Motor stalls at 3000mm/min specifically

kalera

Hi,

I've been using a Duet 2 wifi for a while now for my diy cnc router. I've upgraded the CNC to use linear rails and leadscrews recently. Since then I've been having lots of issues with the motors, especially the Y motors (using 2). I've upgraded to a duet 3 since I'm using 3A motors (thinking that the duet wifi drivers were the issue), but the problem persists.

This is my setup:
Dual motors on the Y axis (Nema 23, 3A rated. "Motech Motor: MT-2315HS300AW-C")
Both motors are connected to a seperate driver
Leadscrew has an 8mm pitch
Steps/mm: 400
Microstepping: 16 with interpolation
24V Power supply is used

The issue:
The motors stall reliably at 3000mm/min after moving about 50-60mm.

What I've tried/checked:
M122 command shows no issues detected after a stall.
Stall detection also doesn't detect the stalls.
Changing motor currents ( testing 2000mA-2500mA on the duet wifi and 3000mA on the Duet3)
Changing acceleration settings
Changing jerk setting
Check alignment of all components. Everything moves smoothly when I remove the motors
Lubricating all rails and leadscrews

I'm completely at a loss here. Does anyone have any ideas on how to fix this?

Phaedrux

@kalera said in Motor stalls at 3000mm/min specifically:

2315HS300AW

Are the specs from this chart right?
http://motechmotor.com/productDetail-0105-45.html

It may be due to the high inductance of the motor and the high rate of rotation required for the lead screw causing too much back EMF.

https://duet3d.dozuki.com/Wiki/Choosing_and_connecting_stepper_motors#Section_Inductance

kalera

Thanks for your reply @Phaedrux

That's indeed the motors I'm using.

After doing the math that means I should have a max speed of 2400mm/min. This would explain the stalls at 3000.
I was able to get the motors running without stalling at 12000 (their max speed at 1500rpm) but this is probably due to the inertia when rotating that fast.

I'll test it out and post an update on wether or not this runs good reliably.

droftarts

@kalera you can also check your maths with the EMF calculator here: https://www.reprapfirmware.org/

Ian

Phaedrux

@droftarts said in Motor stalls at 3000mm/min specifically:

@kalera you can also check your maths with the EMF calculator here: https://www.reprapfirmware.org/

Ian

I ran into an issue with the calculator not allowing me to select a custom lead screw pitch.

droftarts

@Phaedrux oh! I think @wilriker maintains the code for that?

Ian

Phaedrux

@droftarts Yes I think so. I mean to check it out again to see if it wasn't something I was doing wrong.

droftarts

@kalera as you’ve got a Duet 3, you could reduce the micro stepping to x8 and still use interpolation (keeps the motors quiet when moving), unless you really need that much resolution in your Y axis. This should let you run them at higher speed, I think.

Most motors have a full step positional accuracy of +/- 5%, so microstepping above x10 (which is what GeckoDrives use) doesn’t give you more repeatable accuracy.

Ian

wilriker

@droftarts said in Motor stalls at 3000mm/min specifically:

@Phaedrux oh! I think @wilriker maintains the code for that?

Ian

Actually, I don't.

@Phaedrux But I can see that this drop-down is misleading. Just enter the desired lead into the "Leadscrew lead" input field. This will make the Leadscrew preset drop-down switch to the otherwise not selectable "custom" value. In fact all preset drop-downs will switch to custom if you modify any of the assigned values manually.

Phaedrux

@wilriker @droftarts must have been thinking of the acceleration calculator. Is the EMF calc maintained by @chrishamm?

wilriker

@Phaedrux said in Motor stalls at 3000mm/min specifically:

@wilriker @droftarts must have been thinking of the acceleration calculator. Is the EMF calc maintained by @chrishamm?

I think so. But also @dc42 and @T3P3Tony do changes on it every once in a while.

wilriker

@droftarts said in Motor stalls at 3000mm/min specifically:

@kalera as you’ve got a Duet 3, you could reduce the micro stepping to x8 and still use interpolation (keeps the motors quiet when moving), unless you really need that much resolution in your Y axis. This should let you run them at higher speed, I think.

Unfortunately not. Since the problem seems to be Back EMF this is bound to RPM of the stepper - independent of how they are achieved by the driver. If it were steprate then lower microstepping would help. But even a Duet 2 is good for about >15000mm/min on an axis with 400 steps/mm.

kalera

As promised I'd post an update after testing it. It's been running reliable at 2400mm/min so far. Maybe I'll change the leadscrews to a higher pitch later to achieve higher speeds.

I'm still having some issues with stall detection, but I'll search the forums for some answers on that first