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Electroforming onto silicone forms/mandrels

Q. I'm electroforming over silicone mandrels. I have been applying two-part silvering spray to make them conductive prior to electroforming with copper. Silvering is a bit challenging because the silicone is very hydrophobic. Frequently, I get incomplete silver coverage. Wetting agents help to some degree, as do multiple applications of sensitizer.

Does anyone know if there is another castable rubber (e.g., urethane) that would be easier to silver? Can anyone recommend a better wetting agent? Can I treat my silicone mandrels to make them less hydrophobic?

I was planning to electroform copper right over the silver. However, my silver provider was a bit concerned that the current might damage the delicate silver layer. Do you suppose I should try starting with electroless copper or some other gentle flash layer?

I've made some test parts in 5 gallon pails, but I ultimately need to set up a larger line at my warehouse. Unfortunately, the warehouse is not heated or cooled. I'm near Sacramento. Winter temps usually range from 41 °F to 56 °F, and summer temps can reach 105 °F. As long as I'm able to control the temps of my baths, is this reasonable to do in an unheated/uncooled building?

Thanks so much for the help.

David Shelton
- Sacramento California
December 9, 2022

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Q. I'm interested in electroformed molds for prosthesis manufacturing. More specifically, I'd like to plate copper over silicone forms (ie, hand, ear, etc.), to a thickness of ~0.080". The silicone plugs will be discarded, and the electroforms will be used to mold prosthetic parts.

Does anyone have any experience electroforming over silicone plugs?

I understand that plastics are commonly etched => catalyzed with palladium and tin salts => electroless plated => electroplated. Can the same process be used for silicone? Is there anything you would do differently? In particular, I'm not sure about the best way to activate the silicone plugs.

Thanks for your suggestions.

RFQ: I need electroformed molds for prosthesis manufacturing. I can provide silicone forms (i.e., a hand, or ear), and I need them plated with copper or nickel, to a thickness of ~0.080".
Expect small batches of 4-8 parts, and an annual volume of 30-60 pieces.
My local plating shops won't do electroforming. Please E-mail me if this is something you are experienced in.

David Shelton
- Woodland, California
July 30, 2021
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Ed. note: As always, gentle readers: technical replies in public and commercial replies in private please (huh? why?)