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

[Rich Harman]

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]

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]

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]

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]

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]

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]

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]

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]

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!