Centerless Grinding
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Centerless Grinding Barbara Linke Mechanical and Aerospace Engineering, University of California Davis, Davis, CA, USA
Synonyms Centerless grinding
Definition Centerless grinding is a cylindrical grinding process variant without fixing the workpiece along its axis between centers. In external centerless grinding, the workpiece lies between grinding wheel, workrest plate, and control wheel which regulates the speed of the workpiece. In internal centerless grinding, the workpiece lies between rolls or shoes and is driven by a control wheel or a faceplate.
Theory and Application Basic Principles In 1853, Schleicher developed the first centerless grinding machine for needle grinding. In 1917, Heim introduced workrest plate and control wheel, which improved the performance and enlarged the field of application (Hashimoto
et al. 2012). Since then, centerless grinding is highly applicable for large batch and mass production. No clamping steps and no center holes on the workpiece faces are required, which eliminates process steps, reduces time, and diminishes possible form errors (Marinescu et al. 2007). Workpiece loading can be easily automated. Moreover, the linear workpiece support through workrest plate and control wheel enables machining of thin components or machining with high removal rates and minimal deformations (Klocke 2009). Besides the advantages in process performance, machine setup in centerless grinding is complex and needs experienced and skilled workers for highest efficiency. The control wheel, also known as regulating wheel, is a conventional grinding wheel or a steel body with a cemented carbide coating. It slows the workpiece down during grinding through friction. Ideally tangential slipping is negligible, and workpiece speed, vw, depends only on control wheel speed, vcw, and control wheel tilt angle, acw (see Fig. 1). Centerless grinding commonly works in down grinding, i.e., grinding wheel speed and workpiece speed are same directional in the contact zone: vw ¼ vcw cos acw
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The workrest plate, also known as workrest blade, work blade, or workplate, needs to be highly wear-resistant and consists of tool steel or
# CIRP 2016 The International Academy for Production Engineering et al. (eds.), CIRP Encyclopedia of Production Engineering, DOI 10.1007/978-3-642-35950-7_6420-4
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Centerless Grinding
Centerless Grinding, Fig. 1 Centerless throughfeed grinding, after (Klocke 2009)
cast iron with hardened surfaces, cemented carbide inserts or coatings of PCD, or other hard material. Workrest plate angle is important for grinding force directions and process stability. A large workrest plate angle, b, results in comparatively high horizontal forces on the workrest plate which can lead to deflection or resonance vibrations (Meyer 2011). Small workrest plate angles are therefore preferred for large grinding forces, e.g., in the case of high material removal rates. For too small workrest plate angles, however, the normal force between control wheel and workpiece can get too small to controllably decele
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