Author Topic: Electroforming/electrotyping  (Read 4918 times)

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 »