How to Generate a STEP File from Text

To generate a STEP file from text, describe the part precisely with real dimensions and standards, generate and review a preview, verify the result against your actual functional requirement, then export STEP for use in a real CAD package. The quality of the first draft depends almost entirely on how specific the description is — this is the single biggest lever you control in the whole process.

Step-by-step

1. Write the prompt with units, standards, and a clear reference geometry

"A bracket" gives a generation process almost nothing to work with; it has to guess thickness, hole placement, and overall proportions. "An L-shaped bracket, 60mm x 40mm x 5mm thick, with two M6 clearance holes 10mm from each end on the long side" gives it real constraints. Always include:

• Units — "about 20" is not engineering input; specify mm or inches explicitly.
• Standard part callouts where relevant — naming "M10" or "6205 bearing" lets the system pull exact catalog geometry instead of approximating a shape.
• Reference features — "10mm from the edge," "centered on the long axis" — gives the process a concrete anchor instead of an ambiguous "somewhere in the middle."

2. Generate and review the preview before committing further

Check overall proportions first — is this roughly the right size and shape before you get into detail review? A preview is a cheap sanity check; use it to catch a wildly wrong interpretation (wrong overall dimensions, a feature in the wrong location) before spending more time on the full generation cycle.

3. Accept the preview once the shape matches intent — but don't stop reviewing there

"Looks right" and "is right" are different bars. Once the overall shape matches what you described, move to checking the specific numbers that matter for function — see the review checklist below.

4. Download STEP and open it in your CAD tool for final verification

This is the step people skip most often, and it's the one that catches real problems: open the exported STEP file in SolidWorks, Fusion, or whatever you actually use, and check that a dimension you care about reads correctly, that fillets and features are clean, and that the file opens as a proper solid — not an open shell.

5. Escalate if the part is ambiguous or safety-critical

If your description was genuinely ambiguous (multiple reasonable interpretations existed) or the part is safety-critical or load-bearing, treat the generated STEP file as a draft for engineering review, not a final specification. See when to trust automation vs. ask an expert for where this line should be drawn.

Verifying the file itself, not just the picture

The preview tells you whether the shape looks right. The file tells you whether it is right, and you can check the two most important properties in a text editor before opening CAD at all.

A STEP file is plain text in the ISO 10303-21 format. Open it and look for two lines.

1. The schema, in the HEADER section. FILE_SCHEMA names the application protocol: CONFIG_CONTROL_DESIGN is AP203, AUTOMOTIVE_DESIGN is AP214, and AP242_MANAGED_MODEL_BASED_3D_ENGINEERING_MIM_LF is AP242. This matters if your supplier's software is old, or if you were expecting colour or PMI that only the later protocols carry.

2. The shape entity, in the DATA section. Search for MANIFOLD_SOLID_BREP. If it is there, you have a closed solid. If instead you find SHELL_BASED_SURFACE_MODEL, you have surfaces rather than a solid body — the file will open, and CAM will still refuse it until the shells are stitched. GEOMETRIC_CURVE_SET means wireframe only, with no faces at all.

Neither check takes a minute, and together they catch the two failures that otherwise surface after a supplier has already quoted the job. The full anatomy is in what is a STEP file.

A worked example, start to finish

The request:

An L-bracket machined from 6 mm 6082-T6 aluminium plate. Base 80 × 60 mm in the XY plane; vertical wall 80 × 50 mm rising in +Z from the long edge. Four Ø6.6 mm clearance holes for M6 (ISO 273 medium series) on a 60 × 40 mm rectangular pattern, centred on the base. Ø30 mm through bore in the wall, centred 30 mm above the base. R5 fillet at the internal corner, R3 on external vertical corners.

What to check on the result, in this order:

1. Envelope — 80 × 60 × 56 mm overall. Measure it; do not eyeball it.
2. Interfaces first — the four hole positions and the Ø30 bore height, because these are what mate with something else and cost the most when wrong.
3. Hole diameters — 6.6 mm, not 6.0. Modelling a clearance hole at the nominal thread size is the single most common error in generated CAD.
4. The fillet actually exists at the internal corner, and its radius did not silently become something else to make the operation succeed.
5. Wall thickness — 6 mm everywhere it should be, with no thin region introduced by a fillet.
6. File-level check — schema and MANIFOLD_SOLID_BREP, as above.
7. Mass — with aluminium assigned, an implausible mass usually means a units problem or a body that did not merge.

Anything you did not state in the request was assumed by the generator. Those assumed values are where the surprises live, which is why step 2 comes before anything cosmetic.

A review checklist worth actually using

Before you treat a generated STEP file as final, check:

1. Does it open as a closed, valid solid in your CAD package — not an open shell or a set of disconnected surfaces?
2. Do the critical functional dimensions match your requirement — not just "looks about right" but the actual number you need (a bolt-pattern spacing, a bore diameter, a wall thickness)?
3. If the part mates with something else, did you specify (or check) an actual fit relationship — a hole and shaft that are each independently "10mm" is not the same as a toleranced fit pair. See tolerances in CAD: what AI tools usually get wrong.
4. For standard components, does the part match a real catalog part number, not an approximated shape that's merely close?

Common mistakes that produce a bad first draft

• Missing units. "About 20" forces a guess that may not match what you meant by 20 — 20mm and 20 inches are very different brackets.
• Vague fits. "A tight hole for the shaft" carries no actual diameter or tolerance strategy — specify the diameter and, ideally, the fit class you want (see our ISO thread guide for the fastener version of this, and our tolerances guide for the general case).
• Expecting organic, sculptural quality from mechanical-focused tools. A tool built around parametric mechanical features (extrusions, fillets, patterns, standard hardware) is not the right fit for free-form organic shapes — that's a different modeling problem with different tools.
• Treating the preview as the final check. A preview confirms the shape is roughly right; it doesn't confirm the dimensions are exactly right or that the part is manufacturable by your intended process — see DFM 101 for what still needs checking after the preview looks good.

The bottom line

Generating a STEP file from text is a workflow with real checkpoints, not a single black-box step. The description you write, the preview you review, and the final verification in a real CAD tool each catch a different category of problem — skipping any one of them is how a plausible- looking file ends up being the wrong part once it reaches a machine shop.

Related reading: What is a STEP file? · What is text-to-CAD and how does it work? · Revise a model by chat · Why the CAD engine runs in the browser · Text-to-CAD glossary