How to turn a text description into a STEP file

STEP (ISO 10303) is the universal way to move solid models between CAD systems. The hard part has always been creating the model in the first place — sketching, extruding, filleting. Text-to-CAD removes that step: you describe the part, and a real solid comes back. Here is how to get a clean STEP file from a description.

1. Describe the part, not the clicks

Write what the part is and the numbers that matter: overall dimensions, wall thickness, hole sizes and patterns, fillet radii, and any standard interfaces. You do not need to describe modelling operations — just the result.

A good prompt reads like a drawing note: "Mounting bracket, 80 × 60 mm, 5 mm thick, four M6 clearance holes on a 60 × 40 mm pattern, 3 mm fillets on the outer corners."

2. Ask for STEP (AP242) in millimetres

AP242 is the modern STEP application protocol and millimetres is the engineering default. AiCadGen exports AP242 mm by default, which is what SolidWorks, Fusion 360, Onshape, Inventor and FreeCAD all expect — so there is no unit-scaling surprise on import.

3. Check it is a solid, not a mesh

A STEP file should contain B-Rep solids — exact faces and edges you can measure and machine — not a triangulated mesh. This is the key difference from STL. A solid lets feature-recognition tools (SolidWorks FeatureWorks, Fusion’s "Recognize features") rebuild an editable parametric tree.

4. Iterate by refining the description

Rather than re-modelling, change the spec: "make the wall 4 mm and move the holes to a 70 mm pattern." Each iteration regenerates the solid, so you converge on the part you want without manual rework.

Where text-to-CAD fits

For single mechanical parts, brackets, housings, adapters and fixtures, generating a STEP file from text is dramatically faster than starting from a blank sketch. For large assemblies and simulation you will still finish in a full CAD suite — but you can skip straight past the blank-canvas stage.