Printcore not extruding evenly on Ultimaker 3

[sashatinelli 0]

Hi all! 

Our lab uses an Ultimaker 3. We only print out of printcore 2 as printcore 1 is damaged. We are currently seeing an inconsistency in material extrusion (we have changed the material a few times and are seeing the same issue), causing weak prints which break at layers where the material was not properly extruded (see images below).  I suspect it may be a heating issue/ the core is not heating consistently during the printing process. 

The settings for the print below were: dense, fast (0.15) using Ultimaker White PLA. Print temperature was 205C and build plate temperature was 60C. 

Any ideas of how to fix this?

Thanks! 

[gr5 2,210]

This is underextrusion.  It has many many possible causes.  The most common is printing too cold and/or too fast. 

 

1) Are you using default profile settings?  Have you changed any of the temperatures or speeds?

 

2) If not I'd do a cold pull of the nozzle of core 2.  Especially if this is a BB core.  For a BB core do some hot and cold pulls as described in the maintenance menu.  It will help you with the procedure.  The purpose for all of this is that plastic can caramelize in the thinnest part of the nozzle (the last few mm above the tip) and make the diameter of say a 0.4mm nozzle become a 0.3mm nozzle which increases friction and causes underextrusion.

 

2b) Another thing to try is to put a different core in slot 2.  Your printer should have come with two AA 0.4 and one BB 0.4 cores.  It's okay to use BB 0.4 cores with PLA.  Just slice for AA 0.4 and when you go to print it will complain that you have a different core and hit "ignore".

 

3) Feeder.  I'd test the feeder.  Pull the filament out of the print core so you can see it in the bowden.  Then go to "move material" (it's in the menus on the printer front - look around - maybe it's called "move" but make sure for second core).  No need to wait for it to heat up.  Turn the dial and the feeder moves the filament.  Now while doing that, fight the material below the feeder: pull down hard with one hand while spinning the knob to move the material with the other.  You shouldn't be able to stop the pull.  Unless you are very strong.  Typically the feeder pulls with about 7kg or 15 pounds force.  Anything over 9 pounds pulling force I consider "working fine".  If you have lead weights you could old around 10 pound weight (or 7 or 8 pounds) and sort of grip the weight against the filament and then try not to add any more force up or down.

 

Many issues are on the feeder end.  Many issues are on the hot end.  It's good to at least winnow the possibilities.