Any comments on why you chose polypropylene? Personally I think it's a great choice, and has excellent impact resistance. But I was wondering what other criteria you weighed? -- e.g. high melting point.
Any chance of some pics showing lower contrast of the parts? Kinda hard to make out the detail int eh pitch-black plastic.
An M.E. friend of mine recommended polypropylene for several reasons:
It's cheaper than polycarbonate.
It won't crack when you try to tap it.
It is plenty strong (and impact resistant as you said) if given enough support.
It won't craze if glued or painted like polycarbonate will.
I didn't want clear.
Can be welded (I just melted the tab/slots together with my soldering iron).
The pictures were real quickies during lunch at work today. As soon as I find my digital camera I will post better pictures. Anyone else have a Robo-Magellan bot to show?
I would like to post an ongoing build journal detailing the design process. Can anyone reccommend blog software that can post to my website via FTP?
Your ME friend made a good suggestion, IMO. If you're near a Harbor Freight, you might look into their plastic welder, which needs a source of compressed air. About $20 when they have it on sale, which is regularly. I use mine with a Variac to provide some degree of heat setting. Pretty nice for welding various plastics, including PVC, which has a very low melting point (165 degrees, versus about 500 degrees for polypropylene).
It's nice to see Bruce offering to cut plastics other than the usual acrylic and polycarbonate. I see he's now offering to cut PVC, so I would assume he has some form of hood or vent for the gas.
Hi Gordon, I believe you once said that PVC produces **cyanide** gas when burned - as in laser cutting. Would using a plastic welder on PVC also be a problem ??
*Burning* PVC releases hydrogen chloride (plus dioxins, CO, and some other toxic gasses like phosgene). I'm not sure if it release hydrogen cyanide to any great degree, though some other plastics do -- polyurethane for one. Phosgene is a nerve agent that causes choking. You don't want to breath it. HCI is very corrosive, and will tear up your mucous membranes in no time flat.
These gasses are released when the material burns, but not melted. The trick is to soften the plastic so it can be thermoformed, but not burn it. With a welder and a heat setting you can dial in just the right temperature. It takes practice...do it out in the open air first!
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