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Uneven extrusion?

Posted: Mon Apr 05, 2021 8:19 pm
by ketil

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.

Re: Uneven extrusion?

Posted: Tue Apr 06, 2021 4:05 am
by airscapes
Glass bed loose? Jerk wrong due to fat finger when setting Z offset?

Re: Uneven extrusion?

Posted: Tue Apr 06, 2021 5:21 am
by Bioluminous
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.

Re: Uneven extrusion?

Posted: Sun Apr 11, 2021 6:31 pm
by ketil
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.)

Re: Uneven extrusion?

Posted: Mon Apr 12, 2021 5:03 pm
by airscapes
I think the motors are standard steppers.. never looked but is there a model number on them?