You’ve probably seen the term “parametric” used in reference to 3D printable models. On first glance, this seems like shorthand for “customizable” (and it’s true that this is a big part of the appeal).
So what exactly is a parametric model and why would you use them?
What are parametric 3D models?
Parametric as in “parameter”
In practical terms, a parametric 3D model means that a model has been designed with dimensions, constraints, and relationships in mind so that it can be adapted to suit. A “parameter” is a value like length, width, or thickness that changes depending on how the model is customized.
Let’s say that you design a model of a wall hook with a length of 10 cm and a width of 3 cm. Because this model uses rigid values (essentially a ratio), changing the size of the length would also affect the size of the width in equal terms. If you want to change the size of one aspect of the model, you’ll need to scale the whole thing up or down in your slicer, which will either affect all axes or cause certain elements to stretch.
For the hook to be parametric, the parameters used by the model need to have a greater relation beyond a rigid ratio. A parametric model offers much better customization possibilities, allowing you to change the length of the hook without affecting the width, while ensuring that other parts of the model—like how far the hook protrudes and the diameter of the mounting holes—remain the same.
If you’re printing a specific part for use in a single instance—like a replacement knob for a specific appliance—then a model not being parametric is not a big deal. But a parametric model, with customizable widths and mounting points, can be used to create knobs for all manner of appliances.
How this works in practice
STL and 3MF files won’t cut it
The STL and 3MF files that are commonly used by 3D printer slicer software are not customizable parametric models. Such customization requires that the model author provides the original CAD file from the application used to design the model in the first place.
These commonly take the form of Fusion, OpenSCAD, and FreeCAD files. They can be downloaded, opened up in the relevant software, customized, and then used to generate a file format that is compatible with slicer software. When a model author advertises a model as being parametric, these files are offered up for download.
A more convenient way of working is to use the model repository’s customization tool. For example, Bambu Lab’s MakerWorld places a “Customize” badge next to compatible parametric models. Thingiverse does the same.
Click it, and you’ll be taken to an interface that allows you to customize the various parameters. You might even find additional options like customizable text, objects you can toggle on and off, and other design choices. These elements are all based on a set of rules made possible by parametric design principles.
Some examples of parametric models
Objects that you might want to customize
The vast majority of models shared on repositories like MakerWorld, Printables, and Thingiverse are not parametric. This isn’t a big deal, since many of these are unique pieces to begin with. The humble Benchy is not a parametric model, but it doesn’t need to be. If you want a massive Benchy model (for some reason), you could scale the model up by a few hundred percent in your slicer.
Parametric models are typically those to which the “one size fits all” mantra doesn’t apply. Think organizers, adapters, storage solutions, fasteners, mechanical parts like bearings and springs, brackets, tags and keychains, and modular systems.
For example, a set of parametric vacuum hose connectors allows you to connect any hose type to a vacuum of your choosing simply by measuring the dimensions you have available and customizing the model to suit. Generate your own custom QR code luggage tags by specifying thickness, how many lines of text you want, what that text should say, and whether or not the QR code should be displayed.
3D printed hinges, wall vents, IKEA pegboard bins and wire mounts are among some of the other incredibly useful parametric models out there.
If you want to design your own 3D printed models, you’ll need to learn how to parameterize your creations using the specific features in your design software. Before you can do that, you’ll need to pick a 3D modeling app to learn.
