When I started this project it seemed like a straightforward affair, after all I began my career in engineering PC CAD and manufacturing, how hard could it be right? Well, while this project scratches a particular itch of mine to make things, I had a few constraints to factor in. For starters, I’m not a full fledged plastic molding shop. I have desktop equipment, that means machining patterns in wax or tooling board, not molds from steel, which of course takes injection molding off the table. Actually though, that’s not a big deal, yes production will be one at time, but I don’t have massive up front tooling costs. That, and I wanted to more or less replicate some of the techniques the original people would have utilized – thermoset plastics mixed carefully, hand tinted, poured into molds, cured, de-molded, assembled. Other than not throwing the lead mold into a pot to melt down for reuse after de-molding , it’s pretty close.
So this boiled down to a number of repeatable steps:
Step 1, translate a sketch idea into the required CAD drawings
The next step is to virtually assemble all the parts and render it in 3D to get a better notion of what the finished product will actually look like.
Satisfied with what it should look like, the next step is to turn the CAD drawings into CAM instructions for the mill.
Once the patterns are machined, create molds from them in silicon rubber.
Time to cast some polyurethane resin. I cast these under pressure to better achieve a shiny finish. Air bubbles that inevitably get mixed in when combining the resin and catalyst disappear under pressure (Boyle’s law).
A one time step was needed, before I could initially assemble them and that was to design the dial faces in Photoshop.
With all the pieces cast and the dial face done, it’s time for final assembly.
And of course, the finished product.