Hi Mike, Long tirade on 3D Stereo Lithography, nominal PIC content at end. > > I have seen this on beyond 2000 and other shows. I heard they use 2 > >lasers x and y . The epoxy is like the dentist use, when it is exposed to > >ultraviolet light , it hardens instanly. The lasers are computer controlled > >by cadcam , where the lasers intersect the 2 frequenceys combinded create a > >point of ultra violet light and walla, instant prototype. > > Aye ? Anybody care to clarify the physics - how can two light beams 'combine' > to produce UV - I didn't think that was possible to produce a higher frequency > from two beams of lower frequency - give "mu= h * v" etc ? > > I would think it more likely that both beams are lower intensity but, where > they cross the intensity is high enough to cure the epoxy ie By themeselves, > each beam does not have sufficient intensity etc. You are correct in thinking that it is difficult to increase the frequency of light with regular materials. There are however various crystals that will multiply light frequencies but they are not relevant here. Most of the 3D Stereo lithography systems I have seen, read about do not use two beams. This is possible by making use of two beams of differing energy and using one of them to sensitise an exotic material that will then react to the other light colour/color and cause the polymerisation reaction. The usual method is to trace the surface of the vat with a seered UV light or LASER that cures a strip just 0.2 or 0.1 mm thick and this would normally be just above an already existing cured strip just below the surface that it will join with. The transmission of the beam through the material will be quite limited and only works because the thickness it passes through is always the same and very thin, hence my suspicion that dual beam units will be rare. The chemicals are nice and toxic and expensive, Ciba Geigy makes some I seem to recollect. However there is a material on the market that is similar and should be available and is used to make Rubber ink stamps. It is a UV curing rubber that hardens with UV light and the product can be washed with soap water until curing. The result would be a rubber object that you thencure a bit more after washing. The parts that come out of the 3D Stereo Litho machines are very fragile when they come out and any overhanging structures are supported by thin wall honeycomb matrix until the part has been drained and then post-cured. After post-curing the part is much like any other brittle plastic. They are usually used for samples or for making spray metal moulds or investment casting a single component like a replacement hip joint. I seem to recall pricing of US$ 100 per hour and that allows you to build an object about an inch thick the size of the tank, thicker objects need more hours and $. Cannot think of any PIC applications at this point. The UV curing rubber stamp liquid costs US$ 60 for 2 kg from 'Rubber Stamp and Engraving Co.' +27 (11) 838-7882 (this is only useful for South Africa) you need about 3 ml for a 1 x 2" address stamp so the material cost is near US$0.10 per stamp that gets sold for US$20, nice profit (needs the handle too). Perhaps one could use a small PIC servo driven Pantograph with a optical fibre to a UV light source and then make a toy 3DSL machine for US$ 100 instead of US$100 000. Make your own rubber stamps in any event. > PS: You could just as well use a metal powder and a cheap CO2 laser - to fuse > the metal powders together and re-lay the powder a few microns each time you > do a pass - this could build up quite a solid metal prototype - you could > then plate it afterwards to improve its strength and appearance if required. Cheap CO2-LASER is an oxymoron :-) What you propose has been done, not sure if it is a production capable concept but you can certainly sinter the metal powder with a LASER or electron beam perhaps (needs vacuum). Cheers -- Kalle Pihlajasaari kalle@ip.co.za http://www.ip.co.za/ip Interface Products P O Box 15775, DOORNFONTEIN, 2028, South Africa + 27 (11) 402-7750 Fax: 402-7751 http://www.ip.co.za/people/kalle DonTronics, Silicon Studio and Wirz Electronics uP Product Dealer