Crazing on Acrylic

[Scott Shepherd]

I have a customer that wants something done on acrylic. It's a logo, leaning more towards a photograph than anything else. They wanted it cut on the router not a laser. Their image isn't going to work on a router. It's got all sorts of shading, etc. that they want to keep. I asked why they didn't want it lasered and they said they had it lasered once before and it developed all kinds of tiny cracks around it when they cleaned it (obviously cleaned with something it shouldn't have been cleaned with).

I'm looking at this thing over and over, trying to figure out just how a rastered image that's done on clear acrylic (very light power to get it to show up), is crazing. I've seen crazing many times on the edges of things cut, but I can honestly say I've never once seen crazing on something engraving, photo style (not deep engraving).

I thought I'd ask here. Has anyone every experienced any crazing on clear acrylic when it was lightly engraved? The item will be bent around a curve once I'm finished with it, so it will have some tension on it.

[Mike Null]

Steve

My only experience with crazing is with extruded acrylic. I regularly clean cast acrylic with dna with zero instances of crazing.

[Rodne Gold]

All acrylics get stressed by the heat of the laser , any cleaner with certain solvents will promote stress cracking round where its lasered or heat bent etc. Extruded is worse for this than cast acrylic is. Way to stop it is to anneal the acrylic in an 80 degree centigrade oven for one hour per mm thickness after its been worked.

[Scott Shepherd]

Rodney, are you saying that even on something like engraving a photograph into it, it's enough heat to do that? I'm running at 25% power, 100% speed on a 45W laser, so it's just barely marking it. It's all grayscale too, so it's halftoning it. Seems really unlikely to me it will craze. Now on cut edges, I can understand completely. I'm not cutting anything. It's a finished product they want engraved. I did tell them anneal it and their response was "what's that?", followed by "Oh, we're not going to do that".

I think they are just putting too many restrictions on what they want. They want a specific image, they want it done in a way that can't be done, and they don't want to modify anything to make it work. I suspect they've been told "no" by enough people and they are just trying to see if I'm going to get something done or tell them "no" too.

[Richard Rumancik]

I have not seen crazing in an engraved area but I won't say for sure that it can't happen as there are too many possible variables here (actual material, settings used, chemical used to clean, etc.) Maybe the laser is getting blamed for something else. Ask them to see the damaged item if they still have it - see if there is really crazing occuring around the engraved area. Or maybe they have a reject part you can experiemnt with. If they aren't interested in you trying with the laser, then I think they will be a difficult customer and you are better off taking a pass on the job. If they will tell you what the material is you can do some research with the material manufacturer. Maybe if they changed material grade it would help . . . but if they "know" lasering won't work then don't spend any more energy on the project.

[Mark Sipes]

I have found that high % alcohol cleaners will craze acrylics and Lexan. Why not go with glass.

[Dan Hintz]

Can you (re)anneal the piece once it's done? Charge them for the time in the oven, though...

[Joe Pelonio]

I would just pass. You have probably already spent a lot of time on this and would not likely make enough to justify the trouble when they bring it back, crazed or not. Some people are hard to please.

[Scott Shepherd]

Thanks for the input. I can't use glass, it's a pre made piece that will have a curve to it once it's done.

I haven't spent much time on it. They sent me the file, I ran a sample, that's about it other than half dozen phone calls that lasted about 2 minutes each. So I'm about 30-45 minutes into it and it's possible it could have a decent payback if I can make it happen. It's for a market that's fairly large, so I thought it was worth the risk to look into it some. I'll put all the crazing back onto them. It'll be a decision they have to make and take responsibility for.

I talked to them about annealing it after engraving. It I can work it out, that might be an option. We'll see. I don't have high hopes for the project taking off, but who knows. If nothing else, I get a little insight into their business/products. They are coming by tomorrow to look at my sample and bring me some samples and discuss it.

[Richard Rumancik]

If they try annealing be aware that it may affect the part dimensions. When would it be bent? If there are any existing bends annealing will cause the bends to relax and change. I tried annealing a part once and it ended up with marks on it as it is hard to support it during heating. On a wire rack it will pick up marks from the rack. You can't hang it, or it will distort even worse.

[Glen Monaghan]

Sounds like you got it too warm.

[Rodne Gold]

Bending it after you annealed it is useless , the bend will just stress it again
Richard , im sure the annealing oven was too hot , it should be at least 100c below when acrylic will get plastic or rubbery

[Larry Bratton]

I have a customer that wants something done on acrylic. It's a logo, leaning more towards a photograph than anything else. They wanted it cut on the router not a laser. Their image isn't going to work on a router. It's got all sorts of shading, etc. that they want to keep. I asked why they didn't want it lasered and they said they had it lasered once before and it developed all kinds of tiny cracks around it when they cleaned it (obviously cleaned with something it shouldn't have been cleaned with).

I'm looking at this thing over and over, trying to figure out just how a rastered image that's done on clear acrylic (very light power to get it to show up), is crazing. I've seen crazing many times on the edges of things cut, but I can honestly say I've never once seen crazing on something engraving, photo style (not deep engraving).

I thought I'd ask here. Has anyone every experienced any crazing on clear acrylic when it was lightly engraved? The item will be bent around a curve once I'm finished with it, so it will have some tension on it.

Use cast and don't worry about it. I just finished over 500 pieces of cast using acrylic cement and used Goof Off on some parts to clean them. No crazing on any of the cast, but had some extruded tubing in this process that did.

[Scott Shepherd]

Looks like it went well. The items were cast acrylic and formed to a curve. I made a fixture, flattened it out, engraved it, unclamped it, it was back to normal, now with the engraving on it. No need to anneal or do anything more.