A few select Toronto Public Library branches feature ‘Digital Innovation Hubs’ which are equipped with some interesting technology, including Makerbot Replicator 3D printers available for public use. When these machines debuted at the Toronto Reference Library in 2014, I booked myself into the first orientation class I could. (TPL requires anyone interested in using the machines to attend a free clinic to get familiar with the technology.) It took me a while but I finally got around to modelling something that would be practical for printing.

I started with this medium sized (38mm diameter) bakelite radio knob as reference:

Using electronic calipers, I took measurements and set about recreating its shape in SketchUp. This software was pretty cumbersome and definitely not ideal for the purpose. The next time around, I’ll be trying a piece of software with more of a CAD influence, but I haven’t settled on exactly which.

The printer takes a spool of plastic filament and feeds it into a heated element in its extruder head. The extruder zips back and forth, building a model from the bottom up, one tiny cross-section at a time.

As a first effort, I’m happy with the results. Though it’s a little too snug, I can fit the printed knobs onto the 6mm shaft of a pot or rotary switch. There are some adjustments I could make to the model to bring it closer to my reference. The finish and durability of the printed knobs isn’t honestly as nice as the original, but as a prototyping tool, this was cheap, fast and useful. Total cost was $8.40 for the two knobs, which each took about 50 minutes to extrude.

You can access my SketchUp file here if you’d like a closer look.