Manufacturable CAD Models
How to prepare CAD files so they are actually manufacturable: file formats, geometry hygiene, communicating critical dimensions, and what a manufacturer needs beyond the file.
The CAD file is the starting point of every quote and every print, but it is only part of what a manufacturer actually needs. A model can be geometrically valid and still be a poor manufacturing file, either because the geometry itself is unclean, or because it fails to communicate which dimensions and conditions actually matter for the part's function.
File format: STEP over STL
We accept STEP, STL, 3MF, OBJ and IGES up to 200 MB, but STEP is strongly preferred and STL should be treated as a fallback, not a default. STEP describes exact mathematical surfaces, so a hole is still a true cylinder and a fillet is still a true radius no matter how far you zoom in. STL approximates every surface with flat triangles, which means curved features are already slightly faceted before printing even starts, and any correction to a dimension requires access to the original solid model, not the STL.
There is also a practical reason: when we review a STEP file, we can measure exact wall thickness, check true hole diameters, and apply compensation offsets precisely. With an STL, we are working from an approximation of the part, which reduces the accuracy of both the quote and the DFM review.
Geometry hygiene
A surprising number of quote requests contain geometry problems that have nothing to do with printability and everything to do with how the model was built. These are worth checking before sending a file, since they can delay a quote or force assumptions that do not match the real part.
- Open meshes or gaps in an STL, which make it impossible to determine a clear inside and outside of the part.
- Non-manifold geometry, such as edges shared by more than two faces, left over from a messy boolean operation.
- Walls modelled as single zero-thickness surfaces instead of solid volumes, which have no thickness to print at all.
- Fillets and chamfers smaller than about 0.2 mm that add file complexity without being visible in the final print.
- Low mesh resolution on curved surfaces, exported with a coarse tessellation setting that bakes in visible facets.
Communicating what actually matters
Geometry alone does not tell a manufacturer which dimensions are critical and which are not. A drawing or a short note stating that a 20 mm bore needs a sliding fit with a specific shaft, while every other dimension is non-critical, changes how we plan tolerances, orientation and post-processing. Without that information, we either assume everything is critical, which raises cost, or assume nothing is, which risks a wrong fit.
The same applies to load direction and operating conditions. A bracket that only ever sees a static vertical load can be oriented and reinforced very differently from one that sees repeated side impact, even if the two parts look identical in CAD. Temperature exposure, chemical exposure and expected service life all change the material recommendation, and none of them are visible in the geometry.
What to send alongside the file
| Information | Why it matters |
|---|---|
| Critical dimensions and fit type | Focuses tolerance effort where it actually affects function |
| Expected load direction and magnitude | Drives orientation and wall or rib design |
| Operating temperature and chemical exposure | Narrows the material shortlist before printing starts |
| Mating parts or assembly context | Reveals clearance requirements not visible from a single part file |
| Target quantity and timeline | Changes whether prototype shortcuts or series controls apply |
Frequently asked questions
- Do I have to convert my model to STEP before sending it?
- It is not mandatory, we accept STL, 3MF, OBJ and IGES too, but STEP gives us exact geometry to measure and correct, which usually leads to a more accurate quote and fewer follow-up questions.
- What is non-manifold geometry and why does it matter?
- It is geometry where an edge or vertex is shared in a way that does not describe a valid solid, often left over from a boolean operation. Slicing software can misinterpret it, sometimes silently, which risks a print that does not match the intended shape.
- How small a fillet is too small to bother modelling?
- Around 0.2 mm and below is generally not worth modelling for FDM, since the nozzle diameter and layer height mean it will not be reproduced distinctly anyway. It only adds file complexity and slicing time.
- What if I do not know which dimensions are critical yet?
- Tell us what the part mates with and how it is loaded, and we can usually identify the likely critical dimensions ourselves during the DFM review, then confirm them with you before printing.
Have your part reviewed before production
Send us your CAD file together with the application, load and operating conditions. We review geometry, orientation, material and tolerances and come back with concrete change proposals and a quote.
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