Uneven extrusion?

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ketil
Posts: 44
Joined: Wed Apr 09, 2014 9:58 pm

Uneven extrusion?

Post by ketil » Mon Apr 05, 2021 8:19 pm

Hello,

It's been a long time since I've posted here, but my trusty M2 (1. gen) is still with me. I've taken up a project that requires some level of accuracy, but something is amiss. My extrusions are really uneven. I'm attaching photos of a couple of prints as they look under a 20x microscope. Those walls are supposed to be straight, tapering off slightly with height. My printed walls are wavy.

It's not some sort of z-wobble, because the layers that stick out are wider at both ends. So I'm thinking this has to do with the extruder.

I think the extruder set screw has got loose the last few times I dismantled it. But could a loose extruder set screw account for this sort of unevenness?

I'm happy to hear any other hypothesis before I start dismantling stuff.

I'm slicing with PrusaSlicer, and printing via octoprint. Both were recently updated.
Attachments
20210405_182414.jpg
0.25mm layer height
20210405_205828.jpg
0.2mm layer height

airscapes
Posts: 497
Joined: Wed Jan 31, 2018 11:36 pm

Re: Uneven extrusion?

Post by airscapes » Tue Apr 06, 2021 4:05 am

Glass bed loose? Jerk wrong due to fat finger when setting Z offset?

Bioluminous
Posts: 23
Joined: Tue Oct 27, 2020 11:03 pm

Re: Uneven extrusion?

Post by Bioluminous » Tue Apr 06, 2021 5:21 am

Possibly the set screws on the motor pulley are loose. I had a similar look on one of my printers and I traced it to the gears on the motor.

ketil
Posts: 44
Joined: Wed Apr 09, 2014 9:58 pm

Re: Uneven extrusion?

Post by ketil » Sun Apr 11, 2021 6:31 pm

After reading info on the MakerGear wiki for the first time in quite a while, I found:
Check that the X and Y belts are the correct tension - with the bed or extruder at the opposite end of travel from the motor, pinch the belt together ~1 inch (25mm) from the edge of the motor drive pulley; it should be possible to pinch it completely together, but difficult
I checked the belts, and they weren't this tight, so I proceeded to tighten. Unfortunately, I had a moronic episode while doing this, so I overtightened the screws holding the Y-motor to the frame to such an extent that I stripped the threads in the motor screw holes - all 4 holes are now stripped. Stupid explanation, I'm (obviously) a mechanical dunce, and I misinterpreted the twisting as the handle on my screwdriver getting loose, so I squeezed the handle hard and screwed (up) some more. Bad move. I'm kicking myself as I wonder why I didn't stop to double check my assumption.

So now what are my options? Is there anything to do besides getting a replacement motor? If anyone can suggest a source in Europe, or a third party drop-in replacement that might be easier to source in Europe, I'll be saving quite a bit on shipping and taxes. (I guess the standard fix for stripped threads would be to retap the holes for bolts the next size up. Unfortunately the holes in the M2 frame won't fit larger bolts. Extending the holes in the M2 frame would be a serious and irreversible undertaking, clearly something a mechanic of my caliber should not even be considering.)

airscapes
Posts: 497
Joined: Wed Jan 31, 2018 11:36 pm

Re: Uneven extrusion?

Post by airscapes » Mon Apr 12, 2021 5:03 pm

I think the motors are standard steppers.. never looked but is there a model number on them?

ketil
Posts: 44
Joined: Wed Apr 09, 2014 9:58 pm

Re: Uneven extrusion?

Post by ketil » Sat Apr 24, 2021 8:31 pm

Didn't find any info on the motor itself. I checked around, and managed to find a similar-ish motor locally. It was a Wanhao Duplicator i3 Z-motor. The original motor didn't have a connector, the wires simply disappeared into the casing. So I had to cut the wires, and then figure out which wires went where and connecting them. It seems to work well as a drop-in replacement.

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