Hi All,
A little background first…
I’ve been interesed in lasers since I was a teenager (late 60s, early 70s). I read all I could find about them. The cost of even a small HeNe was WAY more than a teenager working at Dairy Queen could afford. While I was in the Air Force in 1977, I happened to be at a Blue Oyster Cult concert and saw their laser show. I was absolutely dumbfounded. Laser shows were just starting to be used and this was the first time I’d ever seen a BIG laser. One of the main people in the development of laser shows was David Infante. (I’ll connect all this in a second.)
I was able to afford a 5mW HeNe after the USAF in 1980. I made all kinds of things with it, mainly laser show oriented. I had a TRS-80 Model 1 as my “show” computer. I built a DAC card to output to laser scanners. I built an ADC card to read potentiometers so that I could input drawings to display. I even worked part-time writing code for a laser show company. I was immersed in lasers and computers.
In 1987, I was working for GEC Avionics as an optics/laser engineer, working on the CO2 laser rangefinder for the M1A1 tank. I was walking through the office one day and heard someone mention the name “David Infante”. I didn’t think there could be too many people with that name, so I went to find out about him. Turns out it was the same guy that had been instrumental in getting laser shows started. He now worked for the same company as I did. We started talking and he suggested that I build a CO2 laser because it was easy and cheap. He was correct on both counts.
That laser is what you see here.
It’s two coaxial Pyrex tubes, 48” long, with a couple of turned aluminum ends, a copper mirror on the rear and a ZnSe output coupler. Epoxy holds it all together. It ran with a neon-sign transformer, a vacuum pump, a submersible water pump, and a tank of pre-mixed laser gas. It put out about 50W. The books all say you should get about 60W per meter of tube length. My mirrors were in pretty bad shape, so I never could get all the power I should have (~72W.)
Hmmmm… what to do with a high-power CO2 laser??? Build an XY table, of course!
Someone had given me a Sears Decorout-or-Planer:
I put it together with some stepper motors and ¼-20 threaded rod and built an XY table. I built a stepper driver card and wrote my own cutting software (I had upgraded to a PC) that read Autocad plot files and sent the data to the laser and XY table. The laser ran full-power all the time. I had a piece of copper pc-board material mounted to a rotary solenoid inside the laser enclosure that would deflect the beam to a piece of fire brick. When I wanted to cut, the solenoid would rotate the copper out of the way of the beam. Here’s some pics of items cut with that system:
The pieces of gravel have holes punched through them with the laser.
Out-of-pocket money for the whole system was a few hundred dollars. It took about 6 months from start to cutting pieces of Plexiglas. Admittedly, I already had a lot of the “stuff” to build the system. I was able to get the mirrors for nothing. I built the XY table for practically nothing. It was amazingly accurate for being built from plywood and 2-by-4s. I used a dial indicator to measure the backlash, and compensated in the software. Check out the start/finish points of these circles:
I just clamped a pen onto the carriage and used it to draw.
At that time (1990), the project was put on indefinite hold (divorce) and everything but the laser was lovingly placed in a dumpster.
Fast-forward to 2009… I was at a craft show and saw a vendor selling bricks that had been written on with a CO2 laser. The company that was making them had made all the lasered bricks in Atlanta’s Centennial Olympic Park. I thought “I was doing that 20 years ago…” That jolted me enough to want to do it again.
I found a Coherent Model 42 Industrial CO2 laser (60W) that was sitting in a warehouse. Since it’s a flowing-gas type, nobody wanted to deal with it. Everyone wants the sealed-tube type. I was able to purchase it for $500. That’s the laser in these pictures:
I started plans to build a cutting/engraving system, and found Bart’s buildlog site. The pictures of Dillon’s (hoda0013) system is pretty much what I was planning. I think my main problem is how to mount the laser. It’s going to have to stay in its enclosure. I could mount it under the table and direct the beam up, or I could do it like the folks here:
The relative positions of the table and laser would have to be maintained very accurately. That means no bumping the table.
I won an auction for four 64” rails with cars on eBay. I’m ordering extrusions this coming week. I already have a GeckoDrive G540 and power supply, and three NEMA 23 steppers from Keling. I’ve got my licensed copy of Mach3. I’ve got a complete machine shop with mill & lathe. And I’m hungry.
Enough rambling. I hope you’re not entirely sick of me already. I want to get this system running so I can cut and engrave to my heart’s content (I couldn’t engrave with the original system… too slow.)
I’ll track all the progress here. If anyone has questions, advice, criticism, etc., just let me know. I’ll appreciate all of it and try to answer any questions as best I can.
Tim Walters
Atlanta, GA