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View Full Version : Unlimited length cutting (Warning: Don't try this at home)



John Blazy
08-16-2016, 7:45 PM
I would not normally do this. I thought of it a while back, but didnt need this ability - that is - removing the cover to expose the laser to shoot out into my shop, and mount the mirror and lens off a centilevered beam to manually push material through it like a bandsaw.

Until now.

I laminate dichroic films on glass and acrylic for commercial architectural spec, so with acrylic I usually crosscut the 4 x 8 sheets on a saw, or stack the sheets to cut all at once to fit them into my laser. The problem is that if any dust particles get on the sheet, and the sheets are flat stacked, or even vertical with the slightest pressure, the dust imprints dents into the laminated surface. So last job, I simply used a manual scoring cutter to score and snap the panels for shipping (customer has their own laser, so they wanted 48 x 48 panels) which minimized the dust tremendously. Way too sore on the arm to score and snap 1/4" acrylic though.

SO now on the job I'm on this week, different customer needs 40 x 40 panels from 15 sheets. Not looking forward to manually scoring the panels.

Gotta cut them without dust.

So I made a cantilevered beam that extends off a post in the shop where the mirror/lens combo fits off the end 14 feet from the laser. Mounted the mirror post through a hole in the beam, and mounted the lens under it at the right position, shielded in a length of conduit for safety shielding (Just repeat to myself - "this is theoretically safe now").

Worked the first time. Doesn't need to be pretty, doesnt cut all the way through when I push to fast, but it snaps right at my line - no dust.

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Bert Kemp
08-16-2016, 8:16 PM
Aren't you the clever one . :D

Kev Williams
08-16-2016, 9:52 PM
...do what you need to do to get the job done. I love it! Something I might do... :D

Gary Hair
08-16-2016, 10:31 PM
You'll either be a good example or a cautionary tale - so far "good example" is ahead.


I would not normally do this. I thought of it a while back, but didnt need this ability - that is - removing the cover to expose the laser to shoot out into my shop, and mount the mirror and lens off a centilevered beam to manually push material through it like a bandsaw.

Until now.

I laminate dichroic films on glass and acrylic for commercial architectural spec, so with acrylic I usually crosscut the 4 x 8 sheets on a saw, or stack the sheets to cut all at once to fit them into my laser. The problem is that if any dust particles get on the sheet, and the sheets are flat stacked, or even vertical with the slightest pressure, the dust imprints dents into the laminated surface. So last job, I simply used a manual scoring cutter to score and snap the panels for shipping (customer has their own laser, so they wanted 48 x 48 panels) which minimized the dust tremendously. Way too sore on the arm to score and snap 1/4" acrylic though.

SO now on the job I'm on this week, different customer needs 40 x 40 panels from 15 sheets. Not looking forward to manually scoring the panels.

Gotta cut them without dust.

So I made a cantilevered beam that extends off a post in the shop where the mirror/lens combo fits off the end 14 feet from the laser. Mounted the mirror post through a hole in the beam, and mounted the lens under it at the right position, shielded in a length of conduit for safety shielding (Just repeat to myself - "this is theoretically safe now").

Worked the first time. Doesn't need to be pretty, doesnt cut all the way through when I push to fast, but it snaps right at my line - no dust.

342408342407

John Blazy
08-17-2016, 10:40 AM
You'll either be a good example or a cautionary tale - so far "good example" is ahead.

I don't really want to be either, although I am kindof both right now, depending on what perspective you take. Anyone that owns a laser knows this can be done, and at the very least has wondered if the laser will put a hole in the wall if the 1st mirror and access panel were removed. So if you know that much, you also know the potential dangers of open laser, so its not like I'm being a bad example to unknowing kids. It's just an informative technique I'm sharing so that if the need arises, you can rough cut certain materials in lengths not limited to your laser bed's max capacity.

I did expect that if I sprinkled sawdust through the beam, there would be a fun fireworks display, but the dust falls through the beam too fast, so no photos there.

However, I did learn that the beam spreads out much sooner than I imagined. The spot that hit a pallet 25 ft away was over 1-1/4" DIA. I also discovered that one needs to clean the lasers primary lens as well as all the mirrors during routine maintenence. It had several spots that cleaned off with lacquer thinner.
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Kev Williams
08-17-2016, 12:02 PM
Laser will never cease to fascinate me... ;)


I did expect that if I sprinkled sawdust through the beam, there would be a fun fireworks display, but the dust falls through the beam too fast, so no photos there.
Spraying Cermark into the beam might get you a fireworks show (ask me how I know)

However, I did learn that the beam spreads out much sooner than I imagined. The spot that hit a pallet 25 ft away was over 1-1/4" DIA.
Interesting- this means that even though the beam expansion within a laser box will be minimal, there WILL be SOME beam expansion, yes? Meaning, if it seems the laser one is using isn't engraving as well at the farthest point from the laser tube as it does at the closest point, then one is not imagining it.. :)

John Blazy
08-17-2016, 12:09 PM
as well at the farthest point from the laser tube as it does at the closest point

Thats what I was thinking - loss of power, farther away, however, the 20mm diameter of the lens "catches" the wider beam, and still focuses all the power. The beam DIA at the 14 feet away from my laser for my "off table" cutting was only about 3/8" DIA max.

John Bronleewe
08-17-2016, 1:44 PM
Great post. At my previous laser gig we accidentally melted a 3/8" diameter spot into a computer keyboard while attempting to adjust mirrors on our newly arrived Chinese laser. The keyboard was about 12' from the machine and right next to where a co-worker was standing. Until that point I hadn't even thought about the beam going such a distance with any real power. As amused as we were it was it was a fast reminder of how easy it would be to seriously injure someone one or burn down the world. :)

I love your use of this mod!

Kev Williams
08-17-2016, 2:04 PM
And don't forget, the larger the incident beam diameter, the smaller the focused beam spot diameter- I'm curious how tiny the beam spot would be if you capture and focus all of that 1.25" diameter beam? :D

David Somers
08-17-2016, 3:27 PM
And of course, the real question is, can we do this with a Glowforge??? <sorry......evil question>

Cool idea John. I have no need to do this with, but it would be fun to try just for the giggle. And pilots were worried about people with laser pointers?? Wait till a creative teen with a Glowforge reads this thread!!!!

Dave Sheldrake
08-17-2016, 4:03 PM
Wait till a creative teen with a Glowforge reads this thread!!!!

I've seen a home built shoulder fired 40 watt glass tube built into a rifle :(

Freehand lasers (a box with the laser head mounted on the end) are quite common in the pyrography game apparently, personally I value my eyesight a bit too much to try them out though :)

John Blazy
08-17-2016, 4:26 PM
Wow - I can totally see a psychotic teen with great electrical skills take apart a glowforge for nefarious reasons. Its not the geeky teen that engineers a hand held version from a GF - its his evil buddy that "borrows" it.

Did a crap load of cutting today - ten sheets - three cuts each, no dust. Shipping Thursday.

Its amazing - no sound at all except a faint hiss. The real danger is breathing the fumes, so I wore a respirator and had our "air assist" shop fan blow the fumes out the bay door.

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Bill George
08-17-2016, 7:27 PM
Add a few more mirrors and I see the basics of a perimeter security system that really protects you! NO do not do this!!

Bert Kemp
08-17-2016, 8:14 PM
Great Idea:D


Add a few more mirrors and I see the basics of a perimeter security system that really protects you! NO do not do this!!

David Somers
08-18-2016, 2:02 PM
Bill,

Add a few more mirrors and I see the basics of a perimeter security system

Sooner or later the neighbors will get curious as to why the postman gets shorter and shorter every day.

Rich Harman
08-18-2016, 7:14 PM
I also discovered that one needs to clean the lasers primary lens as well as all the mirrors...

Do you mean the laser tube's output window? My understanding is that cleaning it (by making contact) can do more harm than good.

John Blazy
08-18-2016, 10:03 PM
I never knew that, Rich. I could not resist cleaning it. You can see the huge spots from the photo. Any dirty area must absorb IR and add heat every time its on, thus heating the lens. It appears to be a lens, as it has the vapor deposition coating on it. The coating did not appear oxidized or damaged after I cleaned it.

Ian Johnson
08-19-2016, 12:25 PM
I had the door covering the tube open while working on alignment, and after awhile noticed there was a burn mark on the wall behind the laser. The "one-way" mirror (don't know what it is called) that merges the red dot laser pointer with the beam was just reflective enough on the back side to send a reflection of the beam that was still strong enough to char the drywall.



Great post. At my previous laser gig we accidentally melted a 3/8" diameter spot into a computer keyboard while attempting to adjust mirrors on our newly arrived Chinese laser. The keyboard was about 12' from the machine and right next to where a co-worker was standing. Until that point I hadn't even thought about the beam going such a distance with any real power. As amused as we were it was it was a fast reminder of how easy it would be to seriously injure someone one or burn down the world. :)

I love your use of this mod!

Rodne Gold
08-19-2016, 1:07 PM
I have always had visions of using a laser from our upstairs balcony to give our neighbours blocking foliage etc a "haircut" so we can have a better view.

John Blazy
08-19-2016, 1:29 PM
I have always had visions of using a laser from our upstairs balcony to give our neighbours blocking foliage etc a "haircut" so we can have a better view.

Its amazing that cutting foliage is literally possible with a 60 - 100 watt co2 laser, if you had the right set up, and complete disregard for safety. I guess its the same thought process when firing a gun - always be aware of the background. Imagine mounting the laser on a tripod, hooked up to the chiller, etc.

That is absolutely the new redneck entertainment. A beer in one hand, and the laser in the other while watching the branches slowly fall to the ground leaving a perfectly level cut as if you took a light saber to it.

Gene Uselman
08-19-2016, 2:53 PM
R.E beam expansion in the machine- my beam out of the tube is 7.55mm and at the farthest point away it is 8.6mm. Just measured it today for Marco at LightObject. Gene

John Blazy
08-19-2016, 4:45 PM
R.E beam expansion in the machine- my beam out of the tube is 7.55mm and at the farthest point away it is 8.6mm. Just measured it today for Marco at LightObject. Gene
This must be the reason that on lasers with a 4 x 8 or larger bed, the laser is mounted on the moving rail.

John Blazy
08-26-2016, 4:06 PM
I'm not intentionally bumping this thread, but I learned some interesting stuff lately related to beam spread. First off, I took one of my laser cut laminates to a steel fabricator who laser cut the SST for the background of my laminate, and we exchanged laser stories. His 4 x 8 bed has the laser mounted on one end (not in the moving rail), and he says he loses noticeable power when cutting at the far end of the bed, and has to compensate for the beam spread. His mirror and lens DIA at the head is way larger than our C02 lasers. I assume his is a YAG or something. I forgot to ask.

Second thing I discovered was today - after cutting the last eight panels of acrylic (using the beam extension contraption that this thread is all about) and then needing to replace the mirror post back into the laser to start the cut files - I grab the mirror post and burnt my hand a bit. I checked the beam spot, and it was perfectly centered in the mirror when I started, so the only thing heating the mirror post housing had to be unseen beam spread. Verified also by the fact that when freehand feeding the 4 x 8 panels through this off-bed head, my left hand would go behind the laser path occasionally, and I could feel significant heat.

Very interesting to say the least.

Kev Williams
08-26-2016, 7:12 PM
Your fab guy's laser could be a C02, I believe the sheet metal shop that does my metal cutting uses a C02 laser... regardless, I wouldn't expect a lot of beam spread on an 8' machine, simply because the machine SHOULD be designed to cut equally everywhere on the table. If not, why have that much table...? And while a wider incident beam may result in a smaller spot beam, it would seem logical that a flaring incident beam may lack the coherence (? or, lets say 'straightness') to be properly focused. And how much of the flaring light waves are hitting and being absorbed by the framework around the mirrors? I'm sure that's why your mirror post was hot. BUT, the beam doesn't have to be flaring to hit the framework, all that takes is some misalignment. :)

Cutting thru steel with a beam of light, that we can't even see, no less. Sure is a step up of from frying ants with a magnifying glass! Fascinating machines, I wish I had more free time just to learn more about 'em!