| Author |
Message |
    
Gerald_D
Registered
Username: Gerald_d
Post Number: 27
Registered: 11-2005
| | Posted on Sunday, January 22, 2006 - 12:14 pm: | 
|
The beast shown below is what we have named the MechMate. We had to find another name because it is not a ShopBot, although many parts are interchangeable. The pics today are after a strip down and during the paint and re-assemble process. Motors and cables must be re-installed (the z-motor is only balancing there):
|
Evan Curtis
Registered
Username: Evan
Post Number: 2
Registered: 12-2005
| | Posted on Monday, January 23, 2006 - 06:41 pm: |
|
Very impressive.
What size is the table?
I like the Z, is that pnuematic assist?
And what is the bearing and rail on the Z?
Is it easy to adjust? I feel the ShopBots Z is one of it's weakeast links.
MechMate looks very robust. Nice work. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 84
Registered: 11-2005
| | Posted on Wednesday, May 24, 2006 - 02:45 pm: |
|
Some long overdue pics:
 |
Paul A
Registered
Username: Paul_a
Post Number: 2
Registered: 12-2005
| | Posted on Thursday, May 25, 2006 - 12:38 pm: |
|
Hi Gerald
A very neat and tidy Job, it looks nice and rigid.
What is the grey and white box with the banana sockets ?..... do you have any idea of the gantry weight.
Regards
Paul |
Gerald_D
Registered
Username: Gerald_d
Post Number: 85
Registered: 11-2005
| | Posted on Thursday, May 25, 2006 - 01:23 pm: |
|
The banana sockets go to the "Inputs" of the control board (one ground/earth). That is where the z-zero plate gets plugged in now, but it could be anything in the future. Thought it would save laying cables and allows spur of the moment experimentation. 
I must remember to weigh the gantry when the motors are dropped. You might have realised (when we met) that I am not that weight-conscious....
Tidying up the electrical box is the main thing now....... |
Gerald_D
Registered
Username: Gerald_d
Post Number: 90
Registered: 11-2005
| | Posted on Friday, May 26, 2006 - 02:02 pm: |
|
The gantry weight/mass, with motors, y-car, hose, cables etc (fully loaded) is 85kg (187lbs). |
mikejohn
Unregistered
| | Posted on Tuesday, May 30, 2006 - 05:48 am: |
|
Gerald
Looking at the spoilboard, this machine appears to have done a fair bit of work.
Are you in a position to make a direct comparison with the original machine?
In particular, your opinion of quality of cut with the more rigid construction, and different drivers/software.
Can you also give an opinion on spindle against router?
I do like the features you have added, in particular the position of the emergency stop botton, the use of a 'brush' type dust foot, and the banana sockets.
Do you have cable chain on the x axis?
Are the x-rails beefier than the PRT, to allow for the reverse position?
It looks good, very good.
...........Mike (forgotten my password  ) |
Gerald_D
Registered
Username: Gerald_d
Post Number: 94
Registered: 11-2005
| | Posted on Tuesday, May 30, 2006 - 07:32 am: |
|
(I can't see everyone's passwords, so you have to restore your own via this link or tell me to give you a temporary new password)
Hi Mike.
Yes, the "MechMate" has been busy, and that spoilboard has had a couple of re-surfacings - I just took the photos on a bad day. (The spoilboard started off as thick as the base board)
A direct comparison to the standard PRT is a bit tricky because the changes have been gradual:
- the standard PRT first got a MechMate gantry and y-car, but the control software/driver was retained, then
- a whole new machine was built with gantry, Mach, & Gecko.
And there are other small things in between too.
But the bottom line is that there was never a WOW moment, when it looked like a major improvement was achieved.
The biggest difference came from changing the 4-piece y-car to the 1-piece y-car with an idler roller under the rail to simulate the hold-down of the y-motor on the opposite side.
Right now we have practically two identical table and gantry systems (except that one gantry is 600mm longer and carries a much heavier spindle/dustfoot). Both have identical direct drive motors and the pinion diameters are very similar. The controls are as follows:
- Short gantry, light load has ShopBot control board with IMS drivers, under DOS software
- Long gantry, heavy load has Gecko drivers under Mach3 software.
The quality of cut and speed is marginally better (10-20%?) on the big machine.
I could make a much higher speed on the Gecko machine because Gecko's can easily be told to "over-drive" the motor currents. My impression is that some of the guys with fast Gecko routers are actually over-driving the motors. (Our Geckos are set to the limits stated by the motor manufacturer)
The spindle is much quieter than the router. So far there is no other big advantage in the type of work that we are doing.
X-axis does not have cable chain...yet. So far we are having good life out of a flexible tube that holds the cables together, even on our earlier machine.
The rails don't have to be any beefier to allow them to be reversed - in fact they could technically be lighter because they are more "under" the load point of the roller. The "reversed" rail makes the table a lot more spacious. Also, during the setup and alignment of the angle-iron rails on top of them, it is a breeze to use small g-clamps to hold the rails together. |
Mike John
Registered
Username: Mikejohn
Post Number: 2
Registered: 12-2005
| | Posted on Tuesday, May 30, 2006 - 08:34 am: |
|
Thanks for the password info.
Without wanting to create further disharmony in the CNC community, I must ask why you feel others are claiming much better improvement when only replacing the driver/software side of things? (although I do note that there are no longer exagerated claims about great improvement on cutting times).
........Mike |
Gerald_D
Registered
Username: Gerald_d
Post Number: 95
Registered: 11-2005
| | Posted on Tuesday, May 30, 2006 - 09:40 am: |
|
Mike,
For a short period (summer 2000?), ShopBot used some very good IMS drivers, and we happen to have one of those machines. So, our experience of the ShopBot drivers is not typical.
Which brings me to the point that there probably isn't a typical (or bench-marked) ShopBot against which claims of improvement can be made. Many different motor sizes, gearbox ratios, pinion sizes, driver types, software versions by ShopBot on the one side, and quality of owner-supplied PC as well as setup on the other side.
Our Gecko experience is also very limited, and we havn't tried to push them, or the motors, to their "smoke" limits. We are plodding along by the conservative book.
Basically, my opinion should count very little in this because a back-to-back comparison between 2 machines should be simple enough to arrange.
(This tangent discussion continued here) |
Mike John
Registered
Username: Mikejohn
Post Number: 9
Registered: 12-2005
| | Posted on Saturday, June 17, 2006 - 05:08 pm: |
|
Gerald
Didn't know where to ask this question, so I put it here!
Did you ever decide on a simple 'keyboard' with minimum keys for Van to operate?
...........Mike |
Gerald_D
Registered
Username: Gerald_d
Post Number: 130
Registered: 11-2005
| | Posted on Saturday, June 17, 2006 - 06:13 pm: |
|
The "Van" that we have now can move the mouse cursor and click on the right buttons on the Mach screen. (A touch-screen would make it even easier). He is happier with the Mach screen compared to the SB DOS screen.
However, that "banana box" and the E-stop boxes are soon to be replaced with the dumb-Van version...
- The E-Stop boxes will get two more buttons each: Resume & Pause.
- The banana box will loose 2 bananas and gain 3 buttons. Then the four buttons will be E-Stop, Resume, Pause,& Z-Zero (black). The two bananas are for the plate "switch".
With that huge table, Van sometimes crawls over to the spindle to do something there, and buttons only at the ends of the gantry are out of reach. The pause/resumes at the ends of the gantry are for moving clamps during a job.
There is a huge difference between E-Stop and Pause. The "E-Stop" on a standard ShopBot is just a gentle request to the control board to please stop movement, and one can happily "resume" after an SB's "E-Stop". In effect, the SB only "pauses".
A true E-stop cuts power to the router/spindle as well as to the stepper motors, on top of the gentle request to the controller. You can be sure that the system loses its sense of position during this crash-stop, and a simple resume will not get you going again. But you have a better chance of having all your fingers after a true E-stop. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 151
Registered: 11-2005
| | Posted on Sunday, July 02, 2006 - 09:00 pm: |
|
At last, the MechMate is complete (99.5%):
That guy is Rapi, been around for only 3 days, and can repeat the same cut file over and over without touching the keyboard. |
David Rosenbleeth
Registered
Username: Dave_r
Post Number: 1
Registered: 07-2006
| | Posted on Sunday, July 02, 2006 - 11:46 pm: |
|
Gerald: Had to register (finally) just to tell you how good it looks. A most excellent and elegant job. I look forward to my "Mech-anized" PRT96.
Dave |
Patrick Toomey
Registered
Username: Patricktoomey
Post Number: 4
Registered: 06-2006
| | Posted on Monday, July 03, 2006 - 01:25 am: |
|
Gerald, That thing looks awesome. The level of workmanship and attention to detail make it look like a high-end commercial machine. Most DIY CNC machines look, shall we say, "home brew". Great work! |
Alan Conolly
Registered
Username: Alan_c
Post Number: 1
Registered: 07-2006
| | Posted on Monday, July 10, 2006 - 08:36 am: |
|
Gerald, Thank you once again for the personal tour over your machine last week, a truly impressive piece of engineering especially the finishing and attention to detail (sealing of unwelded joints areas etc.) The wiring in the panel would also embarrass many a "professional" machine builder. a great inspiration. |
Wayne Painter
Registered
Username: Wayneo
Post Number: 1
Registered: 07-2006
| | Posted on Wednesday, July 26, 2006 - 08:55 pm: |
|
G'day Gerald,
I must say, an awsome looking machine.
I too have added cable chain to the Y-axis almost identical to how you have done. As well, I added cable chain to the X-axis as I did not like the cables dragging back and forth on the concrete floor. This also allows the "bow" on the SB to only be used for the dust collector which has the added plus that it is away from the other cables. I really like the way the cable chains work.
Very nice JOB!
wayneo |
Peter A
Registered
Username: Apples
Post Number: 1
Registered: 09-2006
| | Posted on Friday, September 08, 2006 - 01:37 pm: |
|
Hi,
I have made my own CNC plasma table and I have just gone out the other day and put in a cheap router. It is awesome to watch it cut with the router. I don't know now if it is better to watch plasma cutting or router cutting.
Anyway. I too have use the vee bearings and my machine is a similar size to yours. I had trouble with gantry flex and wobble when driving it from only the one side. So I had to put a motor on the otherside with a rack etc.
When your table is on and the motors are energized. If you put your hand on the gantry end that does not have the motor, can you move it??
Also, because I have never cut wood with a cnc before. How do I hold the wood down? I can't afford a vac. table. I have heard that double sided sticky tape works good?? is this true?
And do you leave "holding tabs" in a part that you cut so that it will hold together in the wood and not fall out etc etc.
Cheers
Apples
Australia |
Gerald_D
Registered
Username: Gerald_d
Post Number: 236
Registered: 11-2005
| | Posted on Friday, September 08, 2006 - 01:49 pm: |
|
Hi Peter
There are motors on both ends of the gantry.
You can find a lot of information on CNC wood routing by looking at http://www.talkshopbot.com/forum/messages/29/29.html |
Mike John
Registered
Username: Mikejohn
Post Number: 81
Registered: 12-2005
| | Posted on Saturday, October 07, 2006 - 11:00 am: |
|
The following 5 posts were first posted here. Since they are of a wider topic than just the Control Box, they were moved to this topic.
It seems to me that any true evaluation and comparisons between the 4 possibilities will not happen on the Shopbot Forum.
Brady has always posted from biased point of view on anything and evrything, from spindle/routers to that awful Part Wizard.
So can we honestly evaluate the current position here.
I had my table made for me locally, as have many (most?) others.
So Tables do not come into the evaluation.
My PRT control box is now considered sub-standard even by ShopBot themselves.
The stepper motors are third party.
There are many add ons and alterations to the basic shopbot, including means of strengthening carriages to take out slop.
G-code is the industry standard for CNC operation.
So, if I dont use a Shopbot table,control box,software, and I am changing the original Shopbot parts, would it be wise to re-invest in another Shopbot?
Is there a comparison between the cost of upgrading the control box/software?
How difficult will it be to get a proficient engineering company to make the mechmate bits from the drawings here?
I have got this far because I bought a Shopbot.
It seems to me I can progress by tying myself to whatever advancements Shopbot decide to introduce, or follow the ideas muted on this forum.
Mike said elsewhere it isn't a question of what Shopbot was in the past, or is today, it's where will they be in the future?
A lot of recent posts have been very technical.
From all the ideas being thrown around, is anyone willing to describe the 'best' CNC machine we could have, today, for reasonable money?
...........Mike |
Gerald_D
Registered
Username: Gerald_d
Post Number: 260
Registered: 11-2005
| | Posted on Saturday, October 07, 2006 - 12:48 pm: |
|
So, if I dont use a Shopbot table,control box,software, and I am changing the original Shopbot parts, would it be wise to re-invest in another Shopbot?
Mike, if you were living in America, where Durham is a quick toll-free call away, and replacement parts will get to you overnight, and want to sing ShopBotYeah My Lord around the camp while holding hands, then ShopBot is the best social option. Somebody will help you with any woes, or take pains to convince you that you are actually doing better than the guys who bought something else. In your case, I don't see any need to invest in another ShopBot. But, if you have been happy with the first one, why not get the same again?
"How difficult will it be to get a proficient engineering company to make the mechmate bits from the drawings here?"
I am doing the drawings to the same standard that I use in my "day-job" company, and those drawings are used fairly painlessly in Brazil, Singapore, Czech Rep., UK and Germany. The drawings here are far from complete, and I am not going to be pressurised for a completion date. The big reasons for the slow drawings are that I don't want the plans to be limited to one size of table only, and I underestimated the number of folk who insist they cannot work in millimeters. (I am also dumbfounded by those who want this huge beast of a machine for serious CNC work, but have no idea what a .dxf drawing is...) |
Gerald_D
Registered
Username: Gerald_d
Post Number: 264
Registered: 11-2005
| | Posted on Saturday, October 07, 2006 - 08:52 pm: |
|
Mike_in_Romania, May I suggest you take a similar route to me....
I first built just a gantry and y-car to get some confidences. Fitted them to the PRT table and rails and swopped over the wires and motors. And that machine is still running in that state more than a year later. Once the confidence was gained there, the MechMate was built from the ground up.
(....which means that I have a surplus PRT gantry and y-car lying somewhere. I actually want to have another look at it now that the "AGension" clan are asking for ways to beef up their moving parts.....) |
Mike John
Registered
Username: Mikejohn
Post Number: 82
Registered: 12-2005
| | Posted on Sunday, October 08, 2006 - 04:40 pm: |
|
Gerald et al
There is a thread onthe Shopbot Forum mainly from the 'other Mike', that seems to suggest an inexpensive upgrade to better than Alpha, a lot less than via Shopbot, and apparently a lot better and safer.
My PRT has the Alpha construction (its a late one).
Is this the way to go before moving on to a second machine (which may be needed late Spring 2007)?
Incidentally, I can't imagine a lot of those postings are going to stay!
.......Mike |
Gerald_D
Registered
Username: Gerald_d
Post Number: 267
Registered: 11-2005
| | Posted on Sunday, October 08, 2006 - 04:53 pm: |
|
Mike, do you have an English-speaking engineering shop nearby who I could communicate directly with? They might be interested in doing a small run of gantries for you to sell in your neck of the woods - it seems as if they produce good quality at low prices. Food for thought.......
When I mentioned the confidence building in the earlier post, I forgot to mention that I also built a very rough Mach/Gecko "control box" which was temporarily plugged into the ShopBot. That also worked. So, after testing my DIY gantry, y-car and control box, and after already having built one table, the only grey area was the z-slide - all that was left to do was to go shopping for more motors and other bits of standard hardware. |
Mike John
Registered
Username: Mikejohn
Post Number: 83
Registered: 12-2005
| | Posted on Sunday, October 08, 2006 - 06:45 pm: |
|
Gerald
English speaking no, but I have a good interpreter
My router mount, which I may have mentioned, cost $20 including VAT.
My table cost, less steel, £400.
I have chatted with them about the Mechmate idea
They say the first one will cost as much as the next 10!!
Which is always the way.
Don't forget, in 85 days our 'internal' market will be over 485 million, dwarfing the USA's 292 million.
We could be on to something  !!!!
.........Mike |
Gerald_D
Registered
Username: Gerald_d
Post Number: 268
Registered: 11-2005
| | Posted on Sunday, October 08, 2006 - 07:16 pm: |
|
"the first one will cost as much as the next 10"
...which means the router mounts come down to $2 and the tables down to $40....we could live with that!  |
Mike Richards
Registered
Username: Richards
Post Number: 40
Registered: 05-2006
| | Posted on Monday, October 09, 2006 - 01:01 am: |
|
Mike J,
As far as I'm concerned, the Alpha motors add nothing to the Shopbot. A PK299-02, PK299-03, or PK299-F4.5 all have the same speed and torque characteristics if driven by Gecko G202 driver and a power supply with about 20X their rated voltage. In fact, the PK steppers w/G202 drivers would have 2X or 4X the resolution of the Alpha motors, since the Alpha motors can be set to either 500 steps per revolution or 1,000 steps per revolution. The other factor is cost. You could basically buy four PK motors, four G202 drivers and rig up a good power supply for the cost of ONE Alpha motor/driver.
I think someone at Shopbot got completely snowed by the feedback feature of the Alpha motors, didn't understand how to implement it, and now is too proud to admit that "lesser" motors would actually work better.
On my machine, the Alpha motors finally work after being geared down 3:1. I'm sure that if I installed PK299-02AA motors, I'd have to gear them down 3:1 also - since they are so similar in every respect, except feedback, to the Alpha motors.
Those of you who are lucky enough to already have geared 1-amp motors only have to decide whether you prefer the Agek/Shopbot or the Ascension/G-code better. Either way, you'll end up with about 5X the resolution and probably 2X the speed (maybe more) based on the fact that the original Shopbot controller card sent out 400 pulses per motor shaft rotation and a Gecko G202 puts out 2,000 pulses per motor shaft rotation. If you ever need a lot more torque and more speed, you can swap out the motors, build or buy a gearbox for each motor, build or buy a bigger power supply and you'd have a machine functionally equal to the Alpha. |
Mike John
Registered
Username: Mikejohn
Post Number: 84
Registered: 12-2005
| | Posted on Monday, October 09, 2006 - 07:22 am: |
|
'Other' Mike
Are you suggesting that the much trumpeted feedback of the Alpha motor is an over rated benefit?
It does seem that is the one thing missing from an 'improved' PRT. As I said before, my carriages etc. are as on the Alpha, so that is not 'missing'.
..........Mike |
Mike Richards
Registered
Username: Richards
Post Number: 41
Registered: 05-2006
| | Posted on Monday, October 09, 2006 - 07:39 am: |
|
Mike J.
The Alpha motor's feedback absolutly does not work - in my opinion. Granted, if something causes the motor to slow down, it can recover and regain its position without losing steps. However, think what happens. If one X-axis motor slows down and the other X-axis motor does not, the cut is 'bent out of shape'. When cutting a circle, if any one of the three motors involved slows down, you end up with an elipse, not a circle. There is NO coordination between the motors. To work properly, if one motor slowed down, all motors should slow down - or the cut will be ruined.
With 3X the torque because of the belt-drive gearboxes on my Alpha, I no longer have any problem with any of the motors slowing down. (I've got 1,800 oz*in of available torque.) The 1-amp 3.6:1 stock motors on the PRT have about 300 oz*in of available torque, which is the main reason that I'm beating the drum for larger PK299-02AA motors with gearboxes as a 'required' upgrade for the PRT machines.
If a PRT machine's stepper is overloaded, it misses steps and the cut is ruined. If an Alpha machine's stepper is overloaded, it slows down and swerves, and the cut is ruined. The net effect in ether case is that the cut is ruined. Why pay $1,200 for an Alpha motor when you can do the same damage with a $200 PK299 motor. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 269
Registered: 11-2005
| | Posted on Monday, October 09, 2006 - 08:20 am: |
|
Mike_R
I am not going to join you on beating the drum for over 1000 oz*in of torque fed into the typical table/rack/pinion we sit with today. What do you want to do with so much torque? Accelerate the gantry faster? (Is it stiff enough). Apply higher cutting loads? (will the spindle/holddowns/racks/pinions/gantry_deflection handle it?). Reach higher jogging speeds? (Is the system safe enough if it should hit an arm or a stop?) Etc.
You happen to have a very high torque now that you've fixed the gearing, but is it usable/desirable as a target by itself?
(PS. anyone else having log in problems at the SB forum?) |
Gerald_D
Registered
Username: Gerald_d
Post Number: 270
Registered: 11-2005
| | Posted on Monday, October 09, 2006 - 08:28 am: |
|
Mike_J
What you have sitting on your floor in terms of table/rails/motors/gantries/gearboxes/etc. are all okay. But the control box on your desk could be seriously improved - as demonstrated by Ascension, Agek and now SB themselves. |
Mike Richards
Registered
Username: Richards
Post Number: 42
Registered: 05-2006
| | Posted on Monday, October 09, 2006 - 08:29 am: |
|
Gerald,
I think the high torque is the secret to the lack of 'chatter' with my 3:1 gearbox. Remember when there was a discussion about the effects of having a motor in 'power-down-mode'? (After staying idle for a very short time, most stepper drivers reduce the holding current to the motor to 20% - 30% of their normal holding torque.) I speculated then, that I thought that the reduced holding torque would let an active axis 'push around' an inactive axis. I don't have any proof, but my 'chatter' problem is gone.
As per Ted Hall's recommendation, I changed the steps per revolution on my Alpha motors from 1,000 to 500, meaning, that in reality, my 3:1 gearbox was only 1.5:1. I don't think that a 1.5:1 ratio was enough to cure the chatter problem.
(I've had no trouble logging in at the SB forum) |
Gerald_D
Registered
Username: Gerald_d
Post Number: 272
Registered: 11-2005
| | Posted on Monday, October 09, 2006 - 08:55 am: |
|
Mike, if the extra torque helps you overcome a "power-down" issue, then that *may* be something unique to Alpha control. Guys with non-Alpha's and torque well under 1000 oz*in are also now getting good quality. |
ralph hampton
Registered
Username: Rhfurniture
Post Number: 20
Registered: 08-2006
| | Posted on Monday, October 09, 2006 - 11:33 am: |
|
Hi guys.
I get a pretty good finish, but only work at slow speeds. But I am always after a better finish. To this end, I am currently working on beefing up the shopbot structure before investing in more silicon. My theory is that chatter is a result of vibration and harmonics - the noise (vibration) from movement in my system is very dependant on fine tuning the speed - jog at 72mm/second is WAY quieter than 70 or 75. I have analysed the situation by feeling extended parts (top of Z axis - very bad) while heavy cutting (45mm deep in utile at present) and will strengthen as a result.
My point is that if vibration > chatter, then maybe a 1.5 x resolution could take a setup away from a vibration state, and maybe shopbot were just unlucky (especially Mike_r) with their alpha (on many but not all machines) in that respect.
r/ |
ralph hampton
Registered
Username: Rhfurniture
Post Number: 21
Registered: 08-2006
| | Posted on Monday, October 09, 2006 - 12:28 pm: |
|
Mike_r: If it was a "powerdown" issue, then surely the chatter would only have appeared when running solely X move or solely Y - which was not the case. The smoothing effect of a belt drive (or to an extent any gear chain) might be more effective than we think, wrt vibrations (remember the beach boys....)
Gerald_d: If it was solely a resolution issue, then why did Mike_r not experiance 2X bad chatter when moving from 1000 step/rev to 500.
It's TEATIME............
R/ |
Mike Richards
Registered
Username: Richards
Post Number: 43
Registered: 05-2006
| | Posted on Monday, October 09, 2006 - 03:23 pm: |
|
Ralph,
Harmonics play a big role in stepper design. The old PH299 motors that I tried are useless with Geckos in a CNC application because of harmonics. The PK299 and the alpha's AS911 motors don't have much of a problem - at least by listening to them. You may have discovered the real culprit that causes chatter. Who knows? Something was causing it.
One of the things about 'chatter' that always bothered me is that the amplitude or height of a chatter mark was several 'steps' high. On an Alpha, each step on a factory configured machine is about 0.0025 inches. Chatter marks can easily be 0.030 to 0.060 inches high - meaning that something is really bouncing around. Harmonics could be part of it. Flex in the machine could be amplifying it. Little green gremlins could be shaking the machine.
Another factor that might be a big part of the problem is that I have a 120-60 size machine. Everything is just a little larger. It could be that one or more axes is a critical length when it comes to vibration. Believe me, before I installed the belt-driven gearboxes, I considered all of this and more. |
ralph hampton
Registered
Username: Rhfurniture
Post Number: 22
Registered: 08-2006
| | Posted on Monday, October 09, 2006 - 03:51 pm: |
|
Little green men get my vote...
Krikey, you are talking about chatter that is 10+ steps high! Surely that cannot be a resolution, or pushing steps ("powerdown") issue.
I'm lucky - I have a benchtop (fixed gantry) and can pile on the steel with impunity.
R/ |
Dick van Randen
Registered
Username: Dvanr
Post Number: 21
Registered: 03-2006
| | Posted on Tuesday, October 10, 2006 - 01:43 am: |
|
Mike R
I didn't see mention of velocity settings in your posts, and I do try to keep up.
It looks like you can change the damping of the controller in the AS controller by using the velocity filter. I have been wanting to play around with it, but have not had time to do the tests associated. Wondered if you had tried or know any more about it.
I always thought it strange that the same setting ( A , they go from 0 to F hex )is used for all three XYZ motors.
 |
Mike Richards
Registered
Username: Richards
Post Number: 44
Registered: 05-2006
| | Posted on Tuesday, October 10, 2006 - 02:32 am: |
|
Dick,
I've totally left the Alpha driver alone, except to change the number of pulses per revolution (which was suggested by Ted Hall at Shopbot). Shopbot has some enhancements in their software that change settings automatically depending on whether you're jogging or moving normally. I really don't want to mess with things when I'm not totally informed about what Shopbot's software does behind the scenes. However, you've pointed out something that might easily enhance the Alpha. |
Dirk Hazeleger
Registered
Username: Dirk
Post Number: 31
Registered: 12-2005
| | Posted on Tuesday, October 10, 2006 - 02:41 am: |
|
I'm wondering what the difference is between Geralds cut quality and the AlphaPRT. I think that from the Pic he's using direct drive on all axis except the Z. I would expect the cuts to be similar since he's using Geckos and should be at the same resolution of the Alpha.
Gerald what kind of jog speed are you getting out of your setup?
My thinking is putting a compatible torque direct drive stepper motor as that of the Alpha Step motors is going to give you the same cut, adding gear reduction just makes it better.
Also if Mike's right about the torque, use a larger motor with more torque to cut the expense of the reducer. |
Dirk Hazeleger
Registered
Username: Dirk
Post Number: 32
Registered: 12-2005
| | Posted on Tuesday, October 10, 2006 - 02:59 am: |
|
My thinking in my last post was the advantage of the Alpha is most prevelant in sheet processing with straight cuts, so the increased resolution of gearing wouldn't be as nesessary but increased torque with larger motors is much less expensive than a reducer to reduce chatter. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 277
Registered: 11-2005
| | Posted on Tuesday, October 10, 2006 - 05:37 am: |
|
Dirk, the cut quality appears to be on a par with the Alpha, if not slightly better. (Geckos are stepping at 2000 pulses/rev while the Alpha is 1000/rev?). This is going on photos and anecdotal evidence alone.
Max jog speed is a figure I avoid stating because I simply don't know how everyone measures it. It is like asking me what the top speed of my car is. Yes, we did take the MechMate up to the point where it loses steps, but this looked like a nasty speed and so we backed off a lot from there. I picked some force value that I wanted to achieve at jog speed (dragging dust shoes/hoses and cable umbilicals) and checked that with the fish scale. If I went to read off the max speed from the Mach3 setup now, you guys are probably going to find it laughably low. (This max speed is also related to the driver current setting, no?) |
Personal Pages