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Underextrution due low temp

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Over time we have some problems with underextrution printing PLA.

When UM2 was new it printed fine with default PLA settings with 220 degree.

To fix this we went up to 230 degree and this fixed it for a while(weeks)

Time goes, and went up to 240.

Now it started to happen again and went up to 245 with good results.

Printing only PLA and same color (orange and blue) from UM store.

Could it be the temperature sensor that is messing up?

Seems that the feedback could be wrong?


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I dont think its the sensor..

The feeder mechanism is slowly breaking to pieces inside for many users... :sad:

Also the teflon tube is slowly deforming in the hotend with use.

If users dont notice there print quality slowly worsening.. they probably will in the near future.

This is a problem that ultimaker is quietly... very busy trying to solve at the moment.... because it is very important for both their reputation and our customer satisfaction.



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Also as you use up the filament the curvature is stronger as you get towards the center of the spool. The stronger curvature can be very significant in the resistance both in the clear bowden tube and also the white teflon seperator (you can see part of the white piece touching the spring in the head).

Also small black pieces of ABS plastic gets ground off the black feeder on the back of the machine and these tiny pieces of plastic can get stuck in the inside of the nozzle.

If the ABS is the only problem the fix should be to remove the nozzle and melt/burn out any plastic then soak in acetone (which dissolves ABS but not PLA).


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I have now disassemble the hotend and done the procedure to get out debris several times from it and put in a new homemade machined teflon tube after the drawings from Ultimaker, and still have problems.

A little debris was found:


I can see the feeder struggle to put more force to push out filament as it is jumping when loading new material. It is not spinning on the filament, but kind of rewinds it.

I also see that the curvature of filament is making more resistance feeding.

My understanding is that there is still something going on in the hot end.

When I had it disassembled and stuck the filament directly into the nozzle through the new teflon insolator it was flowing fine with temperature an 220 degrees.


Right now we are at a point where we can't use the printer :/


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Next likely suspect for your problem: Feeder.

It's important to feed the filament straight into the feeder so a very easy thing to do is put the spool of filament on the floor behind the feeder. This can help quite a bit:

spool On floor


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Also you might want to try an alternate feeder. I think Robert's seems pretty good:


Ian's design is secret for now.

Geek's design for UM2 feeder:


Robert's design is here:


Post #402. Read Robert's post #409 below that one for more details on assembly and such.

Ultimaker's design is in these two posts

Post #279:


post #268


I think this second post is more useful. Anyway, contact Bas for a free metal grommet.

Takei Naodar's design won't fit on the back of the UM2 so you need to also print his very clever spool holder:




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I have read about this feeder in the hack thread, so I'm trying to print iRobertl's version right now with a new roll with less curvature. We also have a ticking bomb with the "error - stopped temp sensor bed fault"

On that issue we did the resolder and checked cable, but still the same.


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We cant print because of the temp sensor fault every print. If I push the connector on the sensor cable side it will fail, so doing the resolder again. Measured the TP100 element(?) and there was 0,16 ohm or something.

It should have been about 100ohm at 23-25 degrees C?

What type of sensor is it exactly?


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