Prusa upgraded to duet, weird extrusion

NitroFreak

@Murloc992 said in Prusa upgraded to duet, weird extrusion:

@NitroFreak said in Prusa upgraded to duet, weird extrusion:

I know what it might be. In the Prusa bear thread they talked about how the 0.9 might not have enough torque to direct drive the extruder.

I just read that you‘re using the 12v PS.
0.9 degree steppers really want 24v otherwise you will not be able to reach good speeds and torque, because you literally only have half the torque vs 24v and torque is further halved because you have the 0.9 instead of a 1.8 stepper. I could imagine the extruder is lacking until it reaches the next full step where it snaps to, resulting in this sort of extrusion inconsistency.

I would suggest you try a 24v power supply

I actually once pushed filament out at 60mm/s, 100mm of it. Nothing skipped. The speed of the extruder wheel spooked me quite a lot though.

Yeah, sounds good, but I have 12V bed, 12V heater, 12V fans, etc..

i doubt it was pushed out at 60mm/s , even my volcano with a BMG grinds filament after 12mm/s filament speed. Maybe you mean print speed? or mm/min?
If you do not want to convert to 24v, i suggest your best bet would be to put the 1.8 degree stepper back in or use a 3:1 gearing

droftarts

Fair enough re assembly, just running out of ideas! @NitroFreak isn’t quite right about torque of 0.9 motors (see https://duet3d.dozuki.com/Wiki/Choosing_and_connecting_stepper_motors#Section_Step_angle ) except at high speed, but the extruder doesn’t turn that fast. Powering with 24V would be a better option for 0.9 degree motors, though.

Ian

Murloc992

@NitroFreak said in Prusa upgraded to duet, weird extrusion:

@Murloc992 said in Prusa upgraded to duet, weird extrusion:

@NitroFreak said in Prusa upgraded to duet, weird extrusion:

I know what it might be. In the Prusa bear thread they talked about how the 0.9 might not have enough torque to direct drive the extruder.

I just read that you‘re using the 12v PS.
0.9 degree steppers really want 24v otherwise you will not be able to reach good speeds and torque, because you literally only have half the torque vs 24v and torque is further halved because you have the 0.9 instead of a 1.8 stepper. I could imagine the extruder is lacking until it reaches the next full step where it snaps to, resulting in this sort of extrusion inconsistency.

I would suggest you try a 24v power supply

I actually once pushed filament out at 60mm/s, 100mm of it. Nothing skipped. The speed of the extruder wheel spooked me quite a lot though.

Yeah, sounds good, but I have 12V bed, 12V heater, 12V fans, etc..

i doubt it was pushed out at 60mm/s , even my volcano with a BMG grinds filament after 12mm/s filament speed. Maybe you mean print speed? or mm/min?
If you do not want to convert to 24v, i suggest your best bet would be to put the 1.8 degree stepper back in or use a 3:1 gearing

Maybe the motor skipped and I didn't hear it? I can try putting the original motor back in, but it also was pulsing, just less.

Like that:

droftarts

How about the other way around; maybe you have the idler overtightened and the BMG gears are meshing badly because they’re too tight?!

Ian

Murloc992

@droftarts said in Prusa upgraded to duet, weird extrusion:

How about the other way around; maybe you have the idler overtightened and the BMG gears are meshing badly because they’re too tight?!

Ian

I have tried the "correct tension" method: so that it just grabs with minimal tension and ofc overtightening, no difference. BUT I have an idea. Let me check.

Murloc992

Nevermind.. I tried limiting the side-to-side play bondtech idler has, even played with currents throughout the layers and nothing seemed to give any effect. I went from original 1200mA, to 1400, 1600, then tried going lower, 1000, 800, 600, 400. It never skipped, the print looks identical. The print is a very slow single wall cube print. 15 minutes for 25x25x25mm.

Murloc992

Fun fact: if I extrude using the web control at 5mm/s, there's no pulsing. If I extrude at 15mm/s (no skipping till 4 in a row, must be heat related) it's extremely smooth. If I extrude at 1mm/s, it pulses INSANELY.

NitroFreak

thats because of the firmware minimum speed of 1.5mm/s iirc?

droftarts

@NitroFreak said in Prusa upgraded to duet, weird extrusion:

thats because of the firmware minimum speed of 1.5mm/s iirc?

It’s 0.5mm/s. from Gcode dictionary in G1 definition:

For CNC users especially: RRF has a default minimum movement speed of 0.5mm/sec. In firmware 2.03 and later this can be changed using the I ('i') parameter of the M203 command.

Ian

droftarts

@Murloc992 not sure when Back EMF kicks in? See https://duet3d.dozuki.com/Wiki/Choosing_and_connecting_stepper_motors#Section_Back_emf_due_to_rotation

Ian

Murloc992

@droftarts said in Prusa upgraded to duet, weird extrusion:

@Murloc992 not sure when Back EMF kicks in? See https://duet3d.dozuki.com/Wiki/Choosing_and_connecting_stepper_motors#Section_Back_emf_due_to_rotation

Ian

Not sure...

Would toying around with CHOPCONF values help here?

Veti

@Murloc992 said in Prusa upgraded to duet, weird extrusion:

Would toying around with CHOPCONF values help here?

no but increasing voltage helps

Murloc992

@Veti said in Prusa upgraded to duet, weird extrusion:

@Murloc992 said in Prusa upgraded to duet, weird extrusion:

Would toying around with CHOPCONF values help here?

no but increasing voltage helps

I literally spent a ton of money on the upgrade.. Just thinking about spending even more on a 24V setup hurts me inside.

Veti

@Murloc992
i dont think you are gonna reach any speed where the emf becomes a problem with the extruder.

Murloc992

@Veti

Then what do you mean

@Veti said in Prusa upgraded to duet, weird extrusion:

no but increasing voltage helps

Aren't you talking about the main PSU? Or Stepper voltage?

NitroFreak

@Veti said in Prusa upgraded to duet, weird extrusion:

@Murloc992
i dont think you are gonna reach any speed where the emf becomes a problem with the extruder.

Thats really the only option left to test why the 0.9 steppers produce that pattern.
24v PSU are not that expensive. i got my meanwell‘s used on ebay for 24€

Murloc992

@NitroFreak said in Prusa upgraded to duet, weird extrusion:

@Veti said in Prusa upgraded to duet, weird extrusion:

@Murloc992
i dont think you are gonna reach any speed where the emf becomes a problem with the extruder.

Thats really the only option left to test why the 0.9 steppers produce that pattern.
24v PSU are not that expensive. i got my meanwell‘s used on ebay for 24€

Yeah, I mean for testing the stepper only. Because I am crap out of luck for other components.

NitroFreak

24v heater cartridges are not that expensive and 24v silicone heated pads are also not that expensive. the 12v fans can be driven by the 24v duet by means of a buck converter

droftarts

@Murloc992 As 1mm/s (I guess that’s X/Y federate?) seems to be the problem, and you’re unlikely to print at that speed normally, what happens if you print the box but set the speed multiplier to 200% or higher?

Ian

droftarts

Thinking about it, what you might be seeing is the effect of running the extruder so slowly, you’re seeing individual steps, and the motor has to stop between each step, which causes a lack of continuity of movement, hence the stuttering. Try setting extruder to x256 microstepping, or turn off interpolation.

Ian