On-line integration of a process planning module with production scheduling

An approach to the on-line integration of process planning and production scheduling is reported. Based on a geometric modeller, a geometric analyser and a knowledge base, the process planner generates alternative process plans and provides automatic tool selection and calculation of the appropriate machining parameters. Time and cost estimations are input to the decision-making module in the production scheduling system that produces optimal scheduling decisions as well as a complete record of the actual state of the factory resources. An information flow, designed as a relational data model, maintains the interaction between the process planning and the production scheduling systems and provides the dynamic feedback to the process planner. Specific geometry features of the blank, the finished part and the cutting tools, and geometry features-based rules are stored in the database of a developed CAPP system by using a separate CAD interface. The integrated production planning and production scheduling system and the CAPP system were validated with rotational parts machining.     

基于实例推理的实时CAPP系统研究

现代生产不仅要求工艺设计系统能够快速响应产品的变化 ,而且要求所编制的工艺规程实用可行。本文开发了一种基于实例推理的实时CAPP系统 ,通过实例推理技术表示以往的工艺规程 ,同时考虑车间的加工能力 ,并将加工后零件的误差信息即时反馈回系统 ,从而快速、实时地生成符合生产要求的工艺规程。由于成功与失败的设计实例都被存入实例库中 ,系统实现了自学习功能 ,推理能力得到不断增强 ,最后通过回转类零件工艺设计实例验证了该系统的有效性     

基于毛坯模型的自动工艺规划

针对大多数现有CAD／CAM系统还不能自动获取并处理尺寸公差、形位公差、表面粗糙度等制造信息，在完成产品设计后无法自动生成相应工艺规划的现状，着重研究对零件设计模型补偿面、体加工特征自动生成毛坯模型后，基于毛坯模型自动提取面、体制造特征的工艺约束信息参数，毛坯模型总体信息参数，结合制造资源数据库、工艺知识库完成工艺规划。将毛坯模型逆变换为设计模型，实现了加工工序过程的拟实验证。     

Computer aided manufacturing planning for mass customization: part 2, automated setup planning

Setup planning plays a crucial role in CAPP to ensure product quality while maintaining acceptable manufacturing cost. The tasks of setup planning include identifying manufacturing features and corresponding manufacturing processes, determining the number of setups, part orientation, locating datum and process sequence in each setup, and selecting machine tools and fixtures. An automated setup planning technique and system has been developed based on not only the tolerance analysis, but also the manufacturing resource capability analysis. The automated setup planning is divided into two levels: setup planning in single part level and in machine station level. Algorithms for setup generation and process sequencing have been developed and a case study of setup planning is presented.     

面向产品的CAPP方法论及其智能化概念体系

提出并论述面向产品的ＣＡＰＰ方法论,建立面向产品的ＣＡＰＰ智能化概念体系,并分析讨论面向产品的ＣＡＰＰ智能化关键技术,实践表明,以面向产品的ＣＡＰＰ方法论为指导,形成基于知识库的智能化交互式ＣＡＰＰ系统框架,才能真正理顺先进性与实用性、普及与提高等各方面的关系,满足企业对ＣＡＰ广泛应用与集成的需求。     

A Surface Area Calculation and CAPP System for Non-Axisymmetric Deep Drawing Products

In this paper a surface area calculation for non-axisymmetric deep drawing products of elliptical shape was constructed for the design of blank shapes of deep drawing products by using an AutoLISP function in AutoCAD software. A computer-aided process planning (CAPP) system for rotationally symmetric deep drawing products has been developed. In this study, a CAPP system for non-axisymmetric deep drawing products of elliptical shape was constructed using process sequence design. The system developed consists of four modules. The first is the recognition of shape module for recognising non-axisymmetric products. The second is a 3D modelling module for calculating the surface area for non-axisymmetric products. The third is a blank design module for creating an oval-shaped blank with an identical surface area. The fourth is a process planning module based on production rules that play the most important role in an expert system for manufacturing. The production rules are generated and upgraded by interviewing field engineers. The drawing coefficient, the punch and die radii for elliptical shape products are considered as the main design parameters. The suitability of this system was verified by applying it to a real deep drawing product. This surface area calculation and CAPP system should be very useful for reducing the lead-time for manufacturing and for improving the accuracy of products.     

Knowledge based process planning system for turned components

Recently, there has been a proliferation of CAD and NC systems for aiding the design and manufacture of components. However, CAD and CAM have not been fully integrated due to the difficulty in automating the intermediate function, process planning. At UMIST research is being carried out towards the integration of CAD and CAM by automating process planning. This paper describes the development of a process planning system for turned components using expert system techniques (EXCAP). This system has been integrated with the CAD system via IGES and with the NC machine using a cutting technology package developed at UMIST. Thus it is currently possible to generate NC programs automatically for relatively simple turned components by feeding in the CAD product data.     

Studies on process plan representation in CAPP systems

Process planning establishes the methods and means of converting the raw material into a finished part. The planning function interacts with the manufacturing system through (a) the design specification, (b) manufacturing resources, and (c) the process plan. Similarly, computer aided process planning (CAPP) establishes the links with its application environment through the analogous models. Though much attention is paid to the modelling of the part and manufacturing resources, modelling of the process plan has been an ignored topic to-date. The present paper discusses the need for modelling the process plan, and proposes a framework for process plan internal representation (PPIR) for the effective integration of CAPP and CAM functions. The implementation of the proposed framework in GIFTS — a CAPP system for rotational parts — is also discussed.     

Multi-agent system for distributed computer-aided process planning problem in e-manufacturing environment

This paper deals with the multi-agent system for distributed computer-aided process planning problem. The proposed architecture consists of three autonomous agents (Global Manager Agent, Design Agent, and Optimization Agent) capable of communicating to each other through eXtensible Markup Language (XML). In contrast to the traditional process planning model, a new paradigm incorporating fixture cost has been conceptualized. Optimization agent is facilitated by the virtues of DNA computing and identifies the optimal/near optimal process plan with the help of available resources. Furthermore, in order to investigate the efficacy of the developed architecture, the manufacturing of a prismatic part having 23 operations has been simulated and solved accordingly. Results obtained reveal the superiority of the proposed architecture.     

异型薄壁壳体强力旋压三维有限元模型的建立

基于ABAQUS/Explicit平台,在解决建模过程中有关旋轮定位、旋轮运动轨迹确定、连续变壁厚坯料壁厚定义的实现等关键问题的基础上,建立了异型薄壁壳体强力旋压三维弹塑性动态显式有限元模型。基于该模型研究发现:在成形过程中后期,旋轮前方易于出现金属堆积,从而使后方材料拉薄,尤其是靠近工件口部的部位壁厚剧烈减薄。提出了通过控制坯料局部厚度和旋轮与芯模间间隙的方法来改善成形过程中金属堆积和壁厚过度减薄现象。     

面向对象的模块化柔性生产线并行设计研究

针对模块化柔性生产线方案设计系统的复杂性,研究了面向对象的并行设计系统。通过把设计过程分解为对系统若干对象的设计,提出了面向对象的模块化柔性生产线并行设计过程模型。在此基础上建立统一的全局数据模型,开发了箱体类零件柔性生产线并行设计原型系统,以支持加工对象的特征设计、工艺规划、系统配置结构设计、模块化机床、刀具等设计的并行运行,并进行了实例验证。     

A production planning in highly automated manufacturing system considering multiple process plans with different energy requirements

This paper focuses on a production planning problem in a highly automated manufacturing system considering multiple process plans with different energy requirements. The system consists of several closely interconnected sub-systems such as the processing system, the material (part) handling system, the tool transport system and the auxiliary system responsible for a supply of cooling/lubricants and a waste disposal. We propose a methodology for an estimation of energy consumption and material flows that are incurred at a system level with respect to multiple process plans for a part type. In addition, this study focuses on a production planning problem with the objective to minimize the weighted sum of energy consumption, inventory holding cost and backorder cost on a FMS considering multiple process plans. The production planning model is developed as a linear programming model. The benefit coming from the adoption of suggested model has been addressed with reference to a real industrial use case study.     

An effective integration approach toward assembly sequence planning and evaluation

An integration strategy for assembly sequence planning and sequence scheme evaluation is proposed. This strategy can be used to plan a reasonable assembly sequence, to optimize a sequence scheme, and to predict whether a collision will occur between the assembly tool and assembled components by considering factors like target components and assembly resources. A hybrid method is presented for assembly sequence modeling that combines human-computer interactive operations to manually build a hierarchical assembly sequence main model and a hybrid graph method to automatically generate sub-assembly sequence schemes of the main model. An optimization algorithm based on time-cost is introduced to handle a best candidate components selection. This relieves the problem of limited capability found when handling large size assembly models with traditional methods. The essential issues involved in system implementation are discussed as well; these include a representation method for the assembly consequence model, an optimization model of assembly sequence planning, and an object-oriented system architecture model employed with multi-agent technology for visually evaluating the assembling process. This system, KM computer-aided assembly process planning, KMCAAPP, has been developed on the basis of our previous work, KMCAD3; KMCAAPP uses the presented approach. KMCAAPP can be integrated with CAD model from KMCAD3D. A case study shows that the presented approach can use large CAD assembly models and delivers a feasible and effective way to integrate the assembly sequence planning process with scheme evaluation by visually evaluating the assembling process. This allows the identification of design errors in a timely manner and mitigates economic loss.     

KBE-based stamping process paths generated for automobile panels

As automobile body panels are one kind of sheet metal part with groups of free form surfaces, the process planning is more complicated than common sheet metal stamping to implode effectively and practically. Based on KBE, new frameworks have been presented as intelligent master model at the system level and as procedure model at the activity level. In accordance with these frameworks, an intelligent CAPP system has been specifically developed. Based on feature technology, features have been extracted and represented by the object-oriented method. Stamping features and their parameters have been defined and extracted based on feature technology and stamping process rules. The whole product knowledge has been represented by frames which directly map to objects (or features) in the object-oriented sense. Relevant appropriate operations features have been assigned to stamping features of a product based on feature-operation criteria, parameters of the stamping feature and their correlativity. This assignment is a decision-making activity using a set of rules with a decision-making tree and model-based reasoning methods. With knowledge between operations, such as operations order constraint (do-after) and operations combination constraint, process paths have been improved based on relevant intelligent reasoning methods. Based on the relationships (preferred-to) between processes and machines/dies, the structure of die and machine for each process can be identified, since the process route has been determined. In this stamping process planning, the procedure and information have been controlled by a process control structure that is associative and integrated.     

同步建模技术在零件特征识别中的应用

特征识别一直是CAPP系统开发的难点,尤其是在相交特征和复杂特征识别方面.本文提出一种基于NX同步建模技术来实现零件特征识别与提取的方法.利用基于同步建模技术的无历史、基于特征的建模系统,合并尺寸驱动和约束驱动技术,结合基于去除切削体分解法可有效解决相交特征的特点,实现零件从毛坯到成品每一步骤改变量的识别.从而达到解决...     

Analogy-Based Multiple Process Planning System with Resource Conflicts

Computer-aided process planning is becoming a widely prevalent technology in modern manufacturing systems. The research presented here describes a new methodology for generating process plans based on the analogy deductive paradigm. The method uses rules that represent relations between two shapes and allow inference of the type: shape A is to shape B as C is to D, where usually D is the unknown shape. The system uses backward chaining and therefore gradually converts the part from its finished (designed) form into its initial form. This method can generate multiple process plans for each given part; the paper also presents a method of selecting the best combination of process plans to maximize the production rate of that part. Once the dominant combination of plans is selected, the paper presents a method to calculate a proper production quantity for each process plan. This method is based on coalition theory and uses Shapley values to evaluate each member of such a coalition. The system has been implemented on a SUN workstation using Quintus Prolog and C++. The current implementation considers prismatic parts only.     

Accuracy prediction in fused deposition modeling

Fused deposition modeling (FDM) is a common additive manufacturing (AM) technology able to fabricate physical prototypes directly from virtual model without geometrical complexity limitations. Initially used to create concept models to help product design stage, FDM developed as regard materials, accuracy, and the overall quality of the output improved, becoming suitable for end use. At present, it is employed in process chains to significantly shorten product development times and costs and to produce parts in small and medium batch. A critical drawback which inhibits its diffusion is the obtainable accuracy. Only few indications, relating the dimensional deviations, exist, and they are conflicting each other, not allowing a reliable prediction. In this paper, a geometrical model of the filament, dependent upon the deposition angle and layer thickness, has been developed in order to predict the obtainable part dimensions. The model has been validated by an experimental campaign. The specimens have been investigated by means of profilometer analysis in order to study macrogeometrical and microgeometrical aspects. Finally, a case study highlighted the reliability of the model. The direct implication of this work is the capability, in process planning, to know in advance if the FDM part dimensions will satisfy the specification and the component will fit with others. Moreover, this model can be employed to choose the suitable manufacturing strategy in order to comply with industrial constrains and scopes.     

凸翻边零件的液压橡皮成形有限元模拟与分析

利用有限元技术,对凸翻边钣金零件的高压橡皮成形过程进行模拟分析.通过增加侧压块和加大毛坯的方式,由数值模拟与分析,指出了侧压块有利于凸翻边件的成形,以及摩擦因素和模具与侧压块之间的距离对凸翻边件成形的影响,为有限元在橡皮成形工艺中的应用积累了参考数据,为其工艺设计提供了参考依据.     

我国高速加工技术现状及发展趋势

高速加工是以较快生产节拍进行加工 ,提高切削和进刀速度是高速加工技术的重要环节。高速加工技术的发展涉及到零件毛坯、刀具、机床、自动控制与检测等多种技术的综合优化 ,需要变革传统的机加工工艺路线。我国引进的轿车零部件数控自动生产线上已广泛应用高速加工技术 ,其主要目的是在确保产品质量的前提下 ,尽量缩短零件的机加工工艺路线 ,加快生产节拍 (轿车发动机生产节拍已缩短为 30秒 ) ,满足轿车高质量、高速率、低成本、大批量、社会化生产的技术要求。高速加工技术必将带动零件毛坯制造、刀具 (工具 )、数控机床、自动控制、在线检测、材料等技术的发展与进步。随着我国制造业加快融入全球化生产制造体系 ,预计高速加工技术将在信息化、柔性化机械加工领域得到进一步发展和推广应用     

Parametric process planning based on feature parameters of parts

This paper presents a model parametric process plan that is dependent on feature parameters of parts, and proposes a solution for the automated process planning of part families. Based on the parametric process plan templates for part families and the feature parameters of new parts, a prototype system is developed. First, parts are grouped into families considering their geometric or manufacturing similarities, and the parametric process plan template is pre-created for each family. Then, to plan the process of a new part, the system extracts feature parameters from its feature-based model and generates an a parametric process plan by searching the template library and solving related constraints. Finally, the system outputs the process plan sheets, if necessary. Although the system cannot creatively generate process plans for brand new parts, the system can meet two important requirements of the real industrial world to CAPP systems, that is good system performance and rapid response.