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Extrusion rate way off.

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Good morning,


I’m on the latest firmware on my UM3. 

I have noticed that my prints aren’t coming out right. Basically it’s suffering underextrusion. I tested with current beta, 3.3.1 and 3.2 cura.  All do the same where I have gaps between the lines.  I bumped up the flow to 150% and that’s fine

110% 120% failed.


i am trying to roll back the firmware but can’t find the files I need.


please help.


rebekah Anderson 

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nope but I am struggling to suggest otherwise. 

I have tried previous versions of cura and it's the same.  My UM2+ prints fine though. 


do you know where I can get the previous version of the firme ware from so I can test it out.






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hooray for the public knowledge! Here is a post from a little while ago where some asks the same thing, with a link to older firmware versions: 

Is the one you need among these?

Are you sure it is firmware related? Did you make a print prior to the update which was fine, and after the update it started to under extrude?

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Well this is what I have.


left it at 150% flow and right is 130% 

line width is set at 0.38


I tried it with cura 3.2 and no different.


i am using bond tech upgrade but there was no difference between um 369.0 steps per mm and 492.45 steps per mm. Which I found odd any aswell. 


Im pretty sure that it should be different when making this change but I am lost on this one. 


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Ok, ignore me. it's something to do with the printcore.  I changed it and it's working well now. although I haven't upgraded the firmware again.

don't understand what is wrong with the print core though.  I cleaned it good and proper. so there shouldn't be anything wrong with it.  having said that I have had issues with that core in the past. 

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That core was only PLA. 

Not sure how many hours but a fair few.


the other core which came with the printer has had all sorts and always worked fine so I don’t understand why the other one is being like it is.  I cleaned it out perfectly too. The only thing I can think of is that the nozzle isn’t 0.4mm. Will set up a print with 0.25 setup. 

As long as it slices based on line width. 🤪


Need to to replace it though but need to wait for some cash to come in. 


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Besides a nozzle size problem it could also be a temperature problem. Check the PT100 temperature sensor in the print core. Is it pushed in far enough? Is it making good thermal contact (check how tight the nut is tightened). Perhaps other people have more tips for checking?

  • Thanks 1

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