Joined: 06 Apr 2005
Posts: 26
Location: Perth, Western Australia
Polycarbonate mass
Hiya, just returned from my friendly local plastics dealer, who gave me some offcuts of various thicknesses of Polycarb so I can test it to destruction. I just thought I'd give you the masses of various gauges.
Obviously, a Feather made completely of 12.5mm is right out, but I'm hoping that 6mm with 9.5mm or 12.5mm structural bracing should work out pretty well.
I'll be attacking some polycarb with axes, hammers and angle grinders later on , braced to replicate the sort of glancing blows that are most likely in combat. _________________ Struggling from the ashes of a fallen civilisation
..Phoenix Rising
Wed Dec 02, 2009 3:08 pm
Glen Experienced Roboteer
Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect
its 1.2g/cm^3 better to remember the cubic densities most cad programs give you a volume then you can just multiply it by that if you want to cad anything.
a robot made from 12.5mm isnt unrealistic at all. theres plenty of robots made out of 6mm steel and thats almost 3 times the weight of the polycarb at 12.5mm thick.
polycarb is okay against the basic weapons if you keep no sharp edges on it and keep the amount of holes in it to the bare minimum also. but if you want to play with the proper spinners and the like over on the east coast no realistic thickness of polycarb would take a direct hit and survive.
I found an article on water bottles that said HDPE is lighter (by water carrying capacity at least) so is it stronger by weight, or simply softer, making it more likely to deform than break on impact?
Wed May 23, 2012 12:17 am
Glen Experienced Roboteer
Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect
HDPE is 0.91g/cm^3 in while polycarb is 1.2 or something like that in density.
The other thing is almost everything causes polycarbonate to crack. Its a great plastic. But its just not that good for robots IMHO. HDPE would be softer but that's probably what you want.
HDPE is great, and UHMW-PE is even better in that it will never crack, only tear. They are soft though and not great for dimensionally accurate parts, but in combat robots things rarely stay dimensionally accurate for long... As mentioned, polycarbonate is pretty amazing but UV degrades rapidly and is very sensitive to many chemicals, making it brittle... but it's clear, hence making good arena panels.
Wed May 23, 2012 12:44 am
Cognisant
Joined: 20 May 2012
Posts: 24
Location: Brisbane
Do I ever love this place, you guys are the best
Wed May 23, 2012 1:03 am
Cognisant
Joined: 20 May 2012
Posts: 24
Location: Brisbane
Would I be right to assume ABS extruded by a 3D printer isn't going to have the same properties as a milled block obtained from a specialist manufacturer?
I saw ABS sheeting at ServoCity, remembered it can be 3D printed and y'know thought to myself wouldn't it be nice if it were that easy.
Tue Jun 12, 2012 12:14 pm
Glen Experienced Roboteer
Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect
if its FDM printed your limited by the strength of the joint between the layers which IIRC is 30% of the strength of an extruded piece. Not particularly strong. Could probably get away with doing that and covering the robot in real armour though. Would be very easy indeed
A couple of robots here are going around sporting frames printed from shapeways which uses a much better type of printing method however. Best ask Daniel about those _________________ www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz
Tue Jun 12, 2012 12:33 pm
Forum Jump:
Page 1 of 1
Forum Rules:
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum