by Liberty4Ever » Thu Oct 04, 2012 7:43 pm
DO NOT use rubbing alcohol (isopropyl alcohol) on acrylic. I've been using a commercial VersaLaser for 5-6 years, and their user manual specifically warns against its use, even though isopropyl alcohol is used to clean other parts. I typically use the borrowed laser on 3rd shift when nobody else is around, so by the time I'm finished, I'm very tired. Recently, even though I knew better and had always used a mild soap and water to clean the acylic lid as the manual states, I flipped a bit in my brain due to sleep deprivation. Someone had splattered some black ink onto the acrylic lid, and I decided I'd clean it off for them. Knowing that soap and water wouldn't work, I sprayed some 91% isopropyl alcohol on it and immediately realized my mistake, just a bit too late. The acrylic lid cracked in several places and is now being replaced. The manufacturer changed the design because of this problem. It was 3/8" thick clear acrylic and the cracking mostly occurred on the surfaces that were stressed because they had been heated and bent, but I have no doubt that flat acrylic would be attacked by isopropyl alcohol at a slower and less dramatic rate.
Another common mistake with acrylic is using paper towels. Most paper towels include some microscopic abrasive bits that will put fine scratches in the acrylic surface. You'll soon have a hazy finish. Use only mild detergent and water and a soft, clean towel for cleaning acrylic. If there is gritty contaminate, I'd flood it with sprayed on detergent and water cleaning solution, and use the clean towel to wipe it in a manner that lifts the floated contaminates away and onto the towel, rather than wiping them across the relatively soft acrylic surface. Even better would be a lid that could be easily removed, taken outside, and sprayed with a hose to remove any grit without any rubbing.
Finally, if you're designing your own laser, you can specify scratch resistant polycarbonate. It's a lot more expensive, but it won't shatter or break like acrylic can, and it has a transparent ceramic coating that is hard and very impervious to scratching. Sometimes, it's sold as "vandal resistant" polycarbonate or bullet proof glass. McMaster-Carr carries it. Search for polycarbonate. For cost, I'm planning on using clear acrylic captured in the slots on an extruded aluminum frame. I'll be the only one using the laser, and I'll try not to pull any all-nighters, so I can be careful with the maintenance. Worst case, if I screw it up, it'll be cheap and easy to replace the acrylic sheet.
Apparently, I didn't build that!