IDEX motor jitter

MaxGyver

I managed to get a slow motion shot of the U axis jitter. This was captured with U and Y driven from the main board.

fcwilt

@dc42

I managed to get a slow motion shot of the U axis jitter. This was captured with U and Y driven from the main board.

Video

You are referring to the left/right motion?

Yes, quite obvious.

And if you connect the X driver to the U axis hardware and the U driver to the X axis hardware the problem moves to the X axis hardware?

Frederick

MaxGyver

@fcwilt said in IDEX motor jitter:

And if you connect the X driver to the U axis hardware and the U driver to the X axis hardware the problem moves to the X axis hardware?

I can test this tomorrow, but when I print with the secondary extruder on the U axis, the same left/right motion is present in X. So I suppose it is not a problem with the U axis hardware.

dc42

@maxgyver do X, Y and U axes have the same steps/mm?

MaxGyver

@dc42 said in IDEX motor jitter:

@maxgyver do X, Y and U axes have the same steps/mm?

Yes.
I did also test different microstepping settings with no improvement.

; Drives
M569 P0 S0 ; Drive 0.0/Z1 motor (rear left)
M569 P1 S1 ; Drive 0.1/Z2 motor (rear right)
M569 P2 S1 ; Drive 0.2/Z3 motor (front right)
M569 P3 S0 ; Drive 0.3/Z4 motor (front left)
M569 P4 S1 ; Drive 0.4/E1 motor
M569 P5 S0 ; Drive 0.5/E2 motor

; Closed loop drives
M569 P123.0 S0 ; X-Motor
M569 P124.0 S0 ; U-Motor
M569 P125.0 S0 ; Y1-Motor
M569 P126.0 S1 ; Y2-Motor
M569.1 P123.0 T2 C20 R125 I500 D0.1 H50 ; Configure the 1HCL board at CAN address 123 with a quadrature encoder on the motor shaft that has 20 steps per motor full step.
M569.1 P124.0 T2 C20 R125 I500 D0.1 H50 ; Configure the 1HCL board at CAN address 124 with a quadrature encoder on the motor shaft that has 20 steps per motor full step.
M569.1 P125.0 T2 C20 R125 I500 D0.1 H50 ; Configure the 1HCL board at CAN address 125 with a quadrature encoder on the motor shaft that has 20 steps per motor full step.
M569.1 P126.0 T2 C20 R125 I500 D0.1 H50 ; Configure the 1HCL board at CAN address 126 with a quadrature encoder on the motor shaft that has 20 steps per motor full step.

; Motion System
M584 X123.0 Y125.0:126.0 Z0:1:2:3 U124.0 E4:5 ; set 4 Z drivers and add one U driver -> Must come earlier than M350,M906,M92, M201, M203, M208, M350, M566, M574, M667 and M669
M350 X32 Y32 Z16 U32 E16:16 I1 ; Configure microstepping with interpolation
M92  X160 Y160 Z640 U160 E400:400  ; Set steps per mm
M203 X42000 Y42000 Z1800 U42000 E10000:10000; A40000 B40000 ; Set maximum speeds (mm/min)
M566 X600 Y600 Z200 U600 E600:600 ; set maximum instantaneous speed changes (mm/min)
M201 X30000 Y30000 Z500 U30000 E30000:30000 ;A6000 B6000 ; Set maximum accelerations (mm/s^2)
M906 X2400 Y2400 Z1200 U2400 E900:900 I25 ;A300 B300 ; Set motor currents (mA) and motor idle factor in per cent
M84 S5 ; Set idle timeout
M917 X50 Y50 Z50 U50 ; Set holding current in percent

; Kinematics
M669 K11 Y1:-1:0:-1	; Matrix mapping for Axis - X:Y:Z:U
;M669 K11 X1:0:0:0 Y1:-1:0:-1 Z0:0:1:0 U0:0:0:1	; Matrix mapping for Axis - X:Y:Z:U
;M669 K1 X1:0:0:0 Y1:-1:0:-1 Z0:0:1:0 U0:0:0:1

M671 X-41:495.5:495.5:-41 Y353:353:23:23 S10 ; lead screw positions and maximum allowed correction S in mm
G90 ; send absolute coordinates...
M83 ; ...but relative extruder moves

; Axis Limits
M208 X0 Y0 Z0 U0 S1 ; set axis minima
M208 X405 Y323 Z350 U405 S0 ; set axis maxima

dc42

@maxgyver if the axes have identical steps/mm and microstepping, then the step pulses should be precisely synchronised. So I think it must be a mechanical problem.

Is there any vibration when you move each of the 3 motors individually? You can use G91 followed by G1 H2 commands to test that.

martin7404

@dc42 In double makfoged he can move individually X and U but for Y he moves all the motors

dc42

@martin7404 said in IDEX motor jitter:

@dc42 In double makfoged he can move individually X and U but for Y he moves all the motors

Yes but you can still command the motors to move individually, and see whether the resulting movement is smooth or not.

MaxGyver

@dc42 Individual motor moves are no problem, the jitter only courses when they have to work in conjunction.

MaxGyver

@dc42 said in IDEX motor jitter:

If the axes have identical steps/mm and microstepping, then the step pulses should be precisely synchronised. So I think it must be a mechanical problem.

When printing with the U-Axis extruder, the jitter is present in the X-Axis extruder and vice versa. The active extruder is moving just fine and the print turns out okay. So I do not see how this can be a mechanical issue.

If it is not a firmware issue, then maybe a CAN related problem?

martin7404

@maxgyver Can you show your belt arrangement scheme

fcwilt

@maxgyver said in IDEX motor jitter:

@dc42 said in IDEX motor jitter:

If the axes have identical steps/mm and microstepping, then the step pulses should be precisely synchronised. So I think it must be a mechanical problem.

When printing with the U-Axis extruder, the jitter is present in the X-Axis extruder and vice versa. The active extruder is moving just fine and the print turns out okay. So I do not see how this can be a mechanical issue.

If it is not a firmware issue, then maybe a CAN related problem?

You could possibly rule out CAN bus problems by running all drivers off the 6HC and disconnecting the expansion boards (and make the needed adjustments to the config file).

Frederick

MaxGyver

So, after almost a week of trying and testing, I found the reason for the strange extruder jitter.

It is due to how the belts are arranged. In short, the X and U belts start oscillating when the extruders are in their respective home positions.

At the home position, the axis belt has one short and one long section from the extruder mounting point to the axis motor pulley. Although I have 9mm gates belts and an overall very sturdy construction, this extra length adds enough springiness to the system that the extruders start to oscillate during moves with strong acceleration. The vibration becomes less prominent the further the extruder is from its home position, since the belt section between extruder and motor-pulley become evenly balanced when the extruder is in the middle of the bed. Hence, I was able to print with one extruder in the middle of the bed while the other extruder was oscillating in its home position.

@dc42 You were absolutely right to assume a mechanical issue.

Thank you all for your suggestions and support.

martin7404

@maxgyver stil.I would like to see your belt arrangment, please
Thank you

fcwilt

@maxgyver

But why does just the inactive axis vibrate? You mentioned that you can print with one axis without problem - correct?

Have you experimented with changing belt tension?

Frederick

MaxGyver

@martin7404 said in IDEX motor jitter:

@maxgyver stil.I would like to see your belt arrangment, please
Thank you

I am working from home right now. I will gladly provide you with some CAD-Screenshots of my belt arrangement later this week.

@fcwilt said in IDEX motor jitter:

But why does just the inactive axis vibrate? You mentioned that you can print with one axis without problem - correct?
Have you experimented with changing belt tension?
Frederick

Yes, I have tried every tension from loose to guitar string high.

The big drawback with CORE XY, H-Belt, Markforged e.t.c is that you create a kinematic system where multiple axis are codependent. Meaning that every little tolerance, vibration and over swing, will translate into the other axis. From what I have learned until now, the reduced moving mass is not worth having much longer belts.

MaxGyver

@martin7404 said in IDEX motor jitter:

@maxgyver stil.I would like to see your belt arrangment, please
Thank you

Sorry for taking so long!

Dual Markforged1.png Dual Markforged2.png

RogerPodacter

i just came across this thread. i just upgraded my CoreXY printer into an IDEX dual markforged kinematics printer, and i now experience this same jitter behavior.

after reading this thread, this behavior must be inherent to this type of kinematics. with CoreXY, the single head is equally tensioned from both sides with 4 belt connections. with dual heads, only 2 belt connections are present on each head. additionally, when the Y gantry moves, the stationary head still has its motor turn in the opposite direction to counter the drag movement.

for whatever reason, the stationary head is slightly out of sync. or possibly because the belts have the long/short end as mentioned earlier, there is slight jitter movement of the stationary head.

i tightened my belts and this greatly reduced the behavior. but its still present on violent acceleration moves. its noticeable because the stationary head is parked on the end stop, and the endstop clicks everytime the head jitters.