A CAD model can be saved in many different formats, and the one you choose has real consequences for what happens next. Pick the wrong type and you can lose precision, strip out useful information, or hand a machinist a file they cannot actually work with. The good news is that a small number of formats cover almost everything you are likely to need on a typical job.
When you brief our CAD team we will tell you which format suits the next step in your project, but it genuinely helps to understand the main ones yourself. Knowing the difference between a solid format and a mesh format, in particular, will save you from the common mistake of sending a file that has quietly thrown away the very detail you cared about most.
Solid formats: STEP and IGES
STEP is the workhorse of engineering exchange and the format to reach for in most situations. It stores the part as true solid geometry with exact surfaces, so it can be opened, measured and edited in almost any CAD package without losing any accuracy at all. For machining, inspection and serious design work that has to be edited later, STEP is almost always the right answer.
IGES is an older surface based standard that still turns up in some industries and older toolchains. It can carry complex surfaces well enough, but it is more prone to small gaps and translation errors than STEP, which can mean tidying up before the file is usable. Where there is a free choice between the two, we will almost always prefer STEP for its reliability and clean translation.
Mesh formats: STL and 3MF
STL describes a part as a mesh of flat triangles that approximate its surface. It is the long standing standard for 3D printing and works fine, but it carries no units, no colour and no material data, and curved surfaces are only ever as smooth as the triangle count allows. A coarse export can leave visible facets on what should be a smooth, flowing curve.
3MF is the modern replacement and a better choice where you have the option. It stores the same mesh far more efficiently and can also carry colour, materials and even print settings inside a single file. That makes it well suited to FDM printing and especially to full colour work, where STL would simply discard the information you need to reproduce the part faithfully.
Other formats you might meet
STEP, IGES, STL and 3MF cover most jobs, but a handful of other formats turn up often enough to be worth knowing. Some are native files tied to one program, others are general exchange formats, and a few are really meant for graphics rather than manufacture. Sending the wrong one of these is a common and easily avoided cause of delay.
- Native files like SLDPRT or F3D, only fully usable in their own software.
- OBJ, a mesh format that carries colour and texture for visuals.
- DXF and DWG, two dimensional formats for drawings and laser profiles.
- PARASOLID, a solid format that some engineering tools prefer.
- PDF, useful for sharing a drawing but never for editing geometry.
Sending us the right file
As a simple rule, send STEP for anything that will be machined or needs to be edited, and STL or 3MF for parts that are heading straight to a printer. Getting this right first time avoids a frustrating round of back and forth where a mesh arrives for a job that needed editable solids, or vice versa, and the project stalls while the correct file is found.
If you only have a mesh and need it turned back into clean editable solid geometry, that is a real job in itself rather than a quick conversion, and our prototype development team can handle it for you. Unsure what you actually have on your computer? Contact us and we will work it out and tell you exactly what to send.