Unit Manufacturing Processes Issues and Opportunities in Research (1995) / Chapter Skim
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3 Mass-Change Processes
3 Mass-Change Processes
Pages 35-50
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From page 35... ...
However, most of the discussion in this report relates to material removal processes. 2 Care must be taken in using diamond tools for machining metals that are strong carbide farmers, such as steel, since the diamond tends to react with such materials if the interface temperature is above about 500 OF.
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From page 36... ...
Current material removal rates are attained by using relatively low feed rates, low depths of cut, and high cutting speeds. These conditions result in reduced chip loads and lower machining forces on tooling and ensure precision of part shape and geometry, particularly for advanced materials in which the present abrasive processes have limited removal rates.
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From page 37... ...
For example, grinding wheel sharpness greatly influences part surface finish. It demands careful control during production, since grinding wheels can dull arid cause surface integrity problems in the workpiece.3 Advanced grinding materials, such as cubic boron nitride, offer improved performance at an increase in wheel costs.
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From page 38... ...
Twenty-one such processes are described in Nontraditional Manufacturing Processes (Benedict, 1987~. Discussed below are laser machining processes,4 which are probably the most rapidly developing nontraditional techniques, and EDM and ECM, which are other widely used nontraditional processes.
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From page 39... ...
In laser drilling of ceramic materials, microcracks develop near the cutting front due to thermally induced stresses but may be controlled through proper selection of parameters. Laser cutting of two-dimensional shapes can be performed with either a continuous-wave beam or pulsed beam.
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From page 40... ...
These surface quality concerns of dross formation, kerf taper, and heat-affected zone formation also exist for laser cutting of ceramics, plastics, and composites. Laser grooving and scribing differ from laser cutting in that the laser beam does not penetrate through the entire thickness of the workpiece.
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From page 41... ...
, as well as link to process planning and factory level activities; · refined partfxturingfor restraint during the high loading encountered during machining with a high metal removal rate; high-capacity chip removal and flushing systems to handle the increased material removal rate; and . s See Chapter 13 for a discussion of these control methods.
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From page 42... ...
Part integrity and performance can be compromised by machining operations that produce microstructural damage or residual stress distributions in the finished part. Enhanced understanding ofthe process conditions related to the occurrence of such situations will lead to better process control methods to minimize integrity problems and enhance product performance.
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From page 43... ...
on finish, geometric tolerance, and surface integrity for a wide range of workpiece materials. In particular, identifying the chip-formation mechanisms in advanced materials, such as structural ceramics, metal matrix composites, and fiber-reinforced composites, is necessary to identify additional influences of the grinding process on material integrity and part performance.
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From page 44... ...
Dressing arid truing techniques of used grinding wheels can introduce variation to the grinding process. Aggressive truing produces a sharp wheel, which requires low grinding forces but produces poor surface finishes.
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From page 45... ...
Future directions for research include the use of new laser types for improved dimensional accuracy and tolerances, the ability to process engineering materials such as metals and ceramics, and the design of new machine tools to increase processing speed significantly. · Development of laser-assisted processes and machine tools.
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From page 46... ...
Effective development of laser processes requires a comprehensive understanding of the physics of beam-material interaction. Current models of laser processing do not account for the products of these complex interactions, including plasma formation, molten layer flow, chemical reaction with a gas jet, and transient thermal effects due to a pulsed beam.
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From page 47... ...
Component surface integrity, finish, and tolerances should be monitored to identify successful candidate electrode materials. Expanding current ECM process capability by the incorporation of pulsed current and the implementation of rotating tool electrodes.
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From page 48... ...
Process simulation based on this understanding and process control, using advanced in-process sensors, will be key technologies. Such processes include electrolyte jet machining, electrolyte abrasive jet machining,three-dimensionalcomputer-numeral-controlelectrochemical grinding, electrochemical discharge machining, electrochemical arc machining with rotating tools, and electrochemical spark machining.
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From page 49... ...
1973. Gasket laser cutting (review)
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