[SScnc]

Forgive me for asking a question that has probably been answered many times but my searches have been a bit overwhelming.

My question is, what type of laser would I need to add to my gantry router that can cut 1/8" to 1/4" acrylic sheet ? And what brand ?

I was reading THIS POST but no one has answered Larry's last question regarding ebay lasers.

I need to do this as inexpensively as possible, even if I have to get a used laser to start with.

Thanks for any advice on this,

Steve

[KTP]

Just watch ebay like a hawk and snag a 20 to 50 watt Synrad laser when they come up. I bought two Firestar V20 Synrad lasers on ebay awhile ago that were made in 2004 and are doing over 25 watts. The seller put 5 up for $499 buy it now. I am still kicking myself for not buying all 5.

25 watts will cut 1/4 inch acrylic slowly in 1 pass (maybe 15 inch/min?) or you can do it in multiple passes. I think you could go 30 inch/min on 1/8" acrylic.

[zax15uk]

Steve,

First I'll state the obvious, lasers are dangerous! I added a small (~200mW) diode laser to my CNC router for engraving and used the vacuum fixture to keep the laser enclosed.

Your application will need more power, 40W+ of CO2 for single pass and I would recommend 100W for a reasonable speed.

If you do decide to add a CO2 laser to your gantry machine I would suggest using flying optics and keeping the tube stationary (it makes cooling easier and will prevent vibration or other factors damaging the tube). You would then need mirrors and optics as well as the tube and PSU.

I don't recommend trying to combine a CNC router and laser since the dust from machining will cause the mirrors/optics to be damaged easily.

Edit: KTP's suggestion of a 20-50W Synrad is an excellent solution if you get the air cooled version, I'm surprised at that price... so yeah that would be a great deal.

Zax.

[SScnc]

Thanks for your replies guys. I'm trying to understand the flying optics setup and how the beam follows the CNC "head". Do you know of a diagram or similar that shows how this setup works ?

And I will not use the gantry for anything except laser use once converted. Thanks for the safety reminder too !

As for cost, what would be considered a good deal on a laser package in the 40 to 100 watt range ?

Steve

[zax15uk]

Steve,

I don't have a diagram, but here's an explanation...

In a 'flying optics' setup the tube is static and mirrors direct the beam along the machine axis. In the simplest configuration the tube would be parallel to the Y-axis and a mirror on the gantry will direct it along the X-axis to the head where it is directed towards the table and through the focus lens. More common is where the tube is along the back of the table and an additional mirror directs it along the Y-axis.

Cost is variable, for example a Chinese made system would be ~$3k compared to a US brand that may be 3X of that price.

If you need a reliable system with local support and less headaches the brand name would be the way to go, but if cost if more important then the Chinese systems offer an excellent alternative. An RF excited laser tube (best) that could be retrofitted to your machine would be a similar cost but a cheaper tube and necessary components can be purchased for less than $1k.

Zax.

[SScnc]

Zax, I think I saw a setup with a stationary tube on some site today before posting here and your description helped explain it allot, thanks for that.

Regarding the last sentence in your post, Is there a list of components for putting a setup together for about a 1000 bucks ?

Steve

[zax15uk]

Steve,

The components and approx prices would be:

40W CO2 laser tube $250
Laser tube PSU $200
3x Reflection Mirrors $75
ZnSe focus lens $85
Mounting Hardware (lens / mirror holders etc) $60
Water pump $15

You could buy it all from one or more sellers on ebay, or direct from China.

The alternative would be to buy a desktop 40W system for ~$1k which has all of the above and more. You could sell the components you don't need (driver board, motors etc) and the final cost would be the same.

Zax/

[SScnc]

Excellent ! Thank you for all your help and valuable info, I really appreciate it and I can now get started.

I have one more quick question for now, do you guys wear some sort of safety glasses that can block the laser light ?

I'm guessing the most danger to the eyes would be reflection off the material being cut ???

Thanks again,

Steve

[KTP]

"I have one more quick question for now, do you guys wear some sort of safety glasses that can block the laser light ? "

Most hardware stores sell co2 laser safety goggles or glasses. They are usually $0.99 to as much as $5 if you get the really nice ones.

[zax15uk]

Steve,

Since the wavelength of CO2 energy is absorbed by most materials (including glass, clear Acrylic etc) it is easy to build an enclosure. I do not wear protective glasses since the laser beam is entirely enclosed and I have safety switches on access panels. Remember reflected light is just as dangerous and the beam is invisible so there is no blink reflex.

The cheapo Acrylic protective glasses with side shields used for CNC machining would work just fine, but exercising caution (as you should with the CNC anyway) is the best safety plan.

Zax.

[bdring]

I am working on a similar project. I am posting everything I learn at this web site.

http://www.buildlog.net/cnc_laser/index.html

I would appreciate any feedback anyone has. I am waiting for some materials, so I am in a bit of a lull. I am doing everything serially so I don't make any expensive and time consuming mistakes.

I have 2 CNC routers that could be converted, but I think they would be way to slow for engraving. They would work for cutting though.

[zax15uk]

bdring,

Excellent project write up.

Your design looks good. I don't see any major issues and think you made good choices in buying pre-made mirror / focus assemblies etc. You mentioned using motors from Xylotex, their driver boards work great too.

Zax.

[mcphill]

I am looking in to the cheapest way for me to play with a CO2 as well. I do have a good amount of experience with industrial lasers, which may provide me with a false sense of confidence in my success ; ) With respect to safety, YES, WEAR SAFETY GLASSES! Stray reflected waves are not actually that dangerous, as they are unfocused, but better safe than sorry with your vision! Any plastic lens safety glasses will filter out UV, so nothing special is needed. I have found some plans that I am going to put together. You can drop the costs WAY down by making a lot of parts and scrounging up the needed components.

Here is my expected price list:

Homemade 40-60W CO2 laser tube $150
*Laser tube PSU (Neon sign PS with some diodes and a capacitor to rectify and smooth the output) $100
3x Reflection Mirrors $75
ZnSe focus lens $85
Mounting Hardware (lens / mirror holders etc) $60
*Water pump $15
*Vacuum pump $100
Misc $300

*These items have already been sourced

I expect it to work, though to be honest, with the trial and error the cost may go up, but I will know what it takes to get it done, and could make successive ones much cheaper. This will be a flow-through design, so CO2 gas will constantly be consumed, but the laser will NEVER degrade in power, as the gas will always be there.

[KTP]

you are leaving out a big cost of cylinder and gas regulator, plus flow control valves, tubing, etc. Maybe this will fit in the $300 misc. but to buy a cylinder of CO2 laser mix will cost around $300 just for the cylinder and mix, unless you rent it.

Also, if you just rectify and filter a neon sign transformer, you will not really have a good way to control the laser power.

I think better to take the $800 to $1000 that you will end up spending to get a bunch of parts that will sit around on a bench for several years and buy a nice used RF excited DC powered laser like a small Synrad, Universal or Coherent.

Or go the Chinese route.

[mcphill]

But where's the FUN it that? ; )

[KTP]

sorry, pissed off that either my connection or cnczone caused me to lose a page of typing.

If I have time later I will explain how you might get a cheap or free co2 laser.

[bdring]

I am definitely thinking of building my own laser tube eventually, but I want a little taste of success with a Chinese tube first.

A thought occurred to me. Can a "dead" Chinese tube be converted to flowing gas? Most tubes probably go bad due to the gas.

[mcphill]

sorry, pissed off that either my connection or cnczone caused me to lose a page of typing.

If I have time later I will explain how you might get a cheap or free co2 laser.

I'm listening! I hope you have the time...

[KTP]

Ok, two ways you might obtain a really inexpensive or even free CO2 laser.

1) Check your yellow pages for medical equipment supply and repair shops. Larger cities usually have one or more of these businesses. I became friends with a worker at one of these and he told me they are actually paid by hospitals to haul off perfectly working medical lasers (CO2, yag, argon, etc.). I have bought several CO2 lasers in the 25 to 70 watt range from these shops, usually for $200 or less.

2) If you are really good on the phone and don't sound like a terrorist, you can score a free laser at your local hospital or clinic if you are lucky. Call the hospital and ask to speak to the biophysics maintenence dept. (or something like that). If you can get hold of one of the guys who has been pushing a bunch of dusty CO2 medical lasers from one storage closet to another, you are well on your way to a free laser. It helps if you describe a worthy project that you will safely use the parts of the laser for, and promise that you will not return the laser to medical use. Saying you want to fry pesky cats in your neighborhood is usually not considered a worthy project. Saying you are constructing a laser engraver to teach underprivledged kids cnc machining techniques would be considered a worthy project

Results may vary. Play safe.

edit: Here is a video of a 50 watt medical laser I scored for free using the above techniques. In under 10 minutes I was able to mount it to my cnc milling machine and cut a gear out of some old blue jeans. It even came with some znse lenses! Total cost for this laser engraving system other than the milling machine was about $0.50 of window screen material to cut on, plus the gas to drive my truck to the hospital to pick up the laser.

http://www.skyko.com/videos/laserdenim.wmv

[C-TECH]

Hi,

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regards
C-TECH