Metal coated resin enclosures?

[sean k]

It was years ago that I did some work trying to build enclosures and most poured casting with metals just won't work unless one goes to bronze which is too expensive. Yesyerday it crossed my mind that resin could be a nice material to cast with and I remember someone mentioning years ago that they cast their circuit in resin but the resin was condusive so everything shorted. That would be exactly what I wanted, to create a grouded sheild, so when I stopped in at the modelling shop I asked for a condusive resin. They didn't have any that they knew of, no dielectric or otherwise characteristics, but we got talking and a guy suggested adding metal powders to the resin. Eventually we all realised what I wanted and they showed me samples of resin casts that had been electracoated with bronzes etc. That was exactly what I wanted.

The pieces shown to me had very thick coatings, up to about .25 - .35 mm, which costed about $45.00, and thats well beyond what I'd want to pay but it's also well beyond the thickness of coating I'd need to have an effective grounded sheild. I'd gues about .05mm would be more than enough to sheild and enclosure exspecially that all these metals tarnish and so would be coated with clear laquer anyways.

The only area I think this idea falls down in is the area around the stomp switch but I reckon a steel or alloy strut, to reinforce the stomp switch mounting point, glued into the enclosure would sort that out and, also at its ends, create mounting points for the backing plate.

I know, well I guessing actually, that the behringer pedals are plastic with a chunk of steel or lead attatched to the base to add mass . Of course my designs will be sculptural and not straight forward copies of whatever boxes we are used to, they gotta stand out in some way to give me an edge,... otherwise I'd just buy plain metal boxes. What do you guys think about this as an option?

[deaconque]

I like this idea a lot.  I'm having a hard time envisioning it though.  Would the box be plated on the inside, outside or both?  It would be cool to be able to plate the outside in copper or brass and then patina it.  The core being resin would also keep the weight down pretty low.  Could be a pretty lucrative business if you could keep costs down.

[John Lyons]

Sounds fun but the hard part is getting something affordable.
You either need to make thousands or make a couple for yourself and treat it as a hobby.
Take that from me...the person who wastes way to much time on trivial asthetics and saving a buck...

Using a resin and then a cunductive coating inside might be something to try.
I may be wrong but metal powders in the resin would have to be a high ratio to be conductive...maybe not though...?

[frank_p]

You are talking about metalizing ?

Ex:
http://www.mmmetalizing.com/services.html

An other thing that can be done is mixing some graphite in the plastic pellets before molding.
I saw a project at the Canadian Research Institute where they blended some plastics with graphite to make parts in milk homogenisation process so to have more heat transfer.

The more you put that graphite, the less the plastic is durable...

Molds for plastic cost a lot but once you have one it last for a very long time.

But I think that for stompbox use it would be safer to have a lost wax process mold because metal pressure castings are more durable and the mold can be made of aluminium (instead of steel for plastic molds).

Aluminium molds for plastic are not very durable.  The problem is that with time the joints (and venting holes) get deformed with the pressure of the clamping force when closing the mold in the injection press.

[sean k]

Thanks for the replies chaps,
                                           I'll make the prototype in a slow cure modelling resin and carve it up as it dries. The stuff I use is two pot and takes about 8 hrs to reach max hard so it's a pleasure to work with. Then I'll make a two piece, well four piece actually, 2 x 2, set of molds in silicone or urethane and aluminium. That means that once the prototype is done I'll coat it in the thickness of silicone I want, in something like plasticene, and then form a two piece set of molds around that. these will then be sand cast in aluminium. When the two aluminium halves are worked to fit precisely then I'll, having removed the plasticene, fit them together, the aluminium set, with the prototype inside and pour in the silicone or urethane to get a precise and slightly flexible inner mold.

Then I ready to pour resin, let is set then clean up, and this resin "body" is coated with a polymer that makes the area coated condusive and will accept electroplating. I won't plate the whole thing but just the outer surface and I can plate it with all sorts of stuff from nickel and chromium to copper, brass and bronze plus a few other metals I would suppose.

I think it's the only way I can sell the pedals I make if I make them total artworks in small runs. It makes up for my complete lack of knowledge in the electronics end. Well not complete but I'm not half as clever understanding how the electrics work as I am mechanically proficient at housing them. I will sell the raw enclosures to anyone who wants them, at any stage.

The beauty of making up molds of this type is that I could also cast wax enclosures and then get them cast in solid bronze using the lost wax method. I'm hoping for a 3mm wall thickness for the enclosures and I'm pretty sure bronze will flow into that from a pour but I'm also hoping steel will flow in those thicknesses as I know a place that will cast, lost wax style, any kind of steel alloy you can think of... Heavy Metal for sure!

[deaconque]

that sounds great.  i'd love to have a copper plated box if the price is right.