MPG Speed

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MPG Speed

Postby mhafele » Thu Oct 03, 2019 1:46 pm

I'm running a Bridgeport that I took off the old anilam cnc controls and upgraded to a UC300ETH-5LPT and UCCNC software. I used the old SEM dc servos, added encoders and I'm using the dg4s drives. I have a simple MPG with a encoder and two rotary switches (xyzabc, 1,10,100) wired to the mpg inputs on the uc300. I've got it working as it should with the macro I found. The selector switch switches between .001, .01, .1 steps. The problem I'm seeing is that at each one of those step selections the servo runs at the max speed from what I can tell. I have the MPG speed multiplier set to 1 per the manual for slower steps. I have the MPG prescaler set to 10 as it seems I can get better movements with this and if I accidentally move two click when I'm using an edge finder I don't over shoot my mark. Withe the full speed servo I can't even used the .01 or .1 step. My entire machine rocks back and forth trying to make those steps at full servo speed.

Any thoughts on how to set an actual speed per click of the mpg encoder? Seems like the mpg settings have more to do with the speed for multiple clicks of the mpg encoder and smoothing out the travel. I'm looking to get slower smooth moves in the small increments for using an edge finder.

Thanks
mhafele
 
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Re: MPG Speed

Postby cncdrive » Sun Oct 06, 2019 9:57 pm

I've created a bug report for my collegues, they will debug this soon.
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Re: MPG Speed

Postby mhafele » Fri Nov 08, 2019 3:45 am

Any update on this?
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Re: MPG Speed

Postby rmtucker » Fri Nov 08, 2019 9:01 am

Make sure the comp acceleration is only set about 20% above the max acceleration.
For some reason even if you are not using backlash compensation it, the mpg seems to use it but the manual does not mention it.
I only found this out by mistake.
Also are you using mm or inches for your set up,as .01/.1 inch steps per click of the encoder are way too fast but ok for mm.
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Re: MPG Speed

Postby mhafele » Sat Nov 09, 2019 1:08 am

That was it. I would have never guessed that. I don't see a reference to comp acceleration anywhere. I get a much more usable mpg now. I am using inches. I have x1 (on the mpg label) set to .001 steps per click and x10 set to .01, the x100 I don't use. I adjust edited the macro to get these where I wanted. I'm still not able to get as accurate as I would like. I would like to be able to have on click move exactly .001. My table movement is close but can be off a few thousands for every click. I think it might be my servo tuning but I kind of got burned out of trying to get that perfect. When I'm cutting aluminum I'm able to get pretty accurate cuts (1.001 dia circles when targeting 1") but would like to be able to pick up edges better. Again this is with a bridgeport, ballscrews, and old SEM servos where I added the AMT encoders, and using DG$ drives.
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