Electroforming/electrotyping

[sorveltaja]

To start this little journey to the world of electroforming/electrotyping, and what I have discovered so far as a beginner, let's see what it is about:

Here is the original plastic part of a model aeroplane:


silicon caulk mould(which shrinks and warps, when it cures, but is way more cheaper than proper molding silicon for testing purposes) and the resulting electroformed object:


then the business side, which I buffed a bit with brass brush on dremel, to bring out more details:

[crueby]

That is an impressive experiment!  What metal is the final part, copper?

[sorveltaja]

Yes, it is copper, because it seems to be the easiest candidate for electroforming. For example, zinc electroplates just fine(very thin layer), but if you attempt to grow the layer thickness any further, it gets sort of dull and powdery, and rubs off very easily. 

[Vixen]

Looks like you can reproduce very fine detail with your technique.
What material or materials do you use to make the mold surface conductive?

Mike

[sorveltaja]

I use fine graphite powder to make the surface conductive. It sticks nicely to silicone mold. But it should preferably be pure graphite, not pigment, like what I once bought.

[crueby]

Does the thickness of the part just depend on how long you let it go?

[steam guy willy]

Hi S ,looking good...i first saw this in the Model engineer in the 60"s with someone making copper exhaust pipes for a radial engine !!

Willy

[sorveltaja]

Crueby, yes longer time means more thickness. But the amount of current is important. If too much, the copper layer is rough and fragile, and all sorts of tree-like formations appear. 
Using too little current means that it takes ages to grow desired thickness. Advantage of using less current means more ductile and smooth layer.
And of course one wants to increase the current as much as possible, to the point where the resulting surface is still smooth, to speed up the process.

Willy, that would be interesting read!

[Noitoen]

Maybe you could use a constant current source to automatic regulate the plating.

[Admiral_dk]

I'm guessing that it compares to other electro chemical processes … and in that case a constant current regulator / power supply will be optimal - amount of current should be dependent on the surface area being formed.

You seems to get a perfect surface, with amassing detailed accuracy 

[b.lindsey]

Pretty amazing and with surprising detail as well. So how long did it take this test part to "grow" to the thickness shown?

Bill

[b.lindsey]

As there seems to be some interest in this, I have moved it here to the additive machining category which seems to fit the process better.

Bill

[sorveltaja]

I guess the industry has very specific programmable devices, where they can adjust countless factors precisely. On the other hand, to keep things simple, any power supply can be used,
as long as the amount of current can be adjusted. At first I used plain wallwart transformer with resistors, and multimeter to adjust the current. After a while, it's not very handy or practical that way.

To overcome that, I bought a bench power supply. That one is linear 30V 5A model:
   

You certainly don't need all that much of voltage or amperage that it delivers in electroforming, but then again it's very usable on other projects as well. It was about 130euros, although similar psu's have quite wide price range, and plenty of models to choose.

For electroforming, I'll just adjust the max. current, and bump up the voltage enough, that it goes to "constant current" -mode, and stays there.

Bill, I don't remember exactly how long time it was, but something like overnight or 12h to get about 0,1-0,2mm layer. Since then I started to take notes. I'm still testing different things to speed up the process.
From what I've read it should be possible to grow 0,1-0,3mm layer in one hour, using simple copper sulfate/sulfuric acid bath.   

[sorveltaja]

Bill, at first I thought to post to additive machining, but wasn't sure. Thanks.

[sorveltaja]

Few things about my current setup:

Bath, which consist 1 liter distilled water, 250g copper sulfate, and 20 milliliters of sulfuric acid(battery acid):

Picture above: on the left side is the copper anode, made of wrapped 1mm copper wire. What surrounds it, is so called "anode bag", made of vacuum cleaner bag to keep any fine copper particles, that the anode releases, away from the rest of the solution:


And here is the geared motor, that is configured to provide linear movement, based on scotch yoke, to provide one of the key factor - agitation: