Overhang warping upwards only on the backside of the print  

RE: Overhang warping upwards only on the backside of the print

The fact that it's directional tends to argue that it's cooling related - the part fan blows from the side and can adequately cool the half that it faces, but cannot hit the back side for the same. Two things come to mind: One, for this part, is cutting it in half and then glue it together an option? And two, if this isn't an option, perhaps slowing down your speed will allow the layer to cool more before the next layer is put down. It appears this is a smaller part, so layer time is small. Also for this second option, setting your fan speed to 100% might not be a bad idea.

RE: Overhang warping upwards only on the backside of the print

Prusa Slicer nowadays has dynamic speed settings for different grades of overhangs. That comes in very handy if you do not want exploding printing times but slow down only where it is necessary. 

In general, like ArtisanByte wrote, this looks like a part cooling limitation. If you can, increase fan speed to 100% and print slower, much slower if needed. But with the conditional overhang setting you can limit the snail speed to the critical overhangs. 

You can also try to simply print several copies of the same part, that also improves overhang performance, especially on small parts with short layer times. 

RE: Overhang warping upwards only on the backside of the print

Hi, thanks for your insight. Cooling indeed sounds like the root cause. But actually, as the fan blows from the left side, I would expect the warping on the right side of the model - that's not what happens, warped is the back side. The model I posted here it's hollow inside and the front rims are also warped from the backside, just not visible as it's inside.

I had a theory the fan output is able to cool down most of the model as it moves but doesn't spend enough time on the back side. As the warping with negative angles happens everywhere, obviously that's not the case.

Thanks for the tip for printing more models at once, I was trying to avoid that to reduce stringing, but it could be a good option, will test it.
Also the manual override for fan and print speed seem to be promising, in theory I can add a modificator just for some layers and backside of the model. 🙄 

I will do some experiments and let you know.

RE: Overhang warping upwards only on the backside of the print

Hi, sometimes it can also help to increase the width of the outer perimeters from default value 0,45 mm to 0,6 mm for best overlaping.

RE: Overhang warping upwards only on the backside of the print

Hi again, so I did some testing and it's starting to frustrate me. A lot.

So,this is the model I am trying to print. It's not an easy shape, but reviews doesn't seem to complain about the quality.

Previous print was from the provided Gcode (without input shaper) and the results can be seen in the first post, back side was warped in negative angles.

Now I tried to change setting for the model by myself:

• Input shaper
• external perimeter width from 0.45 to 0.6
• external perimeter speed from 170mm/s to 140mm/s
• fan speed checked, it was always 100%
• enclosure kept open

Sadly, it's even worse now, and not just one side, but everywhere :'( I will try to play with the settings more, but comments would be awesome!

RE: Overhang warping upwards only on the backside of the print

Your printing your external perimeters way too fast for such a demanding shape. Set external perimeter to eg 60mm/sec and see if that resolves the issue. If not also reduce the speed of all other perimeters. In case it resolves the issues, you could try going faster again.