repair it.
which brings us back to backlash,
this can be determined by two ways, by dropping the geared motors from the rack and feeling the movement in the gears since he is running 30 tooth pinions it will be easy to feel the back lash...( our mutual friend said that he could feel quite a bit of movement here).
which brings me to the second way to check the back lash, and that would be to put 20 tooth pinions on the motors if there is back lash you will see a reduction in the chatter marks, ( this is how I found my problem except I went from 20's to 30's and seen a large increase in backlash)
also I offered to make Nils a set of belt drives for free he supplies the parts and I will supply the labor he chose not to do this.
our mutual friend offered to bring his belt drives and put them on his machine to see if this would correct his problem he also chose not to do this.
all I can say is what I have done to correct the problems that I have had. as stated before you can choose to use this information or not,
but I would be willing to wager that it is back lash not a capacitor ( give me a break )
not the computer, not a program problem it is a plain and simple physical problem,
I guess I deal in reality not, conjecture or make-believe, I also had this issue with my machine and corrected it, my friend had the same problem and corrected his problem, so I speak from experience if you do not want to fix you machine that is your choice, mine works great...
//chopper

sailfl
Tue 13 October 2009, 04:14
Chopper,

I appreciate all the help everyone has offered. I have tried some of the suggestions, others I have not.

I did not take you up on your offer to add belt drives to my machine because I did not want to add another level of complexity with out understanding what is actually wrong with my machine. You are convienced that adding belt drives will fix my problem. I am not convienced that is the solution.

There is a machine is CA that will cut straight cuts at 400 IPM and diagonal cuts at 300 - 400 IPM without a problem. That machine is like mine except for the ground rails. Same geared motors. I can cut a 4" square that has straight cuts a 600 IPM but I can't cut diagonals at 70 IPM.

I think I do have some mechanical issues that I am addressing. I do believe that the Z slide had some play in the V Wheels. I also believe that the C Channel not being level is a mechanical problem which I am addressing.

This is a tough problem to resolve espically when the owner of the machine (ME) isn't mechanically inclined and the people helping me can not see the machine. If I had lots of money to throw at it, I could try every thing but I have limited resources.

chopper
Tue 13 October 2009, 09:08
Nils,
I understand,
I meant no dig on you at all,
it was directed towards all the BS that was spewed, and I realize that you are limited in your mechanical ability, and mean no disrespect by saying it I hope you work it out and get it up and running soon,.you know how to get a hold of me if you need to ..
//chopper

liaoh75
Tue 13 October 2009, 22:15
Hi Chopper,

I've been following this thread with a lot of interest. I am glad to see that at least we know what the problem most likely is. I too am running the same motors Nils is using. Now, the question to you would be why does he have this problem and I don't. I cut 12-18mm Acrylic day in and day out often single pass at that. I am using a metric 1.5 pinion and rack. About the equivilent as Nils. If you can see chatter on anything, nothing is as apparent as acrylic. Now, my cuts are silky smooth with none of problems Nils has. I cut diamond shapes all the time at a wide variety of angles and never once did I ever see the type of patterns that Nils has on his machine. I haven't heard anyone else experiencing the same problem either. What's your take on this? Is it possible he got lemon motors??

sailfl
Wed 14 October 2009, 03:05
David,

It has not been determined what is causing the problem.

MattyZee
Wed 14 October 2009, 04:46
I did not take you up on your offer to add belt drives to my machine because I did not want to add another level of complexity with out understanding what is actually wrong with my machine.

I don't understand this comment Nils. You need to try it to dismiss the possibility that it will fix it. If it is the cause of the problem, then no matter what else you try you won't fix it and you'll never fix the problem.

I would take Chopper up on his offer to try his friends belt reduction. Theres no/mininal cost, low risk and a very good chance of fixing the issue.

All the best with it.

sailfl
Wed 14 October 2009, 08:12
Matt,

When will you able to stop by and help trouble shoot?

chopper
Wed 14 October 2009, 09:20
Hi Chopper,

I've been following this thread with a lot of interest. I am glad to see that at least we know what the problem most likely is. I too am running the same motors Nils is using. Now, the question to you would be why does he have this problem and I don't. I cut 12-18mm Acrylic day in and day out often single pass at that. I am using a metric 1.5 pinion and rack. About the equivilent as Nils. If you can see chatter on anything, nothing is as apparent as acrylic. Now, my cuts are silky smooth with none of problems Nils has. I cut diamond shapes all the time at a wide variety of angles and never once did I ever see the type of patterns that Nils has on his machine. I haven't heard anyone else experiencing the same problem either. What's your take on this? Is it possible he got lemon motors??

I, do not know why yours are silky smooth, try cutting aluminum .250 at the diagonal, with a two fluted up spiral bit, and post the pictures, you can say it is so but we will never know if you cannot show pictures.
also if your motors are new (low hours) this seems to happen as the motors break in mine were fine at first also, with time the backlash becomes more apparent
//chopper

sailfl
Wed 14 October 2009, 14:24
Matt

I apologize for my comment.

Robert M
Wed 21 October 2009, 05:13
Nils..
A thought came cross my mind with my 1st morning coffee….
Could this be an effect due to some parts being out of round tolerances (Ie : Gear bore ctr, gear mesh, motor shafts… etc….moving parts ? )
Robert ;)

chopper
Tue 27 October 2009, 19:44
Hi Chopper,

I've been following this thread with a lot of interest. I am glad to see that at least we know what the problem most likely is. I too am running the same motors Nils is using. Now, the question to you would be why does he have this problem and I don't. I cut 12-18mm Acrylic day in and day out often single pass at that. I am using a metric 1.5 pinion and rack. About the equivilent as Nils. If you can see chatter on anything, nothing is as apparent as acrylic. Now, my cuts are silky smooth with none of problems Nils has. I cut diamond shapes all the time at a wide variety of angles and never once did I ever see the type of patterns that Nils has on his machine. I haven't heard anyone else experiencing the same problem either. What's your take on this? Is it possible he got lemon motors??

still waiting for pictures of your cuts, (plastic is easy to cut) in the meantime here are some more I cut today
6061, .250 thick 2 flute up spiral no lube, remember these are close up photos, things are bigger than normal size....//chopper

MetalHead
Tue 27 October 2009, 20:43
Nils,

Have you tried this cut in passes ? If it is a flex issue small cut passes would eliminate the flex. Look at each pass, maybe even do seperate lines side by side at different speeds 40,50,60 ipm.

Another thing I may have missed. Swap your Z motor with you X or Y then test then swap X and Y. If it is a single motor backlash issue you may be able to move it out this way.

Also note on the Aluminum cuts they are in .020 inch per pass.

If it is a osillation issue your pass cuts may show the imperfections in the same spot each pass.

With the even spacing on the cut path this looks like a cut path instead of chatter or backlash.

Another culprit to look at is your input power to the system. Like Gerald said the Capacitors or even the power from the wall could be suspects. Do you have a UPS OR is your table and PC on seperate circuits? Check your grounds as well.

Just some different ways to look at the issue. Hope this helps.

Also remember once you get the unit cutting at a decent speed and quality that suits you, don't push the edges again just to see what happens. This will cause frustration if the machine acts up running at speeds and feeds you wont use anyway.

chopper
Tue 27 October 2009, 21:02
[QUOTE=MetalHead;31841]Nils,



Another thing I may have missed. Swap your Z motor with you X or Y then test then swap X and Y. If it is a single motor backlash issue you may be able to move it out this way.(the backlash will be in all the gear heads so this will do nothing)

Also note on the Aluminum cuts they are in .020 inch per pass.
what are you referring to here????
If it is a oscillation issue your pass cuts may show the imperfections in the same spot each pass.
I agree with this statement
With the even spacing on the cut path this looks like a cut path instead of chatter or backlash.
(this could be true but unlikely but i didn't write the program so i don't know)

Another culprit to look at is your input power to the system. Like Gerald said the Capacitors or even the power from the wall could be suspects. Do you have a UPS OR is your table and PC on separate circuits? Check your grounds as well. ( do not agree with this statement the problem is.......wait for it..........backlash.......oooooohhhhh)
//chopper

Hillbillie
Wed 28 October 2009, 05:06
I don't have much experience in CNC building, but I have lots of experience in manufacturing especially finding and fixing problems.

This thread reminds me of different problems in a factory. When we have a tough problem that is hard to find the root cause, we have a meeting with several experienced people and discuss possible root causes. We start with the easiest most likely solution and see if that fixes it. If it doesn't we go to the next and the next. During this time we have many tempers flair, but we keep going. We don't give up until we find a solution.

People on this tread is doing the same. Trying different things, coming together with ideas, and eliminating all the variables.

Though the solution is not yet here, we know what it is not.

One thing about using this forum, everything is well documented and can be used in the future.

MetalHead
Wed 28 October 2009, 06:01
Who knows what this issue will end up being.

The more steps we document for him to check here will help others in the future.

Nils another test would be to cut the same diagonal line job 4 to 6 times or look back at jobs you have already ran. Put them side by side like chopper has done and others to see if the cut paths look the same (ie the "chatter" marks line up) .

Richards
Wed 28 October 2009, 15:32
Chopper,
Those are some very fine cuts. I only get that kind of quality when I use my vertical mill. How about posting some photos of your MechMate, especially some closeups of the V-rails? Your MechMate is capable of making cuts that make the rest of us drool. Please share with photos.

chopper
Wed 28 October 2009, 18:02
Chopper,
Those are some very fine cuts. I only get that kind of quality when I use my vertical mill. How about posting some photos of your MechMate, especially some closeups of the V-rails? Your MechMate is capable of making cuts that make the rest of us drool. Please share with photos.

there are pics of it in my build, I dont think there are close ups of the rails,
I will take some photos in the next few days, I had plans on doing that anyway
//chopper

chopper
Wed 28 October 2009, 19:09
I don't have much experience in CNC building, but I have lots of experience in manufacturing especially finding and fixing problems.

This thread reminds me of different problems in a factory. When we have a tough problem that is hard to find the root cause, we have a meeting with several experienced people and discuss possible root causes. We start with the easiest most likely solution and see if that fixes it. If it doesn't we go to the next and the next. During this time we have many tempers flair, but we keep going. We don't give up until we find a solution.

People on this tread is doing the same. Trying different things, coming together with ideas, and eliminating all the variables.

Though the solution is not yet here, we know what it is not.

One thing about using this forum, everything is well documented and can be used in the future.

Hillbillie,
I totally agree with you here, the problem is there is no logical path of deduction being followed, people are grabbing at straws and throwing out random guesses, and I guess one should expect this from an internet forum,
you have people here who do not even have a machine guessing at what the problem might be, never run a machine, or built one and for them it is almost impossible to relate to the problem, yet they spew out ideas that come to them with there morning coffee, not realizing that they are misleading others who may need the help, there are two classes of problems that can happen to a machine like this, one is electrical the other is physical,
there could be two different problems going on at the same time.
To me the easiest way to chase a problem would be to determine if it was a physical or electrical problem,
I have deduced that this is a physical problem, from the nature of what is happening and because of the known backlash problem in the 7.2's
and also knowing that he is also running the 30 tooth pinions,(which will magnify the back lash by going to 20 tooth pinions he will see smaller chatter marks and prove that it is backlash)
if you go back in this post you will see that I had a similar problem with my machine, and it was corrected by changing out the 7.2's to a belt driven system, if you look at the cuts above you will see that I have very little chatter and I am still using a Milwaukee router, so there is still room for improvement by going to a spindle, how ever slight the improvement may be, so what I am trying to say is fix the known problem of backlash, and if that does not fix the problem (which I sincerely doubt)
then chase the fairies in the electrical system if they still exist at this point...

Backlash can do many funny things that are not expected when cutting,
it will shorten the life of your bits, cause loss of accuracy and repeatability..
once the initial cut in the material is made and you have backlash the bit will follow the path of least resistance and follow the previous cut path, so if the cutter jumped around a lot in the first pass it will do it on the rest of them since the backlash is allowing the bit to do so. and the so called pattern could be generated by how the bit made the first pass and the flutes of the bit cut through the material which could quite possibly leave a pattern like what is seen ...
sorry I know I said my other post would be the last on this subject I guess I lied....
I also want to give a little background on myself so you know where I am coming from, for 25 years I did metal fabrication,( never really quit) from welding to forming metal of all kinds,machining of metals and repairing of machines, from semi trucks, bulldozers and fire trucks etc... then I got into the computer world when it was just getting going at least on the networking side of things, I worked for the local university and did everything from installing telephones and computers to
to designing complete networks in each campus building and then install them, (440 buildings) trouble shoot them etc.... so I know of what I speak, and have
quite a bit of experience in the trouble shooting field, both on the fab side and on the electrical side of things, was I ever wrong when trouble shooting of coarse I was but not very often,...
//chopper

lumberjack_jeff
Fri 30 October 2009, 11:34
I use EMC, so I have no practical experience with Mach, but has backlash compensation been tried?
http://www.youtube.com/watch?v=A27nOkTFYDY

Also, wouldn't cutting a small circle quickly identify any significant backlash?

on edit:
After more reading about EMC, I need to test (and correct if necessary) my machine for backlash too.

lumberjack_jeff
Fri 30 October 2009, 12:10
One other thing;
I'm having a hard time reconciling the idea that backlash is to blame for an irregular straight line (diagonal or otherwise). Backlash is normally manifest during changes of direction. Once a stepper begins turning in a given direction, backlash within the mechanism is taken up.

I guess I can envision severe backlash allowing chatter, but elsewhere in the thread (because of the regularity of the pattern) chatter was deemed unlikely.

chopper
Fri 30 October 2009, 16:42
One other thing;
I'm having a hard time reconciling the idea that backlash is to blame for an irregular straight line (diagonal or otherwise). Backlash is normally manifest during changes of direction. Once a stepper begins turning in a given direction, backlash within the mechanism is taken up.

I guess I can envision severe backlash allowing chatter, but elsewhere in the thread (because of the regularity of the pattern) chatter was deemed unlikely.

this is true until forces push against the direction of travel, so as soon as the bit hits the material all bets are off on the back lash being taken up...
I do not know what your experience is with backlash some people do not understand it but I have had this issue and I did extensive research on how to eliminate it it does not just simply go away when the machine is in motion it is always there until removed you cannot wish it gone, and with the problem that I had I put a lot of thought in how to eliminate it, and as you can see by the cuts produced it worked....
//chopper

chopper
Fri 30 October 2009, 16:49
I use EMC, so I have no practical experience with Mach, but has backlash compensation been tried?
http://www.youtube.com/watch?v=A27nOkTFYDY

Also, wouldn't cutting a small circle quickly identify any significant backlash?

on edit:
After more reading about EMC, I need to test (and correct if necessary) my machine for backlash too.

I do not think that the backlash compensation in Mach works very well I did try it with limited results on my machine....
you cannot fix a physical problem with software....
//chopper

Richards
Sat 31 October 2009, 08:03
Although I mostly agree with Chopper about backlash, I'm not sure that the "chatter" marks are the fault of the gearbox or of backlash. Here's an image of the edge quality that I got several years ago. The bottom photo shows a great deal of "chatter". It was cut on my PRT-Alpha that had neither gearboxes or belt-drives. The better cuts were all made with 3:1 belt-drives.

chopper
Sat 31 October 2009, 20:26
Although I mostly agree with Chopper about backlash, I'm not sure that the "chatter" marks are the fault of the gearbox or of backlash. Here's an image of the edge quality that I got several years ago. The bottom photo shows a great deal of "chatter". It was cut on my PRT-Alpha that had neither gearboxes or belt-drives. The better cuts were all made with 3:1 belt-drives.

Mike,
I agree that backlash may not be the only problem Niles is having, but it would be hard to tell what other underlying problems may exist until the backlash is removed,
also I would like to ask what differences are there on my machine compared to others that would allow me to get the cuts I get?
there are some small changes that I made while I was building the machine, but none that I believe would account for the quality of cut on my machine vrs others,other than the belt drives,
the changes on my machine are as follows:

1)...I welded the rack to my machine instead of bolting and using vhb tape

2)...I welded the Z assembly instead of bolting

3)...I modified the spider by welding 1.25 X .625 thick band iron behind the
V wheels for spacers on the Z assembly and on the left side of the spider
I bolted the top and bottom V wheel to the spider with out using an eccentric adjuster, and put the eccentrics on the other 4 wheels so everything squares to the two wheels that were bolted solid.

4)... 4 to 1 belt drives

I also spent a bit of time making sure that things were level, square and true, other than the above my machine is built directly from the same plans every one else is using,...
my friend that has the belt drives on his machine has the same Z assembly
but none of the other changes and he gets really great cuts with his also,
I do not know if he has cut aluminum with his if he has I have not seen the cut quality to compare but I know what he has cut in wood and etc.. have been chatter free, so I do not think that my machine is some kinda fluke since both machines were built by two different people at different times in different states the only two things in common are the Z assembly and the the drives and both are chatter free...
//chopper

chopper
Sat 31 October 2009, 21:33
Mike,
I also wanted to ad that as you see with your belt drives vrs the direct drive that resolution of the step plays a big part in the cut quality also, that is why I went to 4 to 1 on the drives I built and I use the 20 tooth pinions, I do not know if that is a significant enough gain over the 3.1 or 3.6 to make that big of difference, and I also know that is why the 7.2 are so desirable, but the backlash negates the resolution in the end,...
but it still makes me wonder why our machines can achieve the cut quality that my friend and I are achieving and no one else?
my friend actually has cut with a 1/16 of an inch bit with out breaking it, he commonly uses 1/8 inch bits also, and if there were any kind of backlash in the machine those bits would snap of quite quickly,
//chopper

javeria
Sat 31 October 2009, 21:52
Nils - I wanted to add what i experienced,

Till now I was thinking that I was having the chatter marks on my machine due to a single spindle plate used to clamp up the spindle, yesterday i made the second clamp to get it on the Z assy,

upon removal of each part on the Z assy, I found that though the V wheels were holding the plate so tight that even after a considerable effort I could not get a play on the Z plate, but once I had the spring tension removed there was a plenty of play on the top two v bearings, the reasons were the slightly bent bolts on the top two bearings and also that the spider plate has bent and that makes the V wheels not aligned to each other , I did not have any spare bolts nor was willing to remove the whole Z assy to get it right, so currently I will get chatter when I stress the machine more, but on 3d works I did not see any at all.

I am planning for a totally new Z axis redesign -

RDS
Irfan

chopper
Sat 31 October 2009, 23:22
Irfan,
lets see the pics of your cuts, can you cut aluminum with out chatter marks?
I think the aluminum is the true test, if you can cut it with out chatter, you will not have a problem with any other material, I would like to see them to compare cut quality etc.. what is the ratio of your belt drives?
//chopper

sailfl
Sun 01 November 2009, 06:34
Chopper,

Please spell my name correclty

Gerald D
Sun 01 November 2009, 09:14
I havn't looked at this thread for a long time but today I was told that I should check it out.

Quite frankly, I am most disappointed with the tone taken on by some of the members. I am not going to run a forum with these attitudes around and I am sorely tempted to delete this thread and send a couple of guys to the cooler for a week or more.

Richards
Sun 01 November 2009, 09:15
There's been a lot posted on the forum about belt-drives and gearboxes. I searched on the word "chatter" and was directed to "Driving Mechanisms: Rack/pinion, gears, screws, belts & chains". In that section is the thread, "Reduction Drive by belt - a collection of various designs". In the six pages of that thread, you'll find a lot of different designs that have been tried. On page three of the six-page thread, I saw the photos posted by Alan of some mirrors that he cut from oak. I hope that he doesn't mind that I've reposted one of them. That cut was made on his MechMate with motors that had neither belt-drives non gearboxes.

The chatter on a MechMate is very similar to the chatter on a Shopbot when chatter conditions are ideal. That caveat about chatter is important.

On my Shopbot, I didn't always get chatter. On most of the photos posted by MechMate owners, I don't see chatter. But, under the right conditions, especially with non-geared/non-belted motors, many of us get chatter.

On my Shopbot, with 3:1 belt-drive transmissions, MOST of the chatter was eliminated. Sometimes I still got chatter, although the roughness was greatly reduced. Even now, with 7.2:1 Tapered Hob gearboxes, I still get some chatter when the conditions are just right to produce chatter. It could be the gearboxes. It could be the construction of the Shopbot. It could be the lack of maintenance on my machine. It could be almost anything. I've done everything reasonable to eliminate as much chatter as possible, and I just live with what's left and rub it out with a few strokes of sanding. In the case of aluminum, I use a power sander. In the case of plastic, I run over to a nearby glass shop and borrow some time on their wet sander.

Here is Alan's photo:

Alan_c
Sun 01 November 2009, 09:44
Mike,

When I cut those mirrors, it was with two passes at about 4m/min. I have since tried similar cuts at a slower speed and doing rough passes about 1mm away followed by a finishing pass on size. This has given remarkably improved cuts with hardly any chatter. (using spiral / slot drill cutters). I am still going to make reduction drives but it is possible to get very good results if the correct cutting strategy is followed.

chopper
Sun 01 November 2009, 09:56
Chopper,

Please spell my name correclty
sorry it was a typo
//chopper

Richards
Sun 01 November 2009, 10:04
Alan,
Thanks for posting that information. Chatter is often a function of speed and depth of cut. I ran a series of tests on my Shopbot and saw a remarkable difference in chatter depending on how fast the machine was cutting. Recently, I made some cuts in aluminum with the machine running only 50% of the recommend feed speed and only 0.020" per pass. The cuts were very clean and basically chatter free.

There are a lot of factors that have to be watched to get an ideal cut. Many times, when cutting wood, it is much more cost effective to get a quick cut on the machine and then to spend a few more seconds with a sander - especially if I would have to sand anyway.

There was a fellow on the Shopbot forum who sold his original Shopbot because of chatter problems and then bought the newer PRS-Alpha model. He experienced the same chatter problems. He posted a bunch of very blurry pictures that he said showed how bad the problem was. We had to take his word because of the quality of the photos. Because he was using a program that Bruce Clark and I wrote together, I played with his numbers and saw that he had very unrealistic goals. He assumed that since that machine could cut at 12-inches per second, that it should be able to produce perfect parts at that speed. At 5-ips, on my PRT-Alpha, I got almost perfect parts. Shopbot cut some parts at various speeds and also suggested 5-ips as the ideal speed for that material and that type of cutting. He disagreed and returned the machine for a refund.

I've seen some terrible cuts made on a Thermwood when the operator didn't use the right speeds. I've seen some beautiful cuts on my entry-level Shopbot when all the factors were right. The MechMate is a much sturdier machine than my Shopbot. It has less flex and more mass, which would help in those "picky" situations when everything has to be just right for the cut to be perfect.

Although I agree with almost everything that has been posted about the value of adding a belt-drive transmission or a gearbox with zero backlash to a non-geared motor, I don't believe that gear reduction is always the magic bullet that kills all of the common problems that we experience. I've found that gear reduction minimizes the problems to the point that I consider them to be eliminated, but not always.

Your post pointed out the value of a little experimentation to find the best parameters. Thanks.

chopper
Sun 01 November 2009, 10:17
Mike,
I couldn't agree with you more, if you are running a reduction to get rid of the chatter and do not use the proper feeds and speeds the reduction will not save you, be it belt or gear.
//chopper

javeria
Sun 01 November 2009, 11:37
chopper - I don't believe that machining Aluminum is the tru test to test for chatter marks,

while cutting Alu - i reduced the step down and the feed rate of the machine - now what happens is that the Alu is beautifully cut, but when i cut ply / mdf at much higher speeds the chatter reappears

today i observed something while cutting 3d too, if I keep my speeds around 3000mm/min the results are great, any higher speeds and I observe pitting,

but I know what the problem is - its me who did not get my Z assy right , I am probably just going to shift to linear rails soon on the Z axis and I dont have any argument over that in my mind,

Sorry Nils I am cluttering your thread with my problem -

and Mike - I agree fully with you- we have to understand the limits and parameters under which to ascertain that we get good cut quality results.

RGDS
Irfan

Kobus_Joubert
Sun 01 November 2009, 11:58
I agree with Alan. As I only havea little 500 W Makita router on my MM, I cannot take deep high speed cuts. This I realised very soon after completing my machine. From there I take it slow and with cuts not more than 1.5 mm at a time. Like Mike said, that sometimes you get a little bit of chatter and other times less. My chatter is so little that with a light sanding they are completely removed....or it adds to the overall 'effect' of the piece I have cut. I actually would like it to CHATTER all the time when cutting flowers, leaves and wildlife scenes.;)

chopper
Sun 01 November 2009, 12:14
chopper - I don't believe that machining Aluminum is the tru test to test for chatter marks,

while cutting Alu - i reduced the step down and the feed rate of the machine - now what happens is that the Alu is beautifully cut, but when i cut ply / mdf at much higher speeds the chatter reappears

today i observed something while cutting 3d too, if I keep my speeds around 3000mm/min the results are great, any higher speeds and I observe pitting,

but I know what the problem is - its me who did not get my Z assy right , I am probably just going to shift to linear rails soon on the Z axis and I dont have any argument over that in my mind,

Sorry Nils I am cluttering your thread with my problem -

and Mike - I agree fully with you- we have to understand the limits and parameters under which to ascertain that we get good cut quality results.

RGDS
Irfan

I would like to see the cuts you have made in aluminum, yes you can get chatter in any thing you cut I have heard all this before but no one will show their cuts, I would like to compare if you would show them, thanks
//chopper

javeria
Sun 01 November 2009, 12:24
tomorrow sir - its 1 AM here

sailfl
Mon 02 November 2009, 02:35
To All,

Any discussion that has to do with chatter is fine with me. I have been working on a couple things that are relate to fixing my problem but have not posted any thing. It makes sense to have the chatter problem in one thread.

I do thing that my racks are not aligned properly and that is what is causing my noise problem that I have had for ever. I don't think it effects that chatter but there has to be binding or there would be no noise. The grantry purrs when the Y car moves.

I did add spacers under my aluminum rails to fix the C Channel not being straight and I think it helped some.

I will post more when I try some things. I recently cut some grills out of .125" 6061 Aluminum and I will be posting results of that. I rarely break bits but I went through 5 in a learning experience and completing the job.

It is interesting to me that some one with a machine like mine, meaning same characteristics.... preground rails and Milwaukee router, can run their machine at 300 IPM and have no chatter and I can not do the same thing - that was cutting my diagonal cut. He has the same motors that I have.

I also don't believe that there is one solution to this problem. I do believe that factors related to my problems have to do with the way the parts of the table, gantry and Z work. I am working on fixing the Z first.

Robert M
Mon 02 November 2009, 04:13
Nils,
In my amateur to CNC world opinion, I have a tendency to think your problem of chatter / rough cut is a result / consequence of many factors, minute or not on each of them to a point of hard to impossible to locate individually, but combined as a hole, your machine that is ( or others with preground or not rails & a hand router or spindle) get your own result / consequence.
A very important factor, goes to anything build, is attention to small detail while making / producing it !
Not saying you did not take care of details and you where not being matriculate, but what I’m saying is, no one in this forum has the same ability, the same attention to detail, time to make it , acceptance to tolerance and so-on, making each and every ones BEAST a little different vs the next one, even if it comes from the same fabulous, plans!!!.....and that goes with leaving out in the equation, difference in materials to make this beast by it self !

My experience as a hand on making thing for over to many yrs and observering and studying on fabrications methods, and…well….what is going on here as well !!!

My 2cents….No offence to no one was intended and can only HOPE, no one feels offended and NO ONE will attack others for this !!!
AMICALEMENT, Robert ;)

bradyaero
Tue 03 November 2009, 07:21
I never run my machine over 200 IPM, as a matter of fact I run it mostly at about 100 IPM. I don't get chatter marks but my rack and pinion are noisier than I would like. When I disengage the pinions, everything is smooth as glass, when I re-engage them the noise returns.

sailfl
Sun 29 November 2009, 06:58
My progress and what I have tried:

Since the last time I reported, I have not stopped working on my problem but decided not to report because I was getting too much direction and it was more than I could handle.

1) Spider / Z Tube / Z Plate / Router

This is the first place I put my attention. I felt that I was getting some flex no matter how tight I made the eccentric bushings. I knew that I had not done the best job of drilling the holes for the V Wheel bolts on my spider. The spacing was not the same so I always had a problem aligning and tightening the bolts so that I had tight fit and that all was square.

I decided to replace the spider, Z tube and Z plate. With some assistance from Leo in Tennessee, I had my new parts. Once assembled and I knew things were tight, I installed them. But once again, I could see that there was flex taking place even when I had the eccentrics turned to the max.

I determined that my flexing problem had to do with the fact that I did not used a thick enough washer between the Y Car Bracket and the Spider. When I used a thicker washer, I could back off of my eccentrics and my flexing went away.

I don't think I had to replace my spider and Z assembly but I am happy with the new parts so I am selling my Z assembly.

With this first problem fixed, I tried some test cuts but my cutting problem was not fixed.

2) Belt Drives

There were a number of people that thought that I should have taken up the offer of trying belt drives. So this was the next step.

There is a non documented builder in my area that has assisted me when I tried the computer. He graciously agreed to bring his Chopper built belt drives with motors over to my house so I could test them on my machine.

It took building some interface cables because of the different motor connectors used and changing the position because of different pinion gears but we ran a test. I thought that this solution would resolve the problem.

Unfortinately, the resulting cut with the belt drives on my machine did not cut any better than with out the belt drives. In this case, I do not believe that backlash is the cause of my chatter marks.

If I had to do over again, I would not buy geared motors because of the cost but I would buy direct drive motors and use belt drives but belt drivbes were not being talked about when I started my machine.

3) Mach Configuration

I was begining to believe that my problem was a signal problem so I started to look at my Mach configuration. I did find some things that the Mach configuration manual suggested doing but those changes did not make any difference in the way my machine cut.

One thing I did try at the suggestion of Richards was different Acceleration and Velocity speeds. I determined that a very slow accelration around 10 helped my problem.

4) Rack and Pinion Noise

Since I finished my machine, there is been a noise problem on both X Axis when the gantry was rolling. I thought that sound was an indication that my pinions and racks were not engaging correctly. But how do I go about fixing the problem.

I took some measurements and found that my motor plates were not square to the rails. It wasn't much but it was off. I also discovered that one of my X motor mounts had a slight concave to it. It wasn't much but since I had a spare motor mount, I replaced it.

I removed the noise in my X sides by placing some washers between the Gantry and the motor mount on stationary bolt. When I roll the gantry now, there is a smooth sound coming from my X sides.

My cuts have improved but I would like to see them improve more.

I currently have my X motors tuned to Velocity 450 and Acceleration set at 20.


I hope this information will help others. I will continue to work on getting a better cut out of my machine and I will share my results.

Thanks to all that have helped and those that made suggestions.

shaper
Sun 29 November 2009, 17:30
Nils

I've been watching hoping to see a good result, it seams you are on your way to the results you are looking for. Great summation particularly given all that has been said and some things there that I'll be watching when I get to the mechanical side of my build.

Thanks

sailfl
Sun 29 November 2009, 23:38
Jed,

Thanks and I hope you don't go through the process I have been through.

MetalHead
Sun 06 December 2009, 02:55
Nils,

I would be interested to see if this could be something for you to consider.

http://www.geckodrive.com/upload/Step_motor_basics.pdf

Page 10

This talks about cable length (I am sure size and type would also affect this) and the need to add a 470uF cap to the Geckos to create a "Fly Wheel" to smooth out the power feed to the Geckos.

Just another thought as I read more on the Control Systems for the MM.

Mike

Richards
Sun 06 December 2009, 15:51
The early model Geckos, i.e. G201, need a 470uF capacitor if they are positioned more than 10 inches from the power supply. The G202 has the capacitor built in. The G203v has been designed to be used without that capacitor. The G25x (which are used with the G540) are also designed to not need that capacitor.

Adding that capacitor will not hurt, but it may not help, depending on the Gecko model that you own.

Nils,
Your systematic approach will eventually lead you to a solution. Keep in mind that if you can reproduce the problem each time you run a certain type of cut, that you can eliminate unpredictable electrical interference from your list. Electrical interference is almost always random.

One thing that you can try is to run some X-axis cuts with the Y-axis firmly clamped in place with heavy-duty clamps. Then run the same type of test with the Y-axis moving and the X-axis firmly clamped. If both sets of tests show high quality cuts, then you can eliminate major mechanical problems as being the main cause of the chatter.

If possible, run a test using the highest voltage power supply that is allowed for your steppers (32 X SQRT(Inductance)). Use the highest value current limiting resistors on your Geckos that are acceptable for use with your motors, i.e., if your motors are rated at 3A, make sure that you use the correct resistor to let the motor draw 3 amps in operation (Amps X 47) / (7 - Amps). Add another filter capacitor to your power supply temporarily to verify that a weak or faulty filter capacitor is not allowing too much ripple to limit the torque of the stepper motors. (My first computer, an Imsai, had a bad capacitor. Every time I added an additional memory board to the machine, it faulted - no matter which memory board I added. The total current draw caused too much ripple for the on-board voltage regulators.) Remember that the large filter capacitor(s) perform a different function than the 470uF caps that Gecko recommends for the G201 driver.

The reason for running a test at full voltage and full amps is to give the machine maximum reduced current holding torque. The extra filter cap is to ensure than the drivers can always draw from a reservoir that has little or no ripple.

Systematically following a list is sometimes the only way to solve this kind of problem. Always start with the most obvious and work towards the least probable.

javeria
Mon 07 December 2009, 09:37
Nils have you looked at the new Z Assy, I have - it has helped me to solve more than 90% of the problems I had in my 3d cuts.

sailfl
Fri 11 December 2009, 02:07
I thought I would provide some photos of some cuts I made with my machine fixed.

Cut in oak. The flate surface was cut at 70 IPM and the round over at 50 IPM.

The plywood was cut at 200 IPM.

I am pleased with the way the machine is cutting now.

I have not looked at the new Z.

javeria
Fri 11 December 2009, 03:08
so - what fixed it nils?

MetalHead
Fri 11 December 2009, 11:37
For sure tell. After all of the input we would like to know what fixed it !!!

Gerald D
Fri 11 December 2009, 12:05
Were those cuts on the diagonal?

If those major cuts were parallel to the table axes, then the cutter does make a diagonal (half-way through radius) move when rounding a corner. The marks in this photo shouldn't be present if the motion was smooth?:

7598

sailfl
Fri 11 December 2009, 14:37
Gerald

I can't tell what you are looking at from the photo you have circled. The cuts are mostly not on a diagonal.

The round over bit was cutting a little too deep and the 1/2" EM I was using was starting to get dull.

Trust me the cuts are smooth.

jeffa
Fri 11 December 2009, 15:47
Nils,

I have tried to keep up with this thread from time to time. Do you feel that you have fixed the problem? If so, would you be willing to share with us what the problem(s) was(were)?

Thanks,

Jeff

sailfl
Fri 11 December 2009, 18:07
Irfan, Mike, Jeff and every one else,

In Post #164, I tried to explain what I did. Basically, I think it is a combination of things.

1) I do believe there was some flex in the Z / Spider. I used a larger washers between the Y car plate and the Spider. That fixed the flex.

2) For the longest time I have had a noise in my X Axis on both sides. I now believe that my rack and pinions were the cause of that noise.

2.A) I had a problem with my C channel. The legs were not square. I had placed washers under my Aluminum X Rails which helped resolve the squaring of the X Rails.

2.B) There still was noise. I placed washers between the gantry frame 10 20 400 and the X motor swing plates but only on the stationary bolt this allowed me to adjust the pinion gears so that they were in line with the rack. Once I found the right number of washers the noise I was hearing went away. There are a couple spots on one side of the X were there is a slight misalignment but it is less than any thing I was hearing before.

When I did these things, I noticed that my cutting improved on the diagonal and the machine is cutting better over all.

Most likely, I could remove the racks and do a better job of installing them. But the machine is cutting well and the gantry moves smoothly travelling in the X direction. I am not going to mess with what is working.

I hope that helps explain. If you have additional questions, please ask.

Two suggestions. Besure the rack is straight when you install and if you have noise that appears to becoming from the rack area check you alignment.

cab. guy
Sun 17 January 2010, 22:12
Hi Nils, sorry to hear about your problem. I made these test cuts recently using aspire,4-1 belt drives,1.5 diametrical pitch pinions and heathenistic large nema 2913 oriental motors.The bit used is a well used 3/8"compression bit @ 2 passes @300" per min.into .75 mdf.Up close there are no discernible ridges.In your samples on the straight cuts shown,there appears to be a cadence of ridges spaced approximately 3/16" apart.
I cant believe run out on router bearings could cause this,I'm guessing your rotational speed at 100 plus cuts per flute per inch.The O.J. Simpson glove does not match up.I also cannot digest the fact that backlash is the culprit,because on a straight run the gears stay in contact with each
other as a result of constant back force of load( cutter against material).
There are some benefits with larger motors using belt drives as pointed out a few months back,no backlash,massive holding power.Good luck on your find. Ron.

sailfl
Mon 18 January 2010, 03:55
Ron and to any one else that reads this thread

I DO NOT have a problem any more. I am cutting fine. I have fixed my problem and it was NOT by replacing my geared motors with belt drives.

I am using geared motors.

sailfl
Mon 18 January 2010, 03:57
Ron,

Look at the drawings for what you are cutting and check to see if you have small straight lines for your curves. That can be a big problem when you are cutting some thing. Those little straight lines can screw you up.

cab. guy
Mon 18 January 2010, 08:49
Hi Nils, Sorry if I set you off, I was merely in agreement with your suspicions (supportive).

cab. guy
Mon 18 January 2010, 10:23
Nils, I think you are on to something.Can you remember if the cuts were worse in the x-axis vs the y-axis?

sailfl
Mon 18 January 2010, 10:35
Ron,

It will improve the cuts in any direction if you can remove the small straight lines that happen when you work with curves from some drawing packages.

Sorry, if I misunderstood but I also wanted to make it clear that I am no longer having a problem. I also fix the little lines on curves.

Gerald D
Mon 18 January 2010, 10:47
Years ago I complained to Mach that their program couldn't maintain a constant speed from the end of one line segment to the beginning of the next, even if those two line segments are perfectly in one straight line. It is worse on curves. See http://groups.yahoo.com/group/mach1mach2cnc/message/57947

cab. guy
Mon 18 January 2010, 21:31
Mr.Gerald D,If you would indulge me, I would be honored.If a machine in question fallows G-code output provided by design,cad and control software in a perfect world ,is it not doing exactly what It was designed to do? If however that machine deviates its commands or instructions, is it also reasonable to ask why?When I see Nils photo #1 , it appears to have
a type of chatter that was a result of a straight cut.In g-code that would be a straight line,to a machine ,should that command not be recognized as a simple movement from point A to point B without interruption.This is the part that is interesting-Who done it?

sailfl
Tue 19 January 2010, 00:33
Ron,

That cut is the cause of the machine not working correctly.

If you take a curved line and look at it in a cad program that line will look like it is one single line going from point A to point B but taking a curved path. If you continue to zoom in on that line you might find that the curved line is not actually a single curved line but is actually made up of lots of small straight line segments. These small straight line segments are what will cause the cut to not be straight. That is why when you get your curved line into your cam software you have to smooth out the line. That smoothing process will remove most of the small straight lines and will give you a curved line.

Those small straight line segments are the problem.

isladelobos
Tue 19 January 2010, 07:07
This makes perfect sense.
The files must be clean and tailored, this process can be heavy, if the file is from the outside or is designed by third parties.
With Corel Draw is very easy with its node reduction tool.
If I can, and find time, I will prepare a short tutorial to make that easy.

Tiene mucha lógica.
Los archivos hay que limpiarlos y adaptarlos, este proceso se puede hacer pesado, si el archivo proviene del exterior o está diseñado por terceras partes.
Con Corel Draw es muy fácil, con su herramienta de reducción de nodos.
Si puedo, y encuentro tiempo, prepararé una pequeña tutoría para hacerlo fácilmente.

cab. guy
Tue 19 January 2010, 08:27
Nils, I was referring to the diagonal cut in photo 1#. I missed Geralds post#3 in explanation.Ill try this on .75 mdf and aspire,but Geralds statement does sound reasonable.If I understand him correctly Mach3 has speed change issues between 2 competing axises.

domino11
Tue 19 January 2010, 10:25
Nils, how do you do the smoothing?

Kobus_Joubert
Tue 19 January 2010, 11:21
Aspire and V-Carve Pro can also do SMOOTHING.

sailfl
Tue 19 January 2010, 12:18
Heath,

I think most cam programs have smoothing functions that help with the process. I have also redrawn the lines using a cad program.

MetalHead
Wed 20 January 2010, 05:32
This is just another thing to show how accurate these machines are. They cut EXACTLY what they are told to cut. I have seen this in my other drawing programs for Plasma. Corel is notorious for making a arc that has dozens of points in them.

Basically the higher quality drawing programs can see these points as an arc and remove all those "Stop" points along the way making a true arc for the machine to cut.

Great find Nils on figuring that out.

isladelobos
Sat 23 January 2010, 08:22
This is a small, and simple tutorial on how to reduce nodes with Corel Draw. Mp4 (http://www.fuer.es/images/pop2.mp4) and Zip (http://www.fuer.es/images/pop2.zip)