Nett-shape forming: state-of-the-art

“Nett-shape forming” is a generic reference to materials-processing technology which delivers the assemblable form of the component; this, however, does not imply a universal definition of the accuracy with which the process should deliver components since the accuracy with which components are required is a derivative of its function. Further, it is invariably the case that components are made up of both functional and non-functional surfaces/forms, the aim of nett-shape manufacturing technology being to achieve the accurate definition of the former. Several parameters influence the definition of surfaces/forms of components, one of which is the elasticity of tools used in the materials-conversion process; in the forming of components by plastic deformation of engineering materials, the significant parameters are thermal changes during the forming cycle, secondary yielding, elastic recovery of the component, elasticity of tooling and the forming machine, and the thermal contraction of the component after ejection from the forming tools. Obviously, the accuracy with which tools may be produced would feature in nett-shape manufacturing. Since the DICAVITY project referred exclusively to elasticity considerations in nett-forming by the plastic deformation of engineering materials, the expectation of industrial enterprises which manufacture nett-shape components is reviewed, the basis of this expectation being economic. Specific cases of the influence of elasticity on the accuracy of formed components are also reviewed since the subject may not be defined in universal terms which apply to all nett-forming processes.