Today I made some thin plates using polycarbonate and some more aluminum watch parts!
These small plates where an interesting but easy part of making. Since it's plastic, I was able to use double-sided tape to hold it down on the fixture plate I used yesterday. Because of the tape, I couldn't use any coolant (which would only get in the way regardless), so I had to skim the surface with a face mill, then wiped down with degreaser on a rag to ensure the adhesion on the tape would stick.
For the programming side of it, I used a 1/2" three flute square endmill to face the top of the 1/8" thick polycarbonate, flipped and cut it again till it was at its final thickness 0.04" (not actual part height, close to). Then I used a 1/8" three flute square endmill to contour each part, leaving five thou axially to remove later, this was done to ensure the adhesive didn't get on the cutter, thus leaving a lousy finish. I had to account for the tape as well, so I measured the thickness with one side of the paper on it, then measured the paper and subtracted it from the total to get my number. From there, it was as easy as cleaning them up with alcohol and a rag, then inspecting each one. Everything was within 0.0002" (two-tenths), which is well within spec.
From start to finish, the polycarbonate plates took maybe an hour and a half to complete, which was mostly due to trying to find the stock from the scrap piles.
One of the previous projects I worked on a couple of weeks back wanted a few more watch parts made, and so I got to set up the stock and re-run the old program. It took only 30 minutes to set up the machine, cut the aluminum, and mill the first operation out. I did three sets of two and will finish them off tomorrow.