Case Design & Prototype
 
It has been an amazing week - so much to cover!  As you can see from the picture above, I’ve started a case prototype. But, to get there, there’s a story...
 
For my watch, I’ll obviously need a case.  I want to go with something kindof retro looking; something that would fit with the pong theme.  I started with some sketches a while ago, and found a few watches that looked similar to what I envisioned.
 
The Nooka Zoo V2 is closest to what I want -- except, of course, my face will be very different. The Bell & Ross BR-01 is also similar in shape. Ditto for the Speak and Spell.
 
             
 
I bought a small CNC milling machine to, among other things, make the case (thanks, James!). But first, I need to design the case in some sort of CAD program. I was planning on using the excellent 3D graphics program Blender, but that didn’t seem to work too well for me -- it looks excellent for complex organic shapes, but not too well for simpler more mechanical shapes.  My backup plan was borrowing a professional CAD program and learning that, but that fell through. So, I wrote my own :-).  It’s not too much, but it inputs a bunch of primitive shapes defined in a text file and exports an STL file suitable for use by the CNC mill.
 
Here’s what the front will look like:
 
(I used Blender to render the STL file; my cad program is really basic)
 
In the middle is the opening for the OLED display.  There is a horizontal slot cut out that will fit a crystal.
 
And, here’s the far-more-complicated back side:
 
It’s still a rough draft, so bear with me.  The large opening in the middle is for the electronics -- it’s off-center because the OLED display is, too. I want the front to be symmetrical, so there is some wasted space at the top of the picture (I might reclaim that later).  There are 4 holes for mounting a back -- they are oversized in this picture. There are also cutouts for attaching a strap. I can only mill from the top and bottom, so the hole for the band’s spring pin is more like a slot -- that’s somewhat of a work-in-progress.
 
So, off to production!!  I’m using a Roland MDX-20 -- a small, PC-controlled CNC mill.
 
As this was the first time I’ve used the machine, I want to start simple. Instead of the aluminum I plan on using for the final case, this first piece will be milled from a block of mahogany. This should go much faster, and if something goes terribly wrong, hopefully there will be less of a chance of breaking a bit.
 
Speaking of bits, I used the biggest bit I have - a 1/8” bit.  It’s the strongest bit, but it is not capable of cutting tight corners, and it’s too big to drill the screw holes. But, it should get most of the case dimensions correct & provide a good start.
 
After quite some time, the machining was done:
I only milled one side - the machine is capable of milling both sides, but it looked a bit tricky for the first try. As a result, a substantial base is still attached.
 
The opening for the electronics is a little too small -- this should fit in easily. I have to check if it’s my homemade cad program that made the error (quite likely), or if the block moved around a bit during machining. [update: it looks like this is because I used the “rough draft” feature of the mill that gets rid of 99% the material. I need to run the “detailed” setting to finish milling the last bit and leave a nice surface]
And here’s a picture next to the sexiest watch of the 1980’s - the Seiko UC-2000:
So, what’s next?
 
  1. ๏Verify the shape vs. my design
  2. ๏Alter the shape some (for example, I might need to add some relief to the corners so that the OLED fits in better)
  3. ๏Make another wood prototype, but two-sided this time.
  4. ๏I might also try to work on the the case back. I might skip the wood version and go straight to aluminum.
 
 
Sunday, October 15, 2006