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Bob Crimmins
02-22-2017, 1:11 PM
I will be sourcing a new laser in the summer. It's gonna be a 150W gas-assist machine. In my experience with my current 80 watt machine, it's sometimes challenging to etch/engrave soft materials like vinyl and fabric because I have to either diminish the cutting power or increase the speed so much that the quality of the etch suffers. For example, at 25% power and a 300 m/s cut speed yields a poorly-defined edge of the etching. If I increase the speed or reduce the power any more than that, then the quality of the etch is terrible.

Moving up to a 150w machine, I can only imagine that soft materials are going to be even more of a challenge, as even at the lowest workable power settings will blow right through the material. It seems to me that a power-reducing pass through filter/lens would fix this problem -- just flip it into the path of the laser and reduce power by x%. But I don't find anything like this when I search. Is there such a thing?

Thanks,

Bob

Lee DeRaud
02-22-2017, 2:05 PM
It seems to me that a power-reducing pass through filter/lens would fix this problem -- just flip it into the path of the laser and reduce power by x%. But I don't find anything like this when I search. Is there such a thing?I would guess "no", but I could be wrong. The thing is, the excess energy has to go somewhere, most likely absorbed by the "filter", which doesn't bode well for the lifespan of said widget.

(I'm also getting a "wrong tool for the job" vibe, because it sounds like you're using a chainsaw to slice an onion.)

Kev Williams
02-22-2017, 2:18 PM
Guess you could stick a piece of #10 welding goggle glass in the beam path to the last mirror and see what happens ;) --

however, I would expect the beam would etch the glass unless it was coated...?

You could also try to narrow the beam by passing it thru a smaller hole-- it works with my hand held laser pointer... I use it as a thru-the-lens pointer on my Triumph, but the dot was too big. So I took a small piece of .010 brass shim stock and drilled a teeny hole in it, and taped it over the end of the pointer- the difference in dot size is huge...
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Sheldrake will probably explain why this is a bad idea (;) ) but what if you took a cubic inch block of steel, and bored a tapered hole that would collect and narrow the original beam? Like a beam expander in reverse-
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-the block would have to be able to absorb the heat and be black enough to not reflect the beam backwards... All just conjecture, but I would think it would definitely absorb some of the power! And it's not like you'll be hitting it with 150 watts, you would using it at the lowest reliable wattage possible...

--or maybe they HAVE reverse beam-expanders that will do this?

Bob Crimmins
02-22-2017, 2:24 PM
I was sparked to think about this when I read that the red LED alignment laser that some machines use is actually reflected through a two-sided mirror and that the laser beam loses some small amount of power when it passes through the mirror. So, I thought, why not create a filter that would just reduce that power a bit more. I'm aware of the thermodynamic challenges, i.e., that energy has to go somewhere and so I imagine that a filter would be made from some exotic material or would include a slick heat sink.

Bob Crimmins
02-22-2017, 3:04 PM
Oh yeah, and you're right... this is a bit of a "wrong tool for the job" scenario. Regrettably, I don't have room for more than one laser in my shop; I'm already crowded out with an 80w laser plus a 1300x1300 CNC plasma cutter. So I gotta do what I can with what I have. The 'vibe' in my shop is actually "scrappy, creative solutions." Of course that can sometimes lead to rabbit holes or shop fires.

Robert Bonenfant
02-22-2017, 3:15 PM
Try out a Chinese Imported machine - Camfive, Rabbit, Tons of other suppliers. We can engrave just about any materiel that comes our way with a 100 watt tube. The lowest power setting we can go is about 10% with our machines - any lower and we get mixed results, Does your current machine have a onboard power knob - We have the ability to turn our laser power even lower directly at the control on the machine. Most companies will send you test cut/engravings as well.

David Somers
02-22-2017, 3:22 PM
You might also look at a machine with a dual tube? They can be matched in power and used separately to speed up one job, or used to do two jobs at one time. Or you can have two different power tubes in their with one sized appropriately for your soft material engraving, and the other the 120 you wanted. Or you can also do a machine that has a CO2 and Fiber tube in it. (more versatility in terms of materials you can work on, if that is appropriate to your business.)