Metal finishing Q&As since 1989
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I need a conductive filler to electroformed ophthalmic submasters
Q. I need to fill a small gap between a nickel ophthalmic mold and a steel ring. I am using the steel ring to enlarge the size of the mold using electroforming. What is a good conductive material that will act like Bondo and that is easily sandable? I have used conductive silver paints and am currently using a two part silver epoxy. the epoxy works, but it gets air bubbles and leaves low spots when you sand it. It is very expensive and takes to much time.
Can someone help?
optical electroforming - Aguanga, California
2006
A. Adhesives, cements and metallic paints will most surely give you those and other problems. Maybe you should investigate a very low heat welding procedure to close that gap and begin with an all metallic substrate. Laser welding or spark deposition come to mind. Both are expensive but the results are amazing. W/o knowing more details it's really hard say more.
Guillermo MarrufoMonterrey, NL, Mexico
Q. Thanks for the info. My problem is that the parts that I am trying to fill are production jobs. I need to be able to fill the crack over and over again. There must be a material that acts like Bondo. Maybe a high temp conductive wax or something like that.
Kelly Pichel [returning]- Aguanga , California
A. Some other threads on line here (1605, 34583) suggest Lab-metal [on eBay or Amazon] or All-Metal [on eBay or Amazon] as being like Bondo but conductive enough to plate upon if the right sequence is used.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. I tried the All-Metal and I thought it was going to work but when I tested for conductivity, it was not conductive. Is there a special technique that I need to use to make it conductive? I have a piece of flat nickel and a piece of flat stainless steel that I have to bond together and have the electroform plate them into one piece without a seam. Can anybody help me?
Thanks again,
- Aguanga, California
A. A gap, no matter how small, is viewed by the electricity as a perturbance (that's exactly why e-forming resolution is so high). Thick plates from certain electrolytes may eventually bridge over gaps, but if you are going to separate the plate from the mandrel the first surface will show the alteration in that point. If you intend to keep the two parts joined by the deposit maybe after a thick plate and a good re-polish and re-lap you'll get a good surface.
Guillermo MarrufoMonterrey, NL, Mexico
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