Electroforming of a Complex Mould Using an Acid-Mediated Copper Sulphate Bath

Abstract

This work reports a procedure for the fabrication of a complex mould using the technique of electroforming. This was with a view to finding a cheaper and less labour-intensive mould production route practicable locally. A Plaster of Paris electroforming mandrel in the shape of a water bottle was produced and made electrically conducting with a layer of copper conducting paint. Considerations for electroform removal were made by applying a thin, chloroform-dissolvable epoxy layer beneath the conducting copper paint. Uniformity of deposition on the mandrel was accomplished with the construction of a special deposition bath with multiple copper anodes around its perimeter. The electroforming was done in the galvanostatic electro deposition mode for about 240 hrs in a 1 M Cu2SO4 bath with the deposition of elemental copper on the mandrel. Incidences of rising bath pH were mediated with concentrated H2SO4. A free-standing electroform representing the mould cavity was formed in the deposition. The product so formed was a reproduction of the net-shape of the mandrel exhibiting smooth surface finish. The electroforming was cast with an aluminum backing layer to complete its transformation into a split mould. The finished mould was comparable in appearance to the imported moulds in terms of appearance and reproduction of intricate surface patterns. The simplicity and low cost of this method significantly reduced the requirements for expensive instrumentation and highly skilled labour for mould production.