So did you screw right into the holes or did you have to tap them first? I'm only asking because I've had mixed success in regards to screwing into pla without it splitting.... seems to depend upon the model greatly.
No need to drill/tap this model because the screw hole sizes are
exactly the right size . . . at least for my printer and slicer settings.
- The machine screw holes (outer columns) just barely brush against the threads.
- The PCB screw holes (inner columns, top) even survived a test using a #6 sheet metal screw instead of a #4 -- the hole stretched, but did not crack.
- The PCB bottom screw hole (center through-hole, bottom) is slightly larger than the PCB screw holes to prevent the cracking that PBJ noticed in one of the v0.02 prints.
If you print the part and have problems with cracking:
- Change the related screw hole size variable(s) in lines 37-39 of the SCAD file
- Preview
- Render
- Output a custom STL
The consideration that some part designers overlook is that instead of removing a circular hole (green), the software removes an inscribed polygon.(blue)
The number of sides of that blue polygon is controlled by the variable "$fn=" -- the number of fragments used to render a full circle. (Line 41 of the SCAD file)
To produce a hole like the blue hexagon in the picture above, use "$fn=6".
For an octagon, use "$fn=8".
For a 180-sided polygon, use "$fn=180" -- I know it's overkill, but this is a small part so the render time is still reasonable.
Scott