CNC Mold Making
To make the board I started by machining out a mold from insulation foam. Because the foam was only 2" thick and I wanted my board to have a 3" lip in the front and back I stacked 2 pieces of foam and glued them together with Gorilla glue.
After rough cutting with a 1/2" ball end mill and finish cutting with a flat end mill I had the following mold. Because foam is like cutting through air I was able to set the feed rates 3 times as high as for wood and the ShopBot was limited by its ability to accelerate. To save time I also oriented the material to the long direction would go with the axis of the little carriage so there isn't as much mass to accelerate.
Composites - Board Making
I layed out all my materials before mixing up the epoxy. Over the mold I put a layer of bleeder material and covered it with a permeable mesh.
The idea was to then coat the layers of burlap with epoxy and just lay them on top of this pillow, but the epoxy just ran straight through! I tried adding a layer of linen to help easy the flow, which I think worked a bit. I'm definitely not going to make a piece out of just burlap and epoxy again. With my quad body I at least had the cardboard to wrap around, I really should have had a core. A few cups of epoxy just went strait into the bottom layer of bleeder material, which is a waste. I had to use a stupid amount of epoxy to coat it all. I didn't count, but on the order of 10 cups. Epoxy isn't good to get on your bare skin, and even though I was wearing gloves this process was a mess!
When the mess of layering the burlap was done I put the whole contraption in a trash bag, mastic taped one side and turned on the vacuum. The pressure didn't go above 5 psi, so I checked for air leaks and didn't find any... I figured maybe something was wrong with using a trash bag, which is why I hadn't seen it done before, so I put the whole thing into a vacuum clothing bag. Still the pressure didn't rise. Sometimes the pressure is high because something gets stuck in the vacuum tube, but my problem was low down stream pressure.... I realized that upstream the hose wasn't snuggly connected. Fixed! The pressure went up.
It got to about 25 psi within the vacuum bag and when I removed the vacuum bag and re-tried with just the trash bag it went up to 30 psi. I found the double zip-lock seal on the vacuum bags were not as strong as the mastic tape, particularly if the seal was not held straight. If you are going to use a vacuum bag with a seal like that it would be worth wile to tape the bag down to the table to avoid wrinkles in the seam. You can see how tight the trash bag pulled around the batting and mold. You can also feel the warmth from the curing epoxy.
Vinyl Cutting
When the board came out of the vacuum its edges were very rough, so I cut out a vinyl outline to stick to the board as a guide to trim the edges with a skill saw. I had a few problems getting this cut out. The Fab Modules wouldn't connect to the vinyl cutter for some reason, after fiddling with this and getting advice, I used Roland Cut Studios to cut it out. I had some trouble loading any files into Cut Studios, finaly a .bmp worked. Once it was loaded and I tried printing, it wasn't working. Finally James showed me that I only wanted "cutting" not "print & cut" or the vinyl cutter makes a mark and then searches for it, which is just couldn't find. Finally I had a giant snowboard shapped sticker and I cut out the board.
Metal Edges
I bought steel snowboard edges, which are actually attached to boards with epoxy. So my plan was to just glue them on. This is how they looked when I got them. The warning says "Edges are sharp and under tension. They will spring back when undone. Please use caution when opening. It didn't lie, they were supper springing and this quickly turned into a wrestling match. Gloves may also be advised. To help bend them to the shape of the board I built this tool which I saw online while searching how to attach snowboard edges. It is kind of like a can opener without the blade. The idea is to clamp the steel between the two disks and force it to lay flat with the washer as you bend it, but it didn't really work for me because mine was not precise enough to clamp them firmly and I wasn't strong enough to bend it with my hands and no lever arm.
I ended up bending the edges as best I could with a clamp and then just clamping them too the board. There has to be a better way to do this because I spent a lot of time trying to force the springy steel into shape.
After sanding down the base to make it a little smoother I epoxied the edges, which were mostly in shape, to the edge of the board and clamped them down.
Laying the P-Tex Base
Snowboards and skis have a layer of a material called P-tex, which is conformed to the bottom of the board. It can have different base patterns ground into it and can be waxed according to the temperature and the snow moisture content, i.e. some snow is very crystaline, dry and abraisive, while other snow is fresh, moist and have little structure. Depending on the snow and the purpose of the board skiers and snowboarders would wax differently, with harder or softer waxes and different flourination amounts, p-tex is necessary to imbibe the flourine and allow the board to have glide. I bought a roll of p-tex to cut out and lay on the base of my board, but all my ski tools (torch, bench and braces, waxes, scrapers) are at home in Alaska, so I'm going to finish this part there.
Circuitry
The circuit I am using is an Attiny connected to a an LCD board, powered by a standard 9V battery, exactly what I made in output week only with a button and an LED. Ideally when you push the button once the LED turns on and the clock starts. The LCD screen displays the time counting up and when you push a second time the clock stops but the screen stays on. A third push of the button turns the circuit off. Here is the board layout I designed in Eagle, the two large square pads are to connect the circuit to the switch.
Once I got the board soldered up I turned to the programming. I've been having trouble with my computers COM ports, they didn't work anymore, and so over Thanksgiving I bought a new computer. Now I downloaded all the drivers and finally got the FabISP talking to the computer and the code on the board!
I wired up the same LCD screen I couldn't get to work on the new board and it still didn't work. I found the bottom two pins of the Attiny were soldered together, fixed that, as well as a problem with soldering on the 20Hz resonator. These LCD boards are laid out a little differently than most where they start with pin 15 then 16 then 1... but as I followed Neils example I checked every wire and they all connected to the correct pin in the header. The 5V regulator was working and the Attiny was powered. The programs would all load fine, but only the first row of the screen turned on and was just black... I also derped and just connected the switch between GND and VCC, so I can't actually get information from it. Sad, but I just made a jumper wire to the attiny pin 8 which worked until the pin moved so much it fell off the attiny. By this time I'd replaced so many of the components over and over again the traces were falling off like spaghetti.
I made a new board with some of the fixes I'd found, and decided to incorporate a strip of LEDs to run around the edge of the board. The LEDs needed their own power supply, so I used a transistor to control communication from the Attiny turning on/off the separate 12V power supply. I wasn't super happy to have a 9V and a 12V, with more time this could have easily been remedied. This time I used a surface mounted switch instead of a fancy large one, I also incorporated the transistor for the LEDs on the board.
A few of the traces were so close they didn't mill out. I knew this was going to be the case, but a lot more connected than I thought would. After the board was milled I cut the dregs with an exacto, but the first go around I still missed a few, which I had to find later.
I finally got it working and was debugging the programming when *spark* I ended up shorting things a few times. Never solder when your power is connected. I glued the LEDs onto the board with a hot glue gun and continued working on fixing the electronics.
I appeared to have a floating pin, because the lights would turn off and on by my finger coming close to one corner of the board. I cut some more traces and used the internal pull up resistor to read the input from the button.
My final circuit board was really a mess of wires going everywhere, but thats the joy of hacking these surface mount boards. Being under such a time crunch I did get to utilize the exacto knife design technique. At one point I put too much force on the header for the battery and it ripped off. You can see almost in the lower left under the black electric tape I cut out a pad on the edge of the board to solder the big ground wire from the battery and added a little jumper to connect it to the rest of the board.
Finial
After so many hours I could strap my little board to my backpack and bike home well seen. I can push a button and the LEDs all change color.
