underextrusion

[pringpring 0]

Hello guys, before i get lost looking for answers, just need to confirm first that this is an underextrusion proiblem right? thanks!

(and also any links to fix so. it seems to be getting gaps at some point in the whole print like 30% and 60%.)

 

 

[gr5 2,224]

Yes. Severe underextrusion. What print speed, temperature and layer height are you using (these are the 3 variables that affect underextrusion - knowing only 2 of them is useless). Here's a chart with suggested print speeds - use half the value of the blue line in the chart for a given temperature (the blue line is absolute maximum):

http://umforum.ultimaker.com/index.php?/topic/4127-um2-extrusion-rates-revisited/

 

[gr5 2,224]

Do you have a UMO or a UM2? Please update your profile to indicate which printer you have.

 

[pringpring 0]

hi gr5, thanks for the reply. im using cura and my print speed is 30mm/s, temp is 210, and layer height is 0.2. hope this helps

 

[x3nomorph 0]

Hello, can someone please tell me what to do if only one part of the model is underextruded??

On this 3 pictures you can see the problem:

https://www.dropbox.com/s/tl53cj0hayn8f5o/DSCN1068%20%28Large%29.JPG?dl=0

https://www.dropbox.com/s/l7ggkl8e0vbeh4o/DSCN1069%20%28Large%29.JPG?dl=0

https://www.dropbox.com/s/qqvaklzy97ghoao/DSCN1070%20%28Large%29.JPG?dl=0

On the fourth picture can you see strings which the printer leaves after repositioning.... shouldnt be there (ok its not a big problem to remove them).

https://www.dropbox.com/s/0vbg3oi7o990gi0/DSCN1074%20%28Large%29.JPG?dl=0

Would zhop help?

in cura i set the print speed at 80mm/s what was too fast when i started to print. On the "tune" options i lowered the speed to 35% whats about 25mm/s, LH is 0.25mm, normal nozzel 0.4, i tuned the temp to 230° (i tried it lower but the model isnt big and any speed is "fast" for the tiny walls).

Thanks in advance

Edit: PS: At the underextrudion point starts the printer the new layer.

 

[Stavros 1]

Yes.  Severe underextrusion.  What print speed, temperature and layer height are you using (these are the 3 variables that affect underextrusion - knowing only 2 of them is useless).  Here's a chart with suggested print speeds - use half the value of the blue line in the chart for a given temperature (the blue line is absolute maximum):

http://umforum.ultimaker.com/index.php?/topic/4127-um2-extrusion-rates-revisited/

 

Is this the same for a UMO?

[gr5 2,224]

Yes. UMO and UM2 and UM2+ can each put out about 10 pounds or 5kg of force max. but the symptoms are different on the UM2 (plain). On the UM2 it sometimes skips back. On the "plus" and UMO it doesn't skip back but the filament underextrudes. Typically by a small amount at first - say 10%. You can see it as gaps between infill when you have solid infill. but as you go faster and faster you might have only 50% extrusion from what you requested. If you use reading glasses you can see the difference in the length of the marks on the filament - they get longer and longer until they touch each other and it fails completely and you get filament dust at the feeder and zero extrusion out the nozzle.

With the UMO most people don't notice 10% underextrusion so much so they pushed their machine beyond what it can do and it was no big deal. but with the UM2 and the "skip backs" it's much more obvious.

[Stavros 1]

I made this guide for myself. I'm not sure if my units are correct, but if they are would you be so kind as to put it somewhere where other people who might need it can go. Thanks.

[gr5 2,224]

You need to specify cubic, not squared. So multiply by the print speed as well to get volume. 8mm^3/sec and 230C is where UM2's are tested but you are really pushing it there. UMO can do that just fine also. Here's a speed guide table for both UMO and UM2.

Here are my recommended top speeds for .2mm layers (twice as fast for .1mm layers) and .4mm nozzle:

20mm/sec at 200C

30mm/sec at 210C

40mm/sec at 225C

50mm/sec at 240C

The printer can do double these speeds but with huge difficulty and usually with a loss in part quality due to underextrusion. Different colors print best at quite different temperatures and due to imperfect temp sensors, some printers print 10C cool so use these values as an initial starting guideline and if you are still underextruding try raising the temp. But don't go over 240C with PLA.

Now if you want high quality looking parts you want to keep speeds in the 20mm/sec (super high quality) to 35mm/sec (excellent quality) range regardless of layer height because faster than this causes ugly overextruded blobs here and there. These slow speeds keep the nozzle speed constant and the nozzle pressure constant (or close to it) which makes for a nice uniform extrusion.