GB1400081A - Shaping of hollow workpieces - Google Patents

Abstract

1400081 Deep drawing B AVITZUR 28 June 1972 30307/72 Heading B3Q Hollow work 40, Fig. 1a, is wall-ironed through a conical die 36 by a punch with a larger frictional face at the punch that at the die so that tensile stress in the ironed zone III is reduced or eliminated, the semi-cone angle α of the die not exceeding the value determined by the equation where E = elliptic integral; E(α#<SP>3</SP>/ 2 = elliptic integral of second order; m 1 =constant friction factor at the die; m 2 =constant friction factor at the punch. Adjoining cupping and wall ironing dies may be used, Fig. 1b (not shown), or a composite cupping and ironing die (60, Fig. 1c), of the work may be an open-ended tube (Fig. 1d) drawn through the die by a punch-mandrel. Aluminium or steel cans and shell bodies for ammunition may be formed with reductions of 85-90% in a single pass. A large portion or the entire drawing force P may be transmitted by the punch to the work in zone II so as to reduce or eliminate the transmission of force by the end of the punch. The desired "m" values may be obtained in part by limiting or omitting lubrication at the punch and more intensively lubricating the area passing through the die and/or by having a rougher surface on the punch than in the die. Strippers.-The punch may include an outer sleeve on a tapering surface which is expanded slightly on forward strokes, by liquid or an elastomer in the interior of the punch, and contracted on reversals. Lubrication.-A formula is included which relates the viscosity and thickness of a film of lubricant at the die to the velocity necessary for hydrodynamic lubrication.