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1、NONTRADITIONAL MACHINING PROCESSES 1.Mechanical energy processes 2.Electrochemical machining processes 3.Thermal energy processes 4.Chemical machining 5.Application considerations 2012 John Wiley C = specific removal rate which work material; l = current; and t time 2012 John Wiley & Sons, Inc. M P
2、Groover, Introduction to Manufacturing Processes ECM Applications Die sinking - irregular shapes and contours for forging dies, plastic molds, and other tools Multiple hole drilling - many holes can be drilled simultaneously with ECM Holes that are not round Rotating drill is not used in ECM Deburri
3、ng 2012 John Wiley & Sons, Inc. M P Groover, Introduction to Manufacturing Processes Adaptation of ECM to remove burrs or sharp corners on holes in metal parts produced by conventional throughhole drilling 2012 John Wiley & Sons, Inc. M P Groover, Introduction to Manufacturing Processes Electrochemi
4、cal Deburring (ECD) Special form of ECM in which grinding wheel with conductive bond material augments anodic dissolution of metal part surface 2012 John Wiley & Sons, Inc. M P Groover, Introduction to Manufacturing Processes Electrochemical Grinding (ECG) Applications and Advantages of ECG Applicat
5、ions: Sharpening of cemented carbide tools Grinding of surgical needles and other thin-wall tubes, and fragile parts Advantages: Deplating responsible for 95% of metal removal Because machining is mostly by electrochemical action, grinding wheel lasts much longer 2012 John Wiley & Sons, Inc. M P Gro
6、over, Introduction to Manufacturing Processes Thermal Energy Processes - Overview Very high local temperatures Material is removed by fusion or vaporization Physical and metallurgical damage to the new work surface In some cases, resulting finish is so poor that subsequent processing is required 201
7、2 John Wiley & Sons, Inc. M P Groover, Introduction to Manufacturing Processes Thermal Energy Processes Electric discharge machining Electric discharge wire cutting Electron beam machining Laser beam machining 2012 John Wiley & Sons, Inc. M P Groover, Introduction to Manufacturing Processes Electric
8、 Discharge Processes Metal removal by a series of discrete electrical discharges (sparks) causing localized temperatures high enough to melt or vaporize the metal Can be used only on electrically conducting work materials Two main processes: 1. Electric discharge machining 2. Wire electric discharge
9、 machining 2012 John Wiley & Sons, Inc. M P Groover, Introduction to Manufacturing Processes (a) Setup of process and (b) closeup view of gap, showing discharge and metal removal 2012 John Wiley & Sons, Inc. M P Groover, Introduction to Manufacturing Processes Electric Discharge Machining (EDM) EDM
10、Operation One of the most widely used nontraditional processes Shape of finished work surface produced by a shape of electrode tool Sparks occur across a small gap between tool and work Requires dielectric fluid, which creates a path for each discharge as fluid becomes ionized in the gap 2012 John W
11、iley & Sons, Inc. M P Groover, Introduction to Manufacturing Processes Work Materials in EDM Work materials must be electrically conducting Hardness and strength of work material are not factors in EDM Material removal rate depends on melting point of work material 2012 John Wiley & Sons, Inc. M P G
12、roover, Introduction to Manufacturing Processes EDM Applications Tooling for many mechanical processes: molds for plastic injection molding, extrusion dies, wire drawing dies, forging and heading dies, and sheetmetal stamping dies Production parts: delicate parts not rigid enough to withstand conven
13、tional cutting forces, hole drilling where hole axis is at an acute angle to surface, and machining of hard and exotic metals 2012 John Wiley & Sons, Inc. M P Groover, Introduction to Manufacturing Processes Special form of EDM that uses a small diameter wire as electrode to cut a narrow kerf in wor
14、k 2012 John Wiley & Sons, Inc. M P Groover, Introduction to Manufacturing Processes Wire EDM Operation of Wire EDM Work is fed slowly past wire along desired path Similar to a bandsaw operation CNC used for motion control While cutting, wire is continuously advanced between supply spool and takeup s
15、pool to maintain a constant diameter Dielectric required, using nozzles directed at toolwork interface or submerging workpart 2012 John Wiley & Sons, Inc. M P Groover, Introduction to Manufacturing Processes Definition of kerf and overcut in electric discharge wire cutting 2012 John Wiley & Sons, In
16、c. M P Groover, Introduction to Manufacturing Processes Wire EDM Wire EDM Applications Ideal for stamping die components Since kerf is so narrow, it is often possible to fabricate punch and die in a single cut Other tools and parts with intricate outline shapes, such as lathe form tools, extrusion dies, and flat templates 2012 John Wiley & Sons, Inc. M P Groover, Introduction to Manufacturing
