Is it done yet?
rrrrrrrrrrrrr
So, just how did that mirror get like that? Any ideas?
Cliff Jennings said:
Some laser news. After the tube replacement (which probably didn’t need to happen, as it turns out) came the power supply replacement, which was needed. Still not really cutting. But today I found the culprit: it was the mirrors for sure. Here’s a comparison.
After taking over an hour doing a full alignment (I’ve never done that before either), I ran some test pieces. And it’s cutting better than it ever has! So I’m finally diving back into the turbine model again.
I’m thinking that’s a map of Middle Earth on the left…there may be diabolical forces at work here…(https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-foot-in-mouth.gif)
Oh, most definitely, haha!
I don’t know what’s breaking down, but these are the cheapest of the available mirror materials. The replacements (molybdenum) are said to last 3x as long usual (silicon), but have slightly less reflection – so it’s said. But these babies are cutting great!
Oddly, none of the references I’d seen (e.g., “the top ten things stupid people do that result in poor laser performance”) never mentioned mirror breakdown. Only recently (after some frantic searching for solutions) did I see an article saying that one should replace the mirrors every year.
Anyway, this set of 3 cost me $35 on Amazon, but they’re much cheaper direct from China (through Ebay, Banggood, etc.). So I just ordered a couple sets for $14 each (which will take 6 weeks or so to get here, which is fine).
I guess SOME mirrors are better than others…
I wonder if he vapors from what you are cutting corroded the mirrors.
David Maynard said:
I wonder if he vapors from what you are cutting corroded the mirrors.
I don’t know; but I just use acrylic and a little wood, and that’s the two main things these are used on. And it was a wood cutter I read saying they should be replaced every year.
Might just be the heat of the beam attacking the reflective material, but, I don’t know.
I’m guessing the laser heat acts like a catalytic converter and makes acid rain from the acrylic/wood fumes…
A small fan and a fresh air duct …
Irritating toxic gasses and Methyl Methacrylate are combustion by products
https://www.sctech.com/MSDS-Acrylic-Sheets
Are the mirrors glass or a plastic I wonder
Surface coated glass mirrors can be rather fragile. I usually just wipe them off with a lint free cloth. I only use a bit of alcohol on them if they are really crudded up, and even then I try to be gentile, and only have my cloth a bit damp with alcohol.
Cliff, have you considered polished Stainless Steel mirrors? They will be a bit pricey compared to the coated glass, but will likely not deteriorate nearly as quick, at least from the material standpoint.
As for the off-gas process of cutting, I know the byproducts of PVC are Chlorine/Chloride gasses which are very corrosive. Depending on the glues used in the plywood, there could be an issue there as well. Never looked in to acrylic, but like any other result of modern chemistry, I am sure there are aggressive byproducts there as well. I know from your build thread of you cutter, you did plan for an exhaust to the exterior. A look at how the exhaust moves the gasses might be worth a review. If you exhaust draws the gas toward the mirrors that contamination will not do the mirrors any good.
FWIW
Thanks for all your further insights, guys.
John, Bob, there’s a fan for inlet air, and the big vacuum-blower in a little mini-shed outside, and that’s been taking care of the smoke fairly well, at least visually. The suction pulls the smoke away from and beneath the mirrors.
Jerry, I think the mirrors are glass, coated from the near (exposed) side. Bob, I’ve not seen SS mirrors for sale, but some of the more expensive and longer-lasting ones are copper.
Some people use a hole saw and cut their mirrors from old CD’s. I might go there some day, but since I’ve upgraded from the lowest quality silicon mirrors, have 2 more molybdenum sets coming, and am now alert to the issue, I’m looking forward to getting more lifespan evidence.
David, I agree, they’re easy to mess up. One prominent laser guy said have at them with acetone or whatever. But I new think that contributed to my problem. Most times I’ve read what you said, lint-free cloth with alcohol.
Thanks,
Cliff
I’d check for swirling air currents inside the box, like water, eddies and vortexes can form next to a current. I’d use a punk or incense stick/pyramid and a clear plastic top … Something is getting to them.
The laser work is done, and almost everything’s prepped. Need to do 60-some brass rods of various lengths, but that’s it. Until, of course, I start assembling and discover the gremlins on the design. (https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif)
Test fitting up of the base parts…
In case you missed it on all my bloviating, this is acrylic because it has to flatten and fit in my suitcase next October. The parts will be sanded and painted, and I’ll make some sort of clip to hold the outer main bents together.
Linda and I have picked out a spot in the back yard to plant it, away from the layout a bit (this sucker will be 45" tall, and isn’t suitable for Virginia City), but not hidden. At that point I’ll bond the acrylic together, but until then it’ll stay loose.
===>Cliffy
When are you going to market your kits?(https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)
I got a start on the construction this week, yay!
Hi Cliff;
It is looking good. Can’t help but wonder what OSHA would have to say about the ladder built into one of the corner support beams. Times change. People “toughed it out” a whole lot more when the Dexter-Turbines were new. I have hand-bailed (hand fired) full-sized steam locomotives, so I have an appreciation for what our older generations had to do to get the job done.
Best wishes, David Meashey
Thanks David.
I agree, they were tougher. But as you know, their average lifespan was shorter…
I think if an OSHA person saw this, they’d say, “Yep, that’s why we’re here.” (https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif)