Help with "semicircular shape" from the printing bed upwards  

RE: Help with "semicircular shape" from the printing bed upwards

Hi Martin,

the transition between horizontal 0 degrees and vertical 90 degrees is a gentle curve on your model, and there is no support for any elements between 0 degrees and say 40 degrees. so the ends of the unsupported filament droop
there are ways to counter this to one degree or another. 
first option it to turn on supports, but this may not give a lot of support to the lower curve and may insist on supporting the inside of the hole. , you may need to add  and 'Expert' option 
'Enforce support for the first '15 layers   (15 is a guess  at 0.2mm layer height this will force support for 3mm)
and you may choose to tick    'Support no Build plate only'  to prevent the support of the top of the hole. 
this may well help you, however supports themselves can cause poor finish on curved overhangs. 
reducing the filament extrusion temperature (a little) will reduce the tendancy to sag on over hangs, at the possible expense of inter layer bond strength,
reducing the Z contact distance can reduce the distance the filament has in which to sag, at the expense of ease of support removal.
changing the model so that the initial geometry is a 45 degree slope merging into a curve will negate the need for support, at the expense of aesthetics... 
thinner layer height may also help resolve the curve quality
I hope this helps,
regards Joan

 Have you seen the Prusa Slicer user guide?  (Please be aware this covers items that are available in version 2.3.0 Alpha3) 
https://help.prusa3d.com/en/category/prusaslicer_204

RE: Help with "semicircular shape" from the printing bed upwards

As Joan suggested, supports help. Another possibility, if you can modify model, is to cheat around it and not use round surfaces from the bottom. Round surface creates steep overhang, and filament has very hard time to attach to previous layer. If you can chop the curve a little bit and create chamfered surface there at least until the point it can continue with round edge. It will look weird, but will help a lot with printing and if it's functional object, it may not even bother anyone.  In general printers can handle 45 degrees without problems, MINI should be able to handle even 55 degrees from Y. 

As for top layers, you can utilize variable layer height feature in Prusa Slicer.

Here's good video demonstrating the problem:

RE: Help with "semicircular shape" from the printing bed upwards

All the stuff that Joan and Crawlerin said plus sometimes it's possible to reorient the part to get around the problem. In this case, if the inside surfaces are not important, perhaps one of the sides with the curves on the bed. That will give fair sides on the outside and nice curves. Worth a try?

RE: Help with "semicircular shape" from the printing bed upwards

This is a common problem and unfortunately often overlooked when parts are being designed for 3D-printing.
A lot of the models you'll find on .stl archives such as thingiverse or even here at prusaprinters fail in the 3Dprinter-friendly category.

When creating parts like this for 3D printing, it's better to make the ends hexagonal shape rather than round, unless doing so hinders the functionality of the end part.

If you absolutely have to have rounded edges - use support.