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spooner777

Suddenly Underextrusion

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My printer used to run great for the last 2 years, but suddenly I get under extrusion in some areas.

At the moment I am printing a hollow dome with 0.4mm wall thickness. It started off great but then the material turned cloudy and shows signs of under extrusion.

Why would prints change half way through a print? Could something in the extruder have gotten loose or is there any wear? I´didnt print more than 2kg in the last 2 years. I am using the updated extruder.

I am using Faberdashery material and had no problems with it previously. The diameter is 2.77mm. I changed it down during the last print to 2.73mm to improve the extrusion.

 

 

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I've found that changing the filament size or flow to increase flow may actually CAUSE under-extrusion. I've had the exact same problem a few times, and what I 'think' is going on is that the extruder will gradually put more and more pressure on the filament slowly thoughout the print, at some point, either because the nozzle isn't hot enough or just too much plastic is being forced through the pressure becomes too great and then the extruder starts to grind the filament unable to push it at the pace that you want it at. Once it starts grinding, it looses more traction due to bits of chewed up plastic now stuck in the knerled bolt and it just goes downhill from there.

Check your bolt to see if there's plasticy bits in there, and if there's a big semi circle grounded down on your filament.

The other instance where that happened to me mid print where it was just gunk in the nozzle. Cleaned the nozzle, re-printed with the same settings and it was all good.

 

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I can´t check at the moment because it is printing the same part again and the change in texture happened at the same height again. So maybe its a Cura problem? Using 13.06.4. I just installed the update.

I also noticed that the print head does a weird stuttering motion every second layer. Maybe this is because the wall thickness is 0.8mm and the stuttering is there to connect the two layers together. This would explain the more rough surface...

 

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The stuttering seems to be from how the stl is saved. It can have some errors and it prints a bad texture pattern in these areas it also slows the printing.

Changing the stl options and tolerance has improved these issues for me.

The under extrusion has occurred for me due to the filament slipping from it being crushed in the extruder area. I found on constant parts similar to the one you have made setting the retraction to zero has a positive effect. Basically the filament moving back and fourth too much works flat and then it has difficulty moving forward.

Inspect the filament for wear areas or grooves. It is noticeable if this occurred. If so remove that peace start over set retraction below 2.5 mm. This has had positive effects in my prints.

Hope it helps.

Cheers

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My printer used to run great for the last 2 years, but suddenly I get under extrusion in some areas.

At the moment I am printing a hollow dome with 0.4mm wall thickness. It started off great but then the material turned cloudy and shows signs of under extrusion.

Why would prints change half way through a print? Could something in the extruder have gotten loose or is there any wear? I´didnt print more than 2kg in the last 2 years. I am using the updated extruder.

I am using Faberdashery material and had no problems with it previously. The diameter is 2.77mm. I changed it down during the last print to 2.73mm to improve the extrusion.

 

 

Make sure you clean out the extruder drive , and remove any damaged areas of filament. You might check whether the Delrin wheel that presses the filament onto the extruder is still in good shape, and able to rotate freely.

Finally, take a look at the gcode using something like Repetier Host, and see if something different is happening in the region that is causing problems.

 

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I opened the extruder and there are no shavings at all. Everything is clean, the filament is round and the delrin wheel too. I think it has to have something to do with the g-code. I am testing different settings now.

I noticed that on Cura, the colour of the wall changes from red to yellow at the height where the problems start. What could that be?

 

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I don't think this is underextrusion. It could be issues related to movement due to printing infill.

The walls may be .8mm thick in 3 dimensions but when you slice the walls, as they tilt more and more the thickness increases until the top is probably something like 6mm "thick" (meaning wall to wall distance of one of the slices a few below from the top).

So as they get thicker, suddenly infill is required.

So this is more of a model/slicing issue. I don't know what the solution is though. Maybe reduce infill overlap to 0% or even negative 10% (if it lets you do that). There are bugs with infill overlap where it does more than you want sometimes depending on certain angles.

 

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