Let Zack Freedman Give You a Crash Course on Reverse-Engineering for 3D Printing

Once you get past articulated dragons, you’re going to want to use your 3D printer for practical purposes. That will often mean designing your own creations from scratch, but it will also mean copying real-world parts. Broken appliance knobs, for example, can be easily replicated and printed for pennies. To help you learn how to do that, Zack Freedman made a video that acts as a crash course in the art of reverse-engineering for 3D printing.

The term “reverse-engineering” may sound highfalutin, but all it really means is that you’re copying something. In this case, we’re talking about copying the dimensions of a physical object for the purpose of 3D printing a replica. If you have a decent 3D scanner, that can be as easy as scanning, meshing, and printing. But Freedman’s methods work without 3D scanning. You can do this with affordable tools and you’ll get a much more useful parametric model for your effort.

Freedman’s demonstration parts are hard disk sleds for a Rosewill RSV-4000. Rosewill doesn’t sell those sleds alone, so they’re a perfect candidate for reverse-engineering. I used the word “part,” but it would be more accurate to say these are multi-part assemblies. That’s an important distinction for reverse-engineering, because you’ll want to model each part separately. Then you can create an assembly in CAD to make sure they fit together, if you like.

The reverse-engineering process shown in the video does make use of digital calipers, which every 3D printer owner should have in their toolbox. But unlike more traditional techniques, this relies heavily on photography. Snap photos of the parts with a ruler in frame to use for scaling, then you can simply trace them in CAD. To minimize distortion, you want to take those photos with the longest focal length you can get away with at the furthest distance you can reasonably achieve. You also want your camera view to be perfectly perpendicular to the plane of the part you’re tracing. Lighting and background are important, too.

If your photos are good, they should give you reasonable accuracy and precision. Position your photo in CAD, trace, extrude, print, test fit, and repeat. After a few iterations, you should have a pretty decent part. Calipers and radius gauges can help you iron out the fine details.

And here’s a suggestion from me: consider the original design intention. If you measure a hole at 2.98mm, it is likely that hole is actually supposed to be 3mm. The difference is either manufacturing tolerance or misalignment of your calipers.

Just don’t forget that some of us in one particular country design some things using inches, which can confound those assumptions.