生长型设计中的功能公差设计理论

在产品结构设计自动化技术基础上,研究生长型设计中公差进化设计的策略与原则,提出将产品功能要求转化成零部件之间的几何约束关系,并最终表达为对功能尺寸约束的功能公差设计理论。建立成本—公差敏感函数的数学模型,将产品设计、制造、使用以及技术折旧成本作为公差分配的控制约束,并在其中引入产品使用磨损模型,以经济学中的贴现率来表征技术折旧成本,以成本最低为目标函数,以合理的工艺能力指数、装配功能、装配质量作为约束条件,实现基于功能与成本的面向产品全生命周期的尺寸公差分配。最后,设计实例说明所提出的功能公差设计理论能够在生长型设计中成功应用。     

Tolerance evolutionary model and algorithm in product growth design

To guarantee the successful transformation from product functional requirement to geometry constraints and finally to dimension constraints between components in a product, an evolutionary tolerance design strategy is proposed on the basis of automation technology in product structure design. In the first part of this paper, the theory of the growth design and the process of tolerance evolutionary design are introduced. Following the evolution of product structure, product tolerance grows from its initial state, defined by accuracy requirements, to its final state, defined as dimension tolerance and geometric tolerance. In this growing process, the basic units in the product growth design, known as functional surfaces and their nominal features, are used as evolutionary carriers. With the help of these basic units, the method for the construction of a two-layer correlation network is proposed. In the second part, the tolerance assertions to assist tolerance evolutionary design are given, based on which the basic process for an evolutionary design of dimensions chain and geometric tolerance are presented. In order to optimize the allocation of the dimension tolerance, a mathematical model is developed in which a correlated sensitivity function between the cost and the tolerance is created. In the model, the design cost, the manufacturing cost, the usage cost, and the depreciation cost of the product are used as constraints to the tolerance allocation. Considering these costs, a multifactor cost function to express quality loss of the product is developed and is applied into the model. The minimum cost is used as the objective function, and the depreciation cost in the objective function is expressed by the discount rate—terminology in economics. The aim was to achieve a final and ideal balance around assembly, manufacturing, and usage through the control of product precision. In the last part, the successful usage of the proposed tolerance evolutionary strategy in the incremental growth product design is demonstrated through a design example.     

基于广义装配原理的产品生长型设计

通过研究生物生长与产品设计之间的相似性,提出了基于广义装配原理的生长型设计过程,研究了广义装配原理的三个理论构成。首先,在产品生长阶段,为实现生长过程中的自然选择,提出了以复杂度理论为控制因素的设计推理策略;其次,提出了功能公差设计理论,通过加工成本以及基于多因素的模糊质量损失成本体现广义装配成本,在确保产品功能的同时,以较低的装配与制造成本为公差的分配策略;在产品进化阶段,为保证产品良好的装配性能,采用了虚实结合设计技术。将以装配质量因素为核心的产品复杂度、精度以及制造、装配成本等众多设计因素并行集成于生长型设计过程中,实现了以全生命周期装配质量保障为核心的产品生长型设计。     

公差稳健优化设计的研究

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.     

一种设计和工序公差计算机辅助并行设计方法的研究

提出一种计算机辅助设计公差和工序公差并行设计的数学模型，以成本公差函数作为目标函数，以装配功能要求、加工方法、加工余量、工序制造公差范围作为约束条件，并用蒙特卡洛法模拟尺寸装配、模拟退火算法用于优化求解，实现了设计公差和工序公差并行设计，缩短了设计周期。     

生长型设计中公差进化设计方法研究

为实现生长型设计中尺寸链及形位公差项目的自动生成,在产品结构设计自动化技术基础上,研究生长型设计中公差进化设计的策略与原则。指出生长型设计中紧随结构的自顶向下、不断进化,公差进化设计模型也呈现为一种层次式结构;同时由于功能表面及其名义特征所具有的承载功能及几何信息的特点,可作为公差进化演绎的单元载体;在此基础上建立公差进化设计的基本过程模型。提出产品结构进化设计中,构建基于功能表面的装配网络以及基于名义特征的约束网络的双层装配约束网络的基本方法,给出辅助公差进化设计的公差断言;在此基础上,给出基于双层装配约束网络及公差断言的尺寸链及形位公差进化设计的基本过程。以活塞精镗销孔夹具的公差设计为例,说明所提出的公差进化设计方法在生长型设计中的成功应用。     

尺寸公差与形位公差混合优化分配

为解决尺寸公差与形位公差混合优化分配问题,提出了一种公差优化分配方法.根据成本-公差函数和尺寸公差与形位公差的关系,建立了以最小制造总成本为目标的非线性公差混合优化分配模型.该模型的约束包括装配尺寸链的功能要求和加工能力.求解该模型能同时得到优化的尺寸公差和形位公差.最后,分别用公差混合优化分配法和传统方法对一个实例进行公差分配,结果表明所提方法比传统方法更优越.     

并行公差设计与工艺路线技术经济评价方法

在界定并行公差设计概念的基础上,首次系统地给出了以总加工成本最小为目标函数、以装配功能要求、加工方法选择、加工余量公差、经济加工精度范围等为约束条件的优化数学模型,该模型能够对工艺路线进行一定程度地定量技术经济指标评价;论证了该模型是个非凸规划问题;最后给出了并行公差设计的一个仿真实例.     

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.     

Minimum-Loss Assembly Tolerance Allocation by Considering Product Degradation and Time Value of Money

In the optimisation of tolerance allocation for a mechanical assembly, much work has concentrated on the minimum cost– tolerance allocation without considering the quality of the final assembly. Cheng and Maghsoodloo combined the cost– tolerance function and quality loss function, to determine the optimal tolerances for individual components, so that the total assembly cost (including both tolerance cost and quality loss) might be minimised. The objective of this paper is to propose a model for optimal tolerance allocation by considering both tolerance cost and the present worth of quality loss such that the total assembly cost/loss is minimised. The proposed model takes into account the time value of money for quality loss and product degradation over time, and includes two new parameters: the planning horizon and the product user’s discount rate. From the result of this study, a longer planning horizon results in an increase in both tolerance cost and quality loss; however, a larger value of discount rate yields a decrease in both tolerance cost and quality loss.     

基于工序加工能力的并行公差优化设计

提出一种基于工序加工能力的并行工序公差优化设计方法。在产品的初步结构设计阶段，通过相配零件的加工工艺规划把装配功能公差表示为零件的工序公差，建立以加权制造总成本最小为目标，以并行公差链、标准化的工序公差系数、机床最大经济极限公差为约束的非线性并行公差优化设计模型，求解该模型得到最佳的工序公差。最后给出了并行公差优化设计的一个工程实例，结果表明，所提的方法具有比传统串行等精度方法更合理、工序公差数值更大的优点。     

基于多重相关特征质量损失函数的公差优化设计

在重点推导了具有多重相关特征产品的质量损失与尺寸公差的函数关系的基础上,提出了多重相关特征产品的公差优化设计方法,建立了基于制造成本一质量损失的公差优化设计的综合模型,建立该模型的目的是寻求制造成本和质量损失之间的平衡,实现旨在提高产品质量和降低成本的公差优化设计。应用实例验证了所提出方法的有效性。     

产品概念结构设计中的公差进化模型和算法

在产品概念结构设计自动化技术基础上，研究了产品公差设计过程及其特点，提出了四层产品公差结构模型。应用局部公差分配模型与公差设计过程建立了全局公差优化理论模型，提出了以保证产品总精度需求为目标的概念结构设计阶段公差的同步设计算法。实例表明，提出的公差进化模型和算法，避免了人为建模工作，大大提高了公差设计效率和质量，为快速完成多方案的并行设计奠定了基础。     

Tolerance design of mechanical assembly using NSGA II and finite element analysis

The technological and financial limitations in the manufacturing process are the reason for non-achievability of nominal dimension. Therefore, tolerance allocation is of significant importance for assembly. Conventional tolerance allocation methods are limited by an assumption that all parts are rigid. Every mechanical assembly consists of at least one or more flexible parts which undergo significant deformation due to inertia effect. Finite element analysis is used to determine the deformation of components in an assembly. Therefore, integration of statistical tolerance design with finite element analysis will guarantee that the optimal tolerance values of various components of the assembly obtained as end product of the tolerance design will remain within tolerance variation. Then the product can function as intended under a wide range of operating conditions for the duration of its life. In this paper, tolerance design of a piston cylinder assembly is done to demonstrate the proposed methodology.     

虚拟装配中装配公差的检验分析

装配性能分析的主要内容之一是装配公差的分析。阐述了虚拟装配系统中公差并行设计的过程，建立了零件尺寸公差与装配体配合公差的模型，利用约束关系图表达了零件尺寸信息与装配体配合关系信息，利用尺寸公差模型与约束关系图通过有关算法生成装配尺寸链。介绍了公差分析的两种方法，并以孔轴的径向配合为例，利用极值法进行装配公差检验，针对检验时出现的各种不合理结果进行了详细分析，并提出了设计公差相应的修改意见。     

概念设计中的三维公差与结构同步设计研究

为支持产品概念设计的多结构方案优选和成本优化,提出了在概念设计阶段进行公差设计的思想。给出了指导概念结构设计的生长型设计过程模型,应用旋量对功能表面间的几何约束进行分析;在公差表示模型的基础上,自动选择基准框架,生成三维公差链并进行设计计算;开发了相应的软件系统支持设计过程。应用实例表明,公差与结构同步设计能有效地减少设计方案的反复修改,提高了设计的效率和质量,对CAD/CAM集成具有重要意义。     

结构与公差同步设计的产品概念设计优化

为保证概念结构设计的可行性与经济性,提出了将公差设计研究提前到概念设计阶段的思想,并研究了其中的关键技术。首先基于一种结构不断生长的独特设计思路,建立了结构与公差同步设计的过程模型和相应的公差表示模型;然后研究了在设计过程中自动生成局部尺寸链和全局尺寸链的方法,给出了公差同步设计,并根据设计结果提出了概念设计优化的整体框架,实现了基于公差的概念设计优化;最后以活塞夹具设计为例,验证了本方法的有效性。     

并行和协同设计中的变动约束管理方法研究

设计和制造企业多试图同时增加产品的复杂度、减少设计周期、降低产品成本和改善质量。减少成本而又不破坏产品质量的一个很好的使能工具是控制设计和制造过程的变动。本文从并行工程和协同设计的角度出发 ,阐述了产品开发过程中的变动及其管理 ;研究了面向装配、制造和产品性能的变动约束网络的构建 ;给出了面向并行工程和协同设计的变动约束管理的方法 ,以有效地支持参数与公差设计 ;并通过实例分析给予了验证     

A tolerancing optimisation method for product design

Although extensive research has been carried out in the area of tolerancing techniques for product design, concurrent engineering is still very seldom used in this context. This paper introduces a unique tolerancing method which applies the concept of concurrent engineering. The proposed method essentially allocates the required functional assembly tolerances to the component tolerances by formulating the tolerancing problem into a mathematical model and solving the model using a linear programming approach. The component tolerances are first represented in terms of the process tolerances, assigned by process planners at an early stage of the product design. The objective function of the mathematical model, which is to maximise the residual tolerances of the processes, is then established and the constraints formulated based on the assembly requirements and process constraints. The model is subsequently solved using a linear programming approach. Finally, the proposed method is tested on a practical example.     

基于三维偏差分析技术的尺寸公差设计应用

整车开发过程中需要完成成百上千个零件的公差设计,为达到设定的质量目标,高效准确的偏差分析控制成为公差设计中的重要环节。本文介绍了三维偏差分析采用的算法、虚拟样车偏差分析模型建立开发流程、尺寸项目开发中的公差分配设计方法;并结合国内自主开发项目多个实际案例,列举了关键区域三维偏差分析理论计算数值与实际生产数据置信度对比;证明可以通过建立了虚拟工程样车系统,完成车身装配的匹配优化、公差设计,可以减少为实现尺寸匹配而进行多轮物理螺钉车制造活动,节约项目开发时间和成本。