Author Topic: Electroforming/electrotyping  (Read 14544 times)

Offline sorveltaja

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Electroforming/electrotyping
« on: February 24, 2019, 08:12:08 PM »
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:


Offline crueby

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Re: Electroforming/electrotyping
« Reply #1 on: February 24, 2019, 08:23:59 PM »
That is an impressive experiment!  What metal is the final part, copper?

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #2 on: February 24, 2019, 08:55:02 PM »
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. 

Online Vixen

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Re: Electroforming/electrotyping
« Reply #3 on: February 24, 2019, 09:23:37 PM »
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

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Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #4 on: February 24, 2019, 10:22:55 PM »
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.


Offline crueby

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Re: Electroforming/electrotyping
« Reply #5 on: February 24, 2019, 10:37:51 PM »
Does the thickness of the part just depend on how long you let it go?

Offline steam guy willy

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Re: Electroforming/electrotyping
« Reply #6 on: February 24, 2019, 11:00:34 PM »
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

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #7 on: February 25, 2019, 09:07:17 AM »
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!


Offline Noitoen

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Re: Electroforming/electrotyping
« Reply #8 on: February 25, 2019, 09:48:20 AM »
Maybe you could use a constant current source to automatic regulate the plating.

Offline Admiral_dk

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Re: Electroforming/electrotyping
« Reply #9 on: February 25, 2019, 11:43:29 AM »
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  :praise2:

Offline b.lindsey

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Re: Electroforming/electrotyping
« Reply #10 on: February 25, 2019, 12:52:44 PM »
Pretty amazing and with surprising detail as well. So how long did it take this test part to "grow" to the thickness shown?

Bill

Offline b.lindsey

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Re: Electroforming/electrotyping
« Reply #11 on: February 25, 2019, 01:15:37 PM »
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

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #12 on: February 25, 2019, 01:22:20 PM »
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.   

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #13 on: February 25, 2019, 01:25:46 PM »
Bill, at first I thought to post to additive machining, but wasn't sure. Thanks.

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #14 on: February 25, 2019, 06:59:43 PM »
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:

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #15 on: February 26, 2019, 07:52:05 PM »
Here is the result after 28 hour 'marathon'. First 14 hours at 300mA 2,5V, and then another 14 hours at 400mA 3,3V. As it appears, resulting object is still attached to silicone mold. But why all the crossing wires?

They are only needed for one thing - in the beginning, after the mold has been 'blackleaded' or covered with graphite powder, there should be electrical "contacting points", that are in contact with graphite layer, to start copper formation. It should be done at very low amperage, about 30-50mA.

Graphite isn't exactly a good conductor, being more like resistor, so it can't handle high current without popping like fuse. But once the graphite layer is covered with copper, more amperage can be applied.
In the above picture, formation at lower left is an indication of too much current/not enough agitation. That copper layer seems to expand wildly, and needs to be more controlled.

But after all, some of those crossing wires, being 0,5mm wire at the beginning, became so thick and hard, that I couldn't cut them with electronics pliers.

Then the measurement, after the resulting object was released from the mold. The target part of the result was a bit of disappointment, as it is only 0,2mm thick.
Surrounding areas measured as much as ~1mm thickness - exactly opposite results to what I'm after .



Last but not least, is the more important surface, straight out of the mold, which has graphite powder embedded to it. Some say it's more like an "authentic" look, though it's easily buffed away, to bring out the bare metal:


Offline b.lindsey

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Re: Electroforming/electrotyping
« Reply #16 on: February 26, 2019, 09:24:06 PM »
Interesting stuff. How are the wires attached to the thin graphite layer?

Bill

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #17 on: February 27, 2019, 09:05:01 PM »
Bill, to start, some turpentine is applied to cover areas, where graphite powder is to be added later. Graphite powder sticks without turpentine as well, but tends to release loose powder, that end up floating in the electrolyte, when submerged first time:   


Then the graphite powder is applied to the mold:


Next comes the "wire cage". Any copper, or tin plated copper wire is suitable, as long as it's thick enough to poke through the mold. I use 0,5mm, tin plated electrical wire, because I have whole spool of it. It has to be stripped though. Enough of it is used to make the cage, and a hook to hang it in the bath:


After that, 'contact points' are made by brushing some more of graphite powder to areas, where wires go through the mold:


And this is how the copper layer starts to develop, after 15 minutes in the bath:

Online Vixen

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Re: Electroforming/electrotyping
« Reply #18 on: February 27, 2019, 11:29:41 PM »
I am very interested in your electroforming process and experiments. I am impressed with the surface detail you are achieving. I notice you are having difficulty in achieving any useful shell thickness inside the mold. The majority of the material growth appears to be on the wire cage and on the periphery, only a very small proportion is being deposited on the target area.

Could it be that the wire cage is shielding the mold area by drawing all the copper deposition to itself rather than to the mold surface? Is it necessary to have the wire cage in front of the mold? Could the wire cage still act as the 'contacting points', if it were repositioned at the rear of the mold facing away from you copper anode bag?

Many years ago, I served with the Royal Air Force at a large RAF Maintenance Depot in South East Asia. I was given a job in the electroplating shop for a couple of weeks while the regular guy was on leave of absence. I had no particular skills to offer, I was simply standing in the wrong place at the wrong time. The electroplating shop was there to make repairs to aircraft and radar waveguide components. However, there was an illegal sideline for private work. We called them 'Rabbits' because of the speed with which things disappeared from sight whenever the bosses appeared.

Silver plated sports trophies, which tarnished quickly in the tropical heat, were a regular source of illicit income. They did not need  (or get) a thick layer of electro plated silver, just a quick 'flash coat' was enough to make them look like new again.The silver of adequate quality for the anode was cheaply available from jewelry bought in the local market. However the sports trophies were difficult things to electroplate evenly due to the cup like shape. We made a special plating bath just for 'flash coating' these silver cups. The method we used may?? have something to offer for electroforming.

The guy in charge explained that the electroplating always formed on the surface closest to the anode,where the current density was greatest. and never on the far side of the object where the current density was very low. To overcome this problem the object to be plated could be rotated to achieve a more even deposit. A better way was to surround the cup with a circle of interconnected anodes all suspended at about the same distance from the trophy. Agitating the electrolyte also helps. In this way we could quickly re-plate the outside surfaces of the  tarnished sports trophies. The inside of the cup never received any plating, being shielded by the proximity of the outer surfaces to the anodes.

To plate the inside of the cup, it was necessary to suspend a silver chain anode down the center line of the cup, until it almost touched the bottom, but not quite. The current density was then uniform all round the silver chain anode and an even (very thin) silver layer was deposited on the inside of the cup.

This was a long time ago and I may have forgotten many of the details, but the one thing I remember clearly, was the need to control the distribution of the plating current by careful positioning of the anodes. It could be that your wire cage is positioned so close to the copper anode bag that it is drawing all the plating current and so shielding the target surface. Could you find a way to reposition the wire cage on the opposite side of the mold?

Just a thought, which may help, As I said, I am no expert but I have seen it done.by one.

Mike

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Sometimes, it can be a long and winding road

Offline crueby

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Re: Electroforming/electrotyping
« Reply #19 on: February 27, 2019, 11:46:49 PM »
If the wire cage is mainly to suspend the mold, could you use insulated wire for it instead, to keep it from attracting the copper?

Offline Admiral_dk

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Re: Electroforming/electrotyping
« Reply #20 on: February 28, 2019, 11:34:55 AM »
Sound to me like you should try to have the wire inside the mould and leave insulated upwards and having the exposed end come out through what will be the middle of the finished surface.  this way the growth will be from the center.

If I had to do it, I would experiment with making a mould first as before. Then make a very small hole around the middle in a place with as few details as possible or even a few places (or more) depending on the surface area size. place the exposed copper wire(s) close to the surface in the hole(s), bend towards the top on the backside and pour another layer of the mould material, so the exposed parts of the wire on the back is encased. Next steps will be as before, with cleaning, carbon, etc.

I hope I make sense and that it will be useful inspiration (to maybe an even better solution).

Best wishes

Per

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #21 on: February 28, 2019, 08:00:17 PM »
Mike, that's fascinating story. The wire cage definitely robs a lot of copper. At first, I copied what I saw on Youtube videos, where people used wire cages from start to end of the process.

In fact, I just realized, that the cage is needed only at the very beginning. Then it is simply snipped away, leaving only one wire to contact the molds copper layer. Why didn't I think of that earlier

Cage removed from both sides:


Using of the cage could be altogether omitted, if the graphite layer is sprayed/wetted with copper sulfate first, and then iron powder sprinkled to it. That way the copper layer forms instantaneously.
I have tested it with some iron filings, and it works. So then I ordered iron powder, but it's bit too fine, and floats away with liquid.

Ethanol might be working wetting agent for a fine iron powder. But that needs more testing.

There is still a "thief ring" left around the mold. I did read somewhere, that it should prevent tree-like formations on the outer edges. Not sure about that though.

To optimize the deposition even more, masking should be used. I still haven't found a working solution for that. I have tested using acrylic paint, enamel paint, and a pc-pen, that is used on printed circuit boards.


Somehow copper finds its way through them all, and starts happily to grow a new layer on the top of the masking. Something like rubber paint comes to mind, but they are usually sold in spray cans, which doesn't make it any easier, at least when masking smaller objects.

What comes to anode and cathode, they should ideally be positioned face to face with each other. But as was mentioned, it isn't always possible, because of the shape of the cathode and/or to provide enough space for agitation.

There is an invisible 'diffusion layer' on the surface of the cathode, which should be continuously disrupted by agitation. Otherwise it seriously limits the formation of the deposit, and allows all kinds of defects to form.

It seems to be true, as at the beginning, I was using something similar, to what they use on magnetic stirrers. It creates nice little vortex, but makes way too constant movement of liquid(electrolyte), resulting deep groves, and other streaming patterns on the cathode. When I changed to reciprocal agitation, smoothness of deposition increased noticeably.

But still the concave surface(object in the above pictures) doesn't get enough agitation. I'm planning on building something different, to provide more 'aggressive' agitation, as they say.

Once my ordered 3d printer finally arrives, I should(at least in theory) be able to make something like bank of eductors.     
     


 




Offline crueby

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Re: Electroforming/electrotyping
« Reply #22 on: February 28, 2019, 08:38:22 PM »
Would the same silicon used for the mould work for the masking layer? I am not clear on what is being masked?

Offline Zephyrin

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Re: Electroforming/electrotyping
« Reply #23 on: March 01, 2019, 09:01:04 AM »
This is a fascinating study, thanks to share...
ME 189, 634.  issue 4185. 2003.
looking at the Model Engineer ref cited above, the inlet copper manifolds for a WWI Le Rhone rotary engine were beautifully shaped by electroforming, about 0.04" thick, on cast Wood's metal cathodes melted afterwards. no further detail in the techniques used...simply following a method published before, ME, vol 111, pp104-105; issue 2774; 22/07/1954. I don't have issue that old alas!

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #24 on: March 01, 2019, 08:57:32 PM »
Crueby, same silicon might be used for masking - I'll have to test that. What comes to areas to be masked, it works like when you make traces to circuit board, that are to be reserved, while the rest is etched away.

But in this case, the process is inverse, as the areas, where the copper deposition isn't wanted, are masked, leaving only the target surface without mask, to receive deposition.

Zephyrin, thanks. That issue 2774 could be very interesting read. I have also thought of purchasing wood's metal, for that very purpose, that you mentioned.

On the other hand, there is a book called "Electrotyping", which dates back to 1908, that explains processes in quite a simple language.
Although its focus is on the printing stuff, there is a good amount of basics about the subject: https://archive.org/details/electrotypingpra00partiala/page/n4 

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Re: Electroforming/electrotyping
« Reply #25 on: March 01, 2019, 09:40:42 PM »
Have you tried 'coloidal' graphite such as Aquadag? As I understand it, this would be very much finer than the powder you are using appears to be, which might help with the conductivity of the coating. (It was used on the insides of CRTs.) 

Offline steam guy willy

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Re: Electroforming/electrotyping
« Reply #26 on: March 02, 2019, 01:30:09 AM »
HI, here are the pages from the 1954   Vol 111  article on electroplating.....I do have a lot of the M.E. magazines from Vol 1 No 1 up to the present day.......hope this is helpful

Willy

Offline Zephyrin

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Re: Electroforming/electrotyping
« Reply #27 on: March 02, 2019, 10:12:34 AM »
Thanks Willy, quite useful info in these pages !
 
with all the practical hints given in this thread, I would like to have a go...

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #28 on: March 02, 2019, 08:34:47 PM »
Willy, that's wonderfull!. Thanks for providing the pictures. There it says 48 hours for 50 thou(1,27mm) layer thickness, which seems quite good, without agitation(I assume, as it wasn't mentioned).

I have done some tests without agitation, using about 200-300mA for 12 hours, and haven't got even nearly that good results. In the pictures it says potash alum is a part of the electrolyte recipe. Not sure though, what its role is.

ChuckKey, thanks for the tip. I checked Aquadag's availability on the net, and at least in my case, it should be ordered from abroad. Ordinary graphite powder is more widely available, and is also more inexpensive, making it perfect candidate for newcomers like me, when doing numerous experiments.

Zephyrin, sounds good. If you decide to give it a go, let us know.

Lately I haven't done much of electroforming, but instead, hacking together a simple diaphragm pump for agitation, just to see if/how it works.

Offline crueby

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Re: Electroforming/electrotyping
« Reply #29 on: March 02, 2019, 09:08:17 PM »
Do the internals of the pump need to be all plastic to keep it from getting plated?

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #30 on: March 02, 2019, 10:09:17 PM »
Crueby, yes, preferably so. I've been looking for commercially made small pumps, but the specs about their construction materials like valves etc., are always quite sparse. 

Offline steam guy willy

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Re: Electroforming/electrotyping
« Reply #31 on: March 03, 2019, 02:47:15 PM »
Hi All when i used to do stuff with electronics and bought IC's through the post, they always attached them to conducting soft rubbery type of flat stuff that would prevent stray electrical pulses frying them. I had thought of using this materiel for making formers for electro forming applications but never did !! just an idea and one of many that floats around in my brain ??!!!

Willy

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #32 on: March 03, 2019, 08:49:45 PM »
Willy, any ideas, what the conductive material embedded in the rubber might be? Quick look at the wikipedia proposes carbon: https://en.wikipedia.org/wiki/Conductive_elastomer

It just popped to my mind, that the silicone, which is used to make a mold, could be made conductive, by mixing graphite powder to it. But not necessarily to whole batch of silicone, only small portion of it,
which could then be brushed or otherwise applied as a first, thin layer to provide conductivity. After that, plain silicone is applied to fill the rest of the mold.

Not sure though, how the graphite(and conductivity) of the first layer lasts, if the mold is used more than once. 

Offline steam guy willy

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Re: Electroforming/electrotyping
« Reply #33 on: March 03, 2019, 11:21:31 PM »
lots of room for some
R&D here....

Willy

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #34 on: March 08, 2019, 07:46:22 PM »
Very much of an off-topic, but the 3d-printer, that I ordered, has finally arrived. First test object, that is on the print, is a part of the primitive diaphragm pump for agitation, that I had to design throw together, because there doesn't seem to be any drawings available on the net.

The ones, that I've found, from Grabcad and Thingiverse, are basically empty outer shells.

To put that aside, the sound of the printer reminds me of the Cylon of the Battlestar Galactica

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #35 on: March 13, 2019, 08:37:31 PM »
An update: today I tested diaphragm pump, but it needs more tweaking, and maybe some new parts to get it to work. It uses flap valves, which I think are the problem.
It sounds like it has a 'hiccup', when running it, making the flow through it quite lacking:
   

I'm eagerly waiting to get back to electroforming, but some kind of enhanced agitation of electrolyte is a must to get any further.
Be it in a form of air bubbles, or using 'random flow generator' -eductors, can't tell yet.

At the moment I'm about to try out a centrifugal pump, that I found from Thingiverse. With it, there are no valves to worry about, but instead, keeping it watertight may cause problems.
Also, it might need some metal parts, which are exposed to electrolyte. Stainless steel is hopefully inert enough for that purpose.

 

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #36 on: March 20, 2019, 08:34:57 PM »
Another update: I left the centrifugal pump aside, when I found a 3d-model of a dual diaphragm pump: https://grabcad.com/library/long-life-water-pump-1
Must be one of the very few 3d-models online, that actually includes inner parts too.

I've done some changes to the model, like replacing the magnetic drive with a scotch yoke. The electric motor, that I happen to have, has a suitable bracket to fit to the pump body:


Valves are still bit of a question mark. Might have to test different ones. Haven't been able to source small glass balls for that, so I'm going to use 0,5mm thick rubber sheet instead.

And that requires making 'one of a kind' -punches for the job. And that requires lathe and some more tools... So I had to dig out the lathe and some more tools, also for machining 3d-printed surfaces
to fit better together. Lathe and mill sits happily on the floor, where they have enough room:


So that's why the original subject, electroforming, has grown enormous amount of branches.


 

Offline Ian S C

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Re: Electroforming/electrotyping
« Reply #37 on: March 21, 2019, 01:14:39 AM »
Small glass ball, some aerosol spray paint cans use glass ball as mixer thingies, can't remember the size.
Ian S C

Offline modeng2000

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Re: Electroforming/electrotyping
« Reply #38 on: March 21, 2019, 06:41:39 AM »
Hand wash pump bottles have a small glass/plascic ball in the pump.

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #39 on: March 21, 2019, 10:30:21 PM »
Thanks for the tips, guys.

What comes to electroplating, there is an alternative recipe, besides traditional 'copper sulfate and sulfuric acid' one. Here is Richard Lacey's patent: https://patents.google.com/patent/US7235165B2/en

Recipe consist of 32g oxalic acid, 10g trisodium phosphate, 4g ammonium sulfate, and 950ml (distilled) water. From what I understand, after reading the patent, that solution isn't "metal specific", as it doesn't
contain any metal salts.

So I had to get the required ingredients. But not so much of a surprise, that in my country, they don't sell any of that stuff to consumers. I ended up ordering them from UK.

So far, I have done only very basic tests with that recipe on copper some time ago, before I got the adjustable bench power supply.

Once I get that pump/agitation -thing sorted out, there should be whole new territories to explore.

Offline Ian S C

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Re: Electroforming/electrotyping
« Reply #40 on: March 22, 2019, 02:10:26 AM »
Small fish tank air pumps are quite good for agitating fluid baths such as citric asid for copper, or alum fue getting broken taps out of brass. There is enough movement of water set up to keep hings going with even the smallest pump.
Ian S C

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #41 on: March 23, 2019, 09:27:41 PM »
Ian, thanks, that's actually my plan B, if all else fails. But I just have to try out the ''diy options" first. Cant't help it. 

I managed to construct the dual diaphragm pump, but oh boy that thing is one noisy bugger. Sounds like an air compressor.

So I got back to centrifugal pump. Today I tested magnetic coupling, with some 10mm diam. neodymium button magnets, but not enough drive force. Putting a hard drive magnet to the motor side
increased the traction as was expected. Next step is to test it with water. It has two stainless steel parts in the pump chamber, that are to be exposed to the liquid.

If all goes well, I should be able to put it to use in couple of days, to feed eductor(s), or some other 'random flow generator'.

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #42 on: March 25, 2019, 11:41:02 PM »
Again an update: centrifugal pump is on the test run. There was a numerous fixes I had to make it to work though, because I didn't consider the design carefully enough.

This is the current, and also the first version, running at 10V/~1600rpm:


I'll let it run overnight to make sure there are no leaking or other issues. After that, finally back to electroforming.

 

Offline Ian S C

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Re: Electroforming/electrotyping
« Reply #43 on: March 26, 2019, 01:11:24 AM »
I made a bath for etching small circuit boards in, and under it I made a rocking device poweredby a little geared motor, can't remember the speed, probably about 20rpm. the tray the bath sat on moved about 1/4".
Ian S C

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #44 on: March 28, 2019, 12:26:29 AM »
Ian, yes, that is one possible way to provide agitation. When etching, it might also help, if enough straight flow is provided to the surface, to make the copper removal even faster.

Not sure about how the agitation fits for etching, as it is an inverse process to electroforming. Maybe worth testing?


Offline steam guy willy

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Re: Electroforming/electrotyping
« Reply #45 on: March 28, 2019, 02:06:45 AM »
Hi, I think the agitation is necessary to remove the etched detritus from settling on the etched part ??

willy

Offline ddmckee54

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Re: Electroforming/electrotyping
« Reply #46 on: March 28, 2019, 08:05:37 PM »
I think agitation is applicable to both electro-forming and etching.

When electro-forming you'd need a fresh supply of your metal bearing liquid, that hasn't been depleted of the metal ions yet.  I would think that you would need to be careful that you maintained a fairly uniform flow over the entire part.  On the parts that you have formed do you notice a difference in thickness across the part?  Other than what you've seen around the contact points?

With etching you'd want a supply of fresh etchant that isn't contaminated with the metal being etched, and you'd want to flush away any chunks that have fallen off so that you don't have to dissolve any more of them than you already have.  The more copper you dissolve, the weaker your etchant becomes.  Another trick used when etching is to suspend the object being etched upside down in the etchant.  That way any little bits that fall off do not fall back into the part being etched.

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #47 on: March 28, 2019, 11:33:27 PM »
ddmckee54, yes there is quite a big difference on thickness, between outer areas and the center of the electroformed areas. One reason, that I suspect, is that the two molds I have mainly used
for this testing, are both concave, so all 'deeper' areas are starved, what comes to the agitation.

Earlier I used a back and forth rocking flap for agitation, and the results were as mentioned above. It should work well on flatter surfaces though.

At last, a new setup:


Agitation pump isn't running yet, as the graphite layer needs to be covered with copper first. Otherwise, the flow might detach graphite particles, that could end up floating on the rest of the solution.





Offline Ian S C

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Re: Electroforming/electrotyping
« Reply #48 on: March 29, 2019, 09:57:19 AM »
The rocking tray keeps the fluid moving without the bubbles.
Ian S C

Offline ddmckee54

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Re: Electroforming/electrotyping
« Reply #49 on: March 29, 2019, 07:46:50 PM »
Do you vary the voltage and or current any during the process?  Just wondering if you could to start out low, and then once you have the initial layer formed jack it up to speed up the process?

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #50 on: March 29, 2019, 09:29:39 PM »
At first, I usually use ~50mA to grow the copper layer over the graphite. Once the whole graphite surface is covered, the current can be increased.

But not that much:


I got bit too excited to get back to testing the electroforming, and used 500mA/5,2V for 12 hours. Target surface was still only about 0.2mm thick.

There is a "random flow generator" in the bath, that I found from Thingiverse:
 

Last time(first picture above) it was on the midway between the anode and cathode.

Now it is very close to cathode. I also masked outer areas with candle wax. Maybe not an ideal stuff for that, but it seems to hold better than any paints/lacquers, that I tested earlier.

So hopefully, the copper deposition concentrates more on the actual target area.

Current is now 300mA/~3V, so there should be far less of those thorny 'treelike' formations. 


Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #51 on: March 30, 2019, 10:41:10 PM »
After 9 hours at 300mA/3V, the result isn't any better than the previous ones, despite the increased agitation. The candle wax masking limited the overgrow at the outer areas, but the trees do still want to grow. Must be quite fertile ground:


Thickness of the target area is again only ~0,2mm. Making the deposition process faster must be a very complex subject. I seriously doubt, if it is possible at all to achieve that in a home shop.

There is still plenty of things to test, though. One that comes to mind, is to decrease the current to the point, where no tree-like, or any other defects appear, but still using the same agitation.

It should take a lot of time, maybe several days, to achieve thicker copper layer, than what I have achieved so far. I don't mind waiting, as I have also another project going, that takes plenty of time.

 




Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #52 on: April 06, 2019, 11:52:39 PM »
Again more testing. After re-reading some texts and papers, which have simple copper sulfate/sulfuric acid recipes, they almost always use concentrated sulfuric acid.

Haven't thought of that earlier, but I just used the proposed amount of what I have, that is watered down battery acid...

So I ended up adding 100g more battery acid to the bath. Started with 900mA/3,5V, but after 30 minutes, the formed surface was darker red, which is a sign of 'burning', as there was too much of current.

Current was then lowered to 500mA/1,7V. After 12 hours, the target surface thickness was 0.35mm, so the current distribution seems to be a tiny bit better :).

The earlier tree-like, spiky formations on the outer edges were missing. But no worries, they just changed to more like a nugget form.

I really should have taken pics before cropping the nuggets out. These are both from the very same, rather crappy new silicone caulk mold. When fresh, it starts immediately shrinking.
Left one has a thickness of 0,35mm on target surface, while the one on right side has 0,3mm.


Here is the ongoing one, after 11 hours at 300mA/1,1V. Jolly good 'salmon pink' colour, which oxidises quickly, when exposed to air, though. I took it out of the bath just for the picture. As can be seen, the 'wire cage' is missing, as it isn't needed, not even at the very first stage. Just a single wire going through the mold:


To simplify things even more, there seems to be no need for any fancy 'random flow generators' or eductors, as there are no noticeable flow patterns on the formed surfaces(see the pics).
Just plain flow from the pump. 

Addition of the battery acid has lowered the resistance of the bath quite a lot. Before that, 300mA required ~3,2V. Now it is 300mA/~1,1V.


Offline Admiral_dk

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Re: Electroforming/electrotyping
« Reply #53 on: April 07, 2019, 08:56:57 PM »
Nice to hear that you have progress and that it is easy to see the improvement  :ThumbsUp:

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #54 on: April 07, 2019, 11:38:20 PM »
Yes, some progress, but also hiccups. Today was the third time, when I had to interrupt the testing, because the pump started to leak again. First and second time, the electrolyte slowly seeped through the layers of the 3D-printed construction. So I sealed it inside out few times with a thinned lacquer. It seems to do the trick.

Only thing, that causes the leaks so far, is the rubber gasket, which is supposed to seal the main chamber.

I must admit, that I haven't had enough patience, what comes to the pump construction(and also to electroforming).

New gasket needs to be made, and some sort of thorough pressure testing. I have a bicycle tire pump, which I think could be used for that. Not sure when, though.

Conclusion is, that I'm going to set this project aside for a while. I hate when that happens, but that's just the way things go sometimes.

 


Offline Noitoen

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Re: Electroforming/electrotyping
« Reply #55 on: May 02, 2019, 10:36:41 PM »
 :atcomputer:Most recent washing machine drain pumps have a enclosed rotor/impeller with a ceramic shaft and no shaft seals or any other seal other than the casing's "O" ring. You should get it cheap from your local recycling facility. Something like this.
https://www.amazon.com/General-Electric-WH23X10041-Washing-Machine/dp/B00MNOQFD2

Offline sorveltaja

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Re: Electroforming/electrotyping
« Reply #56 on: May 06, 2019, 11:49:13 PM »
Noitoen, thanks for the tip. I've been looking for aquarium pumps, as the smaller ones aren't that pricey. Also they are quite widely available.

Looks like most of them have a stainless steel shaft, which doesn't seem to attract copper at all, if the shaft is isolated from any potential voltage source. The pump, that I printed out, had two stainless steel parts, and after many hours of electroforming, they were still intact. No pitting or corrosion whatsoever.

What comes to 'diy' 3d-printed pump, it just isn't worth the hassle. The printed PLA-plastic layers, at least in my case, are never watertight, even if the surface may look solid.

Of course I could increase the printing temperature from 200C to 220C, only to have the warping problems.

This project is still on the 'shelf', but I've had some ideas about electroplating nickel over the basic copper layer, to make more durable surface. Must order some nickel first, though.

Nickel electroforming - haven't tried it, yet. It might require 'metal specific' nickel sulfate, just like the copper requires copper sulfate. But even then, could simple battery acid/nickel sulfate electrolyte work as well as the battery acid/copper sulfate one does?

As I mentioned in post #39, Richard Lacey's electrolyte isn't(or shouldn't be) metal specific, but it may be suitable only for electroplating. I have tested it shortly only with copper, and the anode extracted large amount of light blue coloured substance, so the anode bag is a must(as it always seems to be).



   
« Last Edit: June 08, 2019, 10:27:17 PM by sorveltaja »

 

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