Inconsistent extrusion / Z Banding

[Roycinger]

Hi,
first and foremost I would like to bring this issue to attention where we can track it all together properly. Discord doesn't seem the right place for me as messages and focused discussions get overscrolled and interrupted with non-related topics very quickly.
Before I start I want to mention that I don't expect this issue to get solved by the Voron Team alone. Moreover, I want to evaluate this together with you so that the entire Voron community can benefit from it.

I started facing this extrusion issue when I completed my 100%-built-by-specc Switchwire. In the beginning I was thinking that the printer wasn't properly tuned yet. So I went through all the tuning steps (aligning belts, rails, tuning for filament, E-steps, run_current etc). The result didn't improve within about 90 or more test prints (where I tested every single extrusion related slicer and firmware setting).
Over the course of a few weeks, I partly reassembled the SW again, paying special attention for accuracy, squareness, etc, results didn't improve. At this point I was still under the impression that the issue was on my side as the issue still persists.
To rule out the AB, I converted my SW to bowden and the issue was gone! So I came to the conclusion that there might be a problem with the AB itself.
Because of that, I reprinted the Clockwork parts, changed the TL gears, changed all bearings, changed the motor, changed the entire hotend, precisely cut the PTFE tube. No change in results at all.
For informational purposes, this is my config: https://pastebin.com/nyULd4ca
Fast forward:
Up to yesterday, I noticed that more and more people are facing the same or similar issues, even if they might be fine with the results.
I got sent a plethora of pictures which I was allowed to use in this Git issue. They all more or less show the same problem,
Please note that most pictures where shot with "bad" light, directly from the top to make the issue apparent.
These are kinda mixed from specc-built v2.4's and SW's.



Cubes from my SW:


Random v0 part printed with my SW:

Another set of v0 parts:

For my part, I could rule out any looseness in the kinematics or topics related to filament (as I made tests with PETG, PLA and ABS from various brands).
Those defects appear either random (not at fixed heights) or depending on print features within the model (plateaus, holes, etc).

For me it comes down to a few points:

• requirement of quality is not the same for every user (they might live with the defects)
• There might be issues with either the AB internat geometry or the ABS shrinkage bothering with the tolerances
• related to the point above: A genuine Bondtech BMG in a direct drive situation in another (non Voron) printer works perfectly without showing these defects
• Using a bowden extruder (M4 in this case) eliminated the issue

Yesterday, I had a brief conversation with Ray. I introduced the topic "Prusa Issue 602", which looks awefully similar to this.
I would be happy if you could either assist with this issue or shed some light on it.

Thanks in advance!

[toskium]

Thank you for submitting this issue. I do experience the same results and I was not yet able to pin down the root cause of it.

[toskium]

To add something to the issue. I was doing input shaper calibration and the outcome of the calibration print is imho interesting.

Since klipper calculates the extruder acceleration according to the xy acceleration the striping pattern changed accordingly.

See the attached picture.

It appears more or less intense starting from acceleration 1250 all the way up to 7500.

[BladeScraper-Designs]

Same here as well. tried new BMG parts, various flow settings, various accels and speeds from 30mm/s and 500acc to 120mm/s and 5k accel, etc. Mechanics are solid and have been checked over and over for loose screws, non-smooth rails, belt tension, etc. The only thing that's left is the extruder.

V2.4 Afterburner DD
SKR 1.3 / TMC2209
StepperOnline 17HS08-1004S
Trianglelabs Dragon
Trianglelabs BMG Components

[Gizzzle]

Can confirm the issue.

[mgineer85]

Just built a v1.8 with bowden. I think I don't see the effect, which aligns to your proposal, right?

[toskium]

Just built a v1.8 with bowden. I think I don't see the effect, which aligns to your proposal, right?

Yes, correct. The issue seems to be exclusive to the clockwork extruder. Your input is much appreciated!

[Serpreme]

Can we make a list of the items that are used and not used between the bowden and direct drive? The gears, motors, wiring, and then we can slowly eliminate those items. We can try to test for things like EMI for example

[Gizzzle]

Can we make a list of the items that are used and not used between the bowden and direct drive? The gears, motors, wiring, and then we can slowly eliminate those items. We can try to test for things like EMI for example

I can eliminate every part on the Afterburner except the hotend, but that's not the problem since the other guys are using a dragon while I'm using a v6. Also EMI is not the issue since I used another motor without cable management which lead to the cable not crossing another cable in it's way to the board.
Stepper driver was also swapped from a LV8729 to a TMC2209

[BladeScraper-Designs]

Added details to my post.

[eddietheengineer]

Hello everyone, I have a recommendation to make.

In order make a proper comparison, I recommend that someone mount a BMG extruder directly to Afterburner in place of the Clockwork module. If the issue clears up, then you can root cause the issue to be something with the clockwork module itself. If the issue persists, then the source of the issue is something else.

I would not compare a bowden and direct drive mount of the same extruder--the physics of printing through a long tube with springy filament is different than when the extruder is right on top of the hotend.

[Gizzzle]

Hello everyone, I have a recommendation to make.

In order make a proper comparison, I recommend that someone mount a BMG extruder directly to Afterburner in place of the Clockwork module. If the issue clears up, then you can root cause the issue to be something with the clockwork module itself. If the issue persists, then the source of the issue is something else.

I would not compare a bowden and direct drive mount of the same extruder--the physics of printing through a long tube with springy filament is different than when the extruder is right on top of the hotend.

We had the idea too, but that's nearly impossible because of the small footprint of the afterburner.

[JayAwesome87]

Same problem since day one. I'm using a Galileo Clockwork now and the problem still persists.

[Roycinger]

In order make a proper comparison, I recommend that someone mount a BMG extruder directly to Afterburner in place of the Clockwork module. If the issue clears up, then you can root cause the issue to be something with the clockwork module itself. If the issue persists, then the source of the issue is something else.

This is easier said than done because of a few points:

• The BMG is 2.6mm thicker than the Clockwork:
  
• The filament path is not the same as the Clockwork's:
  

All in all, almost every single part of the AB would have to be redrawn to accomodate a BMG

[eddietheengineer]

Same problem since day one. I'm using a Galileo Clockwork now and the problem still persists.

Is this the version with planetary gears? If so, this would imply that it's not the Clockwork module itself but something else :) since there are no shared parts between the Galileo Clockwork (planetary) and the standard Clockwork BMG version.

Also, can we make sure to document which printer these examples are from? That would be helpful in the root cause!

[Gizzzle]

I'm using my Ender Switchwire Conversion