Well, I've had some setbacks -- namely, an infection in my jaw gone wild -- and I ran out of money and options and had to move out of my apartment. Now, after a brief stay in my workshop, plus doing a ton of odd jobs, I have all that paid for and I've moved into the basement of a house near my workshop. Just for the hell of it, here are some pics of my apartment after I emptied it out. All that was left on the last day was my bike, synth, and FTIR spectrometer. I built the first DIY book scanner here, so I guess the space is of historical interest.
Life in the workshop was a bit messy, but was not long or bad.
During that time, though, I got a lot of work done on this new scanner build. A whole lot of time and effort has gone into just seeing if things will work. One of my design constraints is that I want the majority of components for this scanner to be able to be produced with a laser cutter. Many high schools and universities have them, so if it can be laser cut, many students can have them and improve them. But to get the design to that stage, I had to find a suitable structural material.
I went to Menards, a local hardware store, and bought 1/4" regular plywood, 1/4" MDF, and 1/4" birch plywood. The first two failed to cut at all. They absorb too much laser energy and the kerf is just enormous. So they are unsuitable materials. However, the 1/4" "baltic birch" ply is actually not a quarter inch thick, it is 5mm thick. Not only that, but it is made with urea glue, which cuts neatly on the laser. There are two problems with 5mm Baltic Birch. The biggest problem is that it does not lay flat. Laser cutters fail horribly on non-flat materials. Even a deviation of 1/16" or a mm or two will put the material out of the focus of the beam. For the first few cuts, I tolerated this shitty situation, but for later cuts, I mounted the plywood to heavy aluminum blocks with double-sided tape. This caused a DRAMATIC improvement in cut quality and consistency, and made things work out well. The settings for the laser were 100% power, 15% speed, 600hz.
My nephew Benjamin is learning to use the cutter. He helped clean it and program up the test plywood parts.
Now that I knew I could cut plywood, I had to figure out a way of sticking two pieces of it together. I decided on a screw and nut based system, and worked out the measurements. This system proved to work fantastically well. This little test box is incredibly strong. I can stand on it, no problem. This is how I will construct camera supports and the rear column.
One constraint for my new scanner is that I want it to be acceptable as carry-on luggage. That means the dimensions cannot exceed 45 linear inches. 22x9x14. It also can't exceed the dimensions of my laser cutting bed -- 24x12". One solution that came to me the other day, though in hindsight it is totally obvious, is to make the base into a box instead of just a flat thing. That way it can be used to stow scanner parts, the power supply can be hidden inside, etc. So I started crafting one just to see how strong it would be. It seems that with a top and a brace or two, this will be acceptable in terms of strength.
The next step was to reduce the size of the folding platen I was working on, and to cut it from plywood to test how strong it is. Results were pretty good -- strength seems acceptable. I toyed with the idea of a front-mounted plate which would stabilize it, but it doesn't seem quite right. I need to think of a way that the U-handle can stabilize the thing with a minimum of parts. Ideas welcome. Also, I need to figure out how to mount the platen to the hingalellogram in a way that it can be easily and quickly removed (because the platen can't fold with the column attached). If anyone has any clever ideas there, let me know.
After re-cutting the folding platen, I realized that I could cut the folding base from plywood. Did that too.
Finally, after lots of messing around with vertical slide mechanisms, I decided just to go with a hingalellogram for now. It is a smart mechanism and a compact one. And it preserves the original platen action of the first scanner I built, which I really like. So here are a few shots of where the hingalellogram is going. I think I'll use the black one.
That's it for today. Gotta get back to work.