Economic considerations in die-form compensation for nett-forming

Engineering components which operate in aggressive environments are invariably manufactured from high-strength, thermally resistant materials. Such materials are difficult to subject to machining, subsequent to the forming operation, with a view to achieving the assemblable form of the component. Further, in circumstances where the geometry of the component is complex, the option of machining the formed component to achieve the assemblable form would be prohibitively expensive. In such circumstances, the aim would be to achieve the nett-form of the functional surfaces of the component in the primary forming operation. A prime consideration in developing the nett-form of the component is the cost of iterative manufacturing trials required to achieve sufficient understanding of the die-form changes which are necessary for nett-forming of engineering components. It is conceivable that an industry operates with a sufficiently small family of components to enable the application of the derived die-compensation procedures for individual products across the entire family. A further consideration in attempting to nett-form the functional surfaces is the cost of fixturing a near-nett-form of the component to enable the removal of excess material. It is recognised that the smaller the amount of excess material, the greater the cost of fixturing the component for machining operations. Technical factors which influence the cost of designing tools for nett-forming refer to the knowledge required for performing physical modelling (PM) trials to derive the pressure contour on the nominal die-cavity, the tri-axial force transducer technology, the capacity for manufacturing tools of a larger scale to support PM experiments, knowledge of the elastic analysis of die-behaviour using finite element techniques and knowledge of die-form compensation algorithms. It would follow that most industries which expect to effect die-form compensation with a view to the nett-forming of engineering components would have to purchase some of the services from specialist laboratories. (C) 2001 Elsevier Science B.V. All rights reserved.