Development of a computer-aided concurrent net shape product and process development environment

This paper presents a systematic approach to developing a collaborative environment for computer-aided concurrent net shape product and process development. This approach includes the steps of (1) conventional development process analysis, (2) development process re-engineering, (3) computer-based system functional requirements analysis, (4) system framework design, and (5) system modeling, integration and implementation. This environment can support concurrent net shape product and process development by providing and integrating functions of product data management, process management and development advisory tools. The results of this research will facilitate the rationalization and automation of net shape product and process development and thus improve the efficiency and quality, and reduce the cost of net shape product development.

IDEF structural analysis methodology was employed to capture the characteristics of net shape product and process development process. The concept of concurrent engineering was used to re-engineer the development process. The technology of system engineering was used to design the computer-aided system framework. Object-oriented analysis, modeling and design methodology, knowledge engineering and data engineering techniques were employed for system modeling and implementation.     

Knowledge integration and sharing for collaborative molding product design and process development

This study presents a systematic approach to developing a knowledge integration and sharing mechanism for collaborative molding product design and process development. The proposed approach includes the steps of (i) collaborative molding product design and process development process modeling, (ii) an ontology-based knowledge model establishment, (iii) knowledge integration and sharing system framework design, (iv) ontology-based knowledge integration and sharing methods development, and (v) ontology-based knowledge integration and sharing mechanism implementation. The mechanism can support collaborative molding product design and process development by providing functions of knowledge integration and sharing. Results of this study facilitate the knowledge integration and sharing of collaborative molding product design and process development to satisfy the product knowledge demands of participants, and thus increase molding product development capability, reduce molding product development cycle time and cost, and ultimately increase molding product marketability.     

PSO-based back-propagation artificial neural network for product and mold cost estimation of plastic injection molding

To simplify complicated traditional cost estimation flow, this study emphasizes the cost estimation approach for plastic injection products and molds. It is expected designers and R&D specialists can consider the competitiveness of product cost in the early stage of product design to reduce product development time and cost resulting from repetitive modification. Therefore, the proposed cost estimation approach combines factor analysis (FA), particle swarm optimization (PSO) and artificial neural network with two back-propagation networks, called FAPSO-TBP. In addition, another artificial neural network estimation approach with a single back-propagation network, called FAPSO-SBP, is also established. To verify the proposed FAPSO-TBP approach, comparisons with the FAPSO-SBP and general back-propagation artificial neural network (GBP) are made. The computational results show the proposed FAPSO-TBP approach is very competitive for the product and mold cost estimation problems of plastic injection molding.     

GreenPro-I: a risk-based life cycle assessment and decision-making methodology for process plant design

In recent years, significant attention and emphasis has been given to cleaner and greener technologies in processes and product manufacturing. This is recognized as a key element in pollution prevention (P2) and development of sustainable strategies. Life cycle assessment (LCA) is a systematic approach that enables implementation of cleaner and greener product and process concepts in industry. In recent times substantial progress has been made in the use of LCA for product evaluation and selection. However, its use in cleaner and greener process design and decision-making has not been explored to a great extent.Process design and decision-making are challenging activities that involve trade-off of conflicting objectives, namely costs, technical feasibility and environmental impacts. These conflicting objectives can be analysed at the early design and decision-making stage by considering the full life cycle of a process or a product. A cleaner and greener process is the one that is cost optimal, technically feasible, and environmentally benign. To obtain these results LCA requires various tools and techniques in a systematic methodology. This paper proposes a holistic and integrated methodology GreenPro-I for process/product design by combining the traditional LCA approach with multi-criteria decision-making methods. This methodology is simple and applicable at the early design stage and is more robust against uncertainty in the data. Application of the methodology has been demonstrated in the paper through a urea production case study.     

Modeling, scheduling and simulation of product development process by extended stochastic high-level evaluation Petri nets

This paper presents a methodology for modeling and simulating product development process-based on the extended stochastic high-level evaluation Petri nets (ESHLEP-N). A product development process is composed of many design activities and the ESHLEP-N model can describe some special features of design activity in detail, such as randomness of its duration, uncertainty of its interruption and complexity of design iteration. Therefore, the ESHLEP-N model is employed to simulate a product development process. The initial product development plan obtained by a mathematical method beforehand is taken as the input of the simulation. Then the simulation procedure is proposed, along with four types of rules, i.e. activity-sequencing rules, resource-assigning rules, state-changing rules and the simulation-terminating rule, for scheduling the design activities. An example of the development process of an automobile drive system in concurrent engineering environment is presented to illustrate the method of the ESHLEP-N-based modeling, simulation procedure and scheduling rules. The simulation results show that the simulation procedure and the scheduling rules are effective.     

The application of surface demoldability and moldability to side-core design in die and mold CAD

In casting, molding and forming processes, the surface geometries of the fabricated products are formed/molded by different functional components of tooling. In plastic injection molding, they are molded by core, cavity or side-cores. In die and mold CAD, how to identify the product surfaces formed/molded by the corresponding tool components for a given product CAD model is critical, as it affects the determination of parting directions, parting lines and parting surfaces, the generation of core and cavity blocks, and finally the design of side-cores and their actuating mechanisms. In this paper, the concepts of surface visibility, demoldability, and moldability are first presented and formulated. The surfaces formed/molded by core, cavity and side-cores are then defined based on the plastic injection molding process. The methodology to identifying and classifying them is further developed. By employing the proposed notions of the demoldability map of surfaces and undercut features, the most preferred demolding direction, the grouping of undercut features, and how to conduct the side-core design is articulated succinctly, and the detailed procedures and processes are presented. Through an industrial case study, the developed methodology for side-core design is systematically presented and the feasibility of the developed approaches is verified.     

Overview of entity-based integrated design product and process models

The development of computer-integrated systems for engineering design requires models to describe and organize the information and activities involved in design. A product model describes the information created during the design process, and a process model describes the associated design activities. Product and process models can be integrated into a single model. An entity-based approach is one way to carry out this integration. An entity-based integrated model uses product entities and process entities to represent design information and design activities, respectively. The relationships among these entities include organizational, interaction and sequence relationships. Organizational relationships organize entities into hierarchies, interaction relationships characterize the nature of entity interactions, and sequence relationships identify the sequences in which process entities are initiated during the design process. This paper presents an overview of the product and process entities, and the organizational, interaction and sequence relationships of entity-based integrated design product and process models. Formal concepts and notation used to represent these entities and relationships are described using a simple design example. © 1998 Published by Elsevier Science Limited. All rights reserved.     

Mathematical model for quality cost optimization

Quality engineering uses robust design in order to improve quality by reducing the effects of variability. Variability of the product can be reduced by two stages. One is parameter design which is adjustable to the nominal value so that output is less sensitive to the cause of variability. Other one is tolerance design which is to reduce the tolerance in order to control variability. All costs incurred in a product life cycle can be divided into two categories—manufacturing cost before the sale to the customer and quality loss after the shipment of the product to the customer. It is very important to find the optimum tolerances for each of the characteristics. A balance between manufacturing cost and quality loss should be arrived at in the tolerance design for quality improvement and cost reduction. For the case of Nominal-The-Best, a mathematical model is developed in order to determine the optimum product tolerance and minimize the total cost which includes the manufacturing cost and the quality loss. Since the process capability index (C_pm) shows the balance of quality responsibility between the design and the manufacturing engineers, this is taken as the basis in developing the functional relationship between the variability of the product and the tolerance. Based on these relationships, the total cost of model can be expressed as a function of product tolerance from which the optimal tolerance limits can be found out. Finally, using this model a tolerance design approach that increases the quality and reduces the cost can be achieved in the early stages of the product process design stage itself.     

Adaptability analysis of design for additive manufacturing by using fuzzy Bayesian network approach

The rapid development of Additive Manufacturing (AM) has been conspicuous and appealing towards manufacturing end-use products and components over the past decade. The continual advancement of AM has brought many advantages such as personalization and customization, reduction of material waste, cutting off the existence of special tooling during fabrication, etc. However, the AM approach has its limitations, such as a lack of knowledge of AM process activities and the progressive industrialization of AM, which makes the design process activities unstable, unpredictable, and have a limited effect. The concept of “design for AM (DFAM)” is increasing, which means we have the opportunity to concentrate almost totally on product functioning. Therefore, the entire design paradigm must be revised to accommodate new production capabilities, geometries, and parameters to avoid molding or machine tooling technology constraints. Few studies have attempted to provide systematic and quantitative knowledge of the relationship between these elements and the feasibility of the design process, making it difficult for designers to assess and control AM industrialization. For this reason, DFAM is needed to reform AM from rapid manufacturing to a mainstream manufacturing method. This paper put forward a framework based on the Fuzzy Bayesian Network (FBN) for DFAM decision-making. Twenty impact factors were encapsulated from experts’ experience and existing literature to investigate the potential adaptability of DFAM. The proposed approach uses expert knowledge and Fuzzy Set Theory (FST) presented with Triangular Fuzzy Numbers (FFN) to perceive the uncertainties. The Bayesian Network (BN) captures the causal relationships and dependencies among the impact components and analyzes the DFAM adaptability for robust probabilistic reasoning. A robot arm claw was used to show the effectiveness of our approach. The results showed that FBN could be used to guide DFAM adaptability in the manufacturing industry.     

A CAD-CAE Integrated Injection Molding Design System

. In the injection molding design process, interaction between design and analysis is very intensive. This is to ensure that the plastic part being designed is manufacturable by the injection molding process. However, such interaction is not supported by current computer-aided systems (CAD and CAE), because design and analysis are realized as isolated modules. Although most of CAE systems provide built-in modeling tools, these are only meant for developing an analysis model with very limited CAD functionality. On the other hand, some CAD systems have allowed certain CAE systems to run under their environments, but inherently they use different data models, thus communication between them is poor. This paper presents an innovative, CAD-CAE integrated, injection molding design system. This system uses an integrated data model for both design and analysis. The system is built on top of existing CAD and CAE systems, which not only greatly saves development effort, but also makes full use of the strong functionality of commercial computer aided systems. The system architecture consists of four layers: a CAD and CAE platform layer; a CAD-CAE feature layer; a model layer; and a GUI layer. Two design cases were studied to illustrate the iterative design-analysis process and use of the developed system.     

基于虚拟现实的塑料注塑成型系统场景可视化

虚拟现实,作为一门新型技术,已成功地应用于工程、设计和制造业领域.该文针对塑料注塑成型复杂的设计、制造、加工过程,将虚拟现实技术应用到塑料注塑成型过程中,并利用Delaunay三角剖分技术结合立体显示技术,开发了一种实用的虚拟场景.在此场景中可实现注射系统的全部设计和制造过程,并结合面向对象的编程技术和OpenGL图形库,实现注射成型系统在虚拟现实场景中的动态可视化,从而能够预先感知注射系统在设计、制造过程中可能出现的问题,并加以解决,实践证明了其可行性.     

Conceptual process planning – an improvement approach using QFD,FMEA, and ABC methods

Conceptual process planning (CPP) is an important technique for assessing the manufacturability and estimating the cost of conceptual design in the early product design stage. This paper presents an approach to develop a quality/cost-based conceptual process planning (QCCPP). This approach aims to determine key process resources with estimation of manufacturing cost, taking into account the risk cost associated to the process plan. It can serve as a useful methodology to support the decision making during the initial planning stage of the product development cycle. Quality function deployment (QFD) method is used to select the process alternatives by incorporating a capability function for process elements called a composite process capability index (CCP). The quality characteristics and the process elements in QFD method have been taken as input to complete process failure mode and effects analysis (FMEA) table. To estimate manufacturing cost, the proposed approach deploys activity-based costing (ABC) method. Then, an extended technique of classical FMEA method is employed to estimate the cost of risks associated to the studied process plan, this technique is called cost-based FMEA. For each resource combination, the output data is gathered in a selection table that helps for detailed process planning in order to improve product quality/cost ratio. A case study is presented to illustrate this approach.     

Occupational ergonomics research and applied contextual design implementation for an industrial shop-floor workstation

The aim of this original research article is to identify the occurrence of work-related ergonomics risk factors, in order to implement context specific human centered design interventions in the injection molding shop-floor workstations of plastic furniture manufacturing factories within the framework of industrially developing countries. Questionnaire study, postural assessment tools, computer aided design, digital human modeling and simulation, and basic work study techniques were used. Plastic processing industry is highly fragmented, consisting of small, medium scale enterprises with tremendous growth potential. Occupational design ergonomics research in the injection molding plastic furniture manufacturing shop-floor workstations is very scarce in industrially developing countries. Shop-floor workers are affected by prevalent awkward working postures and consequent body part discomforts. Useful and easily implementable accessories/fixtures with convenient design features were conceptualized. Virtual ergonomics evaluation of the workstation with proposed accessories/fixtures showed significant reduction of awkward working postures. Physical prototypes of the proposed fixtures were constructed and real human trials were performed in the factories. Time study indicated reduction in operator cycle time when compared with time taken before design modifications. Research methodology, results and design solutions described from an ergonomics perspective would definitely serve as a helpful guide for existing as well as upcoming factories in the injection molded plastic furniture manufacturing industry of industrially developing countries and further similar research endeavors.     

基于控制参数化的注塑工业过程最优反馈控制方法

本文针对一类典型的注塑工业过程系统, 研究了注塑填充过程中产生的熔体流动速度最优跟踪控制问题, 提出了一种基于控制参数化的计算最优反馈控制器设计方法以实现注塑过程中熔融聚合物流动前沿位移的最优跟 踪控制, 进而达到改善注塑零件性能的高效生产目标. 首先, 面向注塑工艺复杂生产过程建立了动态过程系统数学 模型, 提出了注塑机内部熔融聚合物流动前沿位置的动态最优跟踪控制问题; 其次, 设计了一种多级反馈控制律, 通 过控制参数化方法将控制反馈核进行了参数化表示, 将控制器设计问题转化为一序列最优参数决策问题; 然后, 通 过状态灵敏度方程分析方法, 求解出了目标函数及约束条件关于决策变量参数梯度信息的显式表达式, 并基于所提 供的梯度信息结合序列二次规划算法进行了高效优化迭代求解; 最后, 通过实验仿真验证了本文所提出的最优反 馈控制器设计方法的可行性和有效性.     

Integrated product line design and supplier selection: A multi-objective optimization paradigm

Product line design is commonly used to provide higher product variety for satisfying diversified customer needs. To reduce the cost and development time and improve quality of products, companies quite often consider sourcing. Conventionally, product line design and supplier selection are dealt with separately. Some previous studies have been attempted to consider product line design and supplier selection simultaneously but two shortcomings were noted. First, the previous studies considered several objectives as a single objective function in the formulation of optimization models for the integrated problem. Second, positions of product variants to be offered in a product line in competitive markets are not clearly defined that would affect the formulation of marketing strategies for the product line. In this paper, a methodology for integrated product line design and supplier selection is proposed to address the shortcomings in which a multi-objective optimization model is formulated to determine their specifications and select suppliers for maximizing the profit, quality and performance as well as minimizing the cost of the product line. In addition, joint-spacing mapping is introduced to help estimate market share of products and indicate positions of product variants. The proposed methodology can provide decision makers with a better tradeoff among various objectives of product line design, and define market positions of product variants explicitly. The results generated based on the methodology could help companies develop product lines with higher profits, better product quality and larger market share to be obtained. A case study of a product line design of notebook computers was performed to illustrate the effectiveness of the proposed methodology. The results have shown that Pareto optimal product line designs and the specifications of product variants can be determined. Suppliers of components and modules can be selected with considerations of minimum sourcing cost, and maximum performance and quality of product variants. Prices and positions of the product variants can also be determined.     

Parametric design and process parameter optimization for bra cup molding via response surface methodology

Seamless and traceless undergarments have rendered foam sheet molding as an important manufacturing technique for the intimate apparel industry. Seamless bra cups are made by one-step forming technology. The three-dimensional (3D) cup shape is formed by using high temperatures and pressures with flexible polyurethane foams. Nevertheless, the mold head design process and control of the bra cup molding process are highly complicated and error prone. There is limited knowledge about the effects of foam properties, molding parameters and foam cup geometric parameters on molding process optimization. This research presents a response surface methodology as the approach for parametric design and process parameter optimization of bra cup molding. The proposed approach integrates 3D scanning via reverse engineering, parameterized-based remeshing and registration algorithm, non-linear mathematical prediction models for cup shape conformity, a model of foam shrinkage and example-based bra cup design and grading to optimize the bra cup development and production process. The experimental results show that this method is highly effective and more timesaving in the design and development of new products, as well as providing consistent quality control of the bra cup molding process.     

军用型号项目软件复用成本度量模型

针对军用型号项目软件研制过程中普遍存在的软件复用行为,提出了一种复用成本度量方法,对传统的COCOMO2.0成本度量模型进行了改进,采用改进的功能点法估计软件实际规模,适当调整模型中的评估项,增加了度量系统复用的成本驱动因子及系统通用特性统计项（GSC）,建立了相应的量化评估及DI分级表,形成了军用型号项目软件进度、成本估计模型,使用改进的度量模型对某军用型号项目进行了成本度量,验证了方法的有效性。     

A multi-objective framework for the design of vacuum sealed molding process

This paper provides a framework for process design to achieve simultaneous improvement of the multiple features of the product. The methodology provides a way to integrate process parameters with the product features. Many of the features may be conflicting in nature, and thus may limit the use of a particular setting of design parameter of the process to produce the quality product. In this paper we discuss how to resolve the conflicting objectives of the process design problem. A case study for the design of vacuum-sealed molding process using the proposed methodology is included.     

Manufacturing cost modelling for concurrent product development

This research work aims to develop an intelligent knowledge-based system that accomplishes an environment to assist inexperienced users to estimate the manufacturing cost modelling of a product at the conceptual design stage of the product life cycle. Therefore, a quicker response to customers’ expectations is generated. This paper discusses the development process of the proposed system for cost modelling of machining processes. It embodies a CAD solid modelling system, user interface, material selection, process/machine selection, and cost estimation techniques. The main function of the system, besides estimating the product cost, is to generate initial process planning includes generation and selection of machining processes, their sequence and their machining parameters. Therefore, the developed system differs from conventional product cost estimating systems, in that it is structured to support concurrent engineering. Manufacturing knowledge is represented by hybrid knowledge representation techniques, such as production rules, frames and object oriented. To handle the uncertainty in cost estimation model that cannot be addressed by traditional analytical methods, a fuzzy logic-based knowledge representation is implemented in the developed system. Based on the analysis of product life cycle, the estimated cost included material, processing, machine set-up and non-productive costs. A case study is discussed and demonstrated to validate the proposed system.