Project: Laser Cutter (CNC)

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Re: Project: Laser Cutter (CNC)

Postby Jerry » Fri Jul 20, 2012 2:22 am

I have also decided to ditch the CO2 laser. I got a Lightwave frequency tripled YAG (355nm Ultraviolet) that I am going to use in its place. Why? Because I can do this with a pop can:

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Laser cut pop can by macona, on Flickr

Cant do that with a CO2! This laser is very interesting. Many materials, especially metals, absorb this wavelength very well compared to longer wavelengths like standard YAG (1064nm, near-IR) and CO2 (10600nm, IR). The spot size of the laser is also much smaller, as much as 30 times smaller than the spot size from a CO2 laser. This means finer cuts and details as well as higher power densities. Combine all this with the Q-switching of the head which creates pulses in the range of 15kw, you get a very fun toy! And all this at about 6.5 watts average power at 10khz pulse frequency. This laser will mark just about any metal, steel, aluminum, stainless. Even tougher to mark metals like gold and silver. It will also cut glass!

Last night I started trying to figure out how I was going to integrate the new head into the machine. The area where I was going to mount the CO2 assembly looked too small but after measuring it appeared the head would just fit. I mean just, we are talking about 1/16" clearance. First problem I ran into was some steel flanges overhung into the area. Second problem there was a steel piece in the way of getting the head umbilical out of the laser well as well no access for the cooling lines. Initially I was going to use a saw but that would take forever so I rolled it outside and took the small Oxy-Acetlyene torch and cut the offending pieces out. Ground the remains clean and the head dropped in place. I drilled and tapped for the three mounting bolts. I did find it was not sitting down all the way on the well deck because it was formed in a press brake and had slightly radiused corners. Hit it with a hard wheel on a right angle grinder and that problem went away.

Next project is figuring out the optics. I wanted to keep it all internal to the machine but I think it will be much easier to go external and use an enclosed beam path. The remaining room in the laser well area is pretty tight, especially if I install a beam expander.

Chunk'o'aluminum used for a guide for the torch, yellow stuff is heat resistant blanket material to keep hot stuff away from wires.
Image
IMG_2416 by macona, on Flickr

Laser head test fit in well area:
Image
IMG_2417 by macona, on Flickr

Laser head installed. Piece of fluorescent paper was being used to trace the path of the beam. In Continuous Wave mode the laser puts out less than 1mw of UV light, still enough to see the beam with a piece of paper.
Image
IMG_2419 by macona, on Flickr
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Re: Project: Laser Cutter (CNC)

Postby Doug Coulter » Fri Jul 20, 2012 10:53 am

I like where you're going with this one - this is going to be one rocking machine a little down the road, eh? With the peak power that makes - I now understand about your optics problems.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Project: Laser Cutter (CNC)

Postby Jerry » Tue Jul 24, 2012 4:31 am

Here's what happens to 1/2" dia aluminum front surface mirror with UV. Not pretty, well.. kinda is.

Image
Aluminum mirror meets UV laser by macona, on Flickr
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Re: Project: Laser Cutter (CNC)

Postby Jerry » Wed Jul 25, 2012 12:29 am

In the past couple days I got the first two mirror mounts installed and built a base for the beam expander mount. This will bring the beam up to the gantry. The machine had two aluminum end plates on the well area. I measured where the beam will need to pass through it and machined a 3/4" hole in the the plates. The plates themselves bolt to a piece of steel welded across the frame so I used one of the plates as a template to drill a 3/4" hole though it. 3/4" hole though 1/4" of steel with a cordless drill. Not what I consider fun.

The mirror mounts I used are a block unit like the ones I am selling over in the for sale section. They have 3/4" holes in and out so I took a piece of heavy wall brass pipe and turned it down to make a coupler between the plate and the mirror block. For the top mirror I took another mount and reengineered the mounting block to mount to the side and attached it with a couple 10/32 screws. I set the laser to it's CW mode where it just produces a constant beam. Without q-swithing this is less than 1mw. Using a piece of fluorescent paper I can trace out the beam and align the mirrors.

It looks like I am not going to use the beam expander. I loose about a watt though it, but since the beam has very low divergence I should not have to worry about it.

Next up is to figure out the gantry optics and final beam delivery.

The beam expander and mount. If I find one with better optics I may try it again:

Image
IMG_2426 by macona, on Flickr

The laser and beam delivery tubes:

Image
Turn optics installed by macona, on Flickr

Laser running at night. The specular reflection off the black aluminum makes various material fluoresce. The laser is almost the same wavelength as a backlight, 355nm for the laser and 365 for a backlight.

Image
UV Laser at night by macona, on Flickr
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Re: Project: Laser Cutter (CNC)

Postby Jerry » Sun Jul 29, 2012 8:43 pm

I finished the mirror mounts yesterday. The third mount was pretty straight forward. I used a cheap Newport flexure mount an machined a cavity in the support arm to mount it. Then I glued it in place. The mount is intended to take a 3/4" mirror. My mirrors are 1" so I machined a small piece of brass pipe into a mount which sits in the holder.

The final mirror was a little more complex. Since all the available mounting points were behind where the mirror and Z axis slide were I needed to pass the mirror support though the Z axis. I machined a mount that slipped over the bolts for the Z axis linear bearing and made it so it clamps on the mirror mount. It uses a simple flex clamp to grab on to the horizontal mirror mount support which holds a tiny New Focus kinematic mirror mount. The mirror is glued to the mount.

I needed something to support the lens assembly. If I used a C mount I could use existing C mount extensions to move my lens closer to the work. So I needed something with a C mount. I took an old Sony CCD camera that was broken and gutted it for the nose piece and the internal frame. It was the perfect size to mount o the slide. That was glued in place as well.

I still need to make the lens holder and nozzle and finish the electronics.

Here is the third mount. That is the mirror installed.

Image
IMG_2513 by macona, on Flickr

The final mirror support bracket:

Image
Final mirror mount support by macona, on Flickr

The final mirror and lens mount. The lens was temporarily mounted in a short C mount adapter. That is the mirror on the mount. It looks like a piece of glass, but at an angle you can see the coating that reflects the UV.

Image
Final mirror and lens mount by macona, on Flickr
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Re: Project: Laser Cutter (CNC)

Postby Doug Coulter » Sun Jul 29, 2012 11:13 pm

Man, I can't wait to see this baby in action! So, you think you've got mirrors and optics that can live through this? Planning on some kind of air-blast under the lens to deflect any plasma away from the optic?
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Project: Laser Cutter (CNC)

Postby Jerry » Mon Jul 30, 2012 2:21 am

Yes, I have mirrors intended for this wavelength as will as the lens. They came from the same place.

With the optics on the gantry of my laser cutter finished I decided to see what it can do. I dont have the drive hooked up right now so I moved the gantry by hand and cut a little square in some EDM graphite. I took a pic under my stereo microscope, the wire like thing is a hair. The groove is pretty deep relative to it's width.

Image
Cut in edm graphite by macona, on Flickr

Image
Cut in edm graphite by macona, on Flickr
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Re: Project: Laser Cutter (CNC)

Postby Doug Coulter » Mon Jul 30, 2012 10:51 am

Wow! Nothing like starting off with the hard stuff(!) - highest melt/boil point of any element or real close, right? I use graphite around here, both pure and "medicated" in glass/quartz blowing and it takes almost anything. Easy to machine with normal tools (the pure stuff) but heat, nah, little to no effect even at white heat. I'm using it (pure) in fusor parts that might need to be strong while yellow hot - works great at temps that make titanium limp and tungsten suspect. In that case, the worse effect is getting some deuterated hydrocarbon contamination as it runs, and the graphite is ever so slightly sputtered off after a lot of running..

Which yeah, brings up the question - if you're going to cut all the way through things with this - what to use for the backstop to keep from eventually destroying your platen? Something sacrificial?
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Project: Laser Cutter (CNC)

Postby Jerry » Tue Jul 31, 2012 2:31 am

The table is stainless and I will have a grid or honeycomb over that to support the work for a lot of things.

Got more of the basic wiring done tonight and got it hooked to the PC I planned to use. The computer kept locking up. Looks like another bad MoBo. Threw another I had laying around and the OS is reinstalling now. Hope this one works. Going to try Vista on this one, years ago MS sent me free copies of Vista 32 and 64, might as well use them. With all the service packs Vista is pretty decent.
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Re: Project: Laser Cutter (CNC)

Postby johnf » Tue Jul 31, 2012 5:28 am

Jerry
Vista and the word decent are planets apart
even the microsquish employees didn't take it up
try XP 64 bit or windoze 7
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