Motor movement issue

Computiger · 19 Oct 2018, 18:49

Thanks David,

I‘ll check the motor specs with the calculator and play with the values.

regards
Mike

Computiger · 19 Oct 2018, 19:10

My motors type is ACT Motor Nema17 Scrittmotor 17HS5425L20P1-X2 and this is what the calculator told me

Approximate peak back EMF due to rotation per motor: 3.2 V at 150.0 mm/s
list itemApproximate peak back EMF due to inductance per motor: 0.7 V at 150.0 mm/s
list itemStep pulse frequency: 12.0 kHz at 150.0 mm/s
list itemSpeed at which torque starts to drop (low slip angle): 212.0 mm/s @ 24.0 kHz
list itemSpeed at which torque starts to drop (high slip angle): 278.3 mm/s @ 31.5 kHz

dc42 · 19 Oct 2018, 21:59

Two observations:

You are running the motors at less than 50% of their rated current (1200mA). Try higher, e.g. 1800mA or even 2000mA. Then re-run the back emf calculator.
What VIN voltage are you using? If it's 12V and the calculator indicates that the torque will start to drop at too low a speed, changing to 24V will help.

Computiger · 28 Oct 2018, 07:58

I tried wir 2.2A Motor Current. Motors run a bit hot during print. Wasn‘t diffrent.
Also, I tested diffrent motors w/o changing the issue.

Next week I will get a new Power Supply with 24v to change the whole system to this voltage.

I will reply my experience

dc42 · 28 Oct 2018, 12:07

@computiger said in Motor movement issue:

Motors doing stops during G0 and faster G1 (90mm/s). Stops are not at same position by different movements and the position after movement is exact.

Perhaps I misunderstood the problem. Can you explain exactly what you meant?

Computiger · 31 Oct 2018, 16:02

ok, i try to explain again. Hope my english is good enough.

If my carriage moves in x or y direction with 150mm/s or less speed than carriage isn‘t run in constant speed. The carriage starts to stutter.
I tried other motors with less current but I got the same issue.

I am using steel rods with misumi bearings. W/o motors I can move the carriage easy in all directions.

Can it be a issue of the power supply? Maybe a voltage fluctuation?

With my 2nd DuetWifi on an AM8 I didn‘t have this issue. Printer is running with 12V as well.

Doesn‘t matter, I will change my system to 24V and MGN12 linear rails during next weeks.

dc42 · 31 Oct 2018, 16:09

@computiger said in Motor movement issue:

Can it be a issue of the power supply? Maybe a voltage fluctuation?

Yes, it could be. After you see the motors stutter, run M122. In the report, look for the maximum and minimum VIN voltage and the number of under-voltage events.

Computiger · 1 Nov 2018, 07:10

Good to know, thanks David

Computiger · 1 Nov 2018, 18:08

It isn´t the Power supply, values look stable
M122 shows me:
Supply voltage: min 12.2, current 12.4, max 12.5, under voltage events: 0, over voltage events: 0

How I said, I´ll change the system to 24V and MGN Linear rails

Computiger · 22 Nov 2018, 20:44

I found my problem. My motors are ok.
After I renewed my mesh bed level settings, motors could run more than 300mm/s w/o any stutter.

dc42 · 23 Nov 2018, 09:22

@computiger said in Motor movement issue:

I found my problem. My motors are ok.
After I renewed my mesh bed level settings, motors could run more than 300mm/s w/o any stutter.

Enabling mesh bed compensation can cause moves longer than the mesh spacing to slow down at the segment boundaries if the Z jerk is set too low.