[Cathode]

Goal: To build a hobby grade CNC laser cutter that will cut materials up to ¼ inch thick with a work area of 48” x 24”. The machine must be safe, reliable and accurate to 1/40". It will be build using commonly available off the shelf parts and materials. Budget is $2000.

After researching the existing machines, I’ve narrowed my design options down to two possibilities.

Design Option #1: A moving XY table with stationary vertically mounted laser and optics
Advantages:

• No Mirrors Required
• Minimal alignment required
• No power loss on reflections
• Less ways to fail

Disadvantages:

• Wastes space
• Footprint is more than twice the work area
• Long rails are likely to hurt accuracy and add expense

Novel Idea:
Use something like a large salad bowl mounded upside down over the laser head and attached to a vacuum source to exhaust fumes and filter IR. This would save the expensive building a large cover as required by design option #2.

Design Option #2: Flying Optics design with a horizontally mounted laser parallel with x axis. Work is stationary. Beam is reflected onto work surface by mirrors moving on a lightweight gantry.
Example: Emissions Technology
Advantages:

• Moving parts are fast and light
• Compact footprint
• Shorter more precise rails could be used

Disadvantages:

• Requires at least 2 mirrors
• Requires 4 mirrors for the most compact footprint
• Requires precise alignment
• Has serious failure modes resulting in smoke and fire
• Wastes some power on each mirror

Option #1 is technically easier to implement and is far less clever that Option #2.
Option #2 is more practical, but will require more R&D to be made safe and reliable.

Right now I’m leaning towards option #2 and am looking at ways to implement it with only 2 or 3 mirrors. This seems like the way to go. It will be a slight improvement on the emissions technology approach.

If anyone else has build one of these or is planning on building one, I'd like to hear your thoughts.

[cncadmin]

Very nice, my first laser was that size, I build a new one 48" x 60" all servo drive.

[Cathode]

Grettings Sir. I've read many of your posts. Very inspiring! I would never attempt it without this place.

Have you had problems keeping your mirrors in alignment? On that 60" run it would seem a slight vibration could be enough to deflect the beam off target.

[Bubba120]

Rick

your laser source, I'm interested where or how you plan on producing CO2 laser with a small budget as you have. Keep us posted.

Jim B

[cncadmin]

The machine itself is VERY heavy, I used 3x3 8020 as the base. The base is the most important thing, the heaver the better vibration resistant.

[jmg]

Hi Paul,
(CNCadmin)

Do you have pics of your servo machine on this site? And if you don't mind me asking, did you "build" your electronics or buy in a preassembled package of motors, drivers, etc.?

Thanks,
jmg

[Cathode]

I'm probably a little optimistic on the price. I do think it will come in under $2500. The goal is $2000. So far I've spent about $1100 and picked up a 60 watt CO2 Laser, power supply, 3 mirrors, a nice beam expander/reducer. To me the laser is the big unknown, so I want to get that part working first. I already have a working CNC mill, so was planning on buying new stepper motors for this project and borrowing the other CNC components from what I already have. That's going to save about $300 or $400 over someone starting out fresh. I'm budgeting (roughtly) $500 for some very nice linear slides and bearings. The belts and pulleys should come in under $150. The bulk of the remaining parts will come from the local hardware store, the junk yard, and my shop. If I used conduit and skateboad bearings for the linear slides, it would definetly come in under $2000.

Good to hear form you.

[Laser.Tech]

Rick,
I see your still debating your choices on beam delivery. I hope my advice didn't cause you too much worry about beam alignment if you go with a flying optic setup. As long as the beam doesn't start to miss your focusing lens, then some mis-alignment shouldn't be too big a deal as the lens itself will greatly minimize any effect of beam drift (by reducing the beam in size to a point, it is also reducing any beam offset by the same amount). I'm just used to working where a couple thou make a big difference. Sorry.

And of course, many folks on this forum have already done it, with no problems (that I've seen remarked on, anyway).

I look forward to seeing your machine come together...

Brent

[samakthachai]

Hi Ric,
What software do you use to control?

[rakker]

I've seen lasers posted in ebay, that go for roughly 1200 to 2000 with power supplies. You said that you got your 60 watt with optics and a beam expander for approx 1100. Did you get most of your stuff off of ebay, or do you have other sources you don't mind sharing? I'm looking for an 80 to 100 watt laser, which go for around 2K from a seller on ebay. Looking for a middleman who doesn't add 800 to 1000 to the equation, as I think they're available for 700 to 1000 fob China. TIA

[Cathode]

Hi Ric,
What software do you use to control?

So far just Mach 3. Probably Master CAM in the future. You?

[Cathode]

I've seen lasers posted in ebay, that go for roughly 1200 to 2000 with power supplies. You said that you got your 60 watt with optics and a beam expander for approx 1100. Did you get most of your stuff off of ebay, or do you have other sources you don't mind sharing? I'm looking for an 80 to 100 watt laser, which go for around 2K from a seller on ebay. Looking for a middleman who doesn't add 800 to 1000 to the equation, as I think they're available for 700 to 1000 fob China. TIA

I got of the laser stuff from ebay. That is my only source. There are various wattages on ebay right now that look exactly like mine. I've see 100 watt, with power supply, tube, and pump, sell for quite a bit less than 2K. I tested mine (more later) and it does work. The sellers name is crystallabs. He replaced a broken tube for me and has a lot of positive feedback. These sellers seem to be for real, but you have to put up with some uncertainty. The power supplies are made for 50Hz 220V. I'm hoping they don't run hot and break down under load. I believe I got a real bargan on the optics for $50 bucks. Where else but ebay can you find stuff like that?

[Cathode]

:cheers: Finally, I got to test the laser. I hooked everything up, put on my IR safety glasses and flipped the switch. The moment of truth…WOW…it lit right up and burned a hole in a piece of ceramic tile. In just a few seconds it got so bright it hurt my eyes. I immediately turned it off and got really scared that I might have harmed my eyes. I'm pretty sure it was because the tile got so bright, not from IR hitting my eyes. The safety glasses don’t dim visible light at all. Wow these things can harm your eyes in more than one way. That was only on middle power with no optics and it nearly burned a hole in a piece of tile and flamed my retinas in a few seconds. Holy crap! My eyes are Ok, but that is very scary. Maybe you need to wear dark glasses too. I was going to use that same tile to line the bed and didn't think a 60 watt laser would go through it.

I tried moving some wood in front of the beam and it immediately flamed up and left a fairly wide burned path. I was able to burn a hole through a 1/4 inch piece of wood on middle power. This thing really seems to put out. That was the extent of my testing. Sweet.:cheers:

Next I'll measure the power and determine the focal length of my optics.

[Laser.Tech]

Heh heh heh...you'll probably spend the next several days sticking different things in front of it to see what happens. Playing death-ray with plastic army guys is especially fun...(flame2)

Really surprised at the ceramic tile. Didn't know it could burn, I'll have to remember that, never tried it myself. Did it actually penetrate at all, or was it just the surface that charred? It might still be a good choice for a bed liner.

Brent

[KTP]

Of course ceramic tile burns...it is a very good absorber of the 10,600nm wavelength. If you focus the laser beam you can even cut the ceramic tile!

It would still make a good liner for your bed though...basically you want a material that absorbs the beam (not reflect it) so the tile fits the bill. Unfocused, it would take a year for your beam to burn all the way through a thick tile anyway.

[Cathode]

I just finished another round of expirements. I got up enough courage to try it on full power for about a minute on the tile in one spot, being careful not to look at the bright light this time. The tile made a cracking sound at one point but didn't shatter. It melted a real hole a few mm deep. I tried again on the back side, to see if it was just the glaze that melted. I got the same kind of hole. It appears to be melting and vaporizing the tile, but not going very deep. The beam isn't really focused enough to cut very deep. I want to try it on a piece of tile backerboard or cementboard. That might be a good material to use.

Which brings us to my optics assembly (see attachment). It turns out to not be for a CO2 laser, so back to the drawing board.

[Laser.Tech]

Rick,
Too bad about the focus lens assembly. Just last night, I was looking at focus lenses on ebay, there were plenty to choose from, so shouldn't be a problem.

If you decide to keep that focus assembly you bought, maybe it could be modified to accept a ZnSe lens so you could still use it? Just a thought.

Brent

[Cathode]

Yes, I see two kinds of material: ZnSi and GaAs for the lenes. The GaAs is reportedly more durable than ZnSi. The GaAs are $50 each plus shipping for overseas. They don't seem more expensive than ZnSi, so are they really better?

I'm trying to visualize how the magic happens when you put two of the focusing lenes back to back, seperated by twice the focal length. I understand this will give you a narrow collimated beam, with a wide depth of field, ideal for cutting. I'm not seeing it. Anyone?

There is also a ZnSi 200mm FL listed. It comes with a metal holder and air assist nozzle that will same me some fabrication time.

[Laser.Tech]

Rick, as far as ZnSe versus GaAs, hear is a link to a simple comparison:

http://www.directedlight.com/compone..._delivery.html

It's pretty much a toss up, they both have their strong points. Personally, I like ZnSe better for the simple reason you can see thru it.

On using two lenses, sounds like the same principle as using a beam expander? Can you provide a link to more info on this? The systems I've worked on only used one lens (with no expander), so I'm very curious. Then maybe I could shed more light on the reasoning (if someone else doesn't give an answer first...).

Brent

[Cathode]

They say in the ad the beam would be focused for 10+ inches. That would be awesome. Here's the link:

http://cgi.ebay.com/CO2-Laser-Focusi...QQcmdZViewItem