Miniature MechMate suddenly cutting - Johannesburg, S.Africa

[paulus]

Hi all.
I am paul from sunny south africa this will be my first build on this type of make, i have tryde to build a cnc router before but not so good so i am giving it a second try. lets see how this is going to pan out.
i see there is a couple of guys from south africa on the forum i would like to know where you are from if you dont mind.

thanks.:)

[domino11]

Welcome Paul! :)

[JamesJ]

Welcome to the group!

[MetalHead]

Welcome aboard. Stick to the plans and you will have a great CNC machine when you finish.

[hennie]

Welkom, PM my dan gee ek jou my details ek is in JHB en so ook `n hele paar ander manne.

[paulus]

thank you all for welcoming me i truely hope that this one will be 100% when it is done

[paulus]

Hi all
Ok this has taken me longer that I wanted but it is done. Now I am cutting,as you can see this is not a full size machine the cutting area is 600 x 1000.
So far I am happy with what I have done. And I think it looks good.
I just need to put the name on.
O before I forget where do I get a number.
14063

14064

14062.

And here is the big one in the making.


14065

[Alan_c]

Why are your main beams upside down? (and your table supports come to mention it)

[paulus]

Not sure what you mean. I have moved the table suport down so that I don't add weight to the side beams and preventing it from bowing the table. Or am I not thinking right.

[Gerald D]

The table supports must be connected to the side beams, or else you will get a lot of vibration in those beams.

[KenC]

You are thinking right, just paranoid. :)
Don't worry about the side beams bow... you can put a few tons on it & its won't budge...

[paulus]

Ok I hear what you are saying gerald. The other reson why I put it at the bottom is that I used a smaller beam not a 150mm. So that will give me the same Z clearance as a 150 beam. So if I run a short suport from the table suport to the bottom of the side beam then that will take care of the vibration( right?).
Thanks ken for your in put but you will understand now wwhy I say it wil bow as I am using a 100mm beam.

[Gerald D]

The worst bending of the side beams is horizontal, when the y-axis has to reverse direction rapidly. Try cutting some text (letters) and you will be amazed to see all the shaking (probably consider adding diagonal braces on the legs as well)

[paulus]

Ok will do thanks gerald. Who will give a number for my small machine.

[paulus]

Gerald I want to cut a product called( trespa) it is a resin board what will you sugest as cutting speed and feed and the bit to use if you can help. Thanks

[paulus]

Here is a better view of my mini mm 14068

14067

[Alan_c]

Your main beams on the sides are upside down, the long edge (that the rail is supposed to be fixed to) is at the bottom and the shorter edge is at the top, the reason they are done like this is to maximise the length of beam under the rails, the way you have them is of no benefit so you could have just cut them straight...:confused:

[paulus]

:DOk that is what you mean. I cut them longer so that I can do it the other way around. It just looks better to me if it is this way round.:)
Thanks for your comments I am starting to understand why the mm is design the way it is. Talking about that who did design it?

[darren salyer]

In response to post #14, I think with some logos applied, it would certainly qualify for a #.
Enjoy using it.

[paulus]

Good will make a plan to get it on asap thanks.

[swatkins]

Gerald designed the MM !

How about a close up of the Y car !

[KenC]

Paul，with such a short span, even 50mm C channel can take a few tons without problem...
Lately, I did a stress analysis on a pin supported 1200mm span 50x100x5mm Channel, I get 0.01mm deflection at the middle of the span with point load of 10kN.

[swatkins]

Is the Y car in the top pictures a scaled down version?

[Gerald D]

Ken, my gut feel is that your beam calc is not correct. Maybe 10x greater deflection? (I havn't calculated these things for a long time)

[KenC]

I'm surprised too... but the point is we all over design excessively... even if I made mistake on 1 decimal point :) because we trusted our eye too much LOL!!!

The reason for my simulation was to convince a client/friend that there are no need to replace the 50x100mmx5mm thk sheet metal channel beam to a 6". BUT THAN AGAIN, for the sake of indulging his visual/psychological satisfaction, I went with 6"x2" since he is paying the extra :)

[paulus]

To respond to steve, yes it is scaled down it was not easy but I got it done. How ever I need to increas the motor mounting plate thikness to 3mm. And I think what you guys call the Y car I call the X car I made it out of one piece bend the sides and not welded.

[KenC]

This is a genuine Mini MM :)
Great job!

[paulus]

Just want to thank gerald for a great design proudly south african. I am also glad to see not all the great minds have left the country. This machine must be strongly premoted in sa so that the cnc world can be turnd on its head in this country every guy wants to get rich quick on cnc and over charge.

[paulus]

Thanks ken will see how it hold up will keep you guys posted.

[paulus]

Hi all.
Can any one help with this.
I have picked up a constant buzzing noise on one of my motors any idea as to what it can be? It is not very loud.
Thanks

[Gerald D]

Probably resonance. Geckodrives have an adjustment to tune the resonance to a minimum. It could also be a faulty motor with loose laminations. If you swop that motor to another position, does the noise go with it to the new position?

[paulus]

I will try that thanks gerald

[paulus]

Hi.
Man I am having great fun. This is what I have been waiting for. Here is a pic of my first little home project testing the machine.
14085.

Here is my first gearbox proto type for the big MM
.14088[/ATTACH
][ATTACH]14086[/A.TTACH]
.[ATTACH]14087.

And this is my dust foot in the making I will let you guys now how it works.
14089
14090
14091
14092.

Now what is next

[paulus]

Sorry pics are a bit mixed up

[darren salyer]

Nice work, Paul. I like the wine rack, especially.

[paulus]

Thanks darren it is stackable so you can make multipels. It was not easy I burnd a few cutters to get my feed rate right. Still a bit touch and go but I will get the sweet spot like hennie says. The only crap thing is that the spindle I am using can't be ajusted(speed).

[Robert M]

Chin-chin to you paul ;)

[paulus]

Thanks robert.:)

[paulus]

Hi guys.
Me again, i need your help again!. I am picking up a problem with my Z axis.When i do ingraving and i set the Z say to -1mm it will start out ok and then as it moves up and down (re positioning) for the next cut the cut will become shollower.
This does not happen over 200 or 300 lines it take time over 4000 lines of G code.

I have searched under losing steps but cant find any thing on my problem.

Welcome any help on this.

[smreish]

A couple of things to check.
- is your safe z setting being used during the cut?
- Your safe z setting can cause the axis to "park" higher each time you reset to cut the next part. Try playing with the numbers...set it to something odd....like 4.7mm
- could be additive backlash in the z axis (are you using gearbox, direct or belts?)
- is your collet loose? Loose bit will get "pushed" up in the collet over time and cause a shallow cut over time.
- is the engraving bit the same length after use? IE...did it get dull and now effectively "shorter" and causing the cut to be "shallow"

ideas to check

[KenC]

1st thing I'll check is if there is any mechanical loose play such as the pinion gear, chuck, spindle mount or other wobbly things...
2nd I'll check if all my cables are plugged in properly.
3rd I'll lower the acceleration of the Z motor. in motor tuning.
4th I'll check the plunging speed of the CAM.

[paulus]

Tried all of the above with no luck just don't know what the Hell is wrong???

[KenC]

Are you using Z touch-off? if you do, reduce the probing speed.

[Mrayhursh]

my motors also hummed but I tweeked the on the gecko g203v. I do not see that you are using geckos but see if your stepper drivers have a tweeking device. I am guessing this is a potentiometer. Let us know. Thanks

[paulus]

Thanks for all your input have not found the Problem yet but I will keep on hunting for it until I do. I will let You guys know what it was when I find it.
Thanks ones again.
Keep the sugestions coming.

[Richards]

Can you connect a dial indicator to your Z-axis and then make repeated small moves? If the indicator is positioned so that the plunger is always partially depressed, you'll be able to see if the Z-axis returns to the same up and to the same down position. Pausing at each end of travel long enough for the needle to settle will let you see if the moves are repeatable.

If the moves are not repeatable, try slowing down the acceleration to see if ramping might be causing a missed step.

If slowing the acceleration does not correct unrepeatable behavior, then you might have a backlash condition. Most geared motors have a nominal amount of backlash to keep them from binding when they reverse direction. Even a very nominal amount of backlash can become noticeable if repeated moves are made.

Of course I'm assuming that the pinion gear is properly meshed and that it is properly tensioned, with with a spring or other mechanical setting. If the pinion gear is tensioned without a spring, have you verified that pinion gear is seated to the same depth over its entire length of travel? If something is warped or bowed, tension would change as the motor moves along its axis.

[tintin]

Stunning Table !!! just to bad about that blue Bulls sign !!!!! :D

[paulus]

What about the blue bulle sign

[tintin]

More of a SHARK supporter !!!! :)

[hennie]

Paulus,It might be that you are losing steps as the motor is good to take the z-slide up and down but given that you cut into something and your cutter getting blunt with resistance as it cuts away it is basically forcing the cutter into the material.If you get the resistance newtons laws come into play and the motor can`t hold the position and you basically lose steps( My 5 cents).If you use cheap cutters it will happen at 4000 lines!