Why STEP Files Specifically?
If you're reading this, you probably already know that not all 3D file formats are equal. STL files are fine for 3D printing, but they're just triangles. You can't edit an STL in SolidWorks the way you'd edit a native part. You can't run meaningful FEA on it. You can't generate manufacturing drawings from it.
STEP files are different. They contain B-Rep (boundary representation) geometry, which means mathematically exact surfaces, edges, and curves. A circle is a circle, not a 64-sided polygon. A fillet has a precise radius, not an approximation. When you open a STEP file in professional CAD software, you get a real solid body you can measure, modify, and manufacture from.
That's why generating STEP files from text descriptions is useful. It's not about making pretty 3D previews. It's about getting real, usable engineering geometry from a few sentences of plain English.
Step by Step
1. Write a Good Description
Start with what the part is and include the dimensions and features that matter. Here are some examples that work well:
Simple part: "A mounting bracket, 60x40x3mm steel plate, with two M5 clearance holes spaced 40mm apart, and 2mm fillets on all corners."
More complex: "An L-shaped bracket with a 50x30mm base and a 50x40mm vertical wall, both 3mm thick. The base has two countersunk M4 holes, and the vertical wall has a 15mm slot for adjustment."
Assembly: "A phone stand with a 15-degree viewing angle, a 10mm wide cable routing slot in the base, and a rubber-grip lip at the bottom to hold the phone."
Notice what makes these work: specific dimensions, named features (M5, countersunk, slot), and functional intent (cable routing, rubber grip). The AI uses all of this to generate appropriate geometry.
2. Review the 3D Preview
Ragnar generates a 3D preview you can orbit, zoom, and inspect. Check the overall shape and proportions first. Don't worry about getting everything perfect on the first pass.
3. Iterate
This is the part people underestimate. The first generation is a starting point, not a finished product. Describe what needs to change:
- "Make the walls 2mm thicker"
- "Add a 5mm fillet on the top edge"
- "The slot should be centered, not offset"
- "Add four rubber feet on the bottom, 5mm diameter"
Each change builds on the previous result. You don't start over.
4. Export as STEP
Once you're satisfied, download the STEP file. It's ready to import into SolidWorks, Fusion 360, Onshape, FreeCAD, or any other CAD software that reads STEP (which is basically all of them).
Writing Better Descriptions
The quality of your output depends heavily on how you describe what you want. Here are some patterns that consistently produce good results:
Be specific with numbers. "40mm wide" is always better than "medium-sized." "M8 through-hole" is better than "a hole for a bolt." The AI can't read your mind about what "big enough" means.
Name your features. Engineering vocabulary helps. "Countersunk hole," "thru-slot," "fillet," "chamfer," "boss," "pocket." These terms map directly to CAD operations.
Describe function, not just form. Saying "ventilation slots" tells the AI about spacing, orientation, and pattern in a way that "rectangular holes on the side" doesn't.
Go one change at a time. When iterating, make a single change per message. "Make it taller and wider and add holes and change the angle" is harder for the AI to get right compared to making each change separately.
What You Can Expect
Simple parts (brackets, plates, spacers, basic enclosures) typically take 3 to 5 minutes and come out close to ready on the first pass. Multi-part assemblies or complex geometry take longer, usually 10 to 25 minutes, and benefit from a couple rounds of iteration.
The STEP files are standard AP214 format and import cleanly into all major CAD software. Once imported, you have full editing capability: add features, run simulations, create drawings, set up CAM toolpaths.
Try It
Head to app.ragnar.build and describe your first part. The free tier includes 15 credits monthly, so you can test the workflow without committing.