Flexible forming tool concept for producing crankshafts

Abstract

Forging, casting and machining compete on quality and price for the production of crankshafts. Forging and casting are commonly utilized for mass production because the capital investment in equipment and tooling are very high. Machining is employed only in case of small production batches of high quality crankshafts made from materials that are normally difficult to forge or cast because it is time and energy intensive, generates a lot of waste and is generally more costly than forging and casting. As a result of this, conventional manufacturing routes for crankshafts are not suitable for flexible small to medium-batch production and, therefore, are not appropriate for the growing agile manufacturing trends requiring very short life-cycles and very short development and production lead times. This paper is concerned with these issues and is focused on the development of an innovative forming tool concept for producing small to medium-batches of cost competitive crankshafts. The proposed tool concept combines knowledge on buckling of solid rods under compression with flexible construction solutions based on modular dies to allow crankshaft production to change output rapidly. Single cylinder to multi cylinder crankshafts including multiple main bearing journals, crankpins and crank webs can be easily produced by fastening or removing appropriate die modules in the overall tool set. The presentation is illustrated with test cases obtained from finite element modelling and experimentation with a laboratory prototype tool conceived to operate exclusively with lightweight materials exhibiting high ductility in cold forming.