CONCURRENT PRODUCT PORTFOLIO PLANNING AND MIXED PRODUCT ASSEMBLY LINE BALANCING

Reconfigurable products and manufacturing systems have enabled manufacturers to provide "cost effective" variety to the market. In spite of these new technologies, the expense of manufacturing makes it infeasible to supply all the possible variants to the market for some industries. Therefore, the determination of the right number of product variants to offer in the product portfolios becomes an important consideration. The product portfolio planning problem had been independently well studied from marketing and engineering perspectives. However, advantages can be gained from using a concurrent marketing and engineering approach. Concurrent product development strategies specifically for reconfigurable products and manufacturing systems can allow manufacturers to select best product portfolios from marketing, product design and manufacturing perspectives. A methodology for the concurrent design of a product portfolio and assembly system is presented. The objective of the concurrent product portfolio planning and assembly system design problem is to obtain the product variants that will make up the product portfolio such that oversupply of optional modules is minimized and the assembly line efficiency is maximized. Explicit design of the assembly system is obtained during the solution of the problem. It is assumed that the demand for optional modules and the assembly times for these modules are known a priori. A genetic algorithm is used in the solution of the problem. The basic premise of this methodology is that the selected product portfolio has a significant impact on the solution of the assembly line balancing problem. An example is used to validate this hypothesis. The example is then further developed to demonstrate how the methodology can be used to obtain the optimal product portfolio. This approach is intended for use by manufacturers during the early design stages of product family design.     

Assessing the structural complexity of manufacturing systems configurations

Modern manufacturing systems are increasingly required to be flexible and adaptable to changing market demands, which adds to their structural and operational complexity. One of the major challenges at the early design stages is to select a manufacturing system configuration that both satisfies the production functional requirements and is easy to operate and manage. A new metric for assessing the structural complexity of manufacturing system configurations is presented in this paper. The proposed complexity metric incorporates the quantity of information using an entropy approach. It accounts for the complexity inherent in the various modules in the manufacturing system through the use of an index derived from a newly developed manufacturing systems classification code. The code captures the effect of various component types and technologies used in a manufacturing system on the system’s structural complexity. The presented metric would be helpful in selecting the least complex manufacturing system configuration that meets the requirements. An engine cylinder head production system is used to illustrate the application of the proposed methodology in comparing feasible but different manufacturing system configurations capable of producing the cylinder head based on their structurally inherent complexity.     

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。     

Developing an integrated framework for feature-based early manufacturing cost estimation

The major objective of concurrent engineering is to consider the related downstream manufacturing during the design stage. Estimating manufacturing cost during the early design stage is one area that has been given little attention by researchers. However, if the product manufacturing cost can be estimated during the design stage, designers can modify a design to achieve proper performance as well as a reasonable cost at an early stage of the product development process.Basically, manufacturing cost is determined by shape complexity, product precision and tooling process. That is, if these data can be obtained and considered during the design stage, estimating manufacturing cost during the early product development stage will become a feasible task.In this research, a framework for estimating the manufacturing cost in terms of a feature-based approach is proposed. This system tends to estimate the manufacturing cost of a design according to the shapes and precision of its features. The objective of this research is to provide a tool to assist a designer, who has little knowledge about the manufacturing process, to estimate the fabrication cost of a design during its conceptual stage, in order to reduce unnecessary costs in the downstream process.     

Application of Virtual Assembly Tools for Improving Product Design

Virtual product creation and product design analysis are essential for studies in the investigation into assembly feasibility and help reveal practical manufacturing constraints. This paper demonstrates an application of a virtual assembly tool DYNAMO for a grill plate assembly. Virtual simulation and assembly verification is illustrated. Both virtual simulation and assembly verification enable designers to identify potential assembly difficulties encountered in manufacturing and thus save time and cost in real production. The paper also examines factors that influence the efficiency of assembly, namely, assembly method, assembly sequence, and assembly time. Suggestions for redesign for assembly improvement provided by some design for assembly methods are also discussed.     

Deviation modeling of manufactured surfaces from a perspective of manufacturing errors

Assembly analysis, as an important step in the product design stage, provides verifications of product design with specific requirements. The manufactured surfaces that participate in the analysis result from different manufacturing methods and show inconsistency with the designed surfaces due to the effects of numerous manufacturing errors. These deviations have a vital impact on the assembly analysis results and make a big difference on the final product design process. Therefore, consideration of such manufactured surface deviations in assembly analysis is critical in order to achieve an effective product design. In this paper, a general surface deviation modeling and representation approach based on curvilinear coordinate system is proposed. Different curvilinear coordinate systems for various manufacturing methods are defined on nominal product surfaces. By introducing the deviation dimension in the orthogonal direction of the curvilinear coordinates, deviation coordinate systems are formed. The deviation coordinate system could be used to describe deviation surfaces resulting from numerous manufacturing errors with deviation functions. As an example, non-ideal planar surfaces in the face milling process are modelled with the proposed method. With the generated non-ideal planar surfaces, the sealing performance analysis of an assembly is implemented. The validity of the proposed method and its applicability in simulation are verified in the end.     

A model to build manufacturing process chains during embodiment design phases

The methods for manufacturing process selection from early design phases avoid later mistakes and ensure the success during product manufacturing. Currently, the majority of the products need more than one manufacturing process to become finished parts. This is known as a manufacturing processes chain, and it is important that this manufacturing chain is well designed. This paper presents the bases and the activity model (IDEF?) to develop a decision-support system that helps designers and manufacturing engineers to configure manufacturing process chains while the product is being designed. The model schematizes all the activities and information involved in obtaining reliable manufacturing process chains. The support system has been applied to an air-bending die design process to be used to perform either air-bending or bottoming.     

Manufacturing Cost Modeling for Product Design

The process of product design is driven toward achieving design specifications while meeting cost targets. Designers typically have models and tools to aid in functional and performance analysis of the design but few tools and little quantitative information to aid in cost analysis. Estimates of the cost of manufacture often are made through a cost multiplier based on material cost. Manufacturing supplies guidelines to aid in design, but these guidelines often lack the detail needed to make sound design decisions.A need was identified for a quantitative way for modeling manufacturing costs at Motorola. After benchmarking cost modeling efforts around the company, an activity-based costing method was developed to model manufacturing cycle time and cost. Models for 12 key manufacturing steps were developed. The factory operating costs are broken down by time, and cost is allocated to each product according to the processing it requires. The process models were combined into a system-level model, capturing subtle yet realistic operational detail.The framework was implemented in a software program to aid designers in calculating manufacturing costs from limited design information. Since the information tool provides an estimate of manufacturing costs at the design prototype stage, the development engineer can identify and eliminate expensive components and reduce the need for costly manufacturing processing. Using this methodology to make quantitative trade-offs between material and manufacturing costs, significant savings in overall product costs are achieved.     

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.     

电性能仿真平台及其在大型面天线机械结构设计中应用

大型面天线在工程中有着广泛应用,其机械设计与电气设计是分开进行的。天线结构设计人员由于不了解电磁理论,只能依靠经验设计天线机械结构,来保证天线满足电气设计人员提出的精度指标。结果是生产周期很长,成本浪费严重。因此,有必要建立天线电性能仿真平台。在设计天线虚拟电子样机之后,通过该平台来计算天线电性能,判断天线结构是否满足要求。工程中应用此平台,将使结构设计人员提高天线设计与制造效率,减少次品率,降低天线设计与制造的成本。     

Information requirements analysis for holonic manufacturing systems in a virtual environment

The design and development of holonic manufacturing systems requires careful, and sometimes risky, decision making to ensure that they will successfully satisfy the demands of an ever-changing market. In this paper, the authors propose a methodology for a holonic manufacturing systems requirement analysis that is based on a virtual reality approach and aimed at assisting designers of such systems along the entire systems design and development process. Exploiting virtual reality helps the user collect valid information quickly and in a correct form by putting the user and the information support elements in direct relation with the operation of the system in a more realistic environment. A prototype software system tool is designed to realise the features outlined in each phase of the methodology. A virtual manufacturing environment for matching the physical and the information model domains is utilised to delineate the information system requirements of holonic manufacturing systems implementation. A set of rules and a knowledge base is appended to the virtual environment to remove any inconsistency that could arise between the material and the information flows during the requirement analysis.     

复杂机械产品的虚拟装配系统研究

在分析虚拟装配系统需求的基础上,建立复杂机械产品虚拟装配系统的总体框架,研究其涉及的关键技术。并以某减速器为研究对象,应用Visual Basic、SolidWorks和SQLSERVER数据库软件实现了零件参数化设计、产品信息提取、装配序列生成和装配仿真等功能,为复杂机械产品提供一种可视化的交互环境,从而降低了产品设计和制造的成本,提高了装配的品质。     

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 New Approach to Statistical Geometrical Tolerance Analysis

As a first step in developing a synthesis technique for assisting designers to specify tolerances in product design, a new 3D statistical tolerance analysis approach is proposed. A simple two-hole and two-pin (THTP) assembly is used as an example. On the basis of the introduction of an R-vector to represent position tolerance and a feasible assembly test formula, the probability of successful THTP assemblies to engineering specifications is calculated using a Monte Carlo simulation. Important issues in the implementation of the approach are explored. A comparison of the analysis results for the worst case, and this statistical approach, as well as the trade-off analysis between quality loss and manufacturing cost, demon-strates the advantages of the statistical tolerance design technique. The approach and results presented in this paper can be either applied directly to the THTP tolerance synthesis or used as a reference for statistical tolerance design for other engineering applications.     

A design representation scheme for collaborative product development

Design is an integral component of product development, which includes manufacturing. In order to avoid costly reworks and delays, and to reduce the lead-time in product development, effective communication of design concepts among the various stakeholders such as customers, designers and engineers is of utmost importance. In this respect, functional representations provide a methodology, which can be used to describe a design or product effectively. However, function is not the only type of information that needs to be communicated among the various stakeholders during a design process. Other types of information such as design specifications and constraints, which are non-functional, also need to be taken into account. This non-functional information cannot be adequately expressed using existing functional representations. Accordingly, in this work, a novel purpose-behaviour-structure (PBS) representation scheme to capture vital design knowledge for collaborative product development is proposed. The proposed PBS representation scheme can be used by designers working in a collaborative environment for product development. A case study on the design of a vacuum cleaner is used to illustrate the functionality of the PBS representation scheme. The details of the representation scheme are presented in this paper.     

Unification of the a priori inconsistencies checking among assembly constraints in assembly sequence planning

Sequence planning generation is an important problem in assembly line design. A good assembly sequence can help to reduce the cost and time of the manufacturing process. This paper focuses on assembly sequence planning (ASP) known as a hard combinatorial optimization problem. Although the ASP problem has been tackled via even more sophisticated optimization techniques, these techniques are often inefficient for proposing feasible assembly sequences that satisfy the assembly planners’ preferences. This paper presents an approach that makes easier to check the validity of operations in assembly process. It is based on a model of the assembly planners’ preferences by means of strategic constraints. It helps to check a priori the consistency of the assembly constraints (strategic and operative constraints) given by the assembly system designers before and while running an assembly plan generation algorithm. This approach reduces the solution space significantly. A case study is presented to demonstrate the relevance of the proposed approach.     

A Web-based integrated design system: its applications on conceptual design stage

This paper describes the development of a Web-based integrated system for collaborative product development evolving from marketing analysis to prototype generation. The proposed system encompasses a marketing information system (MIS), a human resources management (HRM) system, a supply-chain management (SCM) system, a communication media, an integrated product design studio, a user interface and databases. It enables project planners, marketing analysts, designers, suppliers, and manufacturing planners to work at the early stages to reduce any unnecessary wasted time, resources, and costs, thus increasing the total product quality, maximising the organisation resources used, and reducing the total product cost and product lead time to better face global competition. The tangible advantage of implementing this system is that it provides an integrated environment for total product development from concept to realisation. Therefore, an efficient product development process is generated. One case study is demonstrated and discussed to validate the proposed system.     

Optimal tolerance design for mechanical assembly considering thermal impact

In this paper, a cost–tolerance model based on neural network methods is proposed in order to provide product designers and process planners with an accurate basis for estimating the manufacturing cost. Tolerance allocation among the assembly components is carried out to ensure that the functionality and design quality are satisfied considering the effect of dimensional and geometric tolerance of various components of the assembly by developing a parametric computer aided design (CAD) model. In addition, deformations of various components of mechanical assembly due to inertia and temperature effects are determined and the same is integrated with tolerance design. The benefits of integrating the results of finite element simulation in the early stages of tolerance design are discussed. The proposed method is explained with an application example of motor assembly, where variations due to both dimensional and geometric tolerances are studied. The results show that the proposed methods are much effective, cost, and time saving than the ones considered in literature.     

轿车车身变形设计方法研究与应用

以UG软件为设计研究平台,依据市场或客户对产品的需求决定树状与网状相结合的产品开发模型。通过设定产品的高层几何定义和约束,使得详细设计可以在概念设计完成之前开始实施,产品设计可并行开展。利用WAVE技术建立车身产品的控制结构和控制参数编辑器,采用WAVE和克隆装配技术完成车身的变形设计。克隆装配可以创建与已有装配共享类似结构的装配,满足不同消费者的要求,缩短产品开发周期,降低产品开发成本和制造成本,适应瞬息万变的市场需求。