I’ve been looking for ways to extend the “doodle desk” I put together for Sarah Jane over Christmas this year. One of the ideas I’ve been playing with is adding a large scale Spirograph-like drawing tool.
A friend who is an expert in Autodesk Inventor was able to use the spur gear design accelerator tool to create some nested (internal and external) spur gear patterns, then export them as DXF files. I was able to scale them up to the right size and generate some G-Code cutting paths to drive my CNC router.
I was able to cut out all the gears in about 10 minutes – the stock was some 1/2″ particle board and I used a 1/8″ spiral upcut endmill to do the cutting.
The outer (blue) gear attaches to the base using two wooden dowels, this keeps it in position, and also lets you advance the paper underneath – without using real ["You'll have someone's eye out with that!"] pins like the 1970′s version of the toy.
There was always a bit of a knack to using the original Spirograph, and so a large scale one takes a bit more concentration. Sarah Jane is only 2, and I think it’s a bit beyond her at the moment. She does enjoy watching the patterns form, and then coloring them in afterwards.