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The exact method of conducting a risk assessment may be specified by procurement specifications, industry standards, or government regulations. The design objective may be only compliance with the assessment requirement. However, in the process of performing a written risk assessment and classifying the risk into some severity level, it may result in a benefcial safety audit of the product. Where there is “residual risk,” the design of specific warnings and instructions may be required.
(Mechanical Engineering Handbook, Ed. Frank Kreith, p20-12)
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Compliance is a fairly straightforward concept of acting in accordance with established laws, regulations, protocols, standards, and specifi-cations. The critical issue is around the cost of noncompliance, which can be civil, criminal, reputational, financial, or market based. Corporate compliance typically includes compliance with external laws (enacted by legislative bodies) and regu-lations (created by regulatory bodies) and internal protocols such as policies and procedures.
(Governance, Risk, and Compliance Handbook: Technology, Finance,Enviromental, and International Guidance Best Practices, Anthony Tarantino,2008, pp. 21-22)
4)Die Geometry Angle [Group: Process Parameter]
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The die geometry directly influences material flow. and thereforei it affects the distribution of the effective strain and flow stress in the deformation zone. In forward extrusion, for a given reduction, a larger die angle increases the volume of metal undergoing shear deformation and results in an increase in shear deformation load Pds. On the other hand, the length of the die decreases, which results in a decrease in die friction load, Pdf. Consequently, for a given reduction and given friction conditions, there is an optimum die angle that minimizes the extrusion load.
(Altan T., Ngaile G., Shen G., Cold and Hot Forging:Fundamentals and Applications- Part1, pg.219, Kayra Ermutlu)
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Important factors in an extrusion die are die angle and orifice shape. Die angle. more precisely die half-angle, is shown as a in Figure 19.35(a). For low angles, surface area of the die is large, leading to increased friction at the die-billet interface. Higher friction results in larger ram force. On the other hand, a large die angle causes more turbulence in the metal flow during reduction, increasing the rant force required. Thus, the effect oldie angle on ram force is a II-shaped function. as in figure 19.35(b). An optimum die angle exists, as suggested by our hypothetical plot. The optimum angle depends on various factors (e.g., work material. billet temperature, ansl lubrication) and is therefore difficult to determine for a given extrusion job. Die designers rely on rules of thumb and judgment to decide the appropriate angle.
(Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, Mikell P. Groover, 2010, p. 426)
5)Centerless grinding [Group: Manufacturing Process]
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Centerless grinding is an alternative process for grinding external and internal cylindrical surfaces. As its name suggests, the workpiece is not held between centers. This results in a reduction in work handling time; hence, centerless grinding is often used for high-production work. The setup for external centerless grinding consists of two wheels: the grinding wheel and a regulating wheel. The workparts, which may be many individual short pieces or long rods (e.g., 3-4 m long), are supported by a rest blade and fed through between the two wheels. The grinding wheel does the cutting, rotating at surface speeds of 1200-1800m/min. The regulating wheel rotates at much lower speeds and is inclined at a slight angle I to control throughfeed of the work.
With internal centerless grinding, in place of the rest blade, two support rolls are used to maintain the position of the work. The regulating wheel is tilted at a small inclination angle to control the feed of the work past the grinding wheel. Because of the need to support the grinding wheel, throughfeed of the work as in external centerless grinding is not possible. Therefore this grinding operation cannot achieve the same high-production rates as in the external centerless process. Its advantage is that it is capable of providing very close concentricity between internal and external diameters on tubular part such as a roller bearing race.
(Mikell P. Groover; Fundamentals of Modern Manufacturing Materials, Processes, and Systems 3rd Edition; pg.608-609)
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Centerless grinding is an abrasive machining process by which small chips of material are re-moved front the external surface of a cylindrical metallic or nonmetallic workpiece. This pro-cess relies on the relative rotations of the grinding wheel and regulating wheel to rotate the workpiece. The process does not require chucking or locating the workpiece between centers for rotation.
Process Characteristics
• Requires no chucking or mounting of the workpiece
• Produces close tolerances and smooth surfaces • Is applicable for cylindrical, stepped, form-ed, and conical workpieces
• Is most efficient for through-feed production grinding operations
• Requires coolant
• Is primarily a finishing process
The workpiece is located between the regu-lating and grinding wheels and is supported by a rest blade. The grinding wheel drives the workpiece, and the regulating wheel controls workpiece rotation. The difference in rotating speed between the grinding wheel and the workpiece determines the material removal.
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