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BillieRuben

Settings Based Periodic Under-Extrusion

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I'm struggling with some settings-based periodic under extrusion. I think it started when I upgraded to 3.6. 

Here is an album of annotated images, describing the issue; 

https://imgur.com/a/XKnfrMR

 

Some notes on the issue: 

  • Doesn't happen on brims or skirts, or bridges. Seems to happen on walls, and fill. Which leads me to believe that it's not mechanical, it's settings-based. 

  • Happens regardless of machine. These were on both my CR10s5 and Wanhao Duplicator i3 Mini.

  • Happens on different filaments (including ones I've used to great success previously)

  • Happens regardless of retractions in the area.

  • Happens relatively consistently between layers.

 

Anyone got any ideas as to what I might be doing wrong?

 

 

 

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It looks like the problem is only on the bottom layer.  The bottom layer is extremely sensitive to "leveling" or how close the nozzle is to the bed when printing the bottom layer.

 

It looks to me like your extruder is slipping occasionally and that is probably because you are just a little too close to the bed.  Or maybe your extruder is a bit weak.  Or the teeth in the extruder are a bit weak and the filament slips backwards occasionally.  

 

As a test, hold the filament while it is printing the bottom layer and feel for it moving backwards suddenly followed by these underextrusion spots on the bottom layer.  The fix might be to level about 0.05mm farther from the bed.  yes, one half of one tenth of one mm.  0.05mm.  That might be enough.

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Thanks so much for the reply! 

 

Unfortunately it's not only the first layer. It's all the way through. The last two images are the topmost layer. And watching it print, I can see this issue occuring on every layer right the way through, in the same places on each layer. Note the artifact appears in the layers on the closest corner in images 3&4. 

 

It's definitely not a leveling issue, when I live level the whole bed with a huge brim on a cube it doesn't appear. It doesn't appear on any brims, actually, no matter how wide. Or bridges. Only fill and perimeters. I know leveling can cause a similar effect, but if you zoom in on image 1 you can see it's not squishing the filament, it's simply not extruding it. This is evidenced in the little drippy line that appears instead of a smudgy one from a too-close bed. 

 

And yea, it happens on every layer, so not leveling I'm afraid. :( 

 

The extruder gears seem in good repair on both of the machines I'm working on.

 

:(

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15 minutes ago, BillieRuben said:

It looks like I'm not the only one experiencing this issue since updating to Cura 3.6, here's another user on Reddit:

 

 

Yep, that'd be me. I was right next to the printer when it started doing this unusual underextrusion pattern, and I do not believe my printer is at fault for a few key reasons.

  • The filament can't slip as I bought a bondtech extruder a few months ago, which has completely erased any issues related to filament grinding and slipping for me
  • When I was observing the several layers that started with underextrusion (with some overextrusion around the rest of that perimeter) I heard no clicking from the stepper, so it wasn't missing steps or anything.
  • I only saw underextrusion like this when I upgraded to Cura 3.6.0 last night. I was using 3.5.1 before that.
  • These lines are clustered together in the exact same spot, and are too consistent for me to consider it random underextrusion.

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