Plastic materials?

[Marc Myer]

I'm a new user; been lurking for several weeks and reading old posts. I'm currently still practicing skills with my Epilog 12x18 mini, 35w.

Plastics are still a bit of a question: I'm making mostly vector-cut acrylic items, and I like the polished edge, as they are coated afterwards. Most of my items are only 1/8" thick.
But acrylic is notoriously fragile, and I can't find the stronger T2, T3, DR, etc. around here in Hawaii. Our local plastics suppliers just give me a blank stare when I ask for material suggestions! I'd like to have a pretty good idea of what to use before ordering something from the Mainland. The other option is to just use acrylic and use some really good coatings!

How well does Delrin handle edges? I've read that Polycarbonate leaves charred/irregular edges, so that's out.
The second part is, is it possible to 'overheat' the leading edge of the acrylic enough to round it off a bit? It would make the finished product more pretty, but there's got to be a techinque and a downside.
marc

[Joe Pelonio]

Your problem is the shipping cost and time if no one sells it there. The best I've found in strength is Acrylite Plus by Cyro Industries. I get it locally from:

http://www.tapplastics.com/shop/product.php?pid=348&

Maybe your local people can special order it for you?

[Martin Reynolds]

Black Delrin takes a nice edge, I believe that white chars. But Delrin doesn't always have teh best surface finish.

The stronger acrylics are actually weaker, but less brittle.

PETG is a reasonable material if you want something a bit more like polycarbonate. It cuts nicely, but air assist needs to be lower or the cut solidifies closed. PETG cuts by a mix of evaporation and melting.

[Bill Cunningham]

Delrin (I've only used white) cuts and engraves quite well..
Because delrin has no contrast when engraved, and it's pretty tough stuff, it's more useful for embossing dies (male and female) for use on presses, and desktop embossers ..

[Allan Wright]

I would like to make small items for plastic modeling. Modelers use styrene. I'm unsure if styrene contains PVC. Also could acetate sheet (overhead projector sheets) be used? I'm going to need a very thin semi-rigid plastic material for some items.

[Brian Robison]

Styrene contains no PVC.
Acetate is close to Delrin. Delrin is an Acetal Copolymer.
Delrin is a trade name.
Styrene is a material and PVC is Polyvinyl Chloride again a material.

Hope this helps.

[Joe Pelonio]

I would like to make small items for plastic modeling. Modelers use styrene. I'm unsure if styrene contains PVC. Also could acetate sheet (overhead projector sheets) be used? I'm going to need a very thin semi-rigid plastic material for some items.

Styrene tends to cut with rolled edges, more when thicker. Acetate I cut all the time and it does very nicely except that it tends to fly out the exhaust if you have no vacuum table. You can use a temporary spray adhesive to adhere it to some card stock to solve that problem.

[Allan Wright]

Styrene tends to cut with rolled edges, more when thicker. Acetate I cut all the time and it does very nicely except that it tends to fly out the exhaust if you have no vacuum table. You can use a temporary spray adhesive to adhere it to some card stock to solve that problem.

Nice to know about the acetate. Thanks for that information.

I'm thinking of styrene in the range of .010" - .030" (0.25 - 0.75 mm) thick. Would the 'rolled edge' be very pronounced in parts this thick?

[Richard Rumancik]

I don't think you will have a lot of success rounding the acrylic with the laser. The heat of the laser already puts a lot of edge stress in the material. If you ran out of focus around the edge a second time you might be able to remove a razor sharp edge, but not likely radius it to any significant amount. (The laser path would have to be offset to the inside for second pass). If you add more stress, it will become more brittle, crack prone, and sensitive to chemicals.

Try to beg samples from someone before ordering sheets. Personally I don't like the way PETG cuts for artistic or decorative parts. It has a raised edge and turns whitish. Fine if the edge is hidden or appearance is not an issue.

The impact resistant acrylics might be the best compromise. (Acrylite Plus etc.) Not as glossy an edge but less fragile. Sometimes a bit sticky on the edge. But try to get a sample first to try.

You might want to test cast acrylic vs. extruded acrylic for the "fragility" comparison.

Delrin has it's uses but I don't consider it a general-use material or substitute for acrylic. It is usually quite a bit more expensive. I think you would have problems bonding it or painting it (you said "coating" so you must be applying a finish). Not much sticks to Delrin in my experience. It is considered a "low surface energy plastic" meaning adhesives, tapes, paints, etc won't adhere well.

[Marc Myer]

Thanks for the great advice! I'm currently using the acrylic, which does everything except withstand dropping on the floor!
I'll be using a cool catalytic coating which requires a very smooth surface to look good. It's a three-part chroming process, and I'm looking forward to seeing the results. Now, I just have to find some time.

[Joe Pelonio]

Nice to know about the acetate. Thanks for that information.

I'm thinking of styrene in the range of .010" - .030" (0.25 - 0.75 mm) thick. Would the 'rolled edge' be very pronounced in parts this thick?

I did a job with .0625 that cut leaving a visible bump around the edges,
but have done .015 OK.

[Allan Wright]

Thanks for the information. It's very encouraging! I won't be getting anywhere close to .06. I'll look out for the bump on the .03" and larger sizes. If I'm clever, it might actually be an asset for some items.

[Martin Reynolds]

I'm getting clear polished edges on my PETG. Not 100% - I sometimes get a line where the plastic melts back together, and I am still fighting flashback - but the finish is very good. No whitening, and minimal edge raising. These parts have exposed edges that have to look good.