On the mechanics of sheet-metal bending with confined compressible dies

Abstract In recent years, the elastomer forming technique has found acceptance on the shop floor and is used increasingly as a pressure-transmitting medium for various metal-forming operations. This is due mainly to the introduction of a new range of materials and of new concepts in tooling, which have served to kindle industrial interest in the process. The purpose of this paper is to present a theoretical method whereby the spring-back factor in bending with compressible dies can be predicted from the basic properties of the sheet metal, the tool geometry and the frictional behaviour of the elastomer die. The theory is found to be in good agreement with experimental results. Various relevant parameters are examined within the framework of the present investigation. Experiments were conducted on a variety of sheet metals having widely different work-hardening characteristics. An approximate analysis for predicting the total bending load required is also presented. By use of the theory, it is possible for press and tool designers to develop a fairly simple set of tables or formulae to suit their particular application, making due allowance for the experimental parameters involved.