1、附 录附录A 英文文献On Welding-Installation Fixtures Design of Sheet StampingAbstract: Due to forming error and compliance of stamp-ing, the fixture design of sheet stamping assembly is different from the fixture design of common machining component. In recent years, the new principles and algorithms of fixture design of sheet stamping have been developed. In the paper, the concept of shape closure and force closure, screw theory were firstly introduced. Secondly, the deterministic locating and total fix
2、turing conditions were derived. Thirdly, an “N-2-1”locating principle and optimal design method for sheet stamping were described. Finally, the varia-tional method of robust fixture configuration design for 3-D workpieces was discussed. It can be predicated that the locating error can be reduced by this method.Key Words: Fixture; Sheet Stamping; Optimal Design; Ro-Bust DesignDue to its high productivity and material utilization, stamping is widely used in automobiles, aircraft, and various house
3、hold appliances manufacturing industry. The welding assembly of stamping becomes the key process of those products manufacturing, because welding fixture not only affects the performance of productivity, but also is directly related to the quality of the product. Statistics from the U.S. auto industry show that 72% of the body manufacturing errors are from the position error of welding fixture, so how to effectively reduce and control the positioning error is essential to improve the welding qua
4、lity. Sheet stamping assembly is significantly different from general machining, which not only meets the common requirements of precise positioning, but also gives full consideration to the easy deformation of sheet metal parts and stamping manufacturing characteristics of large deviations to adapt the products quality requirements. Over the last decade, many scholars working in the design of sheet stamping assembly have proposed design theories and methods of some new sheet stamping assembly,
5、and achieved remarkable results. At first, this paper introduces the research progress of fixture design, and then systematically elaborates the N-2-1 locating principle of fixture and the methods of optimal design and robust design, finally makes the conclusion.Manufacturing process (such as machining, welding, assembly and testing, etc.), the fixture is used in three-dimensional positioning and clamping device. The central problem of fixture design is to choose the optimal positioning points a
6、nd determine their best position to achieve the determine constraints positioning of work piece. If the work piece can be full restriction depending on the geometry of contact area will, we called it shape closed; If it also have to be fully bound with friction, we called it force closure. Generally, shape closure stresses dynamic analysis, but force closure focuses on the work piece of static stability. In 1885, Reuleaux first studied the mechanism of two-dimensional objects shape closure, and
7、proved that the formation of two-dimensional objects shape closure need four anchor points 2. After that Somoff proved the formation of three-dimensional objects shape closure need seven anchor points. In 1978, Lakshminarayana 3 further proved the formation of three-dimensional objects shape closure need at least seven anchor points in the perspective of static equilibrium using algebraic theory In 1988, Nguyen researched the mechanism of the machine hands force closure 4, and in 1989 Asada and
8、Kitagawa 5 researched the machine hands shape closure which used for convex and concave parts Generally six positioning principles requires clamping force to make work piece fully constrained, so usually it is force closure.Over the last decade, the spiral theory” widely used in fixture design, which describes the three-dimensional motion as translating along one direction and rotating around this axis. Originally spiral theory proposed by Ball 6, and developed by literature 7 and 8. According t
9、o spiral theory, literature 9 studied seven different types of finger contact, and suggested using finger-like shape to completely fix objects. Literature 10 using the extended spiral theory analyzed that rigid bodys full or part restriction exist frictional clamp. Literature 11 proposed mathematical theory of fixtures automatic layout for prismatic work pieces. Literature 12 discussed the ability of different fixtures position contact preventing work pieces from spiral movement, and proposed a restrict method of work piece movement for the fixture design. Using small spiral model literature 13 discussed the positioning errors of fixture impact work pieces geometry accuracy. Literature 14 researched surface contact and friction problems in the analysis of fixture restriction. Considering dynamic constraints, completely clamping, and tool path errors, literature 15 developed fixture design and analysis software. It can be said
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