Multidisciplinary optimization of injection molding systems

The design of injection molding systems for plastic parts relies heavily on experience and intuition. Recently, mold makers have been compelled to shorten lead times, reduce costs and improve process performance due to global competition. This paper presents a framework, based on a Multidisciplinary Design Optimization (MDO) methodology, which tackles the design of an injection mold by integrating the structural, feeding, ejection and heat-exchange sub-systems to achieve significant improvements. To validate it single objective optimization is presented leading to a 42% reduction in cycle time. We also perform multiple objective optimization simultaneously minimizing cycle time, wasted material and pressure drop. Sensitivity analysis shows a large impact of the sprue diameter (>1.5 normalized sensitivity) highlighting the importance of the feeding subsystem on overall quality. The results show substantial improvements resulting in reduced rework and time savings for the entire mold design process.     

An integrated framework for multi-criteria optimization of thin concrete shells at early design stages

Thin shells are crucially dependent on their shape in order to obtain proper structural performance. In this context, the optimal shape will guarantee performance and safety requirements, while minimizing the use of materials, as well as construction/maintenance costs.Thin shell design is a team-based, multidisciplinary, and iterative process, which requires a high level of interaction between the various parties involved, especially between the Architecture and Engineering teams. As a result of technological development, novel concepts and tools become available to support this process. On the one hand, concepts like Integrated Project Delivery (IPD) show the potential to have a high impact on multidisciplinary environments such as the one in question, supporting the early decision-making process with the availability of as much information as possible. On the other hand, optimization techniques and tools should be highlighted, as they fit the needs and requirements of both the shell shape definition process and the IPD concept. These can be used not only to support advanced design stages, but also to facilitate the initial formulation of shape during the early interactions between architect and structural engineer from an IPD point of view.This paper proposes a methodology aimed at enhancing the interactive and iterative process associated with the early stages of thin shell design, supported by an integrated framework. The latter is based on several tools, namely Rhinoceros 3D, Grasshopper, and Robot Structural Analysis. In order to achieve full integration of the support tools, a custom devised module was developed, so as to allow interoperability between Grasshopper and Robot Structural Analysis. The system resorts to various technologies targeted at improving the shell shape definition process, such as formfinding techniques, parametric and generative models, as well as shape optimization techniques that leverage on multi criteria evolutionary algorithms. The proposed framework is implemented in a set of fictitious scenarios, in which the best thin reinforced concrete shell structures are sought according to given design requirements. Results stemming from this implementation emphasize its interoperability, flexibility, and capability to promote interaction between the elements of the design team, ultimately outputting a set of diverse and creative shell shapes, and thus supporting the pre-design process.     

支持多学科设计优化的集成产品过程建模方法

针对当前主要的设计过程建模方法缺乏表达复杂产品多学科设计过程中资源的组织调用和协作方式等信息,提出一种支持复杂产品多学科设计优化的设计路线图框架过程建模方法.从全面表达设计过程信息的角度出发,描述产品多学科设计优化过程中的主要活动及其协同关系,建立支持多学科设计优化的过程模型;在此基础上,给出了多学科设计优化的过程规划方法,以降低产品设计过程中的迭代,通过构建支持多学科设计优化的集成产品设计过程结构框架,实现产品多学科设计优化的过程集成.最后通过已开发的多学科系统集成平台,应用具体设计实例验证了整套方法的有效性.     

A novel CACD/CAD/CAE integrated design framework for fiber-reinforced plastic parts

This work presents a novel CACD/CAD/CAE integrated framework for design, modeling, and optimization of fiber-reinforced plastic parts, which can greatly enhance the current design practice by realizing partial automation and multi-stage optimization. To support this framework, a new heterogeneous feature model (HFM) has been developed to model the fiber-reinforced objects and to be transferred between engineering modules. To be specific, the CACD (computer-aided conceptual design) module employs the level-set structure and material optimization to produce the initial design with thickness control, and also the initial HFM; the CAD (computer-aided design) module allows manual editing on the HFM to reflect various design intents; then, the injection molding CAE (computer-aided engineering) simulates the manufacturing process, and the response surface method (RSM) is applied to optimize the process parameters of gate location, injection flow rate, mold temperature and melt temperature, to approach the manufactured fiber orientation distribution close to the optimized result produced by the CACD module; besides, the structural analysis CAE module generates the mechanical performance result to support the CACD module, as well as to validate the final design. By applying this framework, the final structural design including the fiber orientation distribution, will perform better in mechanical properties, and consume less matrix and fiber materials; besides, the design maturity can be approached in shorter time. To prove the effectiveness, a plastic gripper design will be comprehensively studied.     

VPML—OOPN集成建模方法及其在企业中的应用

为了支持对企业业务流程进行建模和分析,辅助过程改进,该文提出了VPML—OOPN集成建模方法。该方法提供了模型描述和设计、模型分析和仿真,直至模型实现的一体化框架。最后,设计了旨在实现VPML—OOPN集成建模方法的系统平台。     

Design, fabrication and measurement of ultra-precision micro-structured freeform surfaces

Due to the geometry complexity and high precision requirement, there still possess a lot of challenges in the design, manufacturing and measurement of ultra-precision micro-structured freeform surfaces (e.g. microlens array) with submicrometer form accuracy and surface finish in nanometer range. Successful manufacturing of ultra-precision micro-structured freeform surface not only relies on the high precision of machine tools, but also largely depends on comprehensive consideration of advanced optics design, modelling and optimization of the machining process, freeform surface measurement and characterization.This paper presents the theoretical basis for the establishment of an integrated platform for design, fabrication, and measurement of ultra-precision micro-structured freeform surfaces. The platform mainly consists of four key modules, which are Optics Design Module, Data Exchange Module, Machining Process Simulation and Optimization Module and Freeform Measurement and Evaluation Module. A series of experiments have been conducted to evaluate the performance of the platform and its capability is realized through a trial implementation in design, fabricating and measurement of a microlens array. The results predicted by the system are found to agree well with the experimental results. These show that the proposed integrated platform not only helps to shorten the cycle time for the development of microlens array components but also provides an important means for optimization of the surface quality in ultra-precision machining of micro-structured surfaces. With this successful development of the system, optimal machining parameters, the best cutting strategy, and optimization of the surface quality of the ultra-precision freeform surfaces can be obtained without the need for conducting time-consuming and expensive cutting tests.     

基于iSIGHT平台DOE方法的螺旋桨敞水性能优化设计

传统的螺旋桨设计方法已经满足不了进一步提升其性能的要求,并且现代环境的变化不再仅仅要求螺旋桨某一性能的最优,而是多方面综合性能的最优.iSIGHT多学科优化设计平台提供了完整的设计综合环境和先进的优化设计方法,能够完成设计过程的自动化和智能的设计探索,确定最佳设计参数.基于iSIGHT平台的实验设计方法建立的螺旋桨敞水性能优化方法使螺旋桨效率和最小压力系数都有提高,实现了优化目的.     

基于HTCPN的工程项目群工作流建模与仿真

在工程项目群实施阶段框架模型构建的基础上, 基于分层赋时着色Petri网定义了工程项目群实施阶段工作流模型。借助CPN Tools仿真平台, 以某工程项目群实施阶段为例进行了实例建模与仿真, 验证了基于分层赋时着色Petri网构建工程项目群实施阶段工作流模型的有效性。该工作流模型能够全面、准确地描述项目群复杂系统的实施全过程, 为实现项目群管理中的进度风险分析和流程优化提供技术与方法的支持。     

基于STK的卫星系统设计优化研究

随着小卫星技术的发展，卫星系统的结构和功能也越来越复杂。为了降低卫星系统的造价，提高卫星系统的性能，需要对卫星系统进行设计优化。该文针对目前通用设计软件的不足，提出在STK和ModelCenter的基础上。开发卫星系统设计优化平台，详细阐述了基于STK仿真环境的卫星系统设计优化过程。为实现卫星系统的设计优化，应在任务分析的基础上定义STK场景，确定卫星系统的性能评价指标和设计变量，对设计变量进行敏感性分析，选择关键的设计变最，确定优化目标函数和约束条件并进行优化求解。最后给出了一个卫星系统设计优化的应用实例。     

面向分级设计优化的飞行器参数化建模方法

针对飞行器气动隐身外形综合设计优化问题,提出合适的面向分级设计优化流程,建立适应该流程的渐进分层参数化建模方法;用基于敏度分析的参数影响程度分析方法筛选复杂设计变量;采用多学科设计优化（Multidisplinary Design Optimization,MDO）理论和差分进化算法进行飞行器气动隐身外形的综合设计优化.将该方法用于某飞行器外形设计优化,结果表明：该方法合理可行,可为飞行器外形多学科设计优化提供一定参考.     

Knowledge representation framework for interactive capture and management of reflection process in product concepts development

A design process can be characterized by reflection-in-action; that is, the process consists of a series of problem solving activities and each is embodied with a problem and a solution. In this process, a designer represents a hypothetical concept on each design alternative, deploys and verifies the concept from multiple viewpoints considering other alternatives, and modifies it. An advanced integrated design environment should be based on a representation framework that embodies this process of reflection in concept development, which usually remains in the realm of the designer’s tacit knowledge. This paper proposes a knowledge representation framework for an integrated design environment, named DRIFT (Design Representation Integration Framework of Three layers), which interactively captures and manages reflection processes of generating and verifying design concepts. The core of DRIFT is a three-layered design process model of actions, operations, and argumentation. This model integrates various design tools and captures performed design activities. The action level captures the sequence of design operations. The model operation level captures the transition of design states, recording a design snapshot over design tools, which are integrated through ontology-based representation of design concepts. The argumentation level captures the process of defining problems and corresponding alternative solutions. Integration of three levels with a template of design operation extracted from Design-For-X approaches enables a proposed system to interactively and efficiently capture and manage the process of design concept development through operations over design tools. A design operation template works to limit the number of links between the three levels remaining easy to manage its semantics. This paper also demonstrates a prototype implementation of DRIFT and its application to conceptual design of a small mechatronic system with a system modeling method. The paper concludes with a discussion of some future issues.     

A procedure for plastic parts demoldability analysis

The present work proposes a new systematic procedure for the geometric analysis of plastic parts that will be transformed by injection process. The procedure is based on visualization techniques such as slicing by parallel planes, Scan Line Segment and Z-buffer methods. By these procedures, the fitness of the part geometric design for manufacturing process is evaluated. Part demoldability and parting line are defined, with an outstanding improvement of the traditional methods used for mold design purposes. Therefore, this approach focuses on Design for Manufacturing research area.     

Efficient shape parameterization method for multidisciplinary global optimization and application to integrated ship hull shape optimization workflow

Multidisciplinary global shape optimization requires a geometric parameterization method that keeps the shape generality while lowering the number of free variables. This paper presents a reduced parameter set parameterization method based on integral B-spline surface capable of both shape and topology variations and suitable for global multidisciplinary optimization. The objective of the paper is to illustrate the advantages of the proposed method in comparison to standard parameterization and to prove that the proposed method can be used in an integrated multidisciplinary workflow. Non-linear fitting is used to test the proposed parameterization performance before the actual optimization. The parameterization method can in this way be tested and pre-selected based on previously existing geometries. Fitting tests were conducted on three shapes with dissimilar geometrical features, and great improvement in shape generality while reducing the number of shape parameters was achieved. The best results are obtained for a small number (up to 50) of optimization variables, where a classical applying of parameterization method requires about two times as many optimization variables to obtain the same fitting capacity.The proposed shape parameterization method was tested in a multidisciplinary ship hull optimization workflow to confirm that it can actually be used in multiobjective optimization problems. The workflow integrates shape parameterization with hydrodynamic, structural and geometry analysis tools. In comparison to classical local and global optimization methods, the evolutionary algorithm allows for fully autonomous design with an ability to generate a wide Pareto front without a need for an initial solution.     

Design parameterization and tool integration for CAD-based mechanism optimization

This paper presents an open and integrated tool environment that enables engineers to effectively search, in a CAD solid model form, for a mechanism design with optimal kinematic and dynamic performance. In order to demonstrate the feasibility of such an environment, design parameterization that supports capturing design intents in product solid models must be available, and advanced modeling, simulation, and optimization technologies implemented in engineering software tools must be incorporated. In this paper, the design parameterization capabilities developed previously have been applied to support design optimization of engineering products, including a High Mobility Multi-purpose Wheeled Vehicle (HMMWV). In the proposed environment, Pro/ENGINEER and SolidWorks are supported for product model representation, DADS (Dynamic Analysis and Design System) is employed for dynamic simulation of mechanical systems including ground vehicles, and DOT (Design Optimization Tool) is included for a batch mode design optimization. In addition to the commercial tools, a number of software modules have been implemented to support the integration; e.g., interface modules for data retrieval, and model update modules for updating CAD and simulation models in accordance with design changes. Note that in this research, the overall finite difference method has been adopted to support design sensitivity analysis.     

CAPPFramework设计与实现关键技术研究

CAPPFramework是一个以工艺知识/产品工艺数据为核心,采用综合智能化的工艺设计技术并集成各种应用支持工具,能广泛应用于各种不同层次和类型的企业、企业的不同工艺部门,支持企业CAPP系统渐进式实施与开发过程的应用框架与开发平台式软件。文章介绍了CAPPFramework系统设计与实现的关键技术。     

基于CAD的注塑模具设计与仿真研究

研究了基于CAD技术的注塑模具设计流程,并对模具的工艺参数进行了分析和优化,具体采用CAD注塑模集成系统实现。完成了最优工艺参数方案的确定,通过UG的CAE分析模块的应用并以模拟结果为依据完成了对注塑件应力应变分布情况的分析,应力最大值及位置通过实验对比完成确定,为模具结构的优化方案提供参考。最佳注塑制品工艺参数通过分析相关工艺参数获取,并以音箱零件为例,对注塑模具型腔设计方法进行了探讨。     

卫星有效载荷的多目标多学科设计优化研究

在卫星有效载荷系统研究中,实施多目标多学科优化的可行性设计。首先,分析了开展卫星有效载荷多学科设计优化的关键技术。建立了包含天线、转发器、数据传输、可靠性、成本和质量的多学科分析模型。然后,应用多目标遗传算法对某卫星有效载荷的可靠性和成本进行多目标设计优化,获得最优解集。最后,运用多学科协同优化结合遗传算法进行可靠性单目标设计优化。研究结果表明:有效载荷的多目标多学科设计优化全面考虑了多个学科之间的关系,设计人员可按需选择其满意的优化结果,大幅提高设计效率;协同优化方法有助于实现学科自治、并行设计,提高设计的灵活性和缩短设计周期。     

Shape optimization of heavy load carrying components for structural performance and manufacturing cost

This paper addresses the trade-off between structural performance and manufacturing cost of heavy load carrying components by incorporating virtual machining (VM) technique in computer-aided design (CAD)-based shape optimization problem. A structural shape optimization problem is set up to minimize total cost, subject to the limits on structural performance measures. For every design iteration, finite element analysis (FEA) is conducted to evaluate structural performance, and VM is employed to ascertain machinability and estimate machining time. Design sensitivity coefficients of objective function and constraints are computed and supplied to the optimization algorithm. Based on the gradients, the algorithm determines design changes, which are used to update FEA and VM models. The process is repeated until specified convergence criterion is satisfied. Application programs developed to integrate commercially available CAD/CAM/FEA/Design optimization tools enable implementation in virtual environment and facilitate automation. The application programs can be reused for similar design problems provided that the same set of tools is used.