Backlash causes erratic servo movements

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Re: Backlash causes erratic servo movements

Postby wgpeters » Fri Feb 15, 2019 9:06 pm

I have tested the acceleration parameter all the way down to 0.1 with no improvement. I was set at 1.0
Backlash on my lathe is 0.003 inches.
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Re: Backlash causes erratic servo movements

Postby cncdrive » Fri Feb 15, 2019 10:38 pm

It is not the acceleration parameter, but the comp.acceleration parameter and you can't set it below the value of the acceleration parameter.
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Re: Backlash causes erratic servo movements

Postby wgpeters » Fri Feb 15, 2019 11:27 pm

I don't see any parameter called comp.acceleration in my Mach4 setup screens nor any in the UC100 setups.
Where is this supposed to be, and how do I access it?
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Re: Backlash causes erratic servo movements

Postby cncdrive » Fri Feb 15, 2019 11:44 pm

Ahh, sorry, this forum is about the UCCNC software and so I did not notice that you using Mach4, I expected you using the UCCNC.
In Mach4 there is no such parameter and so the parameter value is automatically set to 150% of the normal acceleration value, so in mach4 you can't adjust that parameter, but 150% should be good to go.
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Re: Backlash causes erratic servo movements

Postby wgpeters » Sat Feb 16, 2019 10:22 pm

Well, it seems to me that the real problem is probably in Mach4 and not the UC100.
I would think that the UC100 just does whatever Mach4 tells it to. The backlash adjustment is in Mach4.
If I set the jog increment to .001 inch, and jog once per second, it works perfect.
If I jog much faster than that, it gets confused, backups up randomly, losing positioning, etc.
Of course Mach says its not their problem, so I'm not sure exactly how the backlash compensation is supposed to work.
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Re: Backlash causes erratic servo movements

Postby dammogreen » Sun Feb 17, 2019 5:05 pm

Well there are 3 of us describing similar issues. I am using UCCNC. I'll have to put a video up when I get a chance to record my trials.
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Re: Backlash causes erratic servo movements

Postby wgpeters » Wed Feb 27, 2019 6:45 pm

I just had some time to do some more experiments.
Mach4 has a parameter to adjust jog rate from 1% to 100%
At 1%, jogging works perfect from the onscreen buttons. At 3% it fails, and at 2% fails sometimes.
Perhaps this is a communication problem with the speed of the USB causing lost or garbled coms from the UC100.

Also, at 1%, the backlash comp works! It seems the backlash problem was actually caused by the jogging problem.
With the backlash set to .0034, the positioning is right on the money according to my dial indicator. Without it, positioning is off by .003+ when changing directions.

So, I have proved that the UC100 does do backlash compensation with Mach4.
This was verified by my dial indicator on the Z axis tested with jogs of .001 .010, .1, and 1 inch travels in both directions.

But, there is still a problem that happens with the pendant. (VistaCNC P1A). If I click the pendant in one direction, and back up a click while the axis is moving, it generates way to many pulses and the axis won't stop. I am going to assume that this problem belongs to the pendant, and not to Mach4 or UC100. It could also be speed problems with the USB ports. Unfortunately, Mach4 is licensed to my laptop, so it will be difficult to test that idea with another computer.

So now, I can use my pendant to accurately touch off on my work piece. I call that success!
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Re: Backlash causes erratic servo movements

Postby ger21 » Wed Feb 27, 2019 10:11 pm

You can generate Mach4 licenses for up to 5 PC's I think, by logging in to your account on the Artsoft site.
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Re: Backlash causes erratic servo movements

Postby wgpeters » Thu Feb 28, 2019 3:11 pm

Machsupport seems to be down, so I can't check that, but my previous reading of the licensing agreement was that it could only be licensed to one computer at a time.
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