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Diagnosing Ultimaker 2 - Wrong Nozzle Size?

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I have inherited an ultimaker 2 extended.


I don't know what nozzle diameter it has, the picture below was using cura recommended settings with a 0.4mm nozzle. About halfway through the print, I increased the material flow and things started to improve a little. Would the wrong nozzle dia cause prints like this?


Any hints or suggestions would be much appreciated.







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The UM2 without an Olsson block has a 0.4 nozzle which cannot be changed. Some users have upgraded the UM2 with Olsson block, and then you are able to change the nozzle. On the changeable nozzles, you find the number 40 and points which indicates the nozzle size.


I guess your nozzle is clogged or you have to replace the PTFE coupler (the white part between Bowden tube and nozzle). Check the UM website how to do hot/cold pulls to clean the nozzle and try it again with Cura default settings.


But under extrusion (this is your problem) can be caused by several other things too. (Temperature, printing too fast, feeder problem)

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1 hour ago, Perchik said:

Can a mismatch between nozzle size in cura and on the machine lead to under (or over) extrusion?

Could be yes, but only when 0.25 is configured, all other nozzle sizes would produce over extrusion. (or a clogged nozzle)


A clean nozzle is a good start point, then make a new test print. Look for the calibration cube, which prints faster than the benchy and should give us a good view of what happened. Use the default Cura profile 0.2 layer height and check the line width if it is 0.4.

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If you would like to use a more gentle atomic pull, you could try my method here (scroll down a bit):



It lets the nozzle cool down much further than usual, and uses gentle wiggling and turning instead of brutally pulling. This avoids the risk of displacing the teflon coupler or nozzle, or bending rods.


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