How to cast plastic?

Hi, I want to make a plastic toy. Specifically the blades of a helicopter. What kind of plastic do I need to use? I think I can get
epoxy resin and the curing agent.
Could you guys give me some insight into how you make your plastic models? i.e. do you carve the molds and cast it or something?
I'm rather new and confused about the whole process I'm afraid so I need a helping hand insofar as description and advice goes.
Thanks in advance to those who reply.
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snipped-for-privacy@yahoo.com wrote:

You carve or otherwise fabricate the master copy of your part, then cast the mold around it (in as many pieces as is necessary to be able to separate the part from the mold).
--
St. John
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snipped-for-privacy@yahoo.com wrote:

i buy mine ready made. scratching a whole kit is a bit beyond my skills.
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Scratchbuilding an entire kit is a very complex task, generally beyond the abilities of a beginner. Nearly everyone on this newsgroup buys commercial kits, which are molded from styrene in tooled steel or copper molds. These molds cost hundreds of thousands of dollars to design and machine. If you want to create a cottage industry kit at home, you would have to make the original parts from any material you can carve or sculpt. Depending on the shape of the part, it can be carved and sanded from wood, styrene plastic sheet, or acrylic, or it might be sculpted from epoxy putty. This part then serves as a master to make an RTV rubber mold. The master is removed from the cured rubber, then a casting medium would be poured in, usually a two-part polyurethane resin (epoxy is thicker and doesn't hold detail as well--it also attacks the rubber, reducing the mold's life). Polyurethane resin kits must be assembled with super glue, as solvent based cements do not affect them, but they can be painted using normal hobby paints. Note that these materials are fragile and are only suitable for display models. If you actually want to make a child's toy that won't be destroyed instantly, you would need to use a softer, tougher plastic like vinyl or polyethylene. These must be injection-molded in steel molds and are beyond abilities of the home manufacturer.
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he never said he wanted a flying model it could be he just wanted a static one
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I do a lot of scratch building, but don't do much casting. The only time I cast parts for a scratch project is when I need to make at LEAST three or four identical pieces. Otherwise it is easier to just make the pieces by carving or fabricating. Last year I did a ship model that required 13 hatches, and a similar number of deck fittings. I did cast the fittings and hatches from urethane resin.
But for hulls, fuselages, car bodies, etc., where there is just one per project, I generally carve from scratch.
An exception was a 1/8 sprint car I did. There were lots of openings where one could see the thickness of the panels, and wood would be too thick. For that car, I did a body pattern, made female plaster mold casts of major areas, and laid up fiberglass into the plaster molds. I used hobby shop fiberglass cloth, which is VERY thin, and can make really thin panels.
Gerald Owens wrote:

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refer to Alan's Hobby, Model & RC Web Links http://homepages.ihug.co.nz/~atong / sub section "Fibreglass, Carbon, Resin Moulding & Casting Cowls, Spats,Canopies "
Covering Models With Fibreglass Cloth by Jim Ryan Fibreglass or make your own FG hull Fibreglass Techniques & Information FibreGlast.Com How To Articles = Spars, Molds, Parts, Skins & U/C How To = Ironsidz Model Car Tech - Resin Casting etc. Molded fuselage - how to pictures The Cheap Little Sucker - make a vacuum pump Vacuum Bagging Wings Water based Polyurethane skin glassing
and lower down Mold, Cast & Vacuum Form items yourself FAQ inc pictorials (see also Fibreglass etc section)
"Fibreglass Techniques & Information"
Model Car Tech Molding & Casting Mold Making Plastex = Plastic Repair or make copies of parts - Kits Plastic Bonding Vacuum Form Vacuum Former - make you own and usuage. Vacuum Former - email Alan for home made & DIY canopy etc. Vacuum form - Pictorial instructions _ click thumbnails for full text. Woodland Scenics - make latex molds, cast plaster etc
regards Alan T. Alan's Hobby, Model & RC Web Links http://homepages.ihug.co.nz/~atong / .................................................................

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