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提出一种基于偏差传递的二维多工位装配夹具系统公差可行稳健设计方法。分析二维多工位装配尺寸偏差传递关系,建立由定位销和零件定位孔(槽)公差引起夹具定位偏差的偏差流状态空间模型。采用数论网格方法对定位销和零件定位孔(槽)公差进行采样,将得到的公差样本代入夹具定位偏差模型,求得夹具定位偏差样本空间,将夹具定位偏差作为状态空间模型的输入偏差,提出基于状态空间模型的二维多工位装配成功率计算方法。继而应用Taguchi正交试验直观分析方法,分析得到影响装配成功率的主要因素即夹具系统定位销副关键公差,运用回归正交组合设计拟合得到二维多工位装配成功率与夹具系统定位销副关键公差的响应面模型。以定位销、零件定位孔(槽)制造成本所构成的装配成本最小化为目标,二维多工位装配成功率为约束,建立二维多工位装配夹具系统定位销和零件定位孔(槽)公差可行稳健设计模型。以汽车车身地板二维三工位装配为例,建立其公差可行稳健设计模型并对该模型进行计算与分析,结果表明在装配成本增幅较小的情况下,采用稳健约束后可显著提高公差设计的可行稳健性。该方法为二维多工位装配夹具系统公差稳健设计提供了一种新途径。 相似文献
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提出一种计入销/孔(槽)公差面向产品质量的薄板装配工艺系统可靠性建模方法。综合考虑定位销公差、零件孔(槽)公差和定位销磨损量,构建薄板装配偏差统计数字特征模型;分析推导定位销过程磨损模型,探讨装配质量与工艺系统可靠性之间的关系,综合考虑定位销故障率和过程磨损量对工艺系统可靠性的影响,建立工艺系统结构可靠性模型和面向装配质量的可靠性模型,继而形成薄板装配工艺系统可靠性建模方法;以车身侧板装配为例,应用提出的建模方法分析车身侧板装配工艺系统可靠性。结果表明:定位销磨损、夹具布局和销/孔(槽)公差是影响车身侧板装配工艺系统可靠性的重要因素。该方法为薄板装配工艺系统可靠性研究提供了一种新的思路。 相似文献
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车身柔性虚拟装配偏差模拟分析 总被引:1,自引:1,他引:0
在轿车样车试制阶段,为了减少车身尺寸功能评估周期和降低评估成本,引入了车身的虚拟装配.针对功能评估中虚拟装配关键技术,包括装配过程夹具偏差、焊接处理及多工位装配等提出解决方案,实现了在考虑制造偏差、夹具偏差、连接偏差和多工位装配基础上的车身虚拟装配.通过案例论证了提出的虚拟装配方法的可行性.结果表明,该模型的准确度较高,适用于柔性薄板零件的装配偏差分析. 相似文献
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公差稳健优化设计的研究 总被引:2,自引:0,他引:2
为了解决产品加工成本与质量稳健的协调性问题,提出了一种新的公差稳健优化设计数学模型.依据公差稳健设计的思想,考虑产品质量的模糊性,以封闭环误差分布概率密度函数的方差和优质品概率之比为设计目标,建立了公差优化设计产品质量稳健性损失成本目标函数,并研究了优质品率和封闭环误差分布方差的确定方法.以加工成本和产品质量稳健性损失成本为目标,以模糊装配可靠度、可取公差极限范围为约束条件,建立了公差多目标优化数学模型.举例说明了文中所述的公差稳健优化设计方法的应用,采用遗传算法实现了公差的多目标优化设计.实例表明,该方法能够协调零件的加工成本和产品质量的稳健性损失成本,使优化指标的综合性能最佳. 相似文献
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《机电工程》2018,(11)
针对当前车身装配系统可靠性评估体系对偏差因素、可靠性要素间的相关性、过程衰退等方面的评价不完备的问题,对定位销定位偏差源的组成结构、结合来料零件定位孔、槽的尺寸质量和定位销本身定位能力水平的定位销磨损模型进行了研究。分析了系统要素可靠性间的相关性,根据Copula连接函数理论建立了相关性模型;对产品上所有关键产品特性(KPC)点在整体产品尺寸质量可靠性中所占权重进行了分配并建模,基于来料-产出流思想对串并联混合系统进行了简化,最终提出了一种综合考虑各偏差源动态输入的动态多工位车身串并联混合装配系统可靠性评估模型;利用此模型对车身某分总成装配系统进行了制造成本优化分配,并且给出了一套动周期预防性维护策略。研究结果表明:该可靠性模型精确度较高,适用于指导生产制造成本的优化和建立预防性维护策略。 相似文献
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提出了一种基于数论网格法的三维单工序装配成功率计算方法。首先,基于三维单工序装配偏差模型,考虑销-孔/槽副任意布局下夹具定位偏差对装配偏差的影响,建立销-孔/槽副任意布局的三维单工序装配偏差模型。然后,阐述了数论网格采样的基本原理,运用数论网格法对零件偏差采样,基于所建立的销-孔/槽副任意布局下的三维单工序装配偏差模型,建立三维单工序装配成功率模型。最后,针对三维薄板零件装配实例,采用所建立的装配成功率模型计算其装配成功率,并采用3DCS对所建立的装配成功率模型进行仿真验证,仿真结果与理论模型计算结果相比,装配成功率相对误差为0.21%,表明了该方法的有效性。 相似文献
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Product and process dimensioning and tolerancing techniques. A state-of-the-art review 总被引:2,自引:0,他引:2
B. K. A. Ngoi C. T. Ong 《The International Journal of Advanced Manufacturing Technology》1998,14(12):910-917
Dimensioning and tolerancing are important engineering processes in the different phases of a product development cycle. The two main phases in a product cycle where dimensioning and tolerancing techniques are extensively employed are in the areas of product design and process planning. Tolerance and dimension assignment in both product design and process planning has an equally important role in keeping the production cost down and, hence, requires equal attention as far as research into these areas are concerned. Another important motivating factor for research is that manual dimension and tolerance assignment is often tedious, time-consuming and requires a considerable amount of skill and experience on the part of the engineer, resulting in inconsistencies and errors. Extensive research, in the area of dimensioning and tolerancing in both product design and process planning, has been carried out with the advancement in computers since the 1970s. The purpose of this paper is to review the state-of-the-art dimensioning and tolerancing techniques in both product design and process planning and explore the opportunities for future research in these areas. 相似文献
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Meifa Huang Yanru Zhong 《The International Journal of Advanced Manufacturing Technology》2008,35(7-8):723-735
In conventional design, tolerancing is divided into two separated sequential stages, i.e., product tolerancing and process
tolerancing. In product tolerancing stage, the assembly functional tolerances are allocated to BP component tolerances. In
the process tolerancing stage, the obtained BP tolerances are further allocated to the process tolerances in terms of the
given process planning. As a result, tolerance design often results in conflict and redesign. An optimal design methodology
for both dimensional and geometrical tolerances (DGTs) is presented and validated in a concurrent design environment. We directly
allocate the required functional assembly DGTs to the pertinent process DGTs by using the given process planning of the related
components. Geometrical tolerances are treated as the equivalent bilateral dimensional tolerances or the additional tolerance
constraints according to their functional roles and engineering semantics in manufacturing. When the process sequences of
the related components have been determined in the assembly structure design stage, we formulate the concurrent tolerance
chains to express the relations between the assembly DGTs and the related component process DGTs by using the integrated tolerance
charts. Concurrent tolerancing which simultaneously optimizes the process tolerance based on the constraints of concurrent
DGTs and the process accuracy is implemented by a linear programming approach. In the optimization model the objective is
to maximize the total weight process DGTs while weight factor is used to evaluate the different manufacturing costs between
different means of manufacturing operations corresponding to the same tolerance value. Economical tolerance bounds of related
operations are given as constraints. Finally, an example is included to demonstrate the proposed methodology. 相似文献
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X. Lai J. K. Gershenson 《The International Journal of Advanced Manufacturing Technology》2008,37(7-8):803-827
Researchers have expanded the definition of product modularity from function-based modularity to life-cycle process-based
modularity, and developed a measure of product modularity and validated a corresponding modular product design method. However,
a correct modularity measure and modular design method are not enough to realize modular product design. How the measure and
design method are used, especially the role of product representation, is an important aspect of modular design and imperative
for realizing the promised cost savings of modularity. In this paper, we develop a representation that includes similarity
and dependency for assembly modularity. The similarity representation is based on assembly cost factors including tool changes
and fixture changes. The process-based design dependency representation is based on design features that impact the assembly
process (faces, fasteners, assembly interference, etc.). This representation captures the cost benefits of modularity and
can be extended to other life-cycle processes. A set of products is used to show the application of this representation in
association with a modularity measure and modular design method. 相似文献
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In multi-station assembly systems, common for mass-customization manufacturing strategies, the product being assembled is held in a fixture attached to a pallet, and the pallet is conveyed between workstations. In high-precision assembly systems, variation in the position of the pallet is one of the largest sources of variation within the error budget, reducing quality and yields. Conventional approaches to locating pallets use pins and bushings, and a method for predicting their repeatability is presented. This paper also presents an exact constraint approach using a split-groove kinematic coupling, which reduces variation in pallet location by an order of magnitude. 相似文献
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Concurrent tolerancing for design and manufacturing based on the present worth of quality loss 总被引:1,自引:1,他引:0
Heping Peng 《The International Journal of Advanced Manufacturing Technology》2012,59(9-12):929-937
The quality loss function developed by Taguchi provides a monetary measure for the deviation of the product quality characteristic from the target value. Product use causes degradation on its quality characteristic, and since such a deviation can be changing over time, so can the quality loss. However, most studies on concurrent tolerancing theory do not consider the quality loss caused by the degradation. In this paper, the present worth of expected quality loss expressed as the function of the pertinent process tolerances in a concurrent tolerancing environment is derived to capture the quality loss due to product degradation over time as a continuous cash flow function under continuous compounding. A new tolerance optimization model, which is to minimize the summation of manufacturing cost and the present worth of expected quality loss, is established to realize the concurrent tolerance allocation for products with multiple quality characteristics. An example of the bevel gear assembly involving concurrent allocation of design and process tolerances is given, demonstrating that the proposed model is feasible in practice. 相似文献