Design Questions
I've got a few questions regarding that have surfaced over the time I've been designing various gizmos and gadgets. I'm generally using Fusion for design and PrusaSlicer for slicing, along with a Core One for printing:
1. Is there a way to designate certain features and areas to have different print settings (e.g. a boss that should get 4 walls while the rest of the print gets 2). I know I can export from Fusion and "paint on" a section with different settings inside the slicer, but this requires me to have design stuff in two different areas. Generally not ideal.
2. Along the same line, the prusaslicer tends to save the "project" as the same 3mf file that Fusion just exported. Which means that when I go and export the part again from fusion, all my project settings are wiped. This is a PITA. Is there a better workflow that I'm missing?
3. Is there a way to create structure INSIDE a part? For instance, I might want to create some miniature struts or beams inside a part, but it seems that exporting only exports the skin and I'm left to try and sturdy things up with infill.
4. Any good recommendations on hole diameter in different filaments (PETG and PLA) for accepting either wood screws or machine screws. I know an M3 machine screw threaded into a hole in PETG won't hold much, but it's generally fine for securing covers and what not. What's a good rule of thumb for undersizing the hole so the threads can bite, but it's not too small that the screw won't fit.
5. Finally, is there a "design guide" somewhere that answers a bunch of these questions? I'd love to see a book or site that takes you through things like when to use chamfers vs fillets, hole size, springs, living hinges, clearances for moving parts, etc. I come from a metal machining background and there's 150 years of these sorts of guides out there for that stuff, but I can't find one for FDM that's not super basic.
RE: Design Questions
1. you could export a custom model and import it to slicer as modifier if you need very fine precise dimensions https://help.prusa3d.com/article/modifiers_1767
2. what I use is export .stl, save under the same name (overwrite) and in PrusaSlicer I press right click on the model and use Reload from disk (gets problematic with more models...
3. exporting model just generates the outer shell, that's why you have perimeters and infill in the slicers. If you need more advanced structures then you need to add them as additional objects in the model via holes so that the outer shell parts will be filled with perimeters. For example if you have a box then put empty space in side to create columens inside of it. Avoid adding separate model because it ends in printing twice in the same spot and this in most cases ends in print failure
4. I usually add extra cylinders around the holes where the inserts are going to be placed and set 5 perimeters or 100% infill in there, if the hole is say 5mm wide then I add modifier in 10mm diameter up to 15mm, it's usually enough. Also if there is no insert in there then I just keep the size of the hole in the size of the screw internal diameter (without the thread), so the thread has enough material to grab. Also I use wooden wide threads for better grip, or those screws used to screw into the metal sheets but they are usually too short for anything more than basic mounting of the grills for the fans.
5. you can start here https://github.com/gregsaun/maker_cheatsheet/blob/master/3d_printing/techniques.md#selective-infill
See my GitHub and printables.com for some 3d stuff that you may like.