Metal Spinning
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Metal Spinning Julian Allwood1 and James A. Polyblank2 1 Department of Engineering, University of Cambridge, Cambridge, UK 2 Department of Engineering, Cambridge University, Cambridge, UK
Definition The term “metal spinning” describes several distinct processes used to form circular sheets of metal into axisymmetric shells. A circular sheet metal blank is centered relative to a shaped mandrel and held between the mandrel and a tailstock. The sheet, mandrel, and tailstock are then rotated about their shared axis on a spinning lathe, while a working tool (generally a roller) gradually works the sheet toward the mandrel, until it conforms.
Theory and Applications Spinning is used to produce axisymmetric shell parts with diameters up to 10 m and with workpieces up to 25 mm in thickness. Almost all parts made by spinning could be made by other processes, including deep drawing, but the advantages of spinning are:
• Only simple tooling is required – the mandrel can be cut from wood or metal on a lathe, so it is cheap. • The very local deformation caused by the working tool means that forming forces are low, and so large and expensive presses are not needed, as would be the case in deep drawing or stamping, for example. • The process can achieve high forming limits, if well controlled. • The process is very nearly a true net-shape process – with little trimming required after process completion. Against this, spinning is a relatively slow process (at least compared with stamping or deep drawing), so it is generally used for low-volume production only. In addition, the mechanics of spinning are not well understood, so the process is usually controlled by skilled craft workers who have an intuitive knowledge of the mechanics. Understanding the mechanics of spinning has been the focus of a great deal of research, which was recently reviewed by Music et al. (2010). They highlighted the difference in mechanics between two distinct forms of spinning in common use: “conventional spinning” (Fig. 1a), in which the outer diameter of the blank reduces during processing and the workpiece is not thinned (although zero thinning is very difficult to achieve in practice) and “shear spinning” (Fig. 1b) in which the outer diameter of the
# CIRP 2016 The International Academy for Production Engineering et al. (eds.), CIRP Encyclopedia of Production Engineering, DOI 10.1007/978-3-642-35950-7_16696-3
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Metal Spinning
workpiece is not reduced and so the sheet is thinned. The control of the outer diameter and the thickness in shear spinning can be achieved by using a blank holder to prevent diameter reduction or by squeezing the material between the tool and the mandrel in order to achieve the thickness dictated by the sine rule. However, in conventional spinning, constant thickness must be achieved by careful design of the tool path: conventional spinning involved many passes of the tool across the workpiece, where shear spinning often occurs in just one pass. The mechanics of the two processes are quite distinct. In conventional spinni
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