[frederik] recently upgraded his K40 to something great. He’s calling it the Layzor, and it has a huge 600×400 mm bed area, a feed-through slot for even wider workpieces, and fancy technology [frederik] is calling an ‘E-stop’. Sounds expensive, doesn’t it?
The build began by scavenging the K40 laser cutter for the electronics and laser tube, then building a new frame out of aluminum extrusion. A few parts had to be custom made, including a few stepper motor mounts and something to hold the laser tube. All of this was tied up in a box with acrylic panels, and went together as easily as any other CNC machine.
The finished project is great. It’s a relatively powerful laser cutter capable of most hobby work, and it was cheap. The total cost for this build was under €500. That’s not including the scavenged K40, but that’s still an amazing price for a very capable laser cutter.
This acrylic case clearly isn’t laser safe though! The metal case is the one good part that doesn’t need replacing.
Yeah, I’m normally not a safety nanny, but watching my optics professor (with decades of experience) blind himself in one eye while “being careful”; I don’t fu*k around with laser safety. At least with power tools you can see/hear and often react fast enough when in real danger. Lasers are silent and impossible to ‘react’ to.
It’s kind of laser safe. Acrylic absorbs the laser, that’s how the laser cuts it. If the laser cuts a hole in the case, turn it off…
Polycarbonate would have been a better choice, but acrylic would probably stand up to a diffuse reflection. Just be ready to hit the E-stop immediately if you smell garlic.
While I’ve met a few night shift laser operators who I had my suspicions about, none of them ever got turned to dust by reflected laser light. Presumably it’s ultraviolet that’s the problem and not far infrared.
Acrylic gives off an intense garlic-like stench when hit by a CO2 laser, for those who haven’t worked with laser cutters. You’d smell if the case was starting to get damaged before a burn-through, although I’m not sure how much warning you’d get. Probably 10-15 seconds in a worst case.
Extruded acrylic smells much worse than cast acrylic. I wouldn’t describe either as garlicky though.
If you’re cutting acrylic anyway then you wouldn’t smell the difference if it was burning through the case.
Maybe something as simple as sticking tinfoil on the inside would do the job. Our use dibond – acrylic with a thin aluminium layer on the outside.
Really, a garlic-like smell? That’s weird. When I was first setting up my K40 and hadn’t gotten the ventilation completely worked out yet– I had, but that case has too damn many holes in it that you either need to plug, or you need something better than the provided squirrel-cage fan –the only smell I recall from lasing acrylic was a very obvious superglue smell. (Which makes a certain amount of sense.) If your garlic smells like cyanoacrylate glue, you have a bigger problem. Haha!
Only when the beam is focused; even the direct beampath of a 40W CO2 laser tube has trouble damaging acrylic, and does little more than scorch balsa wood. The part of the beam that is focused sufficiently to actually cut is only 10-20mm long and is directly below the cutting head.
Diffuse reflections from either the beampath or the cutting will be entirely absorbed by even relatively thin acrylic without damaging it, which is what you want a laser to have an enclosure for.
Opaque as in 99% or something of light gets blocked? It takes much less than 40 watts to cause eye damage.
But yeah, in general you don’t get very focused beam out of these machines accidentally, so it is relatively safe.
Yes – the CO2 wavelength gets absorbed by the acrylic, turning the plastic into a vapor. You get pretty much 100% of the light blocked, right up until it punches a hole in the acrylic. Polycarbonate is similar, but it melts instead of vaporizing and can give you a bit more time before burn-through. If you’re looking at a kilowatt-range CO2 laser, the windows in its enclosure are going to be polycarbonate. On something K40 sized, either one is going to handle cases where the focused beam reflects off the material. Even if you were crazy enough to stick a sheet of polished copper in a K40, the beam after the focal point spreads out and you’ll get a much larger diameter beam with a lower power density hitting the enclosure. I suspect the only real threat would be if you had one of the mirrors come loose and redirect the pre-focused beam into the enclosure.
Actually the case is the worst part of my new K40. The bottom is warped and pops like a drum. If you push up from the bottom it pops into one position, and if you push down from the top it pops to another. I think it will impossible to align the optics with this issue.
Actually, acrylic is fine for CO2 lasers. Acrylic is optically opaque to them, that is why they cut it so well. 10,600nm is not in the visible wavelengths, so even though it is transparent to us, it still blocks the laser light. Diode lasers on the other hand do pass through acrylic.
Darn, I just replaced my K40 with a $2200 chest-freezer-size KH7050. I think this upgrade would have given me exactly what I needed.
I was merely hinting that the KH7050 (I haven’t seen one, so yes, it was “uneducated”) probably has a metal skin, unlike the acrylic skin of the subject of this blog.
Like others who posted before me my gut reaction to that acrylic case is that it seems pretty sketchy. But… I know that when I am cutting acrylic focus makes a big difference. Mere millimeters of height change can be the difference between a good cut and a crappy etch. So… is some random laser reflection really likely to burn through the case? If not can the acrylic attenuate it enough to protect a naked eye?
I’m guessing that it is ok although I wouldn’t want to bet my eyes or those of my family members on it!
At my home, no one is allowed in the room with the laser unless wearing proper protective eyewear. That said, I’d still go for more durable exterior materials and limit myself to a small, thicker window. The one on the KH40 is already sketchy.
A random laser reflection absolutely will not burn through the case, and even unprotected a typical reflection won’t cause eye damage. Most of the people here have very little knowledge of 10.6um lasers it seems.
Safety is always a concern. Acrylic blocks the C02 laser wavelength, but I always wear proper safety goggles when in use. The bottom panel of this machine is steel sheet. Btw, the original K40 also has an acrylic panel with no safety interlocks so I wouldn’t call it safer.
Not even regarding the safety… isn’t it much more expensive to use an enormous amount of extruded alu and relatively expensive acrylic for the case than getting some sheet metal and weld/stud together some kind of solid box?
I’m not going to go claiming it’s totally safe, but think about this… If you’re worried about the laser punching through the acrylic and causing damage, it would have to be focused enough AFTER the reflection from whatever you’re cutting (or any reflective surface under the laser head) to aim directly up to your eye, through the acrylic, which, itself, absorbs the IR light. So unless this thing has huge cracks in the sides for stray, defused light to come out, I wouldn’t worry too much, still wearing my safety glasses.
Go find an old washing machine and use the sheet metal for panels. Techshop never had anyone wear goggles with their acrylic lidded lasers. Idk. Were they safe?
The blog states that they will be no external water cooling and that this was achieved. I can’t see any other motion of cooling though. Anyone know what happened with this?
I got a reply on Frederick’s blog. The water pump and container are inside the case. Maybe not enough coming for heavy use.
The comments here are moronic. The acrylic case is fine. Professional lasers that cost over half a million dollars use acrylic, polycarbonate, or vinyl panels along three edges of the machine for the operator to see what is happening. These machines use 4kW resonators.
10.6um is not a particularly dangerous wavelength and doesn’t blind you like a regular laser will, and you will never get a focused reflection from a laser cutter, ever.
Acrylic Plexiglass Tube
Where I work we have two $400k Mitsubishi that have no shields around the table to prevent reflections from going around the shop. It simply doesn’t happen.
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