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CNC Laser Cutter

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LAN_403

macona

Thu Nov 08 2012, 10:07AM

Registered Member #3272 Joined: Mon Oct 04 2010, 11:40PM
Location: Beaverton, OR
Posts: 101

It was suggested I post about the CNC Laser Cutter i recently (mostly) finished.

It is a medium sized machine, about 20" x 30" travel that was built from an old Hamilton Star lab robot. All the electronics were gutted save for a few parts like power supplies and motors. It is all servo driven, none of that stepper stuff here.

What sets this laser cutter apart from all the other home made lasers is the laser itself. Most people use CO2 lasers, they are cheap (chinese) and are great for cutting organics at their long 10600nm wavelength. There are a couple people out there that use YAGs but they are far and few between, their 1064nm wavelength (IR) is better for metals. Mine uses an even rarer beast, a Diode Pumped Solid State Q-Switched laser that is frequency tripled to 335nm (UV). This allows me to work with materials that you cant touch with a YAG or CO2. For example, I can etch and cut glass, ceramics, and metals. With metals I have managed to burn though .015 shim stock. This is with a laser that puts out about 6 watts average at 10khz repetition rate. The short wavelength means the focused spot size is 30 times smaller than what is possible with a CO2 so the power density is pretty incredible.

Still some things I need to work on. I have no power control from the controller (Mach3). The laser requires a signal to drive the q-switch. Max average power is about 9.5khz so I need to supply it with a variable frequency source, the higher the lower average power, up to about 40khz. The duty cycle is roughly fixed at about a 8us off time. A friend is putting together a little board with a PIC that will take a serial signal from mach and adjust the power.

Also the holes it makes are not quite round. This is a tuning issue with the servos.

So here are a few pics and clips of it working:

Link to build photos:

Cutting .006 stainless:

Cutting kapton:

engraving stainless, (actually went through)

Inducktion

Thu Nov 08 2012, 04:24PM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

Wow, that's pretty impressive!

I want to ask though, how did you get a frequency tripled laser, and how much did all of this cost?

Josh Campbell

Fri Nov 09 2012, 02:25AM

Registered Member #5258 Joined: Sun Jun 10 2012, 10:15PM
Location: Missouri - USA
Posts: 119

Very impressive build. What type of mirrors did you end up using at that wavelength. And what make/model DPSS are you using? I've seen CrystalLaser UV models that go up to 8W but this one looks different.

macona

Fri Nov 09 2012, 06:05AM

Registered Member #3272 Joined: Mon Oct 04 2010, 11:40PM
Location: Beaverton, OR
Posts: 101

I do a lot of trading back and forth with a friend so I really didnt put out much other than time for the laser. We had a few more working versions and sold the ones like mine for about $3k. Someone told me they are about 40 to 50k new. Very nice heads. A friend works on the machines that use them, laser trimmers and etching setups. These are very stable heads, good beam quality. The coherent versions they would have to chase the beam around during alignment. Some pics of the UV heads here:

The laser in this is a Lightwave M210-HD-V06, It has a lot of hours but still seems pretty strong. I also have a Lightwave M612-HD-V03 which is a frequency doubled version (532nm green) that puts out a little over 7 watts average.

Pic of the green head here hitting a piece of graphite I use as a beam stop.:

Lightwave M612-HD-V03 by macona, on Flickr

For mirrors I have specific dielectric mirrors for 355nm and 532nm. They almost look like a normal piece of glass. You can see the final mirror in the pic below. Some have a more apparent coating than others.

Z axis brace by macona, on Flickr

Initially during the installation of the mirror mounts I was just using some generic aluminum first surface mirrors that the mounts had preinstalled. They didnt last long:

Aluminum mirror meets UV laser by macona, on Flickr

Patrick

Fri Nov 09 2012, 06:32AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

super dooper nice! that trashed mirror is a trophy!

Carbon_Rod

Fri Nov 09 2012, 09:10AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

@macona
Is your Collimator lens and cutter head actively cooled?

Unfortunately, I found even fused silica lens rated well within SOA will sometimes spot heat and crack like your mirror if soot or smoke is present.

The 1064nm crowd are typically using a sapphire pump laser, but we know DPSS are only 60% to 80% efficient. Typically, better quality <532nm lasers will also filter out the residual pump stage wavelengths and get rather warm.

Nice build,

macona

Fri Nov 09 2012, 09:24PM

Registered Member #3272 Joined: Mon Oct 04 2010, 11:40PM
Location: Beaverton, OR
Posts: 101

No, at these power levels cooling is not needed. I am not using the collimator as of yet. The ones I tried have lost about a watt though them due to the optics becoming solarized from use. I have a few more to try and see if it makes a difference. It will make my final focus optic last longer and give me a smaller spot size.

These heads use a Nd:YLF crystal pumped by three 40 watt diode bars by coherent.

Linas

Thu Dec 27 2012, 08:58PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

I just don't get something.
You can cut steal with such a low power.
so it because you have high energy at small spot , and even if average power is low?

So can i get something like Nd:YAG rod, use arc lamp for CW pumping, add Q -switch so i could get high power pulse, and try to focus beam to small spot , and will that would be sufficient to cut steel ?

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