Hey gang, I’m almost back to life after a pretty exhausting (and a little bit scary) bout of pneumonia. A trip to the emergency ward + a week of solid couch lounging has left another big hole in the production schedule for my now 6-months-overdue shoe label launch, but things are looking up.
Before my health all went to shit I had just managed to get my second plastic component made and I thought I’d share a little of that process with you while I have an afternoon here at home with nothing much else to do.
If you’re just tuning in now for the first time, here’s a quick refresher.
I am finding it increasingly difficult to source ‘traditional’ and/or industrial standard components here in Melbourne, particularly in the sizes and quantities I would need to make full size runs of what are still essentially bespoke shoes. It seems possible to order things by the pallet-load, or one at a time, but when I need 60? That’s where the problem starts.
That coupled with my Industrial Design background and general stubbornness has led me to a point where I’ve decided to batch manufacture my own components. Yep.
So, below is a bit of a peek in to how I have so far gone about creating my own plastic heels, details and insole units. These will serve as prototypes for me to test strength / wear life / etc / etc before I make some final ones with designed details, logos, leather allowance and all that jazz.
HEEL + CRESCENT CANTILEVER DETAIL
To begin with, I used the wooden heel that I had carved earlier for the buckles-and-straps burgundy prototype. This heel is 5 inches high at the back edge (awesome) and is partnered up with a 1.5 inch platform = mega height, but still some wear-ability. I marked the centre points for a different moulding idea as seen below…
… but this design didnt work. I filled the bottle with silicon, cut out the heel, taped it all back together and filled the cavity with resin.
The problem was that the area needing most detail and accuracy is the top, and this mould always ended up with bubbles and/or not enough plastic filling the mould = too many failed parts.
So I revisited the idea (and YouTube) and decided to go for a more coffin-like mould seeing as my parts have a flat surface. This would still work with curves, it would just mean having to build up some supports from plasticine. To make the most of each resin pour I also snuck in a little crescent shaped detail I hope to use as a heel support.
All clamped up and ready to go.
NOTE! make sure you plug ALL THE LEAKS AROUND THE BASE… one leak like I had = silicon oozing out all afternoon.
The finished mould and recovered master parts.
For this process I used RTV-2 Silicone Rubber from Barnes in Richmond.
Mould detail, showing some locating pilot holes I drilled in to the wood so that I can mount each heel in the same spot with a template rather than having to guess each time. A stitch in time saves nine!
Next step, fillin’ it up! After a quick conversation with the staff at Barnes we decided that a rigid Polyurethane seemed the best option for prototyping. It has a low odour, pours well, is the least toxic of the resins they sell and would give me a strong part that is less brittle than the harder Polyester or Epoxy resins.
Brittle will probably = shattering when pressure is applied.
For these parts I have been using TC-808 78 Shore D Urethane from Barnes
So although these are quite heavy, they are essentially a super-super-hard rubber which means they should bend before they break. The final production run may be from something else once I have refined the process and spoken more to the resin suppliers around town.
I have also purchase a light weight filler, which are tiny tiny hollow balls (like sand) that you can add to resins to reduce their mass, which reduces their weight. The payoff is that the more you add, the more likely to crack apart like compacted sand your part is… I will have to test some varying ratios.
Badly focused detail shot.
So that’s where the heel tests are at. I can mould a new part each hour, and that’s fine for my production levels. Next up is to make a master form for a resin platform.
With some success under my belt with the heels, I decided to try to solve one of my last conundrums, that of how to get hold of insole / shank / shankboard components to match my lasts WITHOUT having to either outsource production (minimum order numbers), go down the path of pressing my own (needing metal moulds, pneumatic pressure, steam etc) or trying to order pre-made ones whenever I needed them and hoping they fit.
A chat with my pal Luke who works in a plastics manufacturing plant got us thinking moulding plastic components might not only answer my short order run needs, but it would allow me to design the heel + insoles as one product. This meant I can design a system for attaching the two (even if it’s just perfectly aligned pilot holes for screws) that would again save me time in the long run.
Step 1 was to attach a metal shank to the last in the place I intend it to be used in the final piece. By thinking a few steps ahead it makes things easier later on.
Next up I wrapped a fat piece of wet veg tanned leather over the last, in the same way that I would go about making an all-leather insole unit.
When the veg tan dried it had formed perfectly to the last bottom, with an indent from the shank pre-formed into the upper surface.
I then coated the veg tan with clear lacquer to give it some surface hardness and to smooth it out as much as possible.
This one I moulded similar to the first (bottle) technique shown at the top, only in a container I had made from foamcore. As recommended by YouTube vids I cut out the leather part using a waving / random carving path to minimise the likelihood of the resin leaking back out.
As you can see, the shank indentation is still there, which will make locating it later dead easy.
This technique requires you to cut out a pouring spout afterwards and most importantly, a vent beside the spout which allows the trapped air to escape as you fill the cavity, rather than needing to escape via bubbles.
Cut out pouring spout on the left, vent on the right.
And there you go… two resin parts fresh out of the mould at 1 hour intervals.
Detail shots. You can see the shank position – the spout and vent will be cut off.
Exact 1:1 replica in Polyurethane.
A quick test of dropping in a shank. I’m not sure yet if the shank will be necessary, and if it is I might look at making one from carbon fibre or something else that is readily obtained, instead of shanks, which I have to get from shoe-specific suppliers.
This part will be glued to a leather or leatherboard (texon) insole, and then the padding foam or gel will be attached to the top of that. Seems a stupid idea to make high-end hand made shoes and NOT fill them with foams and rubber to make them nice and comfortable. You never know, these might actually be comfortable 5″ heels!!
So, that was a lot of typing, but I think it’s worth sharing these ideas. With an industry dying like ours is it would be a shame if future shoe designers weren’t able to make their own things here in Melbourne if they (stupidly) insist on it – like I am.
Listening to : Gravediggaz – 6 Feet Deep