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Andrew Lawrence
07-10-2011, 23:35
I've seen a lot of good looking robots with a type of transparent plastic with writing and pictures such as sponsor information. It's a generally dark plastic. My mentor says he thinks it's plexiglass, but I think it's more of plastic.

Anywho, does anyone know where one could get these? Are they sponsors, or just companies who offer their services?
Joe G.
07-10-2011, 23:44
It's called polycarbonate, also known as Lexan.

Do not use Plexiglas or Acrylic plastic on FRC robots! It is much more brittle than polycarbonate, and can shatter easily. Polycarbonate is quite elastic, which gives it a great deal of strength.
akoscielski3
07-10-2011, 23:45
It's called polycarbonate, also known as Lexan.

Do not use Plexiglas or Acrylic plastic on FRC robots! It is much more brittle than polycarbonate, and can shatter easily. Polycarbonate is quite elastic, which gives it a great deal of strength.

How do they get it black or a darker colour... is i just how they buy it (get donated) or is it painted. The Lexan we get is clear.
Brandon Holley
07-10-2011, 23:45
"Plexiglass" is a brand name referring to a material known as PMMA aka acrylic. There's pretty much no reason this material should be used on a robot as it's extremely brittle and prone to shattering.

The material you are thinking about is polycarbonate sheet. More specifically "smoked" polycarbonate sheet is the dark gray plastic you are referring to. Polycarbonte around here is often referred to by one of it's brand names "lexan".

As for where to buy the material, if you do a search for "smoked lexan" or "smoked polycarbonate" you will find a decent amount of suppliers.

-Brando
Andrew Lawrence
07-10-2011, 23:47
That makes a lot more sense! Thanks!
Tom I
08-10-2011, 00:00
Yeah, I would not recommend plexiglass, or any form of acrylic. It is a lot cheaper than polycarbonate, but for a reason. My team found this out the hard way, as we figured for shielding material we'd go with the cheaper option... It didn't even survive testing, let alone last long enough for Ship Day (now Bag Day?), we switched to lexan and never looked back.
Colin P
08-10-2011, 01:13
Plexiglass (acrylic) will crack and shatter under force. Polycarbonate will flex almost to a complete fold without cracking and can even be worked to an angle using a break. As a general rule, no acrylic ever because it just shatters under continued use.
DonRotolo
08-10-2011, 09:44
Polycarb can also be bent like aluminum: just clamp it and bend it. No need for heat. Drills out more easily too - use WD40 as a lubricant for larger holes.

Oh, and never ever get any Loctite near the stuff, as it will craze (fine cracks) and fail in a very short time.
Dad1279
08-10-2011, 10:28
When in doubt, or you have unmarked material, grab a corner with pliers and try to bend it. Lexan/polycarbonite will bend, plexiglass/acrylic will shatter/break.
Jeffy
08-10-2011, 12:11
Two options to get the smoked look:
1. Use black spray paint. Thin layers of black spray paint will allow light to pass through and give you a "smoked" look

2. Use automotive window tint. This can be had for super cheap at a local auto store (Advance Auto, O'Reilys, Carquest, ect.) Follow the same procedure you would to tint a car window.
Akash Rastogi
08-10-2011, 12:59
The smoked polycarb you are talking about is popular out in Cali, so ask your Cali friends who their specific supplier is. There are certain places most of the teams purchase their thin smoked polycarb from, I am not familiar with the name though.

Ask 1323 or 973
Koko Ed
08-10-2011, 13:23
in 2006 at FLR team 1930 had a plexiglass shielded robot and collided with 229's robot. The plexiglass shattered and littered the field. Do not use plexiglass on the robot. It cannot take a hard impact.
Jeff Pahl
10-10-2011, 10:57
Try TAP Plastics. They have two locations in San Jose.

http://www.tapplastics.com
AustinSchuh
11-10-2011, 23:59
Try TAP Plastics. They have two locations in San Jose.

http://www.tapplastics.com

If you are buying full sheets, Port Plastics in San Jose is going to be a better deal. They only sell 4x8 sheets (or maybe larger), if I remember right.
NickE
12-10-2011, 01:09
If you are buying full sheets, Port Plastics in San Jose is going to be a better deal. They only sell 4x8 sheets (or maybe larger), if I remember right.TAP's prices can be rather high... 254 uses Port Plastics for pretty much all of our polycarb. For thin (1/16") smoked sheets, which Port doesn't carry, we have ordered online in the past.
Phyrxes
12-10-2011, 07:57
We have ordered from http://www.eplastics.com/ in the past but generally make one large order a year to save on shipping anything that can't be rolled up and shipped in a tube.
Gdeaver
12-10-2011, 08:10
Clear PETG is known as the poor man's polycarb. Not as good as poly carb but should be acceptable for some robot apps.
thefro526
12-10-2011, 08:21
Has anyone ever tried applying automotive style window tint to Acrylic sheet and then seeing if it will shatter like an un-tinted sheet?

My gut tells me that the tint should help hold the broken shards of Acrylic together should they crack, I'm just wondering if this is actually true...
Andy Baker
12-10-2011, 08:30
// spam post deleted //

Anyone using acrylic or plexiglas on a FIRST Robotics Competition robot is just asking for trouble, as it shatters. MANY people refer to the clear plastic (polycarbonate) used on these robots as plexiglas, which is incorrect, as stated many times in this thread.

Here is a very simple way to tell the difference between two pieces of clear plastic, of which one is acrylic and the other is polycarbonate: look at the outside edge of the plastic sheet. If the outside edge has a blue tint, then it is polycarbonate. If this same edge is white or frosty-clear, then it is acrylic.

Then, put the acrylic back up on the shelf (or throw it away*) and next take the polycarbonate in your arms and give it a big hug.

Here is a pretty good discussion we had about this same topic a few years ago. (http://www.chiefdelphi.com/forums/showthread.php?t=41571)

Sincerely,
Andy Baker

* I'm actually serious about this. There is no need to have any trace of sheet acrylic in a robot-building shop. If you just put it back up on the shelf, you might as well write on it with a sharpie marker "Don't use this acrylic stuff - it shatters!!!"
Phyrxes
12-10-2011, 09:01
Has anyone ever tried applying automotive style window tint to Acrylic sheet and then seeing if it will shatter like an un-tinted sheet?

My gut tells me that the tint should help hold the broken shards of Acrylic together should they crack, I'm just wondering if this is actually true...

So do it yourself laminate, possibly on both sides, to contain the plastic should it take an impact? Not sure its worth it even for display purposes as it will still likely get dropped by a student carrying it.
Brandon Holley
12-10-2011, 09:59
Has anyone ever tried applying automotive style window tint to Acrylic sheet and then seeing if it will shatter like an un-tinted sheet?

My gut tells me that the tint should help hold the broken shards of Acrylic together should they crack, I'm just wondering if this is actually true...


Just curious as to what the point would be? If you are going to put tint on to a sheet of plastic anyway, why not just use PC?

-Brando
Chris is me
12-10-2011, 10:27
Clear PETG is known as the poor man's polycarb. Not as good as poly carb but should be acceptable for some robot apps.

It's at least easier to laser cut, which can be useful in some applications.
Andy Baker
12-10-2011, 13:23
Here is a very simple way to tell the difference between two pieces of clear plastic, of which one is acrylic and the other is polycarbonate: look at the outside edge of the plastic sheet. If the outside edge has a blue tint, then it is polycarbonate. If this same edge is white or frosty-clear, then it is acrylic.


I should add, being the capitalistic guy that I am, you can now buy 2 ft. x 2 ft. square sheets of polycarbonate plastic from AndyMark in these thicknesses:


1/8" (http://www.andymark.com/product-p/am-0980.htm)
3/32" (http://www.andymark.com/product-p/am-0981.htm)
1/16" (http://www.andymark.com/product-p/am-0982.htm)
1/32" (http://www.andymark.com/product-p/am-0983.htm)


Thank you,
Andy B.
Taylor
12-10-2011, 13:31
I should add, being the capitalistic guy that I am, you can now buy 2 ft. x 2 ft. square sheets of polycarbonate plastic from AndyMark in these thicknesses:


1/8" (http://www.andymark.com/product-p/am-0980.htm)
3/32" (http://www.andymark.com/product-p/am-0981.htm)
1/16" (http://www.andymark.com/product-p/am-0982.htm)
1/32" (http://www.andymark.com/product-p/am-0983.htm)


Thank you,
Andy B.

It would be very cool if these items were made available through FIRST Choice.
Madison
12-10-2011, 13:48
We often prototype with acrylic -- it's much cheaper and easier to laser cut, so we can throw things together quickly. It's very rare -- though not unheard of -- that acrylic ends up on our finished robots, though.