IDEX motor jitter

[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!

[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.