Including a piece of thin polycarbonate sheeting was an experiment for VRC this year. How is your team using it, if it all?
Those of us at RECF and VEX are looking forward to seeing how this new element is used throughout the season.
No answer yet, but I have a question: Driving home tonight I was wondering how the polycarb compares to Vex steel and aluminum parts. Once a part that does the same job is fashioned out of all three, is the polycarb one generally lighter, heavier or about the same as a steel part? or an aluminum part?
Yes - I know this a not a black and white subject. I not looking for a sworn deposition or a PHD thesis; just some general observations/impressions that relate to the trade-off between getting to make odd shapes with polycarb, vs having to pay or not pay a weight penalty in exchange.
Blake
Here are a few observations/facts/deductions relating polycarb to aluminum:
The density of polycarb is a little under half that of aluminum.
A 1/16 inch sheet of polycarb is little over twice the thickness of the aluminum.
The polycarb sheet doesn’t come with hole like the aluminum and steel parts.
So a polycarb piece will probably be slightly heavier than an aluminum piece
Per unit area, polycarb is a lot cheaper than VEX Aluminum.
Polycarb is a lot harder to machine than aluminum (i.e. harder to bend).
You can do a lot more with polycarb (i.e. drill holes wherever you want).
My team has started experimenting with polycarb for our robots, but we haven’t come up with a good use yet, besides decoration.
another thing: polycarb is also extremely flexible (as in not sturdy)
one team mate suggested making a light weight drive out of polycarb itself
but once we got it, it was just too flimsy to do anything
we are using it somewhere ****** because we can drill the holes anywhere we want as mentioned above
overall i think its only good for “bonus stuff” but not for main structural pieces
thing some teams are also making a “claw-like-mechanism” with theirs
(lighter and looks nicer than bent 1x25’s)
Last season KTOR used polycarb(we were allowed in the college competition) as a light weight alternative to adding additional lengths of tank tread to our already heavy robots. The “Super Tread” was able to expand the size of our conveyor without adding what would have needed to be at least 3 more tread sections. The available poly is incredibly versatile, it would be great for a team to post an inspiring polycarb design or two for this season!
I don’t think I’ve seen any polycarb used at our events so far this year, something that I’m honestly a little disappointed in. That being said, at the end of the DC Knights qualifier, an announcement was made asking teams to start to utilize the extra material, to which one student responded “I’ve got this!”. I can’t wait to see what he shows up with at the next event.
Polycarb seems like it would be good for bumpers/corners/edges because it is very smooth, so it will slide along the wall very well. You can paint the inside, so paint doesn’t get scratched, so it will look glossy and beautiful.
Polycarb bends nicely with application of some heat.
Thanks for comparison of material properties between polycarb and aluminum.
For teams with excellent hand craftsmanship skills, (or CNC capability), custom sizes of chain sprockets seem like a possible application for Polycarb.
Polycarb is an excellent heat-molding material for vacu-forming. It would be neat to see some team make use of this to make 3d curved shapes.
It would be interesting to see an aftermarket supply of Vex compatible polycarb parts, or custom contract suppliers, as there are not yet any rules (?) that the teams have to make the parts themselves. Same for College rules plastic block.
Our teams have used it in our designs on 2 of the 3 robots. They had to experiment with heating and bending until they got it to perform as they wanted. I think our teams like the idea of having something that is different than the metal, that they can craft into lightweight, fairly strong parts. One used the full 12 x 24 piece and the second robot used about 2/3 of the 12 x 24 piece.
The main thing I’d use it for is for a piece that has to slide the floor that needs to be flexible; say, the bottom of a roller claw. Metal just gets caught all the time on it.
Two comments:
-
Polycarb bends GREAT in a box-break, with no heat required.
Breaks are CHEAP: http://www.harborfreight.com/18-inch-bending-brake-39103.html -
Be VERY careful when painting polycarb – the wrong type of paint can chemically modify the polycab to the point where it becomes VERY brittle.
Can you tell me how strong the bend is? I’ve done bends with lightweight aluminum and the bend is very weak. I would have thought that the Polycarbonate would have millions of fractures across the bend and not be very strong.
How big is the radius of the workable bend?
Thanks!
We got polycarbonate in last night and started our designs with it.
http://www.boedeker.com/ – 12." X 24." .062 polycarbonate sheets for $ 4.40 each Plus standard Shipping (about .50 cents a sheet. There is a $50 min order.
.062 polycarbonate sheets only comes in clear.
For teams in my area, I will coordinate a purchase if we get 12 or more sheets ordered. So plan on them being $5 each. (McMaster is $7+shipping)
I’d like to place an order on 12 November, that way they can get picked up at the November 20th event at Downingtown.
Anyone planning a bulk purchase anywhere in the Pacific northwest? Rick TYler? :rolleyes:
So I used my oven at home to create a certain undisclosed shape with a piece of polycarb. After the third time that I heated it up in the oven, a bunch of small cracks appeared in it (the first two times that I heated it, I tried free forming it with my hands, which didn’t work out at all; the third time that I formed it I forced it into a mold and then heated it so that it would take the shape of the mold). I am wondering if anyone knows whether or not the cracks will significantly weaken the piece. I think that I can prevent the cracks form showing up if I don’t heat up the piece as many times or force it into a mold.
I preheated my oven to 330 degrees Fahrenheit before I put the piece of polycarb in. It took 10 to 15 minutes to get soft enough to mold. Once I took it out of the oven, it hardened again in under a minute.
My cardboard mold worked fine in the oven at 330 degrees (i.e. it didn’t burst into flames or start falling apart).