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Unformatted text preview: 129 7 ABRASIVE AND NON-TRADITIONAL PROCESSES CHAPTER CONTENTS 7.1 Grinding Defnitions Cutting conditions in grinding Wheel wear SurFace fnish and eFFects oF cutting temperature Grinding wheel Grinding operations 7.2 ¡inishing Processes Introduction ¡inishing processes 7.3 Non-traditional Processes Traditional vs. non-traditional processes Ultrasonic machining Jet macining Electric discharge machining Lasers and other beams 7.1 GRINDING Defnitions Abrasive machining is a material removal process that involves the use oF abrasive cutting tools. There are three principle types oF abrasive cutting tools according to the degree to which abrasive grains are constrained, ¡ bonded abrasive tools : abrasive grains are closely packed into diFFerent shapes, the most common is the abrasive wheel . Grains are held together by bonding material. Abrasive machining process that use bonded abrasives include grinding , honing , superfnishing; ¢ coated abrasive tools : abrasive grains are glued onto a ¢exible cloth, paper or resin backing. Coated abrasives are available in sheets, rolls, endless belts. Processes include abrasive belt grinding , abrasive wire cutting ; £ Free abrasives : abrasive grains are not bonded or glued. Instead, they are introduced either in oil-based ¢uids ( lapping , ultrasonic machining ), or in water ( abrasive water jet cutting ) or air ( abrasive jet machining ), or contained in a semisoFt binder ( buFfng ). Regardless the Form oF the abrasive tool and machining operation considered, all abrasive operations can be considered as material removal processes with geometrically undefned cutting edges , a concept illustrated in the fgure: The concept oF undefned cutting edge in abrasive machining. Grinding 130 Valery Marinov, Manufacturing Technology Abrasive machining can be likened to the other machining operations with multipoint cutting tools. Each abrasive grain acts like a small single cutting tool with undefned geometry but usually with high negative rake angle. Abrasive machining involves a number oF operations, used to achieve ultimate dimensional precision and surFace fnish. ¡rom the principal abrasive operations, grinding is covered in the present section, and some other operations are discussed in the next two sections. Grinding is a material removal process in which abrasive particles arc contained in a bonded grinding wheel that operates at very high surFace speeds. The grinding wheel is usually disk shaped and is precisely balanced For high rotational speeds. Cutting conditions in grinding The geometry oF grinding is shown in the fgure: The geometry oF surFace grinding showing the cutting conditions. The cutting velocity V in grinding is very high. It is related to the rotational speed oF the wheel by V = π DN where d is the wheel diameter, and N is the rotational speed oF the grinding wheel....
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This note was uploaded on 11/10/2010 for the course AEROSPACE AE 1202 taught by Professor Dr.adib during the Spring '10 term at Sharif University of Technology.
- Spring '10