Update after a night of machining and a day of reflection (note: the following is not totally relevant to all of you, but just a reason for the delay):
Workholding is going to be the next big issue I need to tackle, that caused the prototype case to be thrown from the vise once and move during the operation twice. As the internal pocket is machined, the side walls get thinner and thinner. Since I'm holding the part by the long ends (next to the space bar), there is a lot of thin material that can act like a spring. Since aluminum is pretty shifty, it starts to deform, and instead of the whole vise gripping the part, the part bends so that only the corners of the vise are gripping it. This does not provide enough force to combat the cutting forces and torque from the cutter, and the part moves. If it's not fixed, the cases won't actually be able to fit keys. I'm working on this, and have some ideas on how to do it.
Moving forward, it probably means I'll have to make a jig to hold the part vertically. This will counter the bending by pushing the force onto the areas that are still strong because of vertical thickness. It should be simple-ish to make, but that might take another weekend or so. I'm also looking to find a machine shop to do production at, they probably have the experience to recognize this issue earlier
Also damaged my roughing endmill because I was running it too fast in the morning. It was cutting the aluminum so fast that the bit was pulled into the material as it cut around. This became a problem because the bottom of the machine path was about 0.1 inches above the vise jaws. However, the bit got pulled down more than that and hit the jaws. Surprising, it got pushed back up by the hardened steel and continued cutting. Until it reached a pocket, where it had to enter the material vertically. Turns out the bottom of the cutter got scalloped by the steel and the bit can't really plunge/helix into stock very well. I was able to get it in by slowing down the feedrate and stopping midway through as the spindle started to sound like it was about to explode, but a pain overall. As a result, I had to slow down the entire feedrate. From talking to the consultants at the shop, the feed would have worked on a machine more rigid than the one I used (no other CNCs were available at that location). So I'm looking for another machine to do it at the earlier feedrate. (Faster feed means less time = less cost)
So going forward is going to be about making a few minor modifications to the creation process of the case, the design looks fine. All the keys on my 60% actuate fine when in the case. No bits of metal are stuck touching the caps, preventing their motion. The drill holes to attach to the bottom case look fine, and the sides are nice and thin.
I'll try to keep you all updated on the process of machining out both the top case and the slanted bottom. I've got ideas for workholding, they just need to be finalized! I'm also interested to hear what color options you all are thinking.
