Frequently Asked Questions.

I want to make a metal cutting system too. What would you have done differently? Are there ways that I could save time by buying OEM components?

Most of the mechanical parts of the system like the physical CNC table, the chiller, the frame supporting the laser were very easy. This is fun and not very time-consuming. Perhaps the biggest technical hurdle was that I put my laser support system together using a welder which some people may not have.

The optics were pretty much bolt-together parts and I dont think there would have been much time to save there. There are some optics that are specifically designed for the laser itself which would allow you to just take the optics out of the box, connect to the system, and you are ready to go. I was lucky to get my optics from ebay and other sources for fairly cheap, but it was not an instant solution. I would still go with the used parts solution again.

Electronics. Now, this was hard for me. You need to have motor drivers, some laser controls, limit switches and emergency stops. Putting this all togethe under one integrated system was a very large amount of work. I dont know of a commercial system that works for my laser, even an expensive one, so I had to make all that circuitry myself. I used a lot of TTL logic, and to be certain I would never do that again.

So one thing I definitely would do differently is this. I would use microcontrollers. I would have liked to have all inputs and outputs of electronic/electric connections going into a board handling TTL signals, relays, and connections for external limit switches, and then put the logic of the overall system together with microcontroller software. On the other hand, if you want to save some time it would be best to find an alternative to making the electronics your self.

House wiring. There was a lot of wiring I had to do myself, which was fun but also a lot of work. You could definitely save time (not money) to have someone else do that.

There are examples on ebay of complete laser cutters with enough power to cut metal. They are very expensive, and also require wiring ventilation and cooling pretty much similar to what it would be like if you had a shop with a really large milling machine. But that still might be a way to be cutting metal without taking a lot of your time.

So the short answer to your question is this: unless you want to spend $50,000 I think you'd have to do most of it yourself.

Can I cut brass?

I have a glass laser that delivers 100 watts of power, can I cut steel too?

What else do I need to cut?

How much did it cost?

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.

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.

so 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.

I have succeeded in cutting a disk of approximately 1/4 diameter off the tip of my finger though. Hurts like heck but it cuts while it cauterizes, so there's no bleeding.