Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: derek on May 19, 2009, 10:08:38 AM

Title: Choppy cuts in X-Y direction
Post by: derek on May 19, 2009, 10:08:38 AM

I've been dealing with this problem for a while now. Like over a year! I do mostly 3D contour cutting and have been getting really weird choppy cuts. I messed with lookahead and CV settings but never had any success.

I finally attributed it to gantry shake and slowly but surely started making needed improvements. None of my changes made a bit of difference.  Including trying a more powerful computer.

I now have a more traditional piece I'm cutting.

I'm cutting a piece with 72 pockets laid out in a circle. The pockets that are at the 12:00, 3:00, 6:00 and 9:00 positions are smooth as silk. They gradually get choppier until they hit the 45 degree mark and then start improving. There is a noticeable amount of chop on the first pocket that requires X+Y combined movement.

I'm dying ova here!

Title: Re: Choppy cuts in X-Y direction
Post by: vmax549 on May 19, 2009, 10:43:39 AM
Derek you might want to check your power supply voltage while running your code. It is possible that the supply is too small for all motors running at once. Do you ever loose steps??

Can you define CHOPPY better??

Try setting the CV BACH to how it was as mach installed it. Then try running at least 200 lines of look ahead. If it gets better go larger with the look ahead say 400. Keep going untill it does not get any better then stop.

It could be the code you are running as well. Small, short coppy segments of code don't always cut well in mach. look for a large number of short segment moves like .5-.05mm or such. This can drive the CV crazy trying to sort out sometimes.

JUst some thoughts(;-) TP
Title: Re: Choppy cuts in X-Y direction
Post by: jimpinder on May 20, 2009, 03:50:22 AM
What are you using to create the code.

Most drawing package do not produce arcs and circles, but produce straight lines, to the eye they look smooth, but to Mach they look what they are - a lot of straight lines. You description of getting choppier towards 45 degrees reminds me of the effect I get drawing a diagonal line with too much magnification

Look at your code and see if this is the case. If pockets you are cutting are circular, this shold be a G2 or G3 move, in which case I would expect you to get a perfect circle. If the pocket is square or whatever, is there any way you can increase the resolution on your drawing package. My Turbo cad also has a setting for the number of sectors in a circle, which can vary from eight or so, up to whatever - I usuall use 360.
Title: Re: Choppy cuts in X-Y direction
Post by: derek on May 20, 2009, 08:16:08 AM
Well I checked everything that was suggested and I'm leaning towards mechanics. I'll be making some changes today and I'll see if I can get a handle on this.