Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: replicaprops on January 04, 2007, 12:10:15 PM

Title: backlash, how do I determine it from looking at a circle
Post by: replicaprops on January 04, 2007, 12:10:15 PM

I calculated my backlaash originally by clamping a micrometer in the work clamp and moving the table back and fourth a number of times to see what the difference was from actual micrometer readings and the mach 3 dro.
I settled on y= .009 and x =.007.
When im making circle cuts, the circle is not round. How do I use the shape of the circle to determine fine tuning the backlash?

Title: Re: backlash, how do I determine it from looking at a circle
Post by: Chaoticone on January 04, 2007, 12:23:53 PM

I wouldn't. I would use an indicator. The best fix would be to tighten your machine. Do you have preloaded nuts? Ball screws or lead screws? I have not had very good luck with the backlash comp. in Mach. It will get the backlash to 0.000. It is good at that. My steppers just can't take the sudden move to do what Mach tells it to especially on an arc. I have not played with it in a while. There has been many revisions released since.
Post a picture of your circle.

Brett

Title: Re: backlash, how do I determine it from looking at a circle
Post by: replicaprops on January 04, 2007, 12:44:00 PM

I have single ball nuts
Here is the photo of the part I was engraving. All the curves are supposed to be smooth, and they look jagged.
Do you think it could be loose gibbs?
(http://www.replicaprops.com/images1/smallvillephotos/kk2.jpg)

Title: Re: backlash, how do I determine it from looking at a circle
Post by: Chaoticone on January 04, 2007, 12:55:05 PM

Can you post your code? What Cam package did you write your code with?
I think your code is probably a bunch of point-point moves, no arcs. If you're Gibbs were extremely loose they could cause you grief. I doubt that is your problem.

Brett

Title: Re: backlash, how do I determine it from looking at a circle
Post by: replicaprops on January 04, 2007, 01:04:19 PM

I used visual mill to make the code. Do you know how to tell it to use arcs?
G00 G49 G40.1 G17 G80 G50 G90 G20
(Engraving)
T3 M6
G43 H3
M03 S2000
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G01 Z-0.0030  F7.3
Y0.3338  F10.0
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G01 Z-0.0030  F7.3
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Y1.5502
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X0.2954 Y1.5853
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X0.1981 Y1.3373
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Title: Re: backlash, how do I determine it from looking at a circle
Post by: Chaoticone on January 04, 2007, 01:09:26 PM

Yeap, that is point to point. No I or J moves. Can you send me your art in a dxf format? Does visual code have an option for arc fitting vectors?

Brett

Title: Re: backlash, how do I determine it from looking at a circle
Post by: replicaprops on January 04, 2007, 01:18:12 PM

I did the original design within visual mill, so its in the visual mill native format. There is no export option on visual mill to export the curves.
I made it with a font and curves then just ran the code as engraving.
Im going to have to check with the Visual mill user group to see if the code can be generated with arcs.

Title: Re: backlash, how do I determine it from looking at a circle
Post by: replicaprops on January 05, 2007, 10:48:00 AM

The problem has been solved. It was indeed the Arc command. In Visual mill there is a button under machining preferences that reads output arcs as linear segments. By default it is checked. I unchecked it and thenran my backlash tests again. The backlash did need to be adjusted slightly. Thanks, hope someone else finds this usefull in the future.

Title: Re: backlash, how do I determine it from looking at a circle
Post by: Chaoticone on January 05, 2007, 08:50:44 PM

 :)