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Prusa MK3: reproducable Layer shifting  

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Friedrich Nietzsche
(@friedrich-nietzsche)
Active Member
Prusa MK3: reproducable Layer shifting

Hi guys,

since a week or two I am a proud owner Prusa i3 MK3. After assembling it I am in the state of tweaking the printing results. So far the results are already better than my Anet A8, which almost drove me into madness. But I still have the problem, that my printer has some kind of layer shifting in a constant height. It the shift appears suddenly and also vanishes after one or two millimeters. I've tried two benchies, one with and one withoud crash detection (which I read can cause layer shifting) but the shifts seem to appear always and always on the same height. Also the bottom right corner seems to be closer to the nozzle. While the printed filament looks good on the rest of the first layer, it looks to much squeezed, when the extruder prints in the bottom left area. If you need additional images, just say the word.

Thanks

Posted : 03/08/2018 4:51 pm
thrawn86
(@thrawn86)
Honorable Member
Re: Prusa MK3: reproducable Layer shifting

what are you belt tension readings? are all the grub screws on your drive gears tight?

it shifts in the same direction every time? i wonder if it shifts the same direction if you rotate the print 90 degrees.

Posted : 03/08/2018 10:38 pm
nathan0876
(@nathan0876)
Estimable Member
Re: Prusa MK3: reproducable Layer shifting

Good suggestion above, when i had that happen it was a belt tension issue. Was the Tension screw on the left motor on the left/right extruder axis working loose. And also had an issue with the grub screw coming loose from the bed axis.

Posted : 07/08/2018 6:22 pm
Friedrich Nietzsche
(@friedrich-nietzsche)
Active Member
Topic starter answered:
Re: Prusa MK3: reproducable Layer shifting

Hi guys,

sorry for the delay, had some busy days.

I printed now a new benchie 90° rotated. I had to slice it myself, since I did not know how to rotate the gcode of the demo file. The belt tension values according to the printer are around 261 for the x axis and 291 for the y axis. A bit on the higher side. Which is a bit weird, since it was ~220 for both axis, when I first discovered this option.

The new benchie turned out somewhat better, but also samewhat worse. The bow is worse, the layer shifting in the lower centimeter seems worse, but the layer shift in the upper part now is gone

Posted : 07/08/2018 7:44 pm
nathan0876
(@nathan0876)
Estimable Member
Re: Prusa MK3: reproducable Layer shifting

I would try and get that y axis belt tighter, aim for below 250. check the grub screw that was my issue with it.

Posted : 08/08/2018 5:10 pm
Friedrich Nietzsche
(@friedrich-nietzsche)
Active Member
Topic starter answered:
Re: Prusa MK3: reproducable Layer shifting

Hi Guys,

tensioning the y belt made a huge difference from the last to the current print (see attachments). Thank you very much already for that. But I still got this bumps in my print, although somewhat less obvious. And it is always at the same height. This may or may not have something to do with it but they also seem to have the more or less same distance (~12 mm) What could be causing this?

Posted : 11/08/2018 11:38 am
Friedrich Nietzsche
(@friedrich-nietzsche)
Active Member
Topic starter answered:
Re: Prusa MK3: reproducable Layer shifting

So no further ideas?

Posted : 15/08/2018 1:32 pm
darKing
(@darking)
Trusted Member
Re: Prusa MK3: reproducable Layer shifting

The Bump in your last pics is the same height as where the deck begins, right?

Posted : 15/08/2018 3:06 pm
Friedrich Nietzsche
(@friedrich-nietzsche)
Active Member
Topic starter answered:
Re: Prusa MK3: reproducable Layer shifting

Now that you say it: Yes Sir, that's correct. What does that mean?

Posted : 17/08/2018 3:50 pm
nathan0876
(@nathan0876)
Estimable Member
Re: Prusa MK3: reproducable Layer shifting


Now that you say it: Yes Sir, that's correct. What does that mean?

Not sure what it means but all my benchys also have that issue, not as pronounced as yours but they all have it to some extent, i always assumed it was an issue with the STL model itself.

Posted : 17/08/2018 5:43 pm
darKing
(@darking)
Trusted Member
Re: Prusa MK3: reproducable Layer shifting



Now that you say it: Yes Sir, that's correct. What does that mean?

Not sure what it means but all my benchys also have that issue, not as pronounced as yours but they all have it to some extent, i always assumed it was an issue with the STL model itself.

It's not a problem with the STL, more a problem of Layer cooling (shrinking). You can see it in almost every model, when some layers take diffent time to print than others. It's pronounced differently depeding on speed, temp, cooling, material etc. .

What I actually wanted to point out is, it's not a layer shift / it's a different issue than the one in your first post @reinhard.s6

Posted : 20/08/2018 12:21 pm
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