Building a Large Scale Electroforming Tank (Part 1)

120 Gallon Acid Copper Electroforming Tank

As a design studio assistant for Misha Kahn, I was responsible for the 3D printing and post processing operations of the fine art furniture and sculptures in the studio. In our ever longing efforts to push the boundaries of what 3D printed objects can look like - I began experimentation of electroplating 3D prints on a small, tabletop scale.

Electroplating, or more specifically, electroforming is the process of depositing metal ions (copper) onto the surface of a non-conductive material (such as plastic). The object being plated must first be made conductive (with a coating of conductive paint) and connected to a negative terminal (Cathode) of a power supply. A sheet of copper is connected to the positive terminal (Anode) of the power supply. This is the source of the copper that will ultimately be plated onto the object. The object and the copper source are both submerged in a electrolyte solution. When current is run through the system, positively charged copper ions leave the sheet of copper and are drawn towards the surface of the negatively charged object.

Initial Tabletop Electroforming Tank

My starting materials were pre-mixed Acid Copper Electrolyte solution from Rio Grande, a benchtop power supply, graphite paint, and a Tupperware container as my first electroplating set up. The initial results were promising, but still far from a finished product. I was plating FDM 3D prints, which are typically hollow, therefore they float in the electrolyte solution. This made them hard to keep in place and submerged. If the object comes in contact with the anode, a short circuit will occur and the object will be damaged. Furthermore, the graphite paint was very poorly conductive, and took several hours to develop the first strike coat. We tried several formulations of our own using graphite powders and binders, along with commercial conductive paints from (MG Chemicals and Caswell) and ultimately decided that the graphite was not worth the trouble. We stuck to the Copper Conductive paint from Caswell as the most reliable and affordable option.

In addition to electroplating FDM prints, we also tested plating SLA (resin) 3D prints. The SLA prints we used were made of solid photopolymer resin, which eliminated the issue of floating PLA parts. These worked great. The surface finish was naturally smooth, since the print resolution was much better, and the plating was much more uniform and durable.

3D Printed (SLA) picture frame. unplated (left) and plated, unpolished (right).

Polished 3D printed picture frame designed by Misha Kahn.

Other Issues

We had to further troubleshoot the methods of attaching the object to the cathode. Typically you wrap or glue copper wire to the object and paint it over with copper paint. Since the objects we were plating were diverse in buoyancy (hollow vs solid), geometry (spiky, round, hidden pockets), and material composition, the method of attaching the object to the cathode was challenging. When the objects were hollow, the buoyant force was so strong it would break the connection after submerging, or would break when we hade to rotate the object for a second plating. For parts with hidden pockets, they would often plate unevenly or just not at all, so this required some rotating. Other objects with hard edges or sharp points would concentrate the current and form irregular dense nodules. These nodules were embraced as artifacts of the process, but on occasion because too visually distracting and undesired.

As the objects became more complicated, we had to adopt different strategies for each.

• Inflated Resin (Hollow, thin, very buoyant, inert plastic)

  • molding copper lugs into the object for connections

  • casting copper grains into the resin mixture

  • leaving holes in resin inflatables so object would sink

• FDM Prints (Hollow, buoyant, strong, plastic absorbs electrolyte and must be sealed)

  • Sealing object with Lacquer

  • attaching weights (neoprene coated barbells)

  • screwing brass eye hook screws + reinforcing with CA glue

• SLA prints (solid, non-buoyant, brittle, not very large)

  • combination of CA glue and 5 minute epoxy on a hidden area to attach cathode