20 Years in the Making...

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20 Years in the Making...

Postby trwalters001 » Tue Nov 02, 2010 3:13 am

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.

IMG_1007.jpg


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:

decorout-or-planer.jpg


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:

CutItems.jpg


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:

Circles.jpg


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:

IMG_0206 sml.jpg
IMG_0208 sml.jpg


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:

Hungarian Laser Cutter 1.jpg

Hungarian Laser Cutter 3.jpg


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
Last edited by trwalters001 on Tue Nov 16, 2010 9:05 pm, edited 2 times in total.
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Re: 20 Years in the Making...

Postby Tweakie » Tue Nov 02, 2010 12:05 pm

Hi Tim,

I can't wait to see some pictures of your new machine construction. I am glad you have come back into lasers as I think we can all learn a lot from you.

Tweakie.
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Re: 20 Years in the Making...

Postby bdring » Tue Nov 02, 2010 12:24 pm

I would love to build a machine with the laser mounted on the gantry. That seems like the logical place to put it on a larger machine. It removes one axis from the alignment process. The X axis could still be fast enough for engraving. You could also enclose the beam path up to the lens. I think that might work for your laser.
Bart
"If you didn't build it, you will never own it."
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Plans for a home built tube

Postby bdring » Tue Nov 02, 2010 12:29 pm

...Regarding home built tubes. Here are some plans I found a while back. I wonder how much the gas costs to operate per hour?
.
55_Watt_Gas_CO2_Laser_Tube.pdf
(2.4 MiB) Downloaded 1836 times
Bart
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Plans for a home built tube

Postby trwalters001 » Tue Nov 02, 2010 6:53 pm

If I were going to make another laser, I'd use the plans that Bart linked to (or these: http://repairfaq.cis.upenn.edu/sam/rconway/35wtkit.pdf.) I saw those about a year ago. The problem is not the tube, it's the power supply. I know there's a lot of both available on eBay. I've read quite a bit about the (lack of) quality of the tubes and power supplies. The sealed-gas tubes have a relatively short shelf and operating life compared to a flowing-gas type. BUT - there's considerably more hassles with flowing gas.

My tank of laser gas cost $50. It contains 9 cubic meters of gas. You'll go through gas at about 2-2.5 liters per minute, which means:

9,000 liters/2.5lpm = 3600 minutes = 60 hours of operation for $50. Not too shabby...

My laser head is very heavy (54 lbs). Mounting it on the gantry isn't an option for my size system.

Here's some additional info on home-built CO2 lasers:

http://www.repairfaq.org/sam/lasercc2.htm

http://www.wikihow.com/Build-a-Cutting-Laser

-
Last edited by trwalters001 on Thu Nov 11, 2010 1:44 pm, edited 1 time in total.
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Re: 20 Years in the Making...

Postby bdring » Tue Nov 02, 2010 7:02 pm

I almost built the 55w tube a while back. I converted the drawings to Pro/E and made a few modifications. The modifications were to get a few off the shelf items. What are the design guidelines for the anode and cathode? I want to use some off the shelf items, but don't want to compromise the design.

55w_tube.jpg
Bart
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Re: 20 Years in the Making...

Postby trwalters001 » Tue Nov 02, 2010 7:20 pm

My old laser didn't have any "design guidelines"... :lol:

If you look at the first picture in the buildlog, you'll see that the tube is held onto the supports by U-bolts. High-voltage was applied directly to those and was then conducted into the turned aluminum ends. Nothing else. It was pretty much a neon sign with mirrors on the ends. VERY ghetto. But it worked.
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Homemade CO2 Laser

Postby trwalters001 » Fri Nov 05, 2010 6:55 pm

Hi All,

Here's some very good info for anyone who's thinking about building (his/her) own laser:

http://www.laserk.com/newsletters/whiteCO.html

Tim
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Re: 20 Years in the Making...

Postby lasersafe1 » Sat Nov 06, 2010 12:25 am

I can only say that I hope OSHA doesn't visit that shop you showed in your first pictures. Looks a little unsafe with that big laser hanging on the back wall and free space beams. Exhausing the fumes is probably the most important part for the things we cut, so I would never consider a laser without a complete cabinet.

Your first home-made tube looks quite nice. You mentioned enjoying light shows, ditto. I remember going to the Pink Floyd laser concerts at the Planetarium when I was in High School. I ended up working at a National lab and use some quite powerful lasers. I thought a 10W argon laser was impressive and couln't resist playing a little after hours. Those were the days before serious laser safety protocols. I must admit that I couldn't resist my own safety advice and I have played with the new 1 watt 455nm diodes into the night sky (avoiding aircraft of course). What a beautiful color! What amazes me even more is the efficiency. The diode takes 1 amp at about 3.5 volts (3.5 watts) and converts it to 1 watt of light. Unthinkable only a year ago! Add some phosphor and put it in a bulb and this will certainly exceed the efficiency of any compact florescent bulb. Things are changing fast!
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Re: 20 Years in the Making...

Postby trwalters001 » Sat Nov 06, 2010 12:30 pm

Hi Lasersafe1,

Thanks for the good words!

I don't think OSHA will be visiting that shop... It's in Hungary.

I might have shot my green 1W into the sky a few times too... (avoiding aircraft of course). :shock:

After looking at all the buildlogs with guys using sealed lasers attached to their machines, I went ahead and ordered a 70W tube and power supply. I think it will be MUCH less hassle to build and run than the slow-flow unit I was going to use.

I also received my rails and cars this week (four 64"). My biggest decision now is how big to make this thing. Five feet square is pretty big... :D
Last edited by trwalters001 on Sun Nov 07, 2010 3:16 am, edited 1 time in total.
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