How do you make things with plastic at home?

May 11, 2004 6:46 PM

Is there an easy-ish way to make things out of plastic? I had an idea for a fly-swatter-like contraption for catching spiders, and I have no idea how to go about molding something out of plastic. I know how to build out of wood, I can cut, bend, and weld metal, and I even have some idea how glass products can be crafted the old-fashioned way. But plastic? By "easy-ish" I mean: you can do it in your garage with the right tools and materials.
posted by scarabic to Home & Garden (8 answers total)

I researched this myself for a while, and couldn't find a satisfactory solution. Here are two things I found:

1) plastic injection molding: this involves making casts for the plastic out of metal and pouring melted plastic into the casts. I think the cheapest that I could find a machine needed for this was around $500 used (not including making the casts). search google and ebay for "plastic injection molds"

2) You can buy solid sheets of plexiglass from hardware stores and use milling/drilling machines (and/or dremel tools) to carve the plastic into the desired shape. However, this is mostly useful if your desired object is already somewhat shaped like the material you're using.
posted by helios at 6:58 PM on May 11, 2004

Actually, it's relatively easy, picture it like casting metal - at least in the main method I know of.

- Create the shape of the original in clay, wax, wood or whatever.
- Coat the whole model in a layer of some form of release (something so the cast does not stick, i.e vaseline dissolved in mineral spirits, but it depends on the casting material)
- Make a cast (plaster, wax, "rubber", alginate, or a few other options)
- Coat the inside of the newly made mold with the appropriate release. (often liquid soap, but it depends on your choice of materials)
- From that cast use a two part epoxy to make your prototype.

I've used materials from here, and they have a nice how-to as well. They are also very friendly to hobbyists and sell in less than commercial factory quantities.

(I've done this quite a few times, so tell me if anything is unclear)
posted by milovoo at 7:17 PM on May 11, 2004

The epoxy resin is actually really fun to work with -- I'm no Martha Stewart, and I still made some cool stuff out of it.
posted by ph00dz at 7:26 PM on May 11, 2004

I hope you haven't re-invented this.
posted by five fresh fish at 7:41 PM on May 11, 2004

Response by poster: Yes, FFF, it was basically just like that. I'm not planning to build this particular project, though there will always be others. It just brought into relief the fact that I have zero command over plastic. That seems wrong somehow, given how many plastic things we use daily. Thanks for the links, y'all!
posted by scarabic at 8:15 PM on May 11, 2004

Sorry, man. I hate it when that sort of thing happens: a brilliant idea, a flash of insight, a revelation... only to find out someone did it already a week before.
posted by five fresh fish at 9:29 PM on May 11, 2004

Check out Lindsay Technical Books. They've got a couple on homebuilt plastics rigs -- one book on vacuum molding, and another one injection molding. I think both are for thermoplastics (not thermosetting materials) but I could be wrong. The book on injection molding is definitely thermoplastic, not sure about the other.

...in any case, they'll help you build the right tools, and thereby save money. I've got their series on building metalworking tools from scrap, and it's fairly nifty, so I'm guessing that their plastics ones are equally useful.
posted by aramaic at 10:04 PM on May 11, 2004

Vacuum moulding is really easy - make the thing out of wood or clay and then get yourself to a local school or crafts workshop which should have a vaccuum moulder.
posted by skylar at 11:53 PM on May 11, 2004