Lab robot conversion to laser cutter

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Re: Lab robot conversion to laser cutter

Postby macona » Fri Jun 03, 2011 4:35 pm

I only did a little bit of contract machining and fabrication at the end of Coraline.

I got the combiner from this auction:

http://cgi.ebay.com/Beam-Combiner-optic ... 255668ffdd

Good quality optic, not chinese. Also comes with a small Coherent laser diode. Not the cheapest option but I believe it is the best. I dont want to fiddle with mirror edges or whatever.
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Re: Lab robot conversion to laser cutter

Postby trwalters001 » Fri Jun 03, 2011 5:15 pm

I got my laser power meter and bounce mirrors from him (guyovad).
Quick shipping, good seller.

Tim
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Re: Lab robot conversion to laser cutter

Postby kylelnsn » Fri Jun 03, 2011 6:20 pm

I Love the combiner! that is wicked!
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Re: Lab robot conversion to laser cutter

Postby macona » Fri Jul 20, 2012 6:44 am

OK, after a year of doing nothing with the laser I have started back up on it. First thing I did was solve the rigidity issue. The one unsupported end of the short axis flopped around in the breeze with anything resembling a decent acceleration rate. It would be nice if mach supported S-curve accel and decel, but thats life. So what I did was tie both sides of the gantry together using timing belts on a common free running shaft. This makes it pretty rigid. I had to mill out a recess on the upright for the shaft bearing and then tig a cross member between the two rear supports and mill another hole for that bearing. Getting the two holes concentric with each other with no solid point of reference was, well, interesting. Lost of measuring with 1-2-3 blocks and I managed to get it figured out. For the belts I used the longest belts SDP-SI had and cut them down. It is cheaper this way than buying open ended belting by the foot. I used a splice kit to hold the belt down to the gantry. Idler wheels were made from aluminum and timing pulleys for the other end to tension the belts. Once the belts were installed and tensioned I glued them in place to help hold them. It seems like it will work, it made the gantry very rigid. Time will tell.

Shaft side, back of machine:
Image
IMG_2279 by macona, on Flickr

idler side, back of machine:
Image
IMG_2280 by macona, on Flickr

belt splice, front of gantry:
Image
IMG_2281 by macona, on Flickr
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Re: Lab robot conversion to laser cutter

Postby macona » Fri Jul 20, 2012 7:11 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:

Image
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: Lab robot conversion to laser cutter

Postby richmond » Mon Jul 23, 2012 10:43 pm

Alright, that looks rather interesting.

Where/for how much did you acquire that lovely laser?
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Re: Lab robot conversion to laser cutter

Postby macona » Tue Jul 24, 2012 9:22 am

A friend that runs a surplus shop got these from a company that uses them in their wafer marking and trimming equipment. We do trades back and forth so its hard to say how much I pay. We had a couple like this one but putting out less power (about 1 watt less) and we sold those for $2k. I also have a green version that is putting out about 7.2 watts @10KHz.
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Re: Lab robot conversion to laser cutter

Postby macona » Wed Jul 25, 2012 5:23 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.

I had tried the generic first surface mirrors that were in the mirror mounts. They didnt last very long at full power:

Image
Aluminum mirror meets UV laser by macona, on Flickr

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

IMG_2462 (1).jpg
UV Laser at Night
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Re: Lab robot conversion to laser cutter

Postby macona » Mon Jul 30, 2012 1:40 am

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: Lab robot conversion to laser cutter

Postby macona » Mon Jul 30, 2012 7:13 am

Last night I made some hand controlled cuts with the laser cutter in some EDM graphite. I decided to check it out under my stereomicroscope. Here are the results:

The wire like object is a hair.

Image
Cut in edm graphite by macona, on Flickr

7674945728_3564083719_o.jpg
Hand controlled cut in EDM graphite
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