Z banding after changing extruders

The problem: [imgur.com]

I have a CR10 which I have been using since I bought it new (circa August 2016)
It was until recently completely stock and worked flawlessly for many long hours.

I decided to purchase a direct drive extruder kit, and settled on the Microswiss kit from TinyMachines (https://tiny-machines-3d.myshopify.com/products/micro-swiss-direct-drive-extruder-for-creality-cr-10-ender-printers?_pos=1&_sid=c9ad71300&_ss=r)

I installed it, and straight away began getting issue relating to Z banding:
This gallery explains the problem with some pictures: [imgur.com]

The banding is an alternating pattern whose period changes depending on the size of the part - parts larger in the X-Y plane mean the banding period is smaller, while smaller
parts mean the banding period is greater. On small enough parts, the banding is not apparent, especially if the part is printed immediately after the printer is turned on (although I suspect this may be a red herring).
The issue persists between different slicers (slic3r, prusaslicer, cura) and across all temperatures and speeds (although is somewhat alleviated at higher speeds)
I returned the machine to stock configuration, in the hopes that this would cause the issue to disappear, but the problem remained, so I put the direct drive extruder back on.

If anyone has any suggestions, I would greatly appreciate them.
Thank you in advance.


I have tried:
Replacing the stock extruder - issue persists
A range of extruder temperatures - issue persists
A range of print speeds - issue persists, slight reduction at greater speeds
A variety of layer heights - issue persists, period of oscillation changes
Replacing X and Y axis belts and retensioning - issue persists
Increasing Z axis motor current - issue persists
Changing filament brands/colours - issue persists
Greasing Z-axis leadscrew - issue persists
Printing with bed turned off/turned up high - issue persists, slight reduction at cooler temperatures
Printing with no/more cooling - issue persists

Edited 1 time(s). Last edit at 03/22/2020 03:10PM by LinkVanyali.

That sure looks like a Z axis problem to me. The bands look tilted which suggests that the X axis is walking up the Z axis guide rails. The CR10 only drives one side of the Z axis, so I suspect you need to do some alignment. The problem is called "racking" and it occurs because anything that interferes with the undriven end of the X axis movement in Z has a lever arm that is the length of the X axis to twist and press on the bearings on the driven side.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Thank you for your input.

I'm not entirely sure how to go about makeing adjustments, or what to adjust, and a web search for 'racking' doesn't really yield much information
I expect I'd have to start with the eccentric nut on the Z axis rollers?
Do you have any pointers?

Yes, that's what the eccentric nuts are for. I'd start there. I'd disconnect the lead nut from the X axis so the X axis can slide up and down freely, then tweak the eccenntric nut(s) to take out any play in the motion without loading the thing so that it becomes hard to move. Then reconnect the lead nut and try a test print.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Thanks for the feedback. I've been battling for a week now and nothing I did could resolve this.
I eventually caved and installed a second lead screw and nut to the unsupported end of the
X axis and have GREATLY improved the smoothness and accuracy of the Z motion

Unfortunately, the problem persists. I'm about ready to putt my hair out!
It seems only to happen in the Y axis (?) and seems to only happen on the third of 4th print (2 hours runtime or so)
More images here: [imgur.com]

Any ideas?

I've narrowed the issue down to something mechanical. All other potential causes have been tested and have no impact on the print quality issue.
The trouble is that I have no idea which mechanical issue may be causing this.

It is worth nothing that further testing reveals the offsetting to be only in the Y axis, not the X axis. The sides of the parts that are aligned with the X axis are straight and smooth, while the sides aligned with the Y axis show the characteristic spiral ribbing/waviness. The waviness also appears to change in 'size'; with the thickness of the wall of the part - the attached photographs demonstrate the issue.

I truly am at the end of my rope here. I've tried everything I could possible think of.
Any suggestions are most welcome.

Images:
[i.stack.imgur.com]
[i.stack.imgur.com]

I installed the Z axis motor at the top of the frame to help alleviate any misalignment that may be occurring. The Z axis runs extremely smoothly now, just with light figure pressure up and down. The Y axis frame braces have been tightened and I used a square to verify that the frame is parallel to the bed. Prints still come out with some weird diagonal banding!

Images of banding and new leadscrew:
[imgur.com]