plastic molding?

How about using wax..it would IMHO be a bit more suitable. Plastics do not flow well even when melted. Usually plastics use a high pressure injection system to fill a mold, where metal can be sand cast, pressure cast, centrifugal cast etc etc......so unless you have a means of injecting or forcing the melted plsatic into the mold it may be a big headache to try plastic. Just my 2 cents worth..

For all I know you may already have a plastics >>Does anyone know of a plastic that I can buy at my local hardware store that

this is usually called lost wax. look for something called victory brown casting wax. you can also use silicone and/or various types of rubber, which you'll need if your mold has any undercuts in it, or you don't want to destroy the mold to get the object out of.

You could use hot melt glue. Or polyester resin or even acrylic resin dust from sawing sheets of plexiglas. disolve it in methylene chloride. Easiest is the polyester resin. I did itwhen I was twelve years old

I want to cast some basic copies of parts and then make some additions and changes to the plastic mold. I will then re-cast a negative mold to create the metal part. Right now I'm thinking of aluminum parts but right now this is more hobby than anything. How would I tell if a product is made of styrene or polyethelene and what do they melt like? Making an injection system will be simple if thats whats needed.

Yep, injection molds use very high pressure. I think wax would work much better.

A good hobby store will have pourable casting resins. You mix two liquids and pour the mixture into the mold, where it hardens into a plastic.

The urethanes work better but they cost more. Alumilite is one brand.

Polyurethane of the two-part type are commonly used for casting limited quantities of plastic parts. Rigid and flexible are available for making both molds and casts. Some have fillers, some are fast to cure, some are slow to cure, etc. Here is a link to one of a multitude of suppliers:

As to injection molding, thermoplastic resins like polystyrene, need to be heated uniformly, and not overheated or held to long at their processing temperature, which might resemble cold honey, not very pourable. Most recylable plastic products have a recycle symbol somewhere with a number or abriviation like PS for polystyrene. Good luck with your project.

you might look at the hot-melt glues. Some have "fibers" in them and others don't. Those without would probably be prefered. A good release agent would be required.

Hul

HotRod wrote:

I'm just wondering, but not offended. I noticed there was this little bit of HTML coding in your post:

Till the Next Time

And I wondered how it made it to my news client (Netscape 7.2) so that it did its thing.

I thought that newsgroup processing somehow stripped off any HTML code.

My inquiring mind wants to know...

Thanks,

Jeff

Check out this on my homepage.

Some news servers toss into the bit bucket anything with *any* kind of attachments. (And yes, HTML *is* an attachment.)

Others (most) do not.

So -- what you see is a function of which news servers it has had to pass through.

Those that toss are likely to toss the whole article, instead of trying to clean it up.

This makes it better for anyone to make sure that their news articles have *no* HTML in them, so they reach the maximum number of possible readers.

And -- you are safer (from virus infections) using a newsreader which does not even *understand* HTML, so it can't process it. HTLM processing makes it possible to hide nasties.

Enjoy, DoN.

This is a TEXT by definition news group - as many users are in various I/O connections.

Some actually pay - or once paid by KB downloaded. So text was mandated.

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder

Jeff Wisnia wrote:

actually Eastwood Company sells a kit that you can make your own plastic parts from a 2 part plastic ,anything from car emblems to shift knobs and anything you can come up with ,and the plastic is very durable.

Sorry I misread what the poster had said but wax is a good way of trying out pouring a mould and allot more affordable ,even the high end machine shops are using wax to use as a way to machine a part without the expense of using a piece of metal and if it's wrong and don't work you can remelt it and try again,with wax once you find out something is going to come out right ,you just remelt it and use it again next time you need to do a test part. Just an added note ancient romans used to use wax to make bronze items with very intricate designs ,what they did was they made the item from wax with all the design work on it and since it was softer it was allot easier to make the most intricate details on the surface then they would take the wax plug and cover it in clay and then cure it in the air til it dries then they put it in an oven to harden it and melt the wax which I believe they turned it upside down to let all the wax drain out then they took it and poured the molten bronze into the mold and after it was done they just broke the material away and they would have an excellent piece of art whether it be a helmet or a pitcher or just ornate decoration or jewelry ,which they still use this method in mexico or spain in some jewelry shops that make custom pieces but they use plaster of paris instead of clay. Good luck and have fun

Sorry, no. Metal is dense, plastic isn't. So moulds designed for gravity-poured metal just won't fill properly when used for plastic. I don't see this "practice" approach as really telling you that much useful. IMHO you'd be better of making some simple pours with the same techniques and materials you're planning to use in the end.

Bronze into lost foam/sand is a good metal casting technique to begin with.

WOW, thanks for all of the replies. I think for now I'm going to start with plaster of Paris to make some molds and then try some plastic. I have a few plastic parts that I actually want to make so they will never be converted to metal. Thank you for all of the ideas, I'd like to try and find some local plastic at my hardware store that can be melted and injected so that I can just run down the street and get more if needed. But first I need to work on some ventilation.

Sorry Jeff That's a sig line I usually drop when posting to newsgroups. I musta fergot this time

No offense taken Dan, I was just curious.

The responses seem to once again bear out that there's no 100 percent certainty about much of anything on the internet.

Jeff

Famous last words, as we used to say. "Simple" is all relative to ones abilities & experience. For me, making an injection molding system is probably possible, but certainly not simple. YMMV.

Lindsay (Lindsy, Linds... ??) Publishing has a DIY molding system book by Dave Gingery, if you do decide to go that route.

Bob