GB843803A - Process for making molds and dies by electroforming - Google Patents

Abstract

843,803. Making moulds by electro-forming. LYTLE, J. K. July 8, 1958, No. 21878/58. Class 41. In a process for making moulds and dies by electro-forming, the pattern is electro-plated e.g. with copper, the copper shell is stripped off and again plated on the pattern face to form a second shell which is separated by stripping and is mounted in a metal casting framework, and again plated to rigidly connect the third shell thus formed to the framework. The second shell is then removed and the under-side of the third shell and frame is filled e.g. with metal, to reinforce the shell and thus form the final mould. Before each electro deposition the pattern or shell is thinly coated with wax and then bronze powder, graphite, or silver nitrate solution to render the surface conductive. Preferably the 1st and 2nd shells are of copper of 0À015 to 0À063 ins. thick, and the final shell of nickel 0À045 ins. thick. A number of such master moulds may be prepared. A suitable plating apparatus comprises a tank holding electrolyte 69 which is circulated by a pump 77 from a sump 78 to a manifold nozzle 80 electrolyte overflows through a filter 81 to the sump. The pattern to be plated 30 is contained in a wax-impregnated wooden basket 82, above which and resting in a muslin cloth 85, is a sheet copper anode 88 on which pieces of copper are placed e.g. finely divided scrap or shot, to increase the anode surface. The muslin prevents particles falling on to the pattern. The basket side-walls are held together by wooden dowelling giving free passage to the flow of electrolyte. The current is supplied from an A.C. rectifier 66 and bus-bars 63, and a timing device may be included in the circuit to plate for a pre-determined time, when current to rectifier, pump &c. is switched off.