[PICTURES] Occasionally underextrude on external Perimeter and infill ?

Hello. Since a few days I get these ugly underextrudes. I tried several filament lots (three different filaments, all PLA) and every axis/extruder is calibrated very well.
It used to print without this flaw but suddenlty decided to go down south. I went through the pictorial guide and I think that "Infill gaps to perimeter" might be closest to my problem. BUT the spool holder didn't change as of when the issue started so the spool reel might not be the problem as stated in the guide.

Perimeter shot:


On top infill you can see that in some regions there is too few filament extruded but as I said it is perfectly calibrated.



Any ideas?

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Blog: Capotexl
Filament Factory - How to build your own cheap filament extruder
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I am having the exact same issue. Started randomly and every print on every filament I have comes out like this.

Check that your filament isn't slipping in the extruder; this could cause the printer to put out less plastic than it should.

I have disassembled the whole extruder (gears, hobbed bolt) and reassembled everything again. The hobs on the bolt where veeeery slightly off center before but this worked for the last 1 year without flaws. I put another spacer between the big gear (herringbone gear; wade extruder) and now the hobs are perfeclty center. I also disassembled the complete X axis and reassembled it. Tightened the belts. Same thing with the Y axis belt holder under the heated bed.

After calibrating every axis and stepper on the printer a first print of a 2x2x2 hollowed box with single perimeter and 1 bottom layer turned out nice.

Edited 1 time(s). Last edit at 09/13/2015 06:52AM by ianmcmill.

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Blog: Capotexl
Filament Factory - How to build your own cheap filament extruder
Frankenstein Laser Engraver
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I noticed over the years that PLA loves to turn to dust on the bolt.
Too little pressure and the filament can slip, too much pressure and and you either get PLA chips or a badly worn filament side that can get stuck.
Still experimenting with the perfect bolt...
So far I settled for 8mm with a clean shaft and use a 4mm tap for the "hobbing".
Changing from standard crap bolts to high tensile and hardening them when done seems to help quite a bit.
The grooves are much cleaner and there no build up of dust during normal operation.
Whenever I get such weird underextrusion problems I dismantle the gear to clean the bolt and in most cases also clean the hotend.
Normal cleaning every 2 or three rolls, additional cleaning if I change filaments a lot, just to prevent problems down the road.

All above mentioned measures did not solve the issue. I still get those underextrusions.

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Blog: Capotexl
Filament Factory - How to build your own cheap filament extruder
Frankenstein Laser Engraver
Make the world a better place

Okay so I hope my joy is not hasty but the underextrusion is gone and the layers print fine again.

Here is what I did:

I tried several hobbed bolts. There was no improvement. One even chipped the filament. So I went back to my first hobbed bolt and there ya go. It works again.

So what do we learn from this? If something does not work out in the first place, repeat until it works.
Do the same thing again and again and expect another outcome. Do I sound insane? Am I insane?
No you are not!
Oh glad to hear that bro.

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Blog: Capotexl
Filament Factory - How to build your own cheap filament extruder
Frankenstein Laser Engraver
Make the world a better place