GB1015833A - Improvements in or relating to forming devices and methods - Google Patents

Abstract

1,015,833. Stamping; necking. GENERAL DYNAMICS CORPORATION. Feb. 11, 1964 [Feb. 18, 1963], No. 5705/64. Heading B3Q. A method of forming a workpiece comprises applying at least one current pulse to a coil whereby the coil serves as a source of magnetomotive force, disposing the workpiece in a location spatially removed from the coil and guiding and concentrating the flux produced by the force to form the workpiece. A forming coil assembly comprises conductive means 12 split into sections defining a semi-circular cavity 14, an insulated coil 16 disposed about the tubular mouth of the cavity and connected by switch 30, e.g. an ignitron to a source of high amperage pulses. Conductive split dies 46, 48 of copper or beryllium copper, having counterbores and work apertures 18, 20 are bolted to the inner walls of the cavity of each section. To reduce the flux at the points nearest to the coil the asymmetries in the magnetic field at the annular spaces surrounding the workpiece 10 are reduced to zero by increasing the reluctance of the path of the magnetic field by extending the lower portion of the gap 60 between the dies in length by making the body of the dies eccentric relative to the apertures 18, 20, thereof. The section 24 is slit at 36 so that the section does not act as a shorted turn around the flux. In operation the workpiece 10 is insulated and supported in the section 24, the section 26 clamped thereto and the coil energized, the resulting flux being forced into the cavity 14 through the gap 60 to escape through the annular spaces about the workpiece 10, the increased magnetic pressure being greater than the yield strength of the material and effecting swaging thereof in two places. To swage only one area one of the dies is replaced with one having a larger and longer aperture which spreads the flux over a larger area. Flux leakages between the sections is reduced by insulating material 38 placed therebetween.