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jcoutts

Consistent Layer Skip Problem

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Hi Guys,

So where I work we have 4 UM2's and one of the UM is having a consistent skip problem. It basicaly makes the parts unusable. Just wondering if anyone has had this issue and if so what have you done to fix it.

I have also emailed UM help, but have probably a week or two till they get back to me.

Thanks in advanced.

IMAG1088

 

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Is it always the same 2 heights? If so then I guess it must be a z axis issue with the screw or the base plate is hitting something and not moving far enough. But this all seems very unlikely.

Much more likely - I've seen this happen due to the filament getting tangled or even as you get near the end of a spool due to the tight radius of curvature causing problems in both the bowden tube and the white teflon isolator part just above the nozzle. Putting the filament on the floor sometimes helps this. I recommend for this printer only you print 30% slower and 10 or 20C hotter if you don't want to spend many hours diagnosing.

 

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Much more likely - I've seen this happen due to the filament getting tangled or even as you get near the end of a spool due to the tight radius of curvature causing problems in both the bowden tube and the white teflon isolator part just above the nozzle. Putting the filament on the floor sometimes helps this. I recommend for this printer only you print 30% slower and 10 or 20C hotter if you don't want to spend many hours diagnosing.

 

That would be my guess as well.

 

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I understand, but I have had around 6 prints fail in the exact same spot. Its more just the first spot where it skips. Also I know the spool issue, however the spools are quite new with only around 30% of the spool being used so far.

Its definitely an issue with the Z axis or the encoder, I just don't know if there is anything I can do to try and fix the issue

 

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If you put 3 parts side by side is it always the same height? If so then I agree it's the Z axis.

I would get pronterface and install it an connect the printer to a USB and command the bed up and down past that spot many times. Also power it off and pull it up and down past that spot. Make sure there isn't anything anywhere around the platform (in the back where it's hard to see?) that is rubbing against something stationary like the frame. Watch the bed carefully as it goes past that spot. Add a drop of grease (did you get a little green plastic "tube" with grease in it? It's for the Z axis). Or clean the Z screw with wd40 and paper towels and then put some fresh grease on it. Especially in the area that is inside the Z nut when it has that issue.

I really doubt it's the stepper motor - much more likely something mechanical. I suppose you could rotat the Z stepper by 90 degrees to see if the problem moves up or down a millimeter (remove the 4 screws, rotate, re-attach). But this is very unlikely. Plus the problem would repeat at every rotation - approx every 3mm? 6mm?

 

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