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Feeder/Stepper Motor skipping regardless of tension UM2

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Posted · Feeder/Stepper Motor skipping regardless of tension UM2

Well first post on the forums and sadly a support need.

Seems to be a common problem but being less than 2 weeks old and well under a Robbosavvy warranty I don't really want to take my UM2 apart.

Video says it all....

Video shows me manually feeding material and it flows fine out when it does get picked up (this is supplied UM2 silve PLA).

Basically the feeder/stepper is skipping regardless of min or max tension. No problems at all until last night when it failed to print (possibly a clog) and chewed the bejesus out of the PLA at the feeder.

I ran a 260c print for 10 mins, blew out the feeder and the nozzle is clear of black gunk. Seemed to be doing it on slower detailed prints at first but now it does it on manual feeding.

Assume it is slipping on the spline but how easy a fix is that?

All help most welcome.


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Posted · Feeder/Stepper Motor skipping regardless of tension UM2

Tension doesn't do much to skipping - it can increase or decrease grinding though. But that's probably not your problem. Let's get back to "skipping".

If the skipping is happening on the bottom layer you are probably just leveled a bit too close (nozzle too close to glass). But that doesn't affect other layers. If you are skipping on other layers you may be either printing too cold, too fast, or your printer is defective. Here are suggested max printing speeds for .2mm layers (note for .1mm layers you can print twice as fast and so on linearly):

20mm/sec at 200C

30mm/sec at 210C

40mm/sec at 225C

50mm/sec at 240C

Printing at 260C is dangerous for 2 reasons. You can turn your PLA into a caramelized gunk that clogs nozzle (best to get it out with the atomic method) and also the white teflon isolator's life wears out faster at temperatures over 240C. So for PLA I would stick to 240C as the max temp and never leave it at 240C without it printing as after a few minutes the PLA turns to brown nozzle-cloggin gunk.


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Posted · Feeder/Stepper Motor skipping regardless of tension UM2

I'm assuming that you are using "move material" here. You really giving it a proper shove inside the head. The motor skips because there is just too much "pressure" at the hotend.

When I use "move material" I generally give it 3-4 clicks at the time and then wait few seconds and then another 3-4 clicks... etc... If I do more more the extruder will shred the filament. Even at this "3 clicks/wait/3 clicks/wait speed" the flow out from the head is nice and constant.

Try to feed the cord in to the printhead manually and you will get sort of a feeling how little pressure is actually needed for nice flow.


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