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Scott Challoner
02-05-2008, 10:10 AM
My neighbor works in a foundry and they have very expensive cameras mounted in a housing with a clear plastic lens protecting them. The current lenses are a dome shape, but it sounds like they could use them if they are flat. They change these frequently due to the harsh environment so it would be a nice running order. He brought an old one home so I could do some testing on it. Here's what I've found:

It cuts very easily so I'm relatively sure it's not polycarbonate (It would probably yellow too much in the heat anyway)

The lasered edges remained pretty sticky and there was almost no oder which makes me think it is not acrylic.

I tried to heat it up and bend it, but when I did it snapped in two and the broken edges are extremely smooth, but not sticky.

They shut the cameras down if they reach 200F but they want something that will handle 250F. They replace the lenses each week, but I don't think acrylic would be the best choice. I'm thinking this is some type of polyester but I'm not sure. Does anybody have any idea what this material is?

Joe Pelonio
02-05-2008, 10:23 AM
As long as it's unknown I wouldn't try it. PVC for example, cuts beautifully but produces toxic and corrosive gas, There are clear PVC products available. I'd have them go to their supplier for the MSDS on it.

Scott Challoner
02-05-2008, 10:32 AM
Thanks Joe

I guess I wasn't thinking PVC since it is clear. I'll try to get an MSDS for it.

Brian Robison
02-05-2008, 10:39 AM
Scott,
I could probably tell ya if i had a piece of it.
I'm a plastics hot runner engineer.
I've got a nice chart for identifying plastics
by burning a piece.
The chart is too big to scan, I'll try to find it
on the internet and post a link or maybe I'll
do one in Corel.

Brian Robison
02-05-2008, 10:55 AM
Here's a link to one.
http://www.texloc.com/closet/cl_plasticsid.html

Richard Rumancik
02-05-2008, 10:58 AM
I would suggest you go to the website of the camera manufacturer and see if you can discover anything. Then try to talk to someone if you can't determine the material. They may be less than willing if they realize that they will sell fewer replacements of the dome lens if they help you.

You might be able to take a sample to a plastic supplier and get them to help. The charts are helpful but not necessarily easy for a casual user.

Be cautious, however. Is the camera exposed to infra red? Maybe it is a filter, not just protection. Is it used for measuring anything (such as material temperature?) If so, a different material/shape might throw out the calibration. If you substitute materials and then their expensive camera stops working . . .

Not trying to discourage you but just suggest that you investigate first.

Benedict Roussos
02-05-2008, 2:13 PM
very usufull chart Brian!!
Do you know any other links about physical and technical information and MSDS for the plastic we usually a laser engraver cuts (ABS-acrylic cast and XT)??

Brian Robison
02-05-2008, 2:25 PM
Hi Benedict,
That chart is quite generic. Each plastic will have it's own qualities. Most things I do are injection grades of plastics.
The MSDS would have to come from the manufacturer.

Sorry I couldn't be more helpful.

Scott Challoner
02-05-2008, 2:40 PM
Thanks for the link Brian. I can say with some confidence that the material is Polyurethane. Although the flame looked more orange than yellow to me, it did not drip, kept burning, and had a faint odor. I can't tell if it was apple though. As Richard pointed out, I haven't had the proper olfactory training. It did sputter a little bit. As a matter of fact, before it really got going, a few times it popped hard enough to extinguish the flame and lauch a small piece (good thing for goggles).

I will still try to get a material nailed down from the manufactuer. You're right Richard. I don't want to suggest a material and be on the hook for a $60k camera.

If it is Polyurethane, does anybody know if it can be purchased as a 1/8" sheet stock?

Thanks all

Travis Gauger
02-05-2008, 2:59 PM
In my professional life I work for gray and dustile iron foundries. We use "vision" systems through out our foundries that have cameras in close proximity to molten iron. All of our equipment that contains plastic protective lenses similar to what you explain uses Polycarbonate. Our lenses are not as you describe yours, but the setting matches. Hope this helps.

Joe Pelonio
02-05-2008, 3:02 PM
McMaster-Carr has about the best variety of odd plastics I've seen, but you might have to contact them it could be hard to find on the website.

http://www.mcmaster.com/

Brian Robison
02-05-2008, 4:16 PM
Scott,
PC would be the plastic of choice for that application.
Not too fun to cut but it will do it. Mask it first.

Travis Gauger
02-05-2008, 4:19 PM
Onlinemetals.com has a small selection of plastics too, Their prices are way better than McMaster Carr.

Scott Challoner
02-05-2008, 5:45 PM
This stuff definitely isn't PC. It cuts like butter but PC may be an alternative. At least the temperature range is there. I tried cutting it once and didn't like the result, but I'll pick up a piece and give it a try.

Thanks again

Pete Simmons
02-05-2008, 6:02 PM
Brian:

Excuse me if I missed it but on the chart - Which would be Plexiglass and which would be Lexan?

Martin Reynolds
02-06-2008, 1:26 AM
I've seen that kind of cut with the special high impact strength acrylics. They cut clean, but keep a sticky edge. However, they don't stand the heat too well.

You might try boiling a piece of your sample to see if it softens, just in case it is acrylic. If it is, you could try the abrasion coated acrylic - maybe it will stand up to surface damage a little better.

Polycarbonate cuts fine for me, but with ugly edges. However, the camera does not look through that part. PC can handle the temperature you quote. Polyester will collapse at those temperatures.

Jim Huston
02-06-2008, 7:05 AM
Keep in mind that while PC is very tough it also scratches VERY easily!! At one time was part owner of a company that pioneered use of PC in snowmobile windshields. At that time was a huge market. Biggest problem was scratches for fingers!!
JimH

Brian Robison
02-06-2008, 9:26 AM
Pete,
Lexan is a trade mark name for PC (polycarbonate)
and Plexiglass is acrylic.

Doug Griffith
02-06-2008, 10:56 AM
I'm in the vacuum forming industry and we have plastic sheet specially formulated if needed (and if the tonnage is there). Sometimes different materials are extruded together. One sheet we use is ABS with a very thin acrylic cap on each side. Others are blended to give better forming characteristics. In a nutshell, types of plastics are limited but formulations and other tricks are not. Only the manufacturer really knows what it is.

Below is some older information that may be of some use to anyone working with plastics:
http://www.crclarke.co.uk/Support/pdf/thermo.pdf

Cheers

Brian Robison
02-06-2008, 11:00 AM
Doug,
Are you in the UK?

Doug Griffith
02-06-2008, 2:44 PM
Brian,
I'm in Southern California.