[cncadmin]

I'm firing up my laser tube tomorrow, I will try to post some pic and maybe video of it.

[owhite]

I read your post and thought I could come up with some kind of sage wisdom (e.g. "Good luck, and keep your finger out of the beam", or "Remember: you can never keep a laser too cool.")

However, wisdom, sage or otherwise, didnt really spring forth.

I worked for a year and a half on mine and thought the big day would be really big, and in some ways it wasnt. It was more like okay I got the power, the alignment, the watts are fine, put on the oxygen, the focus is good okay, no wonder it cuts.

But anyhoo, good luck! Period.

You've been at it quite a while and its your turn now.

owen

[owhite]

...and?

[cncadmin]

Well, I got the laser all hooked up and got the power supply turned on and hit the trigger voltage button and just hear a clicking noise. To make a long story short the laser tube was hooked up back-wards and the water was being hit with 20k of voltage, and lucky I kept my hands to myself, and did not get electrocuted. After I switched the power around, the laser works perfect and burned a 1/8" hole into a piece of popular. I did not have any instructions to identify the anode and the cathode. The water pump is work but their is a air bubble about 2 inch long on the end of the tube that won't go away, but the water is flowing and I see no problem with it keeping the laser cool.

The big problem is getting the mirror lined up, it's way to much for me to explain, but I have a solution for it. I have to add a 4th mirror to the set-up, but once I do that I should have them all lined up. I hope by this weekend I will have this thing cutting.

[owhite]

not that it sounds like you're looking for advice but I'll offer it anyway...

For the optics leading up to your focusing lens, use a crude system to make sure the beam is hitting the center of the optics through your delivery system. So you could put an index card in front of an optic, turn on the laser then see where it hit, adjust, put in a new card, and hit the laser again, repeat as necessary.

Tape or index cards work great. Be sure to avoid putting smoke from either on your optics.

Do you have a cutting nozzle for flowing air or gas? I did and the problem is the port on the nozzle is only 1mm and alignment into that was very hard. There was a threaded tube that holds the nozzle, what I did was make a "tool" that fits into the tube and locates the exact center of a tube. I would place scotch tape over the tube. The tool put a pin prick into the tape, and this represented exactly where the beam was supposed to hit. Then I'd thread the tube into the cutting head, pulse the laser, look at the beam location, adjust optics and repeat.

Always use a really low power and really short pulse when doing this. Hitting stuff with higher power creates too much scatter and you cant get reliable results.

When the time comes another really great tool is a heat sensitive paper, like the kind that is found on many receipts or fax machines. This allows you to set the laser on really low power, place the paper on work surface where you eventually be cutting, pulse the laser and look at the quality of the beam. The issue is that even if the beam is going to the work surface the beam may not be perfectly round (okay, even moderately round). When that happens there are usually problems with cutting. Again, use really low power pulses.

The other thing the heat sensitive paper allows you to do is optimize the distance between the focussing lens and your part. As you probably know the smaller the beam size the better because that's putting more power into a concentrated spot. In my case if I dont have a 200 micron spot size then I aint cutting metal. So anyway the thermal paper allows you to set the distance, pulse the laser, inspect the spot size, adjust and repeat.

To give you an idea the attached picture shows what happens to the spot size when the distance is changed.

I have some other descriptions of beam adjustment at:

http://www.nilno.com/laser_dir/alignment/650_hole2.jpg

I bought some thermal paper that's embedded on thin cardboard, it was expensive but I have a lot now, if you send me a land mail address to ([email protected]) I'll snailmail you some.


owen

[owhite]

I did not have any instructions to identify the anode and the cathode.

I'm glad this worked out because I once heard that if you hook up the polarity of the laser incorrectly then you permanently damage the tube. I'm glad what I heard was wrong.

[cncadmin]

Well it's not damaged, but I can see why, it could cause plating, but in this case all it did was charge the water, I don't see any damage in the tube and as cheap as the tube is, I can just order another one. I'm hoping to have the mirror all done by this weekend, I'm machining every chance I get. Than I have to do a final adjustment on the mechanics and off I go.

[cncadmin]

not that it sounds like you're looking for advice but I'll offer it anyway...

owen

Thanks what you said is VERY helpful!

[owhite]

is the electronics of your system such that you can control the pulse length and power?

owen

[cncadmin]

is the electronics of your system such that you can control the pulse length and power?

owen

Yes with ether a knob the controls the MA or using TTL through the computer.

BTW I sent you a email.

[owhite]

progress?

you get the alignment paper?

owen

[cncadmin]

The paper works great, I'm still adjusted the mirrors, but I hope to have them all aligned this week.

[unterhaus]

I'm curious what you are using for eye protection. Laser light drives me crazy, I don't ususally like to be in the same room with a laser. I have a class 2 laser that is eye safe as long as you blink enough, which doesn't impress me as being particularly safe. My eyes give me enough problems as it is. Yes I know I'm a wimp. I've seen what looked like yellow plexiglass boxes around class 4 lasers, and I wonder where you could get material like that.

[cncadmin]

I use safety goggles made for blocking indirect IR. http://barrieronline.com/laser/index.php

[Marc Soren]

I wonder how these would work out? ($35 OR SO?)
Supposedly, they are made for Excimer/CO2 only....wonder if that is
what saves some $$$. One could quickly do a test to find out without exposing your self.

http://www.elvex.com/economy-laser-spectacles.htm

Marc and boyz

[cncadmin]

Well today I got almost all the electrical connection hooked up and set-up and ran a test program threw Mach 3 a side from some learning curves with Mach the mechanics work Very well.

Mirrors-

I'm using all gold mirrors which I got off ebay, and mounted them on adj optic mounts, which through much trial and error discovered this was the only way to get the beams to hit the right spot. I also found after much searching the right mirror that I need to combine the IR and the red beam together, that being a beam combiner. I found this over seas and more than 1/2 what I could have gotten it for in the states. I have gone through weeks of fighting with alignment and that was all made simple once I got this mirror. It's far to much for me explain.

Software
Mach 3 is my biggest challenge, I need to use Mach to turn on the laser and regulate the power turn on/off my water pump, red beam and a few other things. I have downloaded and printed the manual so I hope I will find what I'm looking for. I will post pics and videos very soon, I just need to get a few more items straighted out.

[ynneb]

Software
Mach 3 is my biggest challenge, I need to use Mach to turn on the laser and regulate the power turn on/off my water pump, red beam and a few other things. I have downloaded and printed the manual so I hope I will find what I'm looking for. I will post pics and videos very soon, I just need to get a few more items straighted out.

I use the Rutex relay board. This allows 4 items to be turned on and off via Mach2/3
I guess it wouldnt take much to either make your own relay board or just buy one. I can see you will definately need to turn your laser on and off during rapids and once the cut is finished.

EDIT: The relay board http://www.rutex.com/home/r990io.htm
The mother board if you think it appropiate http://www.rutex.com/home/R990mb.htm

__________________

[cncadmin]

I'm using the CNC4PC break-out board, relay board and power supply. I have a DC relay board on the way for controlling the DC items I'll be using as well.

[cncadmin]

BTW I was able to get the machine to run over 300 IPM, it's very fast, using Steppers from HobbyCNC and a Xylotec board, the Xylotec really needs a all windings off though.

I'm using a piece of 1/2" honeycomb alum that I got for 150.00 from Plascore and they cut it to size, very good place to deal with.

[owhite]

I'm using the CNC4PC break-out board, relay board and power supply. I have a DC relay board on the way for controlling the DC items I'll be using as well.

It doesnt sound like it but if you want to get into doing the electronics yourself I'd suggest looking into using AVR programmable chips. These devices let you interpret signals like highs and lows coming from the parallel port to control devices like LEDs, relays, buzzers and most of the gizmos that you typically encounter in CNC. The nice this about them is that if you need to have a higher level of logic, other than just turning stuff on, its a good way to go. For example, if you have to "check that the pump is working before turning the laser on" this type of thing is easy (-ish, depending on your electronics skills).

owen