I've decided to embark on building a rapid prototyping machine. Notionally they're 3D printers, commercial machines have been available since the late 1980s and they've been getting smaller, less expensive and cleaner since then. Desktopfactory.com had been promising a sub-USD5000 desktop model, but ran up against a finance shortfall in 2009 and were subsumed by 3DSystems, the originators of additive RP, who still want to release it. 3DSystems' current model lineup starts at USD10000. Too big, too complex, too expensive for me, which is the drawback of all additive machines apart from the recent open-source projects.
The other method of rapid prototyping is subtractive, ie carving or milling machines. The greatest drawback of subtractive machines is having to cut away lots of waste.
There's a technology that's halfway between the two: Layer Object Manufacture. This involves cutting profiles that are then laminated together out of a substrate. It's a process that has a lot of promise because its resolution can be much more precise if the substrate is stable. The waste is stripped away afterward, instead of having to be cut, and the waste is default support structure for overhanging features. A recently-developed LOM machine is the Mcor Matrix, an Irish-built machine that builds prototypes out of paper. 80gsm paper is .1mm thick, the z layer resolution. Clever, but still more than USD 20000, even if the running costs are minute in comparison to its competitors.
So, I'll draw on others' efforts. Reprap.org is motivated by the idea of a production robot that can reproduce itself, so their efforts are named after the scientists who founded our understanding of evolution, Darwin, Mendel, and so on.
I like what they've achieved, but I have some reservations about their machines. As a polymer deposition machine, it builds 15 cm³ volume per hour, which makes it a less-than-rapid prototyping machine in my view. The idea of finished parts dropping into your lap is attractive, but reprap's not a mass production machine either. The appearance, accuracy and strength of its output is dependent on the deposition nozzle's feed rate and temperature and the stated accuracy of .3mm-.5mm is less than what I want. But to improve that, and to increase the rate of deposition would probably take more mass, more power, and more complication.
So I'm thinking that I'll use the reprap Mendel basic structural design to implement paper LOM. I'm going to use a very-high-speed air-powered engraving tool called "Turbocarver" to route the sheets of paper instead of using a knife blade to slice them, which would require a cutting mat surface to bear against. The Turbocarver will handle a sheet of paper with next-to-no speed reduction (it's only .1mm thick, after all), I'm thinking, and the speed (400K rpm!) should shear the paper fibres with miniscule lateral force.
More about this project as it progresses......
