Parametric modelling: a part you edit by changing a number
Parametric modelling is a way of designing where the shape is defined by dimensions and rules, so you change it by editing a number instead of redrawing.
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How it works
In parametric modelling, see parametric design, you do not save the finished shape but the steps that built it: draw a profile, extrude it, cut a hole. The dimensions are parameters. Change one and the whole model is recalculated.
It is typically done in CAD programs such as Fusion, FreeCAD or Onshape. OpenSCAD takes a completely different approach, where the model is written as code.
Why it suits 3D printing
- Tolerances. After the first test it is enough to change the clearance from 0.2 to 0.3 mm and export again. See tolerances.
- Variants. The same holder in several sizes from one design.
- Quick edits. You change a dimension instead of redrawing.
- Reuse. You can use the design again for the next order.
Parameters worth having
When designing for FDM, make the wall thickness, the clearance between parts, the hole diameter and the fillet radius parameters. Keep the wall thickness a multiple of 0.4 mm, see wall thickness.
Give them clear names, for example clearance or wall, so you can find your way around after a few months.
What to send for printing
A parametric model is exported to STL or 3MF before printing. Keep the original file with you, we only need the finished export. We also accept STEP. If you need another size of the part, change the parameter and send a new export.
Common questions
How is it different from ordinary modelling?
In parametric modelling the shape is defined by dimensions and rules, so you change it with a number. In sculpting or mesh editing you change the surface directly.
What can I model parametrically for free?
FreeCAD and OpenSCAD are free. Fusion and Onshape have a free tier with limits.
Do I have to send the parametric file too?
No. An export to STL, 3MF or STEP is enough.
Related terms
CAD
CAD is computer-aided design, that is software for creating precise 2D and 3D models. A model from CAD is exported to STL or 3MF and sent to print.
Tolerances
Tolerances in 3D printing set how far a printed dimension may differ from the model and how much clearance to leave between parts that are meant to fit together.
Wall thickness
Wall thickness is the distance between the outer and inner surface of a part. In 3D printing it decides the strength and whether a thin detail prints at all.
OpenSCAD
OpenSCAD is a free 3D modelling program in which a shape is not drawn but described by a script. It suits precise, parametric parts that are easy to change with a single number.
FreeCAD
FreeCAD is a free, open source parametric CAD program. It suits precise mechanical parts that you want to edit later by changing dimensions.
Fusion (Fusion 360)
Fusion, long known as Fusion 360, is a parametric CAD program from Autodesk. It suits precise mechanical parts, assemblies and changing dimensions afterwards.
SourcesSources checked 1 November 2026, 3
- Parametric design, Wikipedia, checked 2026-11-01
- OpenSCAD, Wikipedia, checked 2026-11-01
- FreeCAD, Wikipedia, checked 2026-11-01
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No model? No problem, pick a ready one
These sites have thousands of free models. Download an STL or 3MF and upload it here. If you sell it or use it for business, check the model licence. How to pick a model and licence