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UM2 stops printing outer shell


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Posted · UM2 stops printing outer shell

Hello everybody,

After printing several batch prints, my UM2 printer starts to print weird.

I'm trying to print 4 small hooks so you can hang frames to a wall.

The first one is printed normally, but the second one misses the outer shell.

The third and fourth one are completely messed up.





How can this happen?

My Cura settings:

Layer height: 0.1 mm

Shell thickness: 0.8 mm

Bottom / Top thickness: 0.6 mm

Fill Density: 80%

Print speed: 30 mm/s

Initial layer thickness: 0.3 mm

Initial layer line width: 100%

Travel speed: 150 mm/s

Bottom layer speed: 20 mm/s

All the other speeds: 0 mm/s

Thank you for your help

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    Posted · UM2 stops printing outer shell

    This is underextrusion.  Severe underextrusion - it's printing with only about half the desired material.  I'm not sure what is causing it and why it shows up late in your prints.  This is a bit unusual.

    Here are some theories that might explain what you see - from most likely to least likely - I'm sure you can quickly eliminate some of these.

    1) Feeder stepper motor driver is overheating and turning on and off frequently.  Are you printing in a hot room?  Consider removing the larger bottom cover (just 1 or 2 screws), putting the printer on it's side (it prints fine that way) and having a desk fan cool the board - just as an experiment).

    2) Feeder motor is getting hot and losing power

    3) Temperature is dropping - something wrong with the temp sensor - this is actually kind of common - you can get a partial open circuit in the temp probe and it ends up reading high so that printer sends less heat to the nozzle.

    4) outer shell speed is a bit too fast - I know you say 30mm/sec which is fine but could that be overridden by advanced settings?  Does it appear to print much faster on the shell than infill?

    5) knurled sleeve on motor is slipping but only when motor gets hot (try tightening the tiny set screw).

    6) feeder motor gets so hot that the PLA is compressed and squeezed too much and then later gets stuck in the bowden.

    7) too many retractions is squeezing the filament too flat and gets stuck in the bowden (look at the filament inside the bowden - is it squished flat on one side?)

    I'm sure I can come up with more theories - check these first.

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    Posted · UM2 stops printing outer shell

    Check the third fan, the one at the back of the print head. Is it running? It should either run all the time or when your print head reaches 40+C depending on how old your machine is.

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