Case Prototype III
Or, “How To Make a Small Hole with a Large Bit.”
I have made the third case prototype, and I think this is the first case that could work. I made many changes:
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The material is now plastic (Delrin), so it should be more durable than wood but still not as durable as metal. -
I have made a caseback so that it can be sealed. This fit perfectly on the first try! -
The caseback allows attachment of straps -- something that wasn’t possible before.
The most interesting part of this design is how I attached the straps. The pins required to hold them needed to be 0.9mm in diameter, but the smallest milling bit I want to use is 1.6mm in diameter (I’m afraid my 0.8mm and 0.4mm bits are not strong enough to machine aluminum).
The trick is to create the 0.9mm hole by creating the space that is only formed when the case and caseback are assembled together.
The negative side (case) has an oversized hole:
The positive side (caseback) has a protrusion that fills the hole, minus the intended gap:
This works because the drill size does not limit the size of positive protrusions -- only negative ones.
The final result looks like this (caseback on the top, case on the bottom) - a 0.9mm square hole:
With the matte black band and the black OLED display, this case looks pretty wicked. I might make the metal case all-black, too.
Next up:
I’ll be designing the PC Board. I can only get so far because I’m traveling. When I return home, I plan to finish the electrical tests before releasing the PCB design to manufacturing.
Wednesday, November 29, 2006
