What IS this? It's ruining all my otherwise perfect prints
 
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devilhunter
(@devilhunter)
Reputable Member
What IS this? It's ruining all my otherwise perfect prints

What is causing this problem with slight overhangs? And only randomly?

https://imgur.com/a/GSBUT

This started popping up one day, i can't figure out what's causing this, and i've spent MONTHS trying to get rid of it

PLA has this problem a lot more than PETG

Printer:

Prusa i3 MK2s with e3d Titan upgrade, also a stock Prusa i3 MK2 (no upgrades)

custom filament fan that blows so hard (and loud) that most things lift off the bed when printing without a brim (even petg and pressed down really hard) from 3 sides, front, left and right. also tried with stock fan and shroud (blows only from the front, same problem)

205/60 for PLA, 220/65 for PETG

printing with near stock Prusa settings at 20 micron or 15 micron

calibrated extruder to the mm

using latest slic3r Prusa Edition

I've tried:

lowering the head temp in 10 degree steps all the way down to 170 for PLA, did not fix

slowing down print speed to 5mm/s steps down to 10mm/s, did not fix

lowering extruded material down to 0.8 in 0.05 steps, did not fix

using a different material: black PLA is ok, white PLA prints look totally broken, black PETG has it slightly (about half that of black PLA)

tried Cura, stock Slic3r, and Slic3r Prusa Edition, Simplify3D all have this problem.

combination of all the above - did not fix!

using 'Seam position' random halves the damaged areas of the print instead of my 'aligned' that i usually use, but all prints look like crap then (zits everywhere)

Based on looking at the last bullet point there, is this caused by excess material on the Z seam? But Simplify3D's 'reduce material flow at Z-seam' didn't help

Posted : 22/10/2017 9:14 pm
AJS
 AJS
(@ajs)
Noble Member
Re: What IS this? It's ruining all my otherwise perfect prints

Does this happen in any specific direction from fan that blows just below the nozzle? (e.g. more pronounced to back?) Alternate fan duct designs that blow from both sides may help.

Might your custom fan be too powerful? Cooling the filament too fast?

Are you doing "External perimeters first"? (I do not, and that could be having an effect.)

Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage or loss. If you solve your problem, please post the solution…

Posted : 23/10/2017 2:21 am
devilhunter
(@devilhunter)
Reputable Member
Topic starter answered:
Re: What IS this? It's ruining all my otherwise perfect prints

The side that is damaged is sporadic, sometimes it's the front, sometimes it's the sides, sometimes the back.

External perimeters first ain't working at all for overhangs, so it's always inner first.

I could try with lower fan settings, but for PLA in general is that, after the first layer nothing is too much.

Posted : 23/10/2017 9:28 am
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