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Posted · Print with 0.8 Nozzle

I tried to print a plate upward with 0.8 Nozzle. It seems to have over extrusion and beginning and at end , but the middle of the line looks perfect .

This was done on Ultimaker 5 PLA material. Any suggestions on how to fix it ?


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    Posted · Print with 0.8 Nozzle

    1) Of course it will look better if you print flat.  Which way are you going to pull it apart?


    PLA acts like a liquid rubber band as it comes out of the nozzle - it shrinks very rapidly as it cools - in mere milliseconds and it also sticks to itself like snot.  So it's coming out like an already-stretched rubber band pulling with some force between the nozzle and where it last attached well to the print.  So when it gets to the ends it is being pulled inward (before it becomes solid) so your print gets narrower as you go up.  Also because you have too much PLA to fit in the planned volume (which is smaller now that it is stretched inwards) you also get some sideways overextrusion on the ends.


    2) One fix is more cooling - make sure you fans are at 100% but I'm 90% sure your fans are already there. 

    3) You can get more cooling by doing thinner layers or printing a bigger part or:

    4) by printing 2 or even 5 objects


    such that each layer has more time to cool before the next layer is placed down.  But that might invalidate your experiment?  Or maybe your experiment is invalid because people would be printing larger parts normally?  And larger parts would have more time to cool down before the next layer is applied.


    5) It might also help to slow things down.  Try printing at say 35mm/sec or 20mm/sec.  ALL printing speeds.  I hate that most cura profiles have different speeds for infill and wall, etc.  Your part is all one type of infill (not sure which type?  shell?) so there's really only one speed I suspect


    6) Unrelated to cooling - by default the printer has very low values for acceleration and jerk.  This makes the nozzle pause much longer at the ends than the middle - visually it seems very fast but if you timed it and watched it in slow motion you would realize it's just hanging out on the corners "like forever".  You can reduce this a lot by unchecking "acceleration control" and "jerk control".  It will also print faster.  This will reduce the overextrusion on the two ends of travel.


    The other bumps in the middle of the wall - I never really understand what causes those as there are so many causes but almost all causes of bumps are fixed by printing slower.

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    Posted · Print with 0.8 Nozzle

    Thank you for the comment gr5 that helped a lot.
    1) The test is also done in the build direction , the layers are pulled apart.

    I will try to program the nozzle to keep going without extrusion an extra distance forward in gcode.

    2)Fans are on 100%

    3) 4) I will print slower and maybe make pauses between layers or print two parts at the same time .


    5) i will run it at 10mm and maybe try with thermal camera to see differences .

    6)That is a great tip , i will disable that , slice again and check changes in the gcode.


    Thank you for the very helpful tips.

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    Posted · Print with 0.8 Nozzle
    4 hours ago, RamiR9 said:

    try with thermal camera to see differences .

    Yes!  Any opportunity to do some serious measurements is a good thing!  🥰


    Keep in mind that PLA is solid below 52C and around 52C it becomes like clay (aka plasticine).  


    Also 3d printed parts are a bit weaker in this "vertical" direction and my suggestions 1-4 will potentially make a large difference in strength.  Anything that makes it print better at the ends has the potential to also make the part weaker (not as good layer adhesion).


    PLA softens at such a low temperature that it tends to be almost as strong vertically as horizontally but when you switch to higher temp materials like Nylon or ABS you get much weaker layer adhesion unless you do the opposite: turn fans off or very low, don't print 2 at a time, raise air temp by covering the machine.  There is a CNC kitchen video (search for that on youtube) about this subject - adhesion layer strength - how to improve it.

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    Posted · Print with 0.8 Nozzle

    For example check out this graph at 6:02 into this video (link should jump you to 6:02)



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