Motor movement issue

Computiger

Hello,
have some issues during movements of X and Y Motor.
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.

Hope you can help .....

I have a 300x300mm Hypercube (Core XY) with LUM10 and LMU8 Bearings. Motors can use with 2.6A Power max

My conig.g

* M350 X16 Y16 Z16 E16 I1 ; set 16x microstepping with interpolation
M906 X1200 Y1200 Z1500 E400 ; Set motor currents (mA)
M201 X800 Y800 Z15 E1000 ; Accelerations (mm/s^2)
M203 X15000 Y15000 Z100 E3600 ; Maximum speeds (mm/min)
M566 X600 Y600 Z30 E20 ; Maximum jerk speeds mm/minute~~~~

dc42

It sounds to me that you are trying to move the motors faster than they can go for the current and power supply voltage you are using. One option is to reduce the maximum speeds in the M203 command to values that they can manage. If you want to go faster, first use the motor back emf calculator at https://reprapfirmware.org/ to work out the maximum speed that you can achieve with your mechanics and motors before the torque starts to drop.

Computiger

Thanks David,

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

regards
Mike

Computiger

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

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

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

@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

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

@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

Good to know, thanks David

Computiger

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

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

@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.