A printable part follows a small handful of rules: walls thick enough to survive, tolerances generous enough to fit, overhangs gentle enough not to droop, orientation chosen to avoid supports, and the right edge geometry for the right places. This guide collects the numbers that work in practice, plus the printability checks the PrintPal AI CAD agent runs after every render.
A 0.4 mm nozzle prints walls cleanest at integer multiples of 0.4 (0.8, 1.2, 1.6, 2.0). Sub-multiple thicknesses force the slicer to gap-fill, which is weaker and uglier.
For FDM, real-world parts are typically 0.1–0.3 mm bigger than nominal due to extrusion width and over-expansion. Plan for it:
The fix for an overhang is almost always one of:
OpenSCAD doesn't have a one-click chamfer or fillet — you build them with primitives. Which to pick:
Most printability problems disappear with the right orientation. Heuristics:
After every render, the PrintPal AI CAD agent runs:
Failures appear as warn-colored tool cards in chat. You can address them with a one-line prompt (" increase wall to 2 mm ") or let the agent self-correct on the next turn.
Estimate filament cost, electricity, and machine time for a part.
Quick volume-based print-time estimate without slicing.
Pick the right layer height for your nozzle and target finish.
Compensate for material-specific shrinkage on tight-fit parts.
Tell the AI CAD agent your target material and printer, and every render comes back with the right wall thickness, hole clearances, and chamfers built in.