acrylic cast or extruded?

[Ray McAlister]

I bought same sample/scraps acrylics, most not labled, most have cut without any problems but there is a couple of sheets that will not cut 3/16 with 3 or 4 passes. The 1/4 stuff is cutting with in 2 passes(25 watt).
Does cast or extruded make a dirrerence when cutting?
which is better?

Thanks
Ray

[Rodne Gold]

There might be a slight difference in cutting properties tween Extruded and Cast , the extruded shou;d cut easier as its a short polymer chain product.
Easy way to check what it is is to burn some , cast burns with a crackly flame and doesnt melt , extruded burns with a silent flame and drips molten flaming balls.
However , you have a different problem , 25w should cut 1/4" perfectly in one pass , multipass cutting of pex is not really that good as the edge quality depends on the melt being ejected thru the bottom of the cut. When doing multipass you can have misregistration issue due to the expansion of the object with the heat put into it in the first pass , but you will also have nowhere that the melt can be ejected and it will just resolidify in the 1st passes cut.

[Gary Hair]

another way to tell them apart is to raster something onto the acrylic. Cast rasters very well, much better and "frostyer" looking than extruded.

[Mike Null]

If this is all unmarked is it possible that some of it could be polycarbonate? If so you will not be able to cut it with your laser.

[Joe Pelonio]

If this is all unmarked is it possible that some of it could be polycarbonate? If so you will not be able to cut it with your laser.

The first time someone asked me to cut polycarbonate I called and asked Epilog, they said it was OK to cut. I have not done a lot of it because it causes a bright yellow smoke but it does cut nicely on my 45 watt.

As for cast vs extruded both should cut at about the same settings. Cast engraves a lot nicer, extruded leaves a glossier edge when cutting. So, if just cutting, for example 1/4" acrylic letters, I use extruded (also cheaper). If engraving or engraving and cutting I use cast. As mentioned by Rodney cast flames more. One way to tell with most manufacturers is that the cast will have a paper protective film, while extruded will have a clear, white, or blue plastic film.

Ray, if it's taking 3-4 passes on that material only it may have some other plastics in it besides acrylic like ABS or polycarbonate which do take more power. One way to tell is if it bends more before breaking it likely contains ABS or is polycarbonate.

[Mike Null]

Joe:

I tried Lexan without success. Just burning and melting and smoke. I decided to use the saw.

I haven't tried any other polycarbonates so I probably shouldn't have been so general in saying they couldn't be cut.

[Steve McKee]

I tried Lexan without success. Just burning and melting and smoke. I decided to use the saw.

Lexan, haven't thought about that stuff in years. Many, many moons ago I sold outdoor signs made from Lexan, pretty much takes dynamite to destroy it. Probably one of the reasons it's used in the aerospace industry. These two quotes are from Wikipedia, the first makes me wonder if you should try cutting with a laser, I don't think I'll be trying it. (Definition: Phosgene (also known as carbonyl chloride, COCl2) is a highly toxic gas.)

It is a polycarbonate polymer consisting of chains of Bisphenol A alternating with carbonyl chloride, also known as phosgene.

Lexan was also used for the housings of Loran audio cassettes because of its high resistance to warping and melting from heat, a common problem with audio cassettes stored in automobiles on hot summer days.

[Dave Fifield]

I was asked if I could cut 3/16" thick clear polycarbonate sheet with my laser today. I did a search and found this old thread. I tried it just now (only a very small test shape). Full power (45W) at very slow speed doesn't even get all the way through, doesn't cut very clean edges (compared to acrylic), but does create a lot of nasty yellow smoke that discolors the polycarb sheet (and probably isn't too good for the mirrors/lenses in the laser, or my lungs, either!).

I'm going to pass on this job, or get them to go with acrylic - that cuts nicely. I suggest y'all pass on cutting polycarb sheet in the future.

Cheers,