Y-axis starts sliding backwards on larger prints  

Re: Y-axis starts sliding backwards on larger prints

Your custom parts? My guess is your object curling up which cause friction on the print head resulting in a layer shift. Are you printing in low power, if so print at high power.

Your second object, printed at 100% infill? From the photo it hard to tell, about what value was z=? when the print failed. If object is public then post a link to this thread.

As a test, print 1cm by 1cm cubes at various places on the bed to see if it is a mechanical issue.

if you rotate the object by 45 degrees on the bed, does it make a difference?

Re: Y-axis starts sliding backwards on larger prints

Yes, custom parts.
Printing high power.
Z is live adjusted to 0.6 mm.

However, now I've lost all adhesion to the plate, using settings which worked fine before, cleaning the plate and whatever, so I have no f*** idea what is happening here. *sigh*

Re: Y-axis starts sliding backwards on larger prints

The bigger the part, the higher the failure rate.

Run the calibration gcode and upload a photo to this forum.

May want to try some 3M painters tape and give that a try, but only the stuff from 3M.

Regarding the 1st layer, try the following.

- Slow down the flow rate to 30%
- Increase the extruder up to 110%
- Increase the bed temp to 65 C
- Add a 8mm brim

Report back the results.

Re: Y-axis starts sliding backwards on larger prints

Thanks for the advice, even when I'm frustrated as he** 🙂
I think I have to clean the nozzle first. The flow seems a little too weak, so first of all I guess I have to take apart the extruder.

Re: Y-axis starts sliding backwards on larger prints

If the shifting happens to come back, here's another thought:

Whenever i see layers shifting like that my first reaction is pulleys / belts and general "smoothness" of movement along that the axis (you wouldn't be the first with crappy bearings or a skewed frame)

Too loose is not good and too tight could cause issues with friction/binding as well, so we need some sort of a middle ground, which unfortunately is a bit of a guesswork as there's no way to measure the proper tension and the build manuals hint "should sound like an instrument string" is a bit imprecise at best. Maybe somebody could figure out what string/note were actually looking for and we could use a guitar tuner or some such.. anyway, i am drifting off-topic. My motor mount gets bent slightly from the belt tension as well. The pre-built version has an extra spacer to counteract this bending - so i guess a little bending is expected)

So here's another quick checklist:

- the original spool holder is rather poor, sometimes it causes too much friction, which in my case caused underextrusions (extruder skipping) but i guess it could also affect y-axis movement.

- is the motor pulley screwed on tight and the grub screw facing the flat part of the motor shaft?

- with the printer powered off, does the bed move smoothly?
-- If not, how about when you unhook the belt?
--- If its now smooth with no belt attached, try turning the motor shaft by hand, any odd resistances there? (the humming bit you mentioned is intriguing). Also check idler turns freely and if belts are rubbing against the idler (check for black rubber particles around the idler)

Re: Y-axis starts sliding backwards on larger prints

I tried some of your check list items and ended up tightening the y-axis belt which had, apparently, become slack.
First print went without problem (one of the prints from the photos in the first post).

Is it common for the drive belts to become slack over time?