I’ve recently become involved with shoe design and I need some advice on manufacturing processes. Have a look at this shoe:
The main volume (the platform) of this shoe is built of two parts, the bottom shell and a lid/footbed. They snap/screw together and the volume is hollow on the inside.
Suppose I want to manufacture that volume but with a smooth hole in it below the arch from left to right. I’m wondering if any advancements have been made in for example water/gas assist injection molding or foamed injection molding to create the mentioned wedge shape in 1 mold. I’m not talking about cork/wood (CNC’ed) or rubber, and rotomolding doesn’t make sense from a manufacturing standpoint. I would really like to use a hard and cheap material (plastics?) with good surface definition, while keeping the weight relatively light. Also, low on shrinkage if possible.
Will the sole be covered like your picture? Are you looking at reducing tooling up costs?
Because the usual in (womens fashion footwear) is to use what I would normally term a ‘styrene’ mold for the wedge, can’t be more technical than that, it’s a pretty crude material. For one offs, then one would use cork.
Otherwise if it wasn’t covered it would be some kind of polycarbonate mold, screwed together. I used this company http://www.splendorplast.it/ to make me these shoes 15 years ago and looking at their website, not much has changed.
Some designers are experimenting with 3D printing, but TBH, I’m not sure how safe it is yet, everything we make has to be strike and abrasion tested as if the wedge fails in wear, it’s customer injuries and lawsuits. I’m not sure how one would incorporate steel shanks etc in 3D printing.
I don’t know anyone using water jet or gas for mass market womens fashion outsoles, yet. Uppers yes, molds, no. They tend to be much slower in taking on new technology than athletic footwear, the process has barely changed in my 20 years in the trade. Perhaps someone can tell me different? Is your company a member of Satra? They hold information on outsole molding.
There is an YSL wedge in the fall collections which has a slot in the sole, I’ve not seen it IRL in order to tell what it is made of - it looks covered, so it could even be cork.
Grrrr, i hate it when i’ve written a bunch of text but take so long i get logged out, then lose my text when i want to preview it and am sent to the log-in page…
…vented, but the original text was more fun…
Lew, thanks for thinking along with me. And hey presto, we’ve gotten a useful first reply!
Shoenista, thanks for the info and links! I have actually started working at United Nude. There’s plenty of knowledge within the company but in the end, I haven’t come across a cost-effective way to create shapes with lots of volume variation without the usual shrinkage problems. Can you tell me a bit more about this ‘styrene’ mold? I take it you’re not talking about the bubbly white packaging material?
Believe me, you would not want to use styrene for United Nude, it can only be used if you cover it (it is ugly!) and I’d reckon there are shrinkage problems.
I think you need to look outside of footwear TBH, but whatever you do, get a footwear technologist involved in the entire process.
A company I worked at made a metal outsole and we did not involve a footwear technologist, big mistake - it was a disaster!
Good luck!
ETA - I’d be surprised if your company isn’t a member of Satra - I would put the question to them, when I worked in athletic footwear developing cricket and soccer, (and also when I developed the above outsole) they were very helpful, providing me with info about the right manufacturer, shrinkage/expansion rates and even the formulae for the compounds.
