Lapping
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Lapping Eckart Uhlmann Fraunhofer Institut f€ ur Produktionsanlagen und Konstruktionstechnik, Berlin, Germany
Synonyms Free abrasive machining
machining;
Loose
abrasive
Definition Lapping is an abrasive machining process in which abrasive grains dispersed either in a paste or a fluid are applied to the moving surface of an opposing formed tool (the lap) so that the individual grains follow a disordered path (DIN 8589).
Theory and Application Introduction The manufacturing process “lapping” is used to produce functional surfaces of highest geometrically defined shape and having optimum conditions of surface quality. According to DIN 8589, lapping is part of the group of cutting with geometrically undefined cutting edges, and it is suitable for processing almost every material. Lapping is increasingly used to process
workpieces with sealing function, high geometrical precision, as well as workpieces which show characteristic crater surfaces (Spur and Stöferle 1980). In principle, the process could be divided into lapping without and lapping with a shaped counterpart. Lapping without shaped counterpart, for example, the lap blasting, inclines the optimization of the surface topography of the workpiece. Contrarily, lapping with shaped counterpart leads to a higher material removal rate. Workpiece and lapping tool, made up of shaped counterpart and lapping mixture, move toward each other in preferably disordered paths with many directional changes. The loose abrasive, which is distributed in the lapping mixture, is introduced into the contact zone between counterpart and workpiece stochastically and temporally. Due to the lapping pressure, caused by the shaped counterpart, material removal occurs whereby mostly undirected, so-called isotropy, surface textures arise. The advantages and disadvantages of this process are listed in Table 1. Concerning the cutting mechanism, there are differences between processing ductile, metallic materials and brittle hard materials such as glass or ceramics. In case of ductile materials, microplastic deformations of surfaces, hardening, and embrittlement as well as breakaways of particles rather appear. When processing brittle hard materials, micro cracks are induced and crack systems occur, which lead to breakaways of particles (Fig. 1). The structure of the workpiece surface
# CIRP 2016 The International Academy for Production Engineering et al. (eds.), CIRP Encyclopedia of Production Engineering, DOI 10.1007/978-3-642-35950-7_6431-5
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Lapping
Lapping, Table 1 Advantages and disadvantages of lapping Advantages Possibility of processing almost every material and part size Short changeover time as well as low costs for workpiece holders Processing several workpieces in one operation cycle of the machine Undirected process traces and isotropy surface structures
Disadvantages Disposal of the lapping sludge as special waste Comparatively low removal rates at high wastage of grain Necessity of final cleaning of workpieces Processability only of basic geometries of workpieces
Minor
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