OpenSCAD is usually used for 3D modeling. But it also supports a “2D subsystem” for two dimensional drawings (stuff like circle and square). This article teaches you how to make stencils and templates that will match your target measurements exactly. For example, you could make a stencil for a painted sign or guideline for a wood project that uses a jigsaw.

What You Need:

• A ruler that uses the same unit of measure as your drawing. If your drawing is in millimeters, use a metric ruler.
• A desktop paper printer.
• An OpenSCAD drawing.

How to Print in OpenSCAD

Printing a drawing in OpenSCAD is simple:

• Create an OpenSCAD project.
• Render it.
• Export as PDF (File -> Export -> Export as PDF).

This is where the problem starts: your drawing is not 100% proportional, and one millimeter in OpenSCAD will NOT equal one millimeter on the paper in most cases.

For example, my printer would shrink 90mm objects down to 80mm. What a rebel!

Fixing Proportions With scale()

Luckily for us, OpenSCAD is aware of the problem with scaling and provides calibration guides. When you export the PDF, it will have a ruler alongside both edges of the paper.

Make a note of how big the guidelines are on the paper:

OPENSCAD_LENGTH = 90;

In my case, the guidelines went from 0 to 90 and -90 alongside the edge of the page. Don’t worry if your guidelines look different.

After that, I took my ruler and measured how long the guidelines actually were in the real world.

PAPER_LENGTH    = 80;

As I mentioned, even though the guidelines were supposed to be 90mm, my printer printed them out as 80mm. It’s like my printer wanted to play a game of ‘guess the size’.

Now that I know my real-world size versus OpenSCAD size, I can use the OpenSCAD scale() operation:

scale(OPENSCAD_LENGTH / PAPER_LENGTH) {
    // PUT YOUR ORIGINAL OPENSCAD DESIGN HERE
}

At this point, you can export the project as a PDF and print it to paper. Congratulations! You now have a paper stencil/template that is exactly the correct size.

Experiment: Printing Coin-Size Holes

If you want to be sure this process works on your machine, you can try printing US coins onto a paper and lay the coins over the final template to ensure calibration succeeded.

The list below contains the size of common coin sizes (in mm) for US-based readers:

• Quarter - 24.26
• Dime - 17.91
• Nickel - 21.21
• Penny - 19.05

…But I Just Want to Copy/Paste a Snippet

Ok, fine:

OPENSCAD_LENGTH = 90; // FIND THIS ON YOUR PDF OUTPUT!!
PAPER_LENGTH    = 80; // DIFFERENT FOR EVERY PRINTER!!!

scale(OPENSCAD_LENGTH / PAPER_LENGTH) {
    // PLACE YOUR ORIGINAL DESIGN HERE
}