Sunday, July 16, 2017

3D Printed Tourbillons, a coda

In my previous post, I wrote about making 3D printed tourbillon mechanisms. There are a few parts in these designs which are not printed, specifically two small bearings, and a few 2mm and 3mm shafts made of steel. There is not much I can do about the bearings, but I was curious to see if I could replace the shafts with plastic and used them in the version III design. I printed 1.8mm, 2mm and 2.8 mm diameter cylinders at 0.1mm layer resolution. They had to be printed with brim, so I then trimmed the brim off with a sharp knife and lightly sanded them. The 1.8mm shafts work quite smoothly for the spring/balance wheel, the escapement gear and the anchor. The 2mm shafts replace the two shafts which hold the frame together. The 2.8mm is a replacement for the the main 3mm shaft. It's a tight fit in the bearings, and is also too loose for the sprocket to engage with it well. I tried to shim it with a little blue tape the way I had done with the steel shaft, but this didn't work. However, putting a small blob of blu-tak (or similar) in the axis hole of the sprocket did. Here is the tourbillon working with plastic shafts (which I wave at the camera at the start).

One though which follows is that you could made the drive shaft better by printing it and the sprocket with a non-round cross section, like the flattened shafts you get on some stepper motors. They probably would not last as well as the steel ones, but it's an interesting idea, as you can cut the plastic to the exact length very easily.

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