Resin / plastic for shoe inserts

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Resin / plastic for shoe inserts

Author	Message
wobblycogs	wobblycogs posted 12 Years Ago HOT Topic Details
Group: Forum Members Posts: 3, Visits: 14	My dear old mum requires inserts in her shoes for a problem with her feet. The inserts cost about £300 a pair and have to be custom made (by CNC) in the US. She can only afford a single pair but obviously she has more than a single pair of shoes which means a lot of messing about moving things around etc etc. Being the very kind son that I am I've offered to try and make copies of the originals for her. Since I wasn't convinced I could successfully make copies I've gone for the cheap option initially and made a pair of two part molds out of plaster. I don't suppose they will last for more than a couple of castings but at this stage I'm looking more for a proof of concept than mass production. The molds I've made have sufficient detail that I'm confident that if I can get the correct combination of resin and release agent I can produce a workable product. So far I've been using Vaseline as a release agent and it seems to be working well. I don't really have any experience of casting resins though so I'm hoping someone could point me in the right direction. The real inserts are made from some sort of hard, machinable, plastic but I couldn't tell you which. They have no obvious flexibility in the hand but it's possible they might flex slightly when holding a persons full weight. One obvious difficulty I can see is with the centre of the heel area as the insert becomes quite thin, I'd guess about 2mm. Whatever I make the inserts out of I'd like to be able to work the final product (probably by sanding) to make it a custom fit for different pairs of shoes. Any advice is greatly appreciated. Cheers
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Brian_s	Brian_s posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 99, Visits: 2.5K	I find that the Easy Composites Fast cast polyurethane resin and Water clear polyester resin are both brittle when thin. I have used a clear epoxy casting resin which I find very strong. I made a 12mm X 300mm rod of this which did not break when dropped and can be bent a bit without snapping. I can't see that Easy Composites sell it. (Please correct me if I am wrong.) if you search google for "Clear rigid epoxy casting resin" you should find it. They say it can be released in 19 hours but I find that it takes about 48 hours to set at room temperature. Perhaps I have cold rooms. Brian.
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wobblycogs	wobblycogs posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 3, Visits: 14	Thanks for the advice. I was a little concerned about some of the resins being a brittle when set, last thing I wan't is for mum to be walking along with broken plastic rattling around in her shoe! I'm in no rush when it comes to releasing the molds, I'd rather wait a few days and be sure than risk wrecking the piece by opening the mold to early.
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Warren (Staff)	Warren (Staff) posted 12 Years Ago HOT Post Details
Group: Administrators Posts: 2.5K, Visits: 8.5K	How brittle it is, is all relative. Polyester waterclear resins are well known to be brittle. By comparison our Fast-Cast Polyurethane Casting Resin is much less brittle than a polyester waterclear. I would suggest for ease of use, making silicone moulds of the originals, then casting into the silicone moulds. No release agent will be needed when using most casting resins. You may find you need to modify the properties of the resin you choose with filler powders or additives. People often use these to vary the performance of the end product slightly. A bit of development and testing is probably needed to get the best results. Warren Penalver Easy Composites / Carbon Mods - Technical Support Assistant
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wobblycogs	wobblycogs posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 3, Visits: 14	Thanks, I'll have a shot with the resin you suggest and see how it goes. Ideally I'd have made the molds in silicone but I've got a very tight budget at the moment so that wasn't really viable. If the trial run works out I'll probably make a silicone molds as that should allow me to make numerous copies. Thanks.
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FLD	FLD posted 12 Years Ago HOT Post Details
Group: Forum Members Posts: 468, Visits: 2.7K	You should've tried Sub4 biomechanics in Stoke. They do shoe inserts and offered a second pair cheap when I had mine made. Edited 12 Years Ago by FLD
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