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Author Topic: Motor Tuning in Mach 4, Very Stuck  (Read 1965 times)

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Re: Motor Tuning in Mach 4, Very Stuck
« Reply #10 on: January 26, 2019, 05:51:41 PM »
Wow thanks craig, Yes i am aussie thanks for noticing  ;D lol

As i was building i wanted to get the best i could afford hoping i could build something semi impressive but reliable haha

Just wanted to double check in the motor tuning tab am i still sticking to 400 counts per unit? or am i still way off.
Re: Motor Tuning in Mach 4, Very Stuck
« Reply #11 on: January 26, 2019, 06:05:23 PM »
Hi,
you've seen the calculation......2000 pulses per rev and 5mm per rev (pitch) means 2000/5 =400 pulse per mm.

Under the assumptions I have made that is correct. Put 400 in the 'Steps per Unit' setting.

Zero your X axis and MDI g0 x100. <MDI Cycle Start>. How far did it move, it should be 100mm....exactly.
If it has moved exactly 100 mm then leave that setting alone, you'll never touch it again in the life of the machine.
The max velocity and acceleration you can change at will but the steps per unit set the dimensional accuracy of the machine.
If you do a cutting move of g1 x100 f300 say and it only moves 95mm then your part is going to be undersize....rubbish.

As a start set the max velocity to 2500 (mm/min) and try acceleration of 250 (mm/sec2)

Craig
My wife left with my best friend...
     and I miss him!
Re: Motor Tuning in Mach 4, Very Stuck
« Reply #12 on: January 26, 2019, 06:17:05 PM »
Hi Craig thanks for helping me i really appreciate it.

I've put 400 with 2500 and 250 and punched on g0 x100 and its moved 63mm
Re: Motor Tuning in Mach 4, Very Stuck
« Reply #13 on: January 26, 2019, 06:44:07 PM »
Hi Dale,
then something is wrong. It could be that the ESS is issuing 2000 pulses per rev for 20 revs to get your 100mm
travel but the stepper is missing steps. Its possible but unlikely, I would expect there to be unusual noises.

I think it more likely that the settings in the stepper driver are wrong.

I'm guessing that you have the dip switches back to front and you have accidentally set the steps per rev to 3200
not 2000 as you intended.

Now you issue an g1 x100 instruction so Mach/ESS dutifully sends 100 (mm) x 400 (pulse/mm) =40,000 pulses.

If I am correct your stepper driver took those 40,000 pulses and applied them to your motor but at 3200 per rev.
So your motor would turn 40,000 /3200 = 12.5 revolutions and at 5mm per rev =12.5 5 =62.5mm.
Does that sound correct to you?

Have a close look at the bottom of page 14. Compare with the settings required to make 2000 pulse/rev on page 15.

Craig
My wife left with my best friend...
     and I miss him!
Re: Motor Tuning in Mach 4, Very Stuck
« Reply #14 on: January 26, 2019, 06:46:42 PM »
Hi,
sorry, in that last pic I highlighted the settings to make 5000 pulse/rev, please disregard my highlighting.

Craig
My wife left with my best friend...
     and I miss him!
Re: Motor Tuning in Mach 4, Very Stuck
« Reply #15 on: January 26, 2019, 07:11:07 PM »
Hi Craig can confirm i did have the dip switches wrong (working in a small cabinet under the CNC)

So i pulled the stepper motor controllers out and changed them to 2000 and re run g0 x100 and its moves 25mm not 100?

 :o
Re: Motor Tuning in Mach 4, Very Stuck
« Reply #16 on: January 26, 2019, 07:33:49 PM »
Hi,
I still think you have the switches wrong....its easily done.

There is one other remote possibility and that is the difference between PPR and counts per rev.

Encoders have a certain number of lines which is the same as PPR. In the case of your steppers they have 1000
line encoders. When the two encoder channels are combined, they are in quadrature to each other, you end up getting
four times the number of distinct counts per revolution, ie 4000 counts.

I would expect, and am led to believe, the dip switch settings are counts per rev, not lines per rev. I am suspicious that
the actual travel is exactly 1/4 of what was expected.

Please go and double and triple check the dip switches. If they are indeed set to 2000 pulse per rev as you believe
then set your 'Steps per Unit' to 1600 and try the same test. The ESS can handle the extra pulse speeds no trouble.

Craig
My wife left with my best friend...
     and I miss him!
Re: Motor Tuning in Mach 4, Very Stuck
« Reply #17 on: January 26, 2019, 07:50:24 PM »
Hi Craig you mentioning quadrature rings a bell, in the ESS settings under motors i had changed the settings from step/dir to quad a few days ago and forgot about it.

I changed it back to step/dir and ran g0 x100 again and got 93mm am heading in the right direction and i pulled to controllers out again they are 100% in 2000

thanks again for your help
Re: Motor Tuning in Mach 4, Very Stuck
« Reply #18 on: January 26, 2019, 08:45:28 PM »
Hi Dale,

Quote
ran g0 x100 again and got 93mm am heading in the right direction

Not quite sure that is the case. In the previous instances it was a setting that caused a predictable variation between
actual and what you wanted. 93mm vs 100mm we actually expected is much harder to understand.

You can correct it by adjusting the step per unit until it comes right. It is not correct however. The calculation is so
straight forward having to deviate from it means that a fault elsewhere is being overlooked.

One possibility is that the stepper is losing steps at speed. If you try MDI g1 x100 f250 what happens?. The axis will
move but more slowly. If the discrepancy is caused by trying to go too fast then this test should highlight it.

Another possibility is that you have a loose coupler, its surprising how many get caught with such a simple fault.

Craig
My wife left with my best friend...
     and I miss him!
Re: Motor Tuning in Mach 4, Very Stuck
« Reply #19 on: January 26, 2019, 09:24:15 PM »
well i had some lunch and had some time to think and tried it again and bingo its bang on 100mm in the X and Y axis and i have no idea as i didnt change anything so that has me stumped.....

also just a quick question when i press "ref all" all 3 axis barley move to the home switches any idea what i might have done