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Dim3nsioneer

Strange under/overextrusion

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Hi there

This is a very strange one. I tried to print http://www.thingiverse.com/thing:14195 in Colorfabb signal red PLA/PHA. After having measured the filament diameter I-don't-know-how-many-times I set it to 2.85mm in Cura 13.12-test (worked nicely for other prints).

After a few prints with serious underextrusion I also managed to get some fairly reasonable settings (not fully convincing quality) such as 50mm/s at 220°C with more or less closed surfaces.

Then I scaled the model by 2 in z-direction, i.e. the thickness was set to 5mm from previous 2.5mm. I was actually baffled by the result.

Snowman Over-Extrusion

The print is 'normal' (which means about the same quality as the original 2.5mm print) up to 2.5mm. After that point, an enormous overextrusion happened.

I put this into the Cura section as I think it is rather a software than hardware issue (would be quite a coincidence if my Ultimaker decides at exact the original height to go crazy, wouldn't it?). However, it could also be the model itself. I just had a look into it and for me, it looks ok...

Any ideas?

 

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On some of my prints a few weeks ago, something similar was happening - I think Cura was pre-emptively raising the nozzle temp, in anticipation of the fan being turned on full blast (and thus cooling the nozzle somewhat).

Did you watch the nozzle temp when this happened? I bet the temp spiked and you started getting overextrusion.

 

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Must be your magic hands then... :wink:

I printed it again this morning. It came out ok (with the exception of the hole in the hat). So it was definitively something hardware-related. After having another look at the failed print, I think it might be caused by partial delamination as the print is significantly thinner at one end (and the material difference most probably distributed over the rest of the print).

 

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