I’ve noticed that a LOT of teams use clear, thin plastic sheeting on their robots. Thin, but still very rigid, and clear (but still a bit flexible). Many teams used it this year to go around the outside of their spirals.
I want to call it acetal, or acetate - but when I went to look on mcmaster the sheer amount and variety of plastic sheeting made be scratch my head a bit. I know it isn’t vinyl, which is not nearly as rigid and is quite heavy. So what’s the right name for the thin semi-rigid plastic most teams use on their bots?
You can see it here on Foley Freeze on the outside of their spiral:
It’s polycarbonate. Acrylic sheet I would not reccomend as it could not withstand any force on a competition robot. Polycarbonate is rather easy to work with, can roll up, is relatively flexible, and can be bent with heat.
With proper use, you could even use very thick polycarbonate sheet to build your whole robot if you wanted to.
Definitely polycarb. Trust me, you do NOT want to use acrylic sheets. We, for some odd reason, had some lying around the shop, mistook it for polycarb, and started trying to get it on the robot. We realized our mistake when it began cracking and shattering when we started putting the rivets in.
We used .020 and .030 thick polycarbonate on our bots this year.
You actually don’t need a heat gun to bend it, it bends just fine in a normal sheet metal break. It works out much cleaner and nicer. Also cuts nicely in a shear.
McMaster is a little funny about what they define as film vs. sheet. 0.040" and less is film and 1/16" and greater is sheet. Go figure. We have usually used McMaster 8574K29 0.040" film in the past.
I’ve bought polycarbonate as thin as 0.010 to cover the outside of the robot with. That thin it comes in a roll. 48" wide by however long you want. It seemed like they called anything that was “rollable” film and stuff that shipped and stored flat “sheet”.
Try to find a local plastics supplier that supplies to sign and screen printing shops if you are looking for large pieces of thinner film. If they don’t have it, they can probably get it for you with their regular deliveries. Shipping will kill you if you have to buy it mail order.
I used to use Calsak Plastics when I lived in ATL, but they don’t have a warehouse in your part of the country. Their website is http://www.calsakplastics.com , at least you can look at a pretty wide range of what may be available. Wish they had a warehouse near here in MN. I’m still looking for a polycarbonate supplier here that will charge me less than retail
Polycarbonate sheet can also be bent cold in the box and pan brake and other sheet metal working tools.
Thin polycarb also cuts quite nicely with a sharp knife. Thicker pieces respond well to woodworking equipment… table saws, jointers, bandsaws or jig saws come to mind.
I’m not sure if I’m referring to anything by the right names and everything, but I think you can use a jointer with an obtuse-angled fence to make different “rounded off” (kind of) edges on thick pieces. I’m sure there’s a more technical name for this process I’m forgetting, but my team and I did this to finish some structural pieces.
well you could create an angled straight edge with a joiner but i don’t know why you wouldn’t do that on a table saw as it seems like it would be a much safer method. If I needed a complex edge treatment i would use a router or router table.
Mostly you use it to make the edge look pretty after you’ve cut it on the table saw. It doesn’t make much difference on thin pieces, but on the thicker pieces it really tidies things up. It isn’t quite as important to do this with Lexan as it is with Acrylic, but it still can improve the appearance of the finished product.
If you are looking for a clear plastic film, one of the best materials to use is PET Polyester. This is the stuff that they make pop bottles out of. It has very good tensile strength and puncture resistence, it is crystal clear, and best of all, it is dirt cheap (Several times cheaper than Polycabonate), plus you can buy it in big rolls instead of sheets so you have less waste. Available at Mcmaster-carr or any plastic supplier. We have used it as thin as 0.010" on several robots.
