Another new toy, a Laser welder

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Re: Another new toy, a Laser welder

Postby Jerry » Fri Jun 14, 2013 6:13 pm

From what info I found it is a Nd:glass laser.

Loaded up and ready to come home:

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Untitled by macona, on Flickr

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Untitled by macona, on Flickr
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Re: Another new toy, a Laser welder

Postby Jerry » Sun Jun 16, 2013 11:07 pm

Gut it unloaded and in the garage after about 2 hours of jockeying stuff around. I rolled it off the back of the trailer with a pallet jack and a come-a-long. Didnt fit in the garage as well in real life as it did on paper. A friend said I could put it in his shop so I loaded it back up this morning and took it over.

Took over the spares and stuff as well and went though some of it. A lot of goodies to be had, a thermometer type laser power probe, new set of laser goggle (Little sticky, old plastic), IR laser viewing plates, and lots of spare parts. Everything there to install the LD optics for drilling.

The laser has two set ups. A short cavity configuration where the laser runs at 400 watts average power in a multimode TEM state or in a longer cavity configuration that includes a intracavity telescope and a water cooled aperture. This brings the power down to 120 watts average but makes the beam single mode TEM00 which gives the smallest spot possible for drilling and cutting.

I still need to bring over the laser power supply and get that wired in. My friend has three phase in his shop so the power wont be an issue any more, well, probably. The laser is configurable to 208v, 220v, and 380v, his shop is 240v. The manual does not spec line voltage tolerances so I need to contact JK lasers and see if there will be a problem. Worst case, I have to get a three phase autotransformer to buck the voltage down. Once that is solved and I can determine the laser works I will move on to finishing the CNC portion of the machine.

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IMG_6623 by macona, on Flickr

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IMG_6626 by macona, on Flickr

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IMG_6630 by macona, on Flickr

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IMG_6632 by macona, on Flickr
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Re: Another new toy, a Laser welder

Postby Doug Coulter » Wed Jun 19, 2013 5:04 pm

*Most* high power supplies like this one simply brute-force rectify the input (perhaps with a switch at a tap in the setup that either does or doesn't multiply the input by 2 - both my Glassman and my Volt do that one, automatically, and the Glassman was 3 phase), then use some switcher to get the desired output for the outer world. I suspect you won't have much issue with a slightly off input voltage, but sure, it's wise to check that first. I know I would if I could. That stuff is way too cool to burn out on the first day.
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: Another new toy, a Laser welder

Postby Jerry » Fri Jun 21, 2013 4:46 pm

There are two three phase transformers on the line, one for each lamp, that boost the incoming voltage which is rectified to 425vdc. There are two 1000uf filter caps and then the main cap bank has 24 more 1000uf caps.

Lumonics didn't have any info on this machine but successor to it has a 6% input tolerance so I am going with that. I got a couple bucking transformers to drop the voltage down to the 220 range and will set the laser for that.
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Re: Another new toy, a Laser welder

Postby Jerry » Fri Jun 21, 2013 11:09 pm

Last night I went over to the shop and dug through the manuals and schematics. Found some more info on what it was originally being used for, the final hermetic seal on the Tek 2467 and Tek 7707 tubes. The 2467 I can find info on, the 7707 I can't, I will head down to the Tek museum locally to see if anyone knows about this guy. The tubes used a microchannel plate to amplify the electron beam in tube to get a brighter image at very fast scan times.

I pulled the cover off the resonator to take a look. Someone in the past had taken out the intracavity telescope used in drilling and cutting as well as a beam path sealing tube. Both of these are in the drawer so they just need to be cleaned up. That will have to wait until next week, I am waiting to get some Chromatographic grade methanol to clean the optics. I pulled off the beam guards between the mirrors and the yag rod and took a peak down there. It looks pretty good, the rod is clear.

Today I hooked up some high voltage to the cap banks. The cap banks consist of 24 1000uf, 450v caps. They get charged to 425v max and the energy is dumped into the flash lamps with a giant transistor. I have a small DC/DC front end converter that gives me 380v out from 85 to 120v in. I slowly charged the banks and they seem to be happy to at least 380v.

More pics:
Down the rod:
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Components from left to right, beam expanding telescope (collimator), shutter and water cooled beam dump, energy monitor section, output couple mount, optical cavity, total reflector mount. After that is where the intracavity telescope mounts and the beam path cover. In this picture the laser is set up for welding, it has a very short cavity with flat mirrors on both ends. You get a powerful fat beam that is multimode, not great beam quality. This is fine for welding. For things where you need to get down much smaller they add the intracavity telescope, replace the front mirror with an etalon and the high reflector is replaced with a water cooled aperture and moved back and another mirror with a 10m curvature is installed at the far end of the rail. This gives a lower powered, high quality beam that can be focused much tighter.

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Re: Another new toy, a Laser welder

Postby Jerry » Sat Jul 13, 2013 1:25 am

Ran 50' of 6ga wire for power and installed the two bucking transformers a couple weeks ago. The circuit breaker for the panel showed up the day before yesterday and I installed that and finally got power to the machine. The bucking transformers are doing their job dropping the 240v to 220v. I fired up the controls and the computer to be greeted with Windows NT 4.0 and a Novell login screen. I used a linux boot disk to reset the passwords and deleted Novell. I should be able to give the drives and motors a test run tomorrow.

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IMG_2181 by macona, on Flickr

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IMG_2191 by macona, on Flickr
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Re: Another new toy, a Laser welder

Postby Jerry » Fri Jul 19, 2013 2:09 am

I took the computer back a few days ago and put it back together. I could not get it to initialize the servos. The next day I went back over and messed around with it some more and it started working. I think I had an IRQ error with the Mechatrolink II card that communicates with the servo drives. I managed to get it jogging but it is pretty out of tune. The X axis oscillated so much it broke the helical coupling. Luckily I had another at home that I machined to fit.

I had figured the software commanded the position of the drives through the Mechatrolink interface but it looks like it actually sends analog speed values to the drives and takes the encoder data and completes the loop in the PC. So it is a fully closed loop system.

I ended up removing all the helical couplers and replacing them with bellows type. They are much stiffer torsionally and the flex was causing wind up which resulted in very unstable operation. After replacing them the machine acted totally different. I used the Yaskawa software to set the inertia comp settings and to find the resonant freq. It takes that data and figures out the tuning parameters from that. Worked pretty well.

Once I got the drives tuned to the machine I had to get the control software tuned to the drives. This was a pain in the rear. The software has a lot of parameters you can use but nothing that really said what applied to my drive system. When this version was released it was the first to support Mechatrolink and the set up data is rather incomplete. But after about 4-5 hours of messing with the parameters I finally got it tuned pretty well. The A axis may have to be redesigned. It is not very happy, tuning wise, the inertial mismatch is too big. I may have to use a gearbox to drive it. I will also have to retune the Z axis when I put the weld head back on. At this point I think I can reinstall the way covers, there should be nothing more to do under there.

Couple pics, one of the old coupler and one of the new ones.

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Re: Another new toy, a Laser welder

Postby Doug Coulter » Fri Jul 19, 2013 6:31 pm

Oh my, if it's using a PC as part of a PID type controller, with the speed of the PC (or it's interrupt or latency jitter) affecting the net tuning, you've got trouble...you might have to replace some of that with more modern "smarter" stuff that has control over its own timing. PC's pretty much suck for that, and in fact I made a living for quite some time taking advantage of that kind of thing by making little time-deterministic controllers that the PC could then just say "go there" to, or take (buffered and timestamped) data from at the PC's leisure. Else you could almost just not make some systems work at all with any sort of realtime constaint - a servo might hunt one day, and be overdamped the next (second) - there's what we used to call "the pentium pause" tossed in at random, when it seems even the PC opsys isn't getting cycles. Gaaaacccckkkk. And it only got worse with time. Believe it or not - and I'm a dyed in the wool linux guy - win98 was actually the last PC opsys you could do any kind of decent real time work in, smooth multihreading and half-decent interrupt response times. Even then, only half-decent. At 115kbaud a PIC running 8 mhz could easily swamp a PC buffered serial port with more interrupts per second than the PC could handle...and the PC couldn't really output bytes in a continuous stream at that rate either, just bursts at that speed. Pretty sick when you can outdo a PC with 8 bit iP's going about 1 mips.

(Jerry, I hadn't commented before because I get tired of seeing only my name as "last post" on everything here - but this is yet another great project of yours, kudos!)

Do you know if I could get a microchannel plate anywhere for reuse, or did the ones they used die when exposed to air? After all, I DO have a pretty nice vac system and some things to use that sort of thing for.
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: Another new toy, a Laser welder

Postby Jerry » Sat Jul 20, 2013 10:40 pm

The software used RTX, a real time extension for Windows. This allows it to do what it needs to. The CNC software I have will only run under Win NT 4 or Win 2000.

You might look for an old CRT for one of the MCP scopes like the Tek 2467.
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Re: Another new toy, a Laser welder

Postby Jerry » Wed Jul 24, 2013 12:41 pm

Monday night I finally got the power supply moved over. Man, is that thing heavy. The lift gate was protesting.

Last night I wired and plumbed in the power supply. I need to fill it with distilled water next and I should be ready to see what happens.

Here is a pic of the power supply with the covers off. Top left is the "DC Chassis" It rectifies and filters power from the two main three phase transformers in the base of the supply. It also has the bleed resistors to drain the caps when it is shut down. Below that is the heat exchanger. It takes city water through a temperature control valve and passes it through a heat exchanger. The pump circulates water to the head first passing through carbon particulate and deionizing filters. Unlike many other arc lamp driven systems the electrodes are not immersed in water.

Top right is the circuit card rack. It has the logic for the power supply and handles the interfacing between the console/cnc and the power supply as well as controls the shutter and interlocks. Below that is the two flash lamp supplies, one supply per lamp. Each has twenty four 1000uf, 450v caps. A massive bipolar transistor controls the output to the lamps. The supply can control repetition rate, pulse length, and pulse intensity.

The two modules on the bottom on either side are the ignitors and simmer modules. The supply always keeps the lamp lit with a low current passing through. This makes firing more reliable and also makes it easier to time the flashes. Behind each modules is a 3 phase transformer, each one feeds on half of the DC Chassis.

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Laser PowerSupply by macona, on Flickr
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