The major benefit of parametric modeling is the ease of introducing changes into your model’s design. This allows you to make both major and minor changes to your designs with very little time or effort. Sometimes it can be surprising how much change just a small change can make to a given design.

This page shows how to construct a simple box shape, and how changing it’s parameters can change it’s overall design. The real power of parametric modeling is much more valuable with more complex parts, but this example shows hot is works.

The parametric modeling software I use is a combination of the Rhino3D modeling software with the Grasshopper add-on. Grasshopper provides the parametric interface to Rhino3D – all the following screenshots showing geometry are from Rhino, but the screenshots showing the actual parameters and the geometry definitions are from Grasshopper.

Here is how to parametrically construct a box based on a simple 2D polygon:

Create a 7 sided polygon with a 10 mm radius:

Add a fillet with radius 2 mm to smooth out the corners:

Use the polygon to make a 2D surface

Extrude the surface up 10 mm to make a 3D solid

Scale the solid by a factor of 90% and move it up 2.5 mm

Subtract the scaled shape from the original

The result is a valid model that can be sliced with no errors and printed with no problems.

So where is the value of parametric modeling? The answer is the ability to make rapid changes. To see how this is done look at the Grasshopper definition of the box shown above

Here is a totally different box made from the same Grasshopper definition after a few parameter changes

Here is the revised Grasshopper definition for this version

Can you see the changes? By making very simple changes to the parameter sliders the geometry changes in real time; this makes it easy to check out different shapes/sizes etc. and settle on one you want. Here is an unedited short video showing how this looks when you actually make parameter changes

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