Prompting a CAD agent is closer to writing a one-paragraph engineering brief than chatting with a chatbot. The agent rewards specificity about envelope, hardware, and fit. This page is a field guide of templates, anti-patterns, and tweaks that turn first-turn renders into printable parts.
Use this skeleton for any mechanical part. Fill in or drop sections as you need them:
OpenSCAD is unit-agnostic — internally everything is just a number. By convention, every PrintPal generation treats the unit as millimetres , and slicers import the same way. Spell it out in the prompt to avoid ambiguity, especially when you reference small dimensions (a "0.4 chamfer" could mean 0.4 mm or 0.4 in — say "0.4 mm").
The agent recognises common fasteners and motor footprints. Use the standard name and let it pick the right clearance + countersink dimensions:
For things that have to mate, ask for the right slip-fit clearance up-front rather than fighting it later:
Example phrasing: "M3 hole with 0.2 mm slip clearance" or "bore for 608ZZ with 0.1 mm press fit".
Once the part exists, prefer targeted changes anchored on @feature references:
Reach for an image when words run out:
They're all real prompts that produced real printable parts. Modify them for your specs and you'll be exporting STL inside a minute.