Help to buy a Laser

[Jasonbit]

Hello guys,

I am looking for help to identify a place where I can buy a laser for a CNC Laser. I googled on Ebay and I found this: https://www.ebay.com/itm/15W-Laser-Head-Engraving-Module-w-TTL-450nm-Blu-ray-Wood-Marking-Cutting-Tool/183757888176?epid=24012513715&hash=item2ac8d2dab0:g:UNYAAOSwTi1bbr2I

This seller asks for this product $109. This is a normal price or I should search anothers salespeople?

[UPDATE]
I am a newbie guy on electronic and I intend build a simple CNC Laser to do some stuff and start learning more about CNC and Lasers.

[Fred27]

Your best bet would be to look at the K40 40W lasers you see on eBay. You get a working starting point for and a proper laser for about the same price as the laser and PSU on their own.

They're common and well documented - including their faults. The electronics are rubbish, but any EEVBlog reader should be OK with sorting that out.

The usual disclaimer: Be careful and keep your eyesight.

[Domagoj T]

What do you want to do with a laser? 15W is fairly limiting. You should not expect to be able to cut more than some card stock and mark wood with that.
Couple of years ago I bought the K40 for about $400 (and spent another ~$400 on various stuff to make it a bit better). It's 40W, fully functional machine (but horrible software). By the time you finish building a machine yourself it will be more expensive than that and not nearly as good.

If your goal is just learning about and building a CNC machine, you don't need even that.

[Jasonbit]

Thanks to your answer.

Therefore, I must invest in a laser of at least 40W. It is?
Is the model "K40 40W lasers" a machine?
()

I live in an apartment and would like to build a CNC. But a they make a lot of noise  I will choose to replace the wood routers with a laser. (the aim is not to cut wood. But mark or cut plastic). The cnc and engine structure is almost finished. Now the laser is missing, which is a new world for me.

[UPDATE]
Maybe I will consider the wood router 
()

[moffy]

I have one of the "15W" blue lasers with a little CNC. It is really a 5W diode, but very powerful. I got a custom orange transparent acrylic cover made to avoid blinding accidents. It is an impressive diode and has no trouble burning wood.

[Domagoj T]

Yes, that blue box is a K40. K40 is just a broad name for a 40W CO2 laser with working area of about 200 mm x 300 mm. There are many manufacturers of it, and each makes a little bit different product. The prices vary a lot, and additional features are as varied as it gets.
My K40 laser itself is almost silent. There is some noise from the power supply fan, but not much. The loud parts are air evacuation fan (absolutely necessary) and the air assist pump (highly recommended). K40 is water cooled, so you'll need a water pump as well (they are not loud) and either a big bucket of water or a dedicated water chiller (which may or may not be loud depending on type, I don't have it so can't tell from experience).
If you're already done with the mechanical parts for the machine, then a CO2 laser tube such as ones found in K40 is probably not suitable for you. The laser tube itself is about half a meter long, so you likely won't be able to fit it on the machine. The usual approach with K40 is to have the laser tube fixed in the back of the machine and move mirrors that guide the laser beam where it needs to go, then finally use a lens to concentrate it just before the material you cut.

Cutting plastic is tricky. Acrylic (Polymethyl methacrylate, plexiglass, perspex) cuts perfectly on my laser, but stinks (remember air evacuation). That is pretty much the only plastic that is good for cutting with a laser. Styrene, which is otherwise excellent for hobby work does not cut well - it melts and deforms along the cut. PVC cuts ok-ish, but contains chlorine and during cutting releases it as chlorine gas, which forms hydrochloric acid with moisture in air. The result is that everything in the vicinity will rust very quickly, not to mention the health issues related to inhaling it. So keep that in mind, the only plastic you should cut with a laser is acrylic.

Wood (specifically plywood) cuts nicely. I had excellent results with 3mm ply, but again, not all plywood is the same. There are special ones designed for laser cutting and if you decide to go that route you should stick to those. Regular plywood doesn't cut cleanly, it just burns and leaves horrible edges. From what I gathered in my research into this, the problem is the type of glue used in regular plywood. I haven't tried cutting natural wood, mainly because I don't have any nice thin pieces, but I expect it to work fine.

In any case, you should have a strong ventilation to suck the air from the laser enclosure and dump it outside the building, or you could invest in a (rather expensive) air filtration system.
Moffy said it already, but it can never be said enough times, please have an enclosure around the machine. At these laser powers you can end up blind from a momentary exposure to the laser. A sudden unexpected reflection from something shiny is enough to permanently damage eyes. At these wavelengths eyes can't see the laser, and there is no blinking reflex to protect you. The second video you posted is exactly the thing you should not do. Having the laser beam in open space is dangerous (acrylic box is suitable, but metal is better if you can manage it). In addition to the enclosure, get yourself some safety glasses that are designed for laser wavelength you use.

[Fred27]

@Domagoj T - I find that cast acrylic cuts and smells far better that extruded acrylic. No idea why, but it really does.

[james_s]

CO2 is far safer than high power visible diodes, especially 405nm diodes which are far brighter than they appear. A CO2 laser is 10,600nm, it's essentially a heat beam it is much easier to block and you don't have to worry nearly so much about reflections blinding you.

[Domagoj T]

@Domagoj T - I find that cast acrylic cuts and smells far better that extruded acrylic. No idea why, but it really does.

I never noticed that. Perhaps I never had contact with one of the them. I buy my acrylic from a company that does laser cutting, so that might be the reason. The stuff that I have is certainly not noxious, but my family members do ask me to close as many doors as I can.
Thanks for the tip though, I'll avoid stuff declared as extruded.

[Fred27]

Cast acrylic still smells, just nowhere near as bad. Your family will ask you to close door, but at least they won't shout at you like my wife did when I accidentally vented the fumes from extruded acrylic back through the cooker hood in the kitchen! 

[wizard69]

CO2 is far safer than high power visible diodes, especially 405nm diodes which are far brighter than they appear. A CO2 laser is 10,600nm, it's essentially a heat beam it is much easier to block and you don't have to worry nearly so much about reflections blinding you.

You really should worry about any laser.   As such an home built laser should have safety interlocks and an enclosure opaque to the laser energy used.   The fact that you can't see the beam actually makes CO2 lasers in my mind more dangerous.

In any event what everybody needs to do is to respect what a laser is and the fact that you can't beat the speed of light.   Laser damage to the eyes is somethign that medical science can not realistically do anything about.

[wizard69]

If you buy a low cost laser head you will get a low cost solution that is also low performance and may be low quality.    Good laser solutions are expensive and likewise power is expensive.    The 40 watt CO2 lasers are probably a minimal power level to consider if you want a versatile machine.

The other gotcha is that different wavelength lasers will behave differently on materials.   It would well be worth your time to research the materials you intend to work with and how different laser wavelengths interact with them.

Industry right now seems t have a strong movement to fiber based lasers.   It might be worth looking into the usual low cost suppliers to see if anybody has a reasonable solution for fiber lasers.    I can see fiber lasers as the go to solution for DIY hardware as prices come down.

[james_s]

You really should worry about any laser.   As such an home built laser should have safety interlocks and an enclosure opaque to the laser energy used.   The fact that you can't see the beam actually makes CO2 lasers in my mind more dangerous.

In any event what everybody needs to do is to respect what a laser is and the fact that you can't beat the speed of light.   Laser damage to the eyes is somethign that medical science can not realistically do anything about.

You should respect any laser, not worry about it. Lasers have been one of my hobbies for decades, yes they can be dangerous but so can electricity and many other things. The important thing is to be aware of the dangers and take reasonable precautions.

Either way a CO2 laser is much safer. Ordinary transparent materials like glass and acrylic are quite opaque to the wavelength. So are the lenses of our eyes. A hit of sufficient power can cook the flesh but it's not going to focus and burn a hole in your retina. At a given power level 405nm is one of the more dangerous types because while it's visible, it does not look very bright, and it is not attenuated much by transparent materials. The most dangerous IMO are the short IR wavelengths, they behave like light but are nearly to entirely invisible.

[beanflying]

You might like to have a look here at my 40W Laser. While it shares a wattage with the K40 it has a lot of improved features over the budget one. https://www.eevblog.com/forum/reviews/40w-300x200mm-laser-cutter-engraver-vollerun/

As others have mentioned Diode Lasers are almost certainly not rated correctly and running one without an enclosure is just plain stupid.

I have just started assembling the bits for a 100W 1250x900mm Laser based one this video series below comes with available plans for a smaller 40W one too. The Plans material lists and how to are well worth the few $ https://www.furtherfabrication.com/resources?category=Y400