Making a mould

I'd appreciate some pointers on how to make a mould.
I had some orthotic shoe inserts made, they're of pretty hard plastic.
I'd like to make a few more pair, as they're very expensive to buy, custom made.
Could I make a mould myself at home, then pour in plastic, and make them myself?
I'd appreciate any tips on how to do this, and where to buy the plastic. I guess Plaster of Parris isn't too hard to find.
Thanks
T
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I'm not aware of any plastic that you could mold at home that would stand up to the abuse shoe inserts need to survive.
If you want mulitple inserts, you are better off spending your time negotiating with your orthotist and shopping around.
Greg (modeler and mechanical engineer)

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Greg wrote:

Actually there are a number of resins that could be used at home to replicate them that have the correct propeties. The drawback is you shouldn't try to DIY any kind of medical device, just generally a bad idea.
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What resin would you recommend, and where could I buy such a thing..
Thanks

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Zzaaarathustra wrote:

You can experiment with a 2 piece plaster of paris mold and use pure silicon caulk as the insert. Once the mold is made, you can experiment with various rubber/plastic compounds.

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Caulk is soft and flexible, it'd make a poor substitute for the hard plastic of his custom-made orthotic shoe insert. It's also too thick to pour and cures on exposure to air, so it won't work in a 2-sided mold or a deep 1-sided mold.
I have to agree with Greg's & Ron's advice: Do NOT try to duplicate an orthotic shoe insert yourself. Leave it to the orthotic experts, they know what the requirements & tolerances are for that insert, and we don't. You could waste a lot of money on experiments and never get it exactly right.
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Zzaaarathustra wrote:

No, but plaster is not an easy mold material to use. If you think those inserts are expensive, wait till you see the prices of RTV mold making materials and the price of urethane casting resin.
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Zzaaarathustra wrote:

There used to be a mould kit available for making tin gaming pieces. A mate of mine used to have the stuff for making Dungeons & Dragons characters. It resulted in a cast being of relatively hard rubber that could take molten metal and would move enough to allow the tin or alloy piece to fall out.
I've just done a search and found this;
<http://www.bare-metal.com/hyperlast/mold_1.html
Richard.
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Go for it, you paid for the deisng and fit with the original insert. Refer to details available at http://homepages.ihug.co.nz/~atong / under: 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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Guys, guys - you're missing the point!
There is more to an orthopedic device than shape. This guy doesn't want to make a MODEL of an orthotic insert. It's got to FUNCTION as well. We can assume that he has already tried over-the-counter shoe inserts, so he must have some serious problems.
To work properly orthotics need to have the same stiffness, elasticity and durability. His feet are screwed up NOW. He doesn't need to experiment walking around on a bunch of crude copies that are like boards, or mush, or rocks, and which fall apart in a few days or weeks.
If orthodics could be made cheaper materials, they would be. That's how the marketplace works. If "Zzaaarathustra" thinks he's being ripped off, he should shop around and negotiate - not start a second career and subject his feet to further torture. In the long run it would be a frustrating, painful waste of time.
I've got enough stuff on my workbench to mold copies of my teeth. But I don't think for one minute that I should make my own crowns.
Greg

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Greg wrote:

Thash eashy for you tchoo shay! Sorry, one fell out.
Richard.
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If anyone knows what resin to use, to make a simple plastic insert, that is made of inflexible, hard plastic, then please let me know.
Thanks
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Zzaaarathustra wrote:

Strangely enough I've just sent an email to a mate of mine who used to use all sorts of stuff for film work. I should have red your post first.
I'll ask him as he lent me a book on the subject!
Surely you mean very slightly flexible otherwise it might snap ?
Richard.
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I'd appreciate the info, they seem hard to me, but perhaps a little flexible.
Cheers

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