From Prompt to Print
One of the most satisfying things you can do with AI CAD is describe a part, generate it, and hold a physical version in your hands an hour later. The workflow is straightforward, but there are a few things worth knowing to avoid wasted filament and failed prints.
The Basic Workflow
1. Describe and Generate
Open app.ragnar.build and describe your part. For 3D printing specifically, think about:
- Wall thickness. Most FDM printers need at least 1.2mm walls (3 perimeters at 0.4mm nozzle). Going below 1mm usually results in weak, translucent walls or print failures.
- Overhangs. If your design has features angling out more than 45 degrees from vertical, you'll need support material. You can sometimes avoid this by designing with printability in mind: "add a 45-degree chamfer under the overhang" or "make the bottom surface flat."
- Small features. Holes under 2mm, text smaller than 8mm, thin ribs under 1mm. These push the limits of most consumer printers. Mention specific sizes so the AI doesn't generate features too small to print.
2. Review and Iterate
Rotate the 3D preview and look at the model from the bottom. That's your first layer, and it determines how well the print sticks to the bed. A flat, stable base means easier printing. If the bottom is uneven or has a tiny contact area, consider asking the AI to add a wider base or flip the orientation.
Check for overhangs and bridges that might need support. If you see a feature that would be hard to print, describe an alternative: "Change the overhang to a 45-degree slope" or "add a support rib under the shelf."
3. Export as STL
For 3D printing, export the STL file. This gives you the triangulated mesh that slicers expect. Ragnar also exports STEP if you want to make modifications in CAD software before printing, but for direct-to-slicer workflows, STL is what you want.
4. Slice and Print
Open your STL in your slicer of choice (PrusaSlicer, Cura, Bambu Studio, OrcaSlicer, etc.) and set your print parameters. For AI-generated models, there's nothing special about the slicing process. It's a standard STL file. Apply your usual material profiles and settings.
Designing for Printability
When describing parts for 3D printing, these tips will save you time:
Specify wall thickness explicitly. "2mm wall thickness" removes any ambiguity. This is especially important for enclosures and hollow parts.
Think about orientation. The strongest direction of an FDM print is along the XY plane (within a layer). The weakest is along Z (between layers). If your bracket needs to handle load in a specific direction, design it so the layers run parallel to the load, not perpendicular.
Mention tolerances for fits. If your part needs to fit around a bolt or slide into a slot, add 0.2 to 0.3mm of clearance. "A hole for an M5 bolt" should be described as "a 5.3mm hole" or "an M5 clearance hole" rather than "a 5mm hole."
Chamfer the bottom edge. Adding "a 0.5mm chamfer on the bottom edges" helps with bed adhesion and prevents elephant's foot from affecting fit.
Avoid unnecessary complexity. A bracket with simple 90-degree bends prints faster and stronger than one with curved organic surfaces. If the part is going straight to the printer and aesthetics aren't critical, simpler is better.
Common Issues and How to Avoid Them
Walls Too Thin
If the AI generates features thinner than your nozzle width (typically 0.4mm), the slicer will either skip them entirely or produce flimsy single-wall extrusions. Specify minimum thickness in your description.
Unsupported Overhangs
An overhanging feature that looked fine in the 3D preview can produce spaghetti on the printer. Before exporting, check for features that extend horizontally without support. Either redesign with a chamfer or accept that you'll need support material.
Tight Tolerances
3D printing (especially FDM) adds about 0.1 to 0.3mm of dimensional variation. A hole described as "exactly 10mm" will probably print closer to 9.8mm due to material squish. Account for this by either oversizing holes slightly in your description or planning to post-process with a drill.
Flat Surfaces Warping
Large flat surfaces on the build plate can warp, especially with ABS or ASA. If your part has a large base, consider asking for "a 2mm grid rib pattern on the bottom surface" to break up the flat area and reduce warping.
Going Further: STL vs STEP for Printing
For simple parts going straight to the printer, STL export is all you need.
But if you want to make modifications first (add assembly features, adjust tolerances precisely, or run it through DFM analysis), export as STEP instead. Open it in Fusion 360 or your preferred CAD tool, make your changes, then export STL from there with full control over the mesh resolution.
Start Printing
Describe your first part at app.ragnar.build, export the STL, and send it to your slicer. For simple parts like phone stands, cable clips, or desk organizers, you can go from idea to printing in under 10 minutes.