基于制造成本与质量损失的并行公差设计

研究产品质量损失与产品尺寸公差的关系 ,提出具有多个相关装配尺寸产品的质量损失 ,并把它表示成工序公差的函数。利用成本 -公差函数和产品的质量损失函数 ,给出基于产品最低制造成本和多个相关装配尺寸产品质量损失的并行公差设计优化模型 ,实现公差的并行设计 ,最后通过工程实例验证所提出的方法     

基于信噪比多元质量损失和制造成本的并行公差设计

质量损失是由于产品的功能波动所造成的,损失大小可由质量函数确定。在无量纲“标准化”多元质量损失函数的基础上,采用信噪比衡量各质量指标的波动,建立一般情形下的基于信噪比的多元质量损失模型,并把它表示成多个相关装配尺寸产品的工序公差函数。利用成本-公差函数和产品质量损失函数,给出基于产品最低制造成本和多个相关装配尺寸产品质量损失的并行公差设计优化模型,实现公差的并行设计,最后通过工程实例验证所提出的方法。     

The study of cost-tolerance model by incorporating process capability index into product lifecycle cost

To reduce the cost of manufacturing systems, many studies of cost minimization have been performed. Since tolerance design significantly affects the manufacturers’ cost, the optimization of cost-tolerance allocation will be an important issue for reducing these costs. Costs incurred in a product life-cycle include manufacturing cost and quality loss. However, most cost-tolerance optimization models frequently ignore the concept of quality loss and may not lead to an accurate analysis of the tolerance. Until now, process capability analysis has been the tool used to evaluate the adequacy of a production tool in meeting a quality target. Hence, the concept of process capability analysis should be included into the cost-tolerance optimization model. In this study, a flexible cost-tolerance optimization model will be constructed by integrating the process capability index into the product life-cycle cost function. The constructed cost-tolerance optimization model simultaneously considers the manufacturing cost of the components, the process capability of the manufacturing operations, and the quality loss of products. The decision-maker can apply the proposed cost-tolerance optimization model to determine a reasonable tolerance with minimum total cost including consideration of the process capability .     

Concurrent design process analysis and optimization for aluminum profile extrusion product development

Owing to intricate interdependency and information feedback among tasks, the concurrent design process probably cannot converge to the correct solution when there are wrong integration and improper interaction between activities. Therefore research on concurrent design process optimization is necessary. In the paper, a novel methodology is proposed to analyze and optimize the concurrent engineering process scientifically. Based on design structure matrix and graph theory, coupled task recognition and design task level plotting are performed for the concurrent design process of aluminum profile extrusion product development. Three factors are used to describe the coupling property of activity, namely sensitivity, complexity and affection factors, which provide the basis to analyze development process quantitatively. And an optimism algorithm is presented to define the initial iteration order of coupled task set. Finally a rational and efficient concurrent design process model is constructed, which can make aluminum profile product development faster, with lower costs and higher quality. The methodology proposed is also applicable to other concurrent engineering fields.     

Simultaneous process mean and process tolerance determination with asymmetrical loss function

Process design involves process mean and process tolerance determination. Process mean determination is finding the best settings for product quality, without affecting manufacturing cost. However, process tolerance determination is a manufacturing process selection which generally affects manufacturing cost and product quality. In this study, asymmetric quality loss is considered in measuring product quality, and tolerance cost is adopted in representing manufacturing cost. To reflect the combined effect of process mean and process tolerance completely, failure cost is added to the category of manufacturing cost. Then, based on the sum of these three costs, a simultaneous optimization of process mean and process tolerance is determined for process planning in the early stages of development.     

Process capability-based tolerance design to minimise manufacturing loss

In this paper we propose a nonlinear programming model, composed of a cumulative standard normal probability function and manufacturing cost, to design process tolerances. The tolerances are standardised in conjunction with the process capability of the machinery to minimise the total manufacturing loss that occurs owing to non-conforming parts. The proposed model has been applied to a workpiece manufactured through ten operations and solved by GINO (General INteractive Optimizer). A comparison between the results obtained by the proposed model and other methods indicates that robust process tolerances can be obtained by the new formulation.     

Dimensional and geometrical tolerance balancing in concurrent design

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.     

QFD based optimal process quality planning

Process quality planning is an important activity of quality assurance. It aims to determine manufacturing processes with appropriate process capability to produce product characteristics. Quality function deployment (QFD) is a powerful tool for quality planning, which starts with identifying customer needs and ends with determining process plans. However, most studies on quality planning by QFD are limited to the product planning stage. The approach to process quality planning through QFD has rarely been discussed. This paper adopts the optimal QFD model and further develops it for process quality planning. By incorporating an empirical capability function for process elements, a composite process capability index (CCp) is presented to reflect the overall process quality level. Constraints including technical feasibility, correlations among process elements, project budget and development time are considered. A case study of the numerical control (NC) machining process quality for a thin-walled complex window frame of airship is given to illustrate how the proposed model can be effectively applied by process quality team to determine the optimal target level of process elements concerning with resources utilization .     

Optimal tolerance design of assembly for minimum quality loss and manufacturing cost using metaheuristic algorithms

Tolerance allocation is a design tool for reducing overall cost of manufacturing while meeting target levels for quality. An important consideration in product design is the assignment of design and manufacturing tolerances to individual component dimensions so that the product can be produced economically and functions properly. The allocation of tolerances among the components of a mechanical assembly can significantly affect the resulting manufacturing costs. In this work, the tolerance allocation problem is formulated as a non-linear integer model by considering both the manufacturing cost of each component by alternate processes and the quality loss of assemblies so as to minimise the manufacturing cost. Metaheuristics techniques such as genetic algorithm and particle swarm optimisation are used to solve the model and obtain the global optimal solution for tolerance design. An example for illustrating the optimisation model and the solution procedure is provided. Results are compared with conventional technique and the performances are analysed.     

基于混合群集智能算法的并行公差优化设计

通过对并行公差优化设计的分析,将其视为一种混合变量组合优化问题.首先给出了并行公差优化设计的数学模型,然后将其映射为一类特殊的旅行商问题--顺序多路旅行商问题,从而降低了问题的求解难度.利用蚁群优化算法和粒子群优化算法,分别在求解离散和连续变量优化时的优势,提出了一种求解并行公差优化设计问题的混合群集智能算法.通过一个计算实例,将混合群集智能算法分别与遗传算法和模拟退火算法进行了比较,结果表明,前者具有更强的搜索能力和较高的效率.同时,混合群集智能算法也为求解一般意义的混合变量优化问题提供了借鉴和参考.     

Concurrent process/inspection planning for a customized manufacturing system based on genetic algorithm

Producing products with multiple quality characteristics is always one of the concerns for an advanced manufacturing system. To assure product quality, finite manufacturing resources (i.e., process workstations and inspection stations) could be available and employed. The manufacturing resource allocation problem then occurs, therefore, process planning and inspection planning should be performed. Both of these are traditionally regarded as individual tasks and conducted separately. Actually, these two tasks are related. Greater performance of an advanced manufacturing system can be achieved if process planning and inspection planning can be performed concurrently to manage the limited manufacturing resources. Since the product variety in batch production or job-shop production will be increased for satisfying the changing requirements of various customers, the specified tolerance of each quality characteristic will vary from time to time. Except for finite manufacturing resource constraints, the manufacturing capability, inspection capability, and tolerance specified by customer requirement are also considered for a customized manufacturing system in this research. Then, the unit cost model is constructed to represent the overall performance of an advanced manufacturing system by considering both internal and external costs. Process planning and inspection planning can then be concurrently solved by practically reflecting the customer requirements. Since determining the optimal manufacturing resource allocation plan seems to be impractical as the problem size becomes quite large, in this research, genetic algorithm is successfully applied with the realistic unit cost embedded. The performance of genetic algorithm is measured in comparison with the enumeration method that generates the optimal solution. The result shows that a near-optimal manufacturing resource allocation plan can be determined efficiently for meeting the changing requirement of customers as the problem size becomes quite large.     

基于协同优化的工艺设计与调度并行集成

分析了现有工艺设计与生产调度的集成方式,包括柔性工艺设计、动态工艺设计、基于仿真的工艺设计、及并行工艺设计,讨论了各集成方式的优缺点,在此基础之上提出了基于协同优化的工艺设计与生产调度并行集成模型,并讨论了该模型的核心技术,即基于免疫遗传算法的工艺及调度方案协同优化.     

基于资金时间价值的并行公差优化设计

总结了经典的成本公差模型,基于资金的时间价值原理对经典成本公差模型进行优化,提出了多种优化后的成本公差模型计算方法。利用优化后的成本公差模型,将制造成本、质量损失成本同时考虑到并行公差设计的目标函数中,实现了并行公差的优化设计。通过工程实例证明了所提方法的有效性,结果表明,优化后的成本公差模型更贴近实际,计算得到的总成本更为合理,有效地反应了物价上涨、通货膨胀、资金的时间价值等现实因素。     

基于DSM的产品设计过程建模研究

良好的过程模型是产品开发成功的关键。设计结构矩阵(DSM,DesignStructureMatrix)以任务信息依赖为中心,突出任务执行次序,为产品设计提供了一种有效的过程建模方法。这里在介绍设计任务间的依赖关系、DSM、设计迭代的基础上,以二级同轴减速器轴系模块的设计为例,详细描述了任务分解、设计结构矩阵的构建和优化、交互型活动解耦等过程,并给出了基于设计结构矩阵的过程模型。最后对设计结构矩阵提出了若干扩展意见。     

基于产品进化机理的纺织工艺并行设计系统

为了帮助纺织产业引入新的生产模式以应对经济全球化挑战,基于产品进化机理和产品全生命周期思想,提出纺织工艺智能化并行设计系统架构,研究了知识获取与进化、全息质量诊断和质量预测等关键技术,开发完成了一套适合纺织生产的并行工艺设计软件.通过初步的工程实践显示,该系统能综合纺织生产中的多种质量影响因素,通过质量预测实现工艺并行设计与优化,产品开发效率明显提高,行业应用前景可期.     

Determining the process tolerances based on the manufacturing process capability

An efficient approach has been developed for determining the process tolerances. This approach simplifies the traditional procedures of tolerance chart balancing and takes into account the capability of the process producing the workpiece. A mathematical model, based on the modified rooted tree chart, has been established. By using the model, the process tolerance can be obtained effectively and accurately without the effort of finding the additional tolerances. The work done previously by Ngoi is examined and several drawbacks are identified. A comparison between the results generated by the proposed method and by Ngoi is also made.Notation d _i additional tolerance to be added - f _j jth functional relationship betweent _i andd _i - m the number of blueprint specifications - n the number of operations - r _i the failure rate - estimated standard deviation ofith operation - T _i initial tolerance - TB _j blueprint tolerance - TP _i upper limit of process tolerance - _i process tolerance for operationi - x _i standardised process tolerance - w _i weighting value - Z the minimum value amongx _i      

基于多约束聚类的钢铁合同组批质量设计方法

针对面向订单生产的钢铁企业多品种小批晕的市场需求与大批量的生产组织特点,分析了面向组批生产计划的钢铁产品质量设计的特点以及生产计划的集成性,提出了基于带空间和容量约束的聚类分析的组批质量设计方法.该方法引入了质晕特性取值范围空间约束和设备容量约束,基于改进的微粒群算法对组批内不同品种合同质量特性差异的聚类分析,对组批质量特性综合值进行标准+α的优化设计.在满足设备容量要求的前提下尽可能减少质量的浪费,并且为组批生产计划的决策提供质量方面的量化依据,实现质量设计与生产计划之间的无缝集成.     

Concurrent tolerancing for design and manufacturing based on the present worth of quality loss

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.     

Product and process dimensioning and tolerancing techniques. A state-of-the-art review

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.