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Author Topic: Origin position -x keeps creeping when returning back to Zero----HELP !!!  (Read 3371 times)

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Offline maxy

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 :(I did several tests and the machine will not return to it's origin....I have cadded out a 5x5 square and turned it on a 45 degree angle flat on the table, I mark Z position by touching down on my surface. Then the bit starts it's cutting on the middle line which is what im looking for is alignment when the bit completes it's cutting, but what im getting is the alignment is not lineing back up to it's starting cut, and it's off in the -x position by about 1/16th and when it returns to it's zero position it's also off by 1/16 in the -x.

Each time i run the program it creeps another 1/16th in the -X.....and the DRO reads x-0 y-0....My y position is perfect. When i run a circle it seems all proper except when it returns back to origin....

We know it's not mechanical....we have checked all our setting that we know, we ran the program on our other CNC's and it works 100% on them...So is it MACH3...something weve missed....

As A NOTE: if we touch down and set x0 y0 and make a program to move 12" in the positive x and return back to it's origin it's out by maybe 1/64 without any real cutting at all, and if we keep running this program it just keeps adding up the negative error an moving a 64th back more each time.

thanks Jeff
« Last Edit: February 01, 2008, 12:25:34 AM by maxy »

Offline Chip

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Re: Origin position -x keeps creeping when returning back to Zero----HELP !!!
« Reply #1 on: February 01, 2008, 06:45:38 PM »
Hi, Jeff

Have you tried reducing Velocity and Acceleration Settings in Motor Tuning, Use G00 moves to set it up.

If I understand what your saying, Your at x0, y0 making positive moves and on return the machine is moving to a more negative position each time,

But Mach indicates x0 y0 home position ?

If your Velocity and Acceleration Settings are to close together, Decelerating to late and slipping past the x0 y0 position is possible.

Let us now, More info on your mill, ver of Mach3 (Under Help About), May Help.

Thanks, Chip
Re: Origin position -x keeps creeping when returning back to Zero----HELP !!!
« Reply #2 on: December 07, 2013, 01:10:15 PM »
I ran into your same problem Maxy.

After cutting each level of a job, the origin moved further and further SouthWest. While Mach3 DROs indicated 0,0 the mill's DROs lost 0.150 at each cut.

I tried air cutting the job with similar results.

I finally tried chip suggestion above and set the acceleration as slow as it would go and... BINGO! The cutter goes back to an origin every DRO can agree on.

I'll fiddle with the acceleration a bit more to find a higher value that works, but even at the bottom end the machine works very nicely.

I hope it works for you too.

Ciao, Marco.
Re: Origin position -x keeps creeping when returning back to Zero----HELP !!!
« Reply #3 on: December 08, 2013, 08:33:42 AM »
One more thing...

Snugging the couplers' fasteners allows you to run faster motor acceleration before they start slipping again.

Run a few cycles of "air cutting" with the motor acceleration set to minimum, then GOTO ZERO, compare Mach3 with your machine DROs, and see how high you can push your motor's acceleration before slippage occurs again.

Good luck, Marco.