Can I cut brass?
No. I cant either. The industry would love to cut brass and they aint figured it out either. I gather it's a problem due to the heat transmission of brass and copper. It spreads out its heat over the area of the cut too effectively. If you cant concentrate the heat on a particular area, the metal doesn't get obliterated. Steel is a lovely and cooperative metal.
I have a glass laser that delivers 100 watts of power, can I cut steel too?
Probably not. Its really hard to tell what power my laser actually delivers. The ambigiuity is because the product literature says that they modulate the output. The laser sends out higher bursts of energy that probably exceed 100 watts. The total delivery of power integrated over time is 100 watts. But according to the manual, they claim that by peaking the delivery over short bursts that it actually develops intermittant delivery of 250 watts. I dont know if its really doing that -- I do know that other lasers (e.g., YAG) also work on the principle of quick bursts that deliver much higher power.
If you have a sealed glass laser, it delivers continuously, and it doesn't do this burst trick that the Coherent does. That's not to say you cant get some cutting power. Maybe you could cut stuff that's 0.005 inches, or better. The key, as you may very well know, is to think about your optics. If you really want to explore the issue you may want to read this section.
Your goal is to get a tight beam, and a DOF that is thicker than the object that you want to cut. If I was in your shoes one place I'd do some research is to find out what power density is required to cut metal. I was told over the phone by Coherent guy (hey better than an incoherent one) that it is 10^6 watts/in^2 for steel. But there's a chance that he's wrong. Once thing I know, is that I can control my power output with electronics going to the laser. When I take that down to 50% of the max, it still cuts, maybe not as well but it still cuts. It suggests to me theres still hope for the glass tube guys.
If I have a laser - what else do I need to cut?You must have a functioning cutting head, that delivers oxygen that flows through the nozzle. You also need a cnc table running the part around underneath the nozzle.
How much did it cost?
Its rude question but...total estimated cost is about $15k or so. The laser itself was $6500, I bought a cnc table for $500, and the optics were another $2500. A chiller from ebay cost me $500. There were lots of other incidental costs like a lot of electronics, motors, motor controllers, 220 volt wiring, cooling and ventilation. The biggest operational cost is oxygen. A tank of oxygen is $55 and can easily be used up in a weekend. The operational cost of electricity is negligible. The stainless is pretty cheap, around $1 a pound.
Then there's time. The project took 2 years, but if I had to do it again it could get done in about 6-12 months.
I was thinking earlier today about all these CNC machines when all of a sudden I looked over at my printer and realised that with a few modifications it might be made into a basic CNC.
I dont think this approach works. The problem is lateral thrust.
If your printer is buzzing along, try putting your hand in the way of the movement, you'll see that even a bit of resistance will prevent most of the electromechanical gizmos from moving. Now think about instead of that printer head on a little gantry system, you've substituted in a cutting tool like a small dremel.
You can imagine that you'd have problems with the printer mechanics moving a cutting tool in wood, but you also have problems just with forward inertia. If the heavy cutting tool is moving in one direction, reversing that movement quickly will wont happen perfectly, it will try to reverse, some belt or gear or stepper will slip a little. (If you clamp your fingers on small steppers when they are moving, they just stop.)
Since most systems of that kind lack feedback about the exact position of the gantry after that slip happens you dont have a good relationship between what the computer is treating as an x-y position, and what's actually happening on the printer. this'll screw ya up.
But, some cutting tools offer little or resistance, like a laser beam being moved around by flying optics, or really really really fast cutting tools (like a high speed bit in a dental drill). so then all you have to do is deal with the forward-reverse inertia problem. there are other applications, like if you're spraying paint or something, that would also have no resistance. also if you're cutting something really soft. but be advised I used to have a balsa wood cutter and there aint no way a printer could handle pushing a bit through that with any accuracy.
So for cutting tools, you want to have something stronger than a printer. be advised though, if you want to make something it just aint that hard. there's steppers and pulleys and belts and drivers and premade systems galore, just gotta make a little investment. search ebay using the term "linear actuator" or "xy table" or "cnc table", at least some of those searches will show something cheap.
The other way to think of it is go ahead and buy a plotter on ebay and hack it up, they have all the parts in there. you either hack the existing driver, or get a cheap motor driver board and connect the motors to that. its incredibly instructive to see how a system works. it wont handle moving a cutting tool but its still very instructive. I started by getting a laboratory robot that moved around small liquids, was really good for showing basic principles.
It just boils down to how much lateral force a cutting tool needs, and the forces involved when redirecting movement of the cutting tool. my guess is that in most cases you could just clamp your finger down on the motors that are moving your printer and you could stop the movement. to be sure, the older printers and the larger format plotters might have a chance. the other option would be to use the mechanical parts from an old system and swap in bigger steppers.
Can your laser cut thru your finger. That'll leave a mark.
No. This laser cant cant cut through a whole finger. One reason is that co2 lasers cant penetrate through water, which is what meat mostly is made of. The other reason is because of divergence, the power density of the beam drops off very very quickly as it leaves the cutting nozzle. Its the molecular equivalent of shooting at a target with a shotgun that's a mile away.
I have succeeded in cutting a disk of approximately 1/4 diameter off the tip of my finger though. Hurts a lot but no bleeding.