Billet Shearing
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Billet Shearing Bernd-Arno Behrens* Institute of Forming Technology and Machines (IFUM), Leibniz Universit€at Hannover (LUH), Garbsen, Germany
Synonyms Cropping; Shear cutting; Shearing
Definition Billet shearing is a chipless production process of raw parts for bulk metal-forming operations by cutting semifinished products as bars and wires into billets.
Process In the production of steel raw parts for bulk metal-forming operations, billet shearing is the most applied and productive method (Doege et al. 1986). The material lossless process is characterized by a good automation capacity, high production rates, short cycle times of 1 part per second or less, and high profitability in processing diameters up to 120 mm of steel material (Doege and Behrens 2007). Compared to sawing processes shearing is inferior with respect to the achievable billet quality but clearly superior concerning productivity (Oudin and Ravalard 1978). While the profile of the processed semifinished products is mostly circular or square shaped, shearing of multi-edged profiles or tubes is also possible. The shearing process is firmly established in processing steel materials. Shearing of nonferrous metals, like aluminum or copper, is possible in general but still challenging concerning achievable billet qualities (Behrens et al. 2013). Shearing processes were mainly carried out at room temperature. There are also strategies for shearing semifinished products heated up to forging temperatures.
Shearing Procedure In a shearing operation two shear blades move past each other, so that a billet is cut off a remaining bar. A shearing operation with a conventional tool adjustment is shown in Fig. 1. The bar is clamped between the bar holder and the stationary bar blade plus the bar holder abutment. The billet blade moves past the bar blade at a defined velocity and cuts the billet off the remaining bar section. The two blades were arranged with a defined shear clearance, which is one of the most important process parameters in billet shearing. The position of the billet blade and the respective shearing force progression during different stages of a shearing operation are shown in Fig. 2.
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CIRP Encyclopedia of Production Engineering DOI 10.1007/978-3-642-35950-7_16803-1 # CIRP 2014
Fig. 1 Principle shearing procedure (Scheuermann 1974)
Fig. 2 Stages of shearing operation and respective shearing force (Hartke 1987)
At the beginning of the shearing operation, the moving billet blade sets down on the bar, which causes elastic and plastic deformation of the bar material after compensating settling effects and bearing play of the machine (Fig. 2a). Afterwards, both shearing blades penetrate the bar material and create smooth cut surfaces on the front ends of the billet and bar (Fig. 2b). Plastic deformation occurs in an increasing area until the deformability of the material is exceeded which causes an increasing amount of pores in the area of wide plastic deformation. The continuous enlargement of pore siz
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