Dave N6NZ wrote:
On Jan 24, 2010, at 4:43 AM, Bob Paddock wrote:CO2 laser is the wrong wavelength to cut metal. Only a couple percent of the radiation is absorbed. Great for plastics, though, and many other materials. With respect to >PCB etching, one thing I've thought about but haven't yet tried is simply using paint. Apply a thin code of flat black paint as a resist (I'm guessing enamel would work best) >and let the laser ablate the paint where you want to etch.We already use commercial grade pre-photosensitized FR4 laminate, so doing painting and such is not needed. My only concern was that there might be issues of the wave-lengths between the LASER and the laminate being miss-matched, but if the process is actually based on heat then it is a non-issue.Now that will depend on your photochemistry. CO2 laser is not in the visible spectrum. You'd have to check the sensitivity of the photo emulsion w.r.t. wavelength. Most litho films are not sensitive even to red, but do go up into ultra-violet. I can't remember if CO2 is longer or shorter than visible light. In any case, you'd get by with very low power. So now for the wacky idea of the day... an interesting hack would be to make a tool head for a RepRap or some other cheap X/Y bed that simply holds a green laser pointer. -dave
Dave,I have been following the RepRap project with interest. A 3D printer that anyone can make is a very cool scratch to itch. I am fascinated by the artwork of the sculpter, Bathsheba Grossman. She really shows what is possible with 3D printing. (http://www.bathsheba.com) Maybe the RepRap will progress to this level of precision, eventually. I am very impressed with the parts that people are currently making with it.
I like the idea of using a cnc mill to vector plot the pcb artwork onto a photo-resist board with a laser. I do not think mounting a laser would be very difficult. There must be a low intensity laser that is in the correct frequency range to cure the resist. You could make different apertures easily by creating transparent slides with a single white dot against a black background.
As far as a cheap x/y bed, how about doing it with a cheap machine that is massive and solid, like rock? I have been following the epoxy-granite thread on cnczone.com for a long time:
http://www.cnczone.com/forums/showthread.php?t=30155 (It is a HUGE thread with 3828 posts, currently.)
Epoxy-granite is basically moldable rock. It is made out of aggregates of different sizes (mainly quartz), which are measured in certain ratios, so that they pack together very tightly. The spaces between where aggregates of one size touch are filled by smaller aggregates on down through several orders of magnitude. The size of aggregates range from 4mm in diameter down to a couple of microns. The epoxy (10-20% by volume) is added to hold everything together.
Epoxy-granite is relatively cheap. It can approach the strength of aluminum, but you can embed rebar in the casting to increase its tensile strength. One of the nice properties of e/g is that it has 10 times the damping properties of iron. That means better surface finish on the machined parts, and longer tool life. Also, people should be able to find most of the materials near local industrial centers. I have been experimenting with e/g and I am currently building a benchtop cnc lathe. I have a blog on it here:
http://www.cnczone.com/forums/showthread.php?t=42308 I am going to post many more pictures of my progress.After, I finish the cnc lathe, I am on to a small epoxy-granite cnc gantry mill. I think it will have a 13" x 13" table. My goal is a massive, rigid, and accurate machine that can produce precision parts and mill pcb's.
Thanks, Dave _______________________________________________ geda-user mailing list geda-user@xxxxxxxxxxxxxx http://www.seul.org/cgi-bin/mailman/listinfo/geda-user