面向制造的曲面设计系统

为了支持面向制造的曲面设计,提出了一个基于计算机辅助设计／计算机辅助制造系统的嵌人式计算平台,该计算平台主要包括约束信息建模和可制造性分析2个功能模块。通过对曲面可制造性判据的抽象,建立了应用信息模型,用于从曲面几何形状中提取制造约束信息。应用于曲面加工问题,给出了根据约束信息计算可行刀具方向的具体方法。面向模具零件分型曲面的设计,建立了可制造性分析工具。针对一个雕塑曲面零件设计实例,通过对模具分型方向和加工约束进行分析,给出了可行的分型曲面设计结果,验证了所提出的曲面可制造性分析方法的可行性。     

Manufacturability Analysis for a Sculptured Surface Using Visibility Cone Computation

This paper presents a general algorithm to obtain a feasible tool-approach direction for sculptured surface machining based on convex analysis. The visibility cone which represents the aggregate of all visible directions is constructed to describe geometric constraints. Combined with the convex hull computation algorithm, a detailed procedure for computing the visibility cone has been developed. The visibility cone can be used as an effective tool for manufacturability analysis of the sculptured surface when applied to CNC machining tool-path planning. After the visibility cone is acquired, tool orientation can be adjusted to adapt itself to the local geometry of the sculptured surface at each cut contact position. The proposed methodology can be applied to computer-aided planning and programming of cutter-path generation for 5-axis sculptured-surface machining.     

曲面的可视方向信息计算

为了支持并行设计与制造,研究曲面可视方向信息的咨询方法。提出从曲面的几何数据中提取和分析可视方向信息,建立计算曲面可视方向的算法,并给出计算结果。借助于该方法,能够在设计阶段有效地获取一制造相关的方向信息,实现对设计的可制造性分析。     

An Intelligent Knowledge-Based System for Product Cost Modelling

An intelligent knowledge-based system for product cost modellingis presented in this paper. The developed system has the capability of selecting a material, as well as machining processes and parameters based on a set of design and production parameters; and of estimating the product cost throughout the entire product development cycle including assembly cost. The proposed system is applied without the need for detailed design information, so that it can be used at an early design stage, and, consequently, redesign cost and longer lead time can be avoided. Hybrid knowledge representation techniques, such as production rules, frame and object oriented are employed to represent manufacturing knowledge. Fuzzy logic-based knowledge representation is applied to deal with uncertainty in the knowledge of cost model to generate reliable cost estimation. This paper deals with cost modelling of both a machining component and an injection moulding component, which is a process that gives high production rates, excellent quality and accuracy of products, and low manufacturing cost. Based on the analysis of the moulded product life cycle, a computer-based cost model was developed which integrated the relationship between cost factors, product development activities, and product geometry. The estimated cost included the costs of material, mould and processing. The system has been validated through a case study.     

Feedrate optimisation/scheduling on sculptured surface machining: a comprehensive review, applications and future directions

Free-form or sculptured surface milling is one of the continually used manufacturing processes for die/mould, aerospace (especially turbine blades), precision machine design, bio-medical devices and automotive industries. Developments of machining technologies for quality enhancement of machining results have become a very important fact in current real industry. Therefore, reducing milling time, tool wear, cutter deflection and improving surface texture quality and machining operations through adaptation and optimisation of tool feedrates based on changing surface geometry in sculptured surface machining is a great step in this direction. Various feedrate optimisation strategies have different feedrate rescheduling control parameters such as chip thickness, material removal rate (MRR), min(mrr,chip,force), max(expo.Acc/dec) and resultant forces. Some commercial CAM softwares come with MRR-based feedrate optimisation algorithms which have a very short calculation time. However, commercial feedrate scheduling systems have some limitations in generating the scheduled feedrates because they use the MRR or the cutting force model which is dependent on milling conditions. However, for the processes in which machining precision/accuracy is very important, it is inevitable that mechanistic force-based feedrate optimisation approaches, for which the calculation time is improved, will be integrated into commercial CAM software packages. Here, developing only the mechanistic cutting force-based algorithm is not enough. In this paper, improvement and optimisation of machining feedrate value, which is one of the cutting parameters which has a tremendous effect on the precise machining of free-form surfaces, was discussed by using the virtual machining framework. For this purpose, the boundary representation solid modelling technique-based free-form milling simulation and feedrate optimisation system integrated with commercial CAD/CAM software is developed for three-axis ball-end milling. This review study includes the information regarding the following topics: The algorithms developed for the feedrate value optimisation, MRR calculation approaches, cutting force computation methods, details of algorithms, the effects on the surface accuracy, the effects on the machining time, the capabilities of the present commercial CAM software packages, the encountered difficulties and overcoming those difficulties, recent developments and future research directions.     

A case study on the object-oriented framework for modeling product families with the dominant variation of the topology in the one-of-a-kind production

Traditional configuration-based product family modeling techniques do not yield favorable solutions for modeling the product families with the dominant product topology variations. This paper presents the case study for the modeling of variations of the product configuration, parameters, and topologies in mass production of custom windows and doors in a one-of-a-kind production (OKP) company. The case study is based on the object-oriented product family modeling framework we developed for OKP which is characterized by the dominant product variation by topology. The problem of variation in topology in our framework is solved by the manual model transformation in the computer-aided design module which creates a new metamodel of products with the desired topology and which is the basis for a further, automatic model transformation. Usage of our framework has a positive effect on the level of the product customizations and shortening of the leading time which helps OKP companies in obtaining a better position at the market. Our software solution for the designing and manufacturing of custom windows and doors based on our framework is implemented in more than 300 mostly small- and medium-sized enterprises. It proves our concept which can be used for the realization of the information systems for computer-aided one-of-a-kind production in the companies with a different production plan.     

Assessing mould costs analysing manufacturing processes of cavities

Pressure die casting mould manufacturing companies have difficulties assessing manufacturing costs for bid generation. In particular, manufacturing effort of mould cavities could hardly be predicted accurately. Due to varying complexity of casting part geometry, processing time of manufacturing cavities appears to be a rather unpredictable factor influencing costs calculation of moulds. This article introduces a novel method for generating and analysing computer-aided design (CAD) models of mould cavities to compute the tool accessibility. Using geometrical information of cavities, working areas for different milling head geometries are determined, and processing times are calculated. Thereupon, a three-step accessibility analysis (AA) has been conducted. Beside the AA method, a CAD-based application of the calculation tool ??visual form calculator?? (VFC), developed at IFW, is presented. Using the VFC, companies are now able to generate a virtual model of the contour element in order to assess mould costs accurately when analysing manufacturing processes of cavities.     

A Hybrid Intelligent Systems Approach for Die Design in Sheet Metal Forming

Die design is heavily experience based and the die design process is an iterative procedure of trial and error in order to obtain a final die design for the successful manufacture of stampings. Most automotive industries use internal guidelines and past experience for die design. Even though powerful computer-aided design systems are being used in automotive industry, the lack of adequate analysis tools at the initial die geometry design stage hinders the die manufacturing process, and also necessitates lead times of the order of 5–30 weeks [1]. At the concept design stage, and during the initial die development process, the variations in geometry and process conditions are so large that it is prohibitively expensive to use 3D finite element analysis. The complexity of die design heuristic knowledge hinders the development and application of knowledge-based systems. Hybrid intelligent systems are computer programs in which at least one of the constituent models simulates intelligent behaviour [2]. These models could be knowledge-based systems, artificial neural networks, fuzzy logic systems, etc. In this approach both artificial neural networks, knowledge-based systems and finite-element analysis (FEA) for modelling the design process are used. A simulation-based design approach [3] for the die design process is followed. Artificial neural networks (ANNs) are preliminary design tools which indicate the formability of the component geometry, for the selected process and material conditions. The ANN module is trained from FEA results for a generic set of component geometries, process conditions, and material properties. The final die design validation is carried out by FEA. The intelligent frame-work incorporates rules for material selection, process parameter selection and their modification. Component geometry is a critical parameter which affects the manufacturability of the given part. Hence, an intelligent geometry handling module, which automatically modifies and optimises the geometry of the designed die, is implemented in the present system. Knowledge-based blackboard architecture is used for the integration of various analysis models such as CAD, FEA, and ANN, as an intelligent framework for die design [4]. The hybrid intelligent system provides an integrated decision support environment for simulation and analysis of the forming process, both during the initial die design phase and during the die tryout phase. The hybrid intelligent systems approach supports the capability for automatic evaluation of prospective die design for manufacturability, and performs automatic modification of design inputs. Applications of the hybrid intelligent system for die design are described together with a comparison with shop floor data.     

并行工程下基于特征的零件可制造性研究

结合并行工程的思想，对零件可制造性进行较详细的分析，提出并行工程环境下基于特征的可制造性分析方法，研究并建立基于特征的可制造性零件定义模型及评价体系，全面合理地对零件的可制造性进行评价和反馈，从而指导产品设计。最后以涡轮叶片榫头特征的可制造性分析为应用实例，说明该方法的有效性和实用性。     

并行工程下的面向制造的设计

结合并行工程的思想,对面向制造的设计进行了较详细的分析,指出面向制造的设计与并行工程的关系,提出了并行工程环境下面向制造的设计技术中存在的问题及对策,全面合理地对零件的面向制造的设计进行了评价,从而指导产品设计。     

An Improved Sculptured Part Surface Design Method with Jerk Continuity Consideration for Smooth Machining

This paper presents an investigation of jerk continuity in milling operations for sculptured surfaces of mechanical parts. It has been realised that chattering in machining operations can cause detrimental effects on the quality of machined parts as well as on the life of the cutting tool. One of the major reasons of chattering is known to be the rough transition of cutter accelerations when traversing through desired part sur-faces. The problem becomes serious when machining sculptured surfaces of parts. In this work, an effective computer-aided sculptured surface design technique is proposed. The ultimate goal is to achieve smooth and near chattering-free machining for producing precision parts. The proposed surface design scheme models the part’s sculptured surfaces in such a way that it warrants a smooth "jerk" transition at the boundaries of common surface patches on the part. This results in a drastic reduction of large step changes of cutter accelerations during machining operations which will in turn eliminate a good portion of the chattering effects. Three theorems concerning the necessary jerk continuity conditions for surface patches connections are developed and their proofs are presented. Examples of an aerofoil and a concept car model are implemented, using the proposed modelling approach, to demonstrate its effectiveness.     

Five-Axis NC Machining of Sculptured Surfaces

This paper presents a new method for the determination of tool position and orientation for NC milling of sculptured surfaces with a five-axis NC machine. This method uses an analysis of local curvatures of the surface and the tool geometry. Based on matching these local properties, optimal tool axis orientations are selected so that the gouging error in machining is eliminated or controlled within a specific tolerance. An accurate technique is also proposed for the computation of cusp height of the machined surface. By eliminating gouging and controlling scallops within a specified tolerance, it is expected that the time-consuming manual grind-ing process could be greatly reduced or completely eliminated in the finish machining of complex die or mould surfaces.     

Selection of the Machining Inclination Angle in High-Speed Ball End Milling

High-speed machining is a key issue for current die and mould manufacturing. Though this technology has great potential for high productivity, tool wear accelerated by high cutting speeds and hard materials is a barrier. In this work, we attempted to reduce tool wear by controlling the machining inclination angle between the tool and the workpiece. To do this, the range of cutting angles engaged in the cutting using a ball end cutter is obtained from the boundary lines describing machined sculptured surfaces represented by the cutting envelop condition and the geometric relationships of successive tool paths. Then, the chip cross-sectional area and chip length can be obtained from the calculated cutting edge and the rotational engagement angle. The simulation results showed that a machining inclination angle of 15° was good enough from the point view of machineability, and this value was verified by a cutting experiment using high-speed ball end milling.     

模具制造中的并行工程研究

并行工程是保证模具交货期和质量的有效手段。本文通过分析模具制造的特点和我国模具制造企业存在的问题,从组织机构和技术手段两方面,对实施模具并行工程的可行性进行了论证,提出了模具制造并行工程的基本框架和实现模具并行工程的关键技术以及实现这些关键技术的手段和方法。这些方法已在注塑模和压铸模的设计制造中得到部分应用,取得了很好的效果。     

基于CADDS5．0系统的船体外壳建模

CADDS5．0系统是一套新型船舶三维生产设计系统,造型手段齐全,其图形文件是独立的且是基于路径管理的。因此,其对于图档的管理灵活,可以随时在项目中添加图形文件。基本库及船体外壳曲面的建立是全面开拍CADDS5系统应用前的必要准备。基本库文件主要包含Sectlib（型材库）和Material（材质库）。基于CADDS5．0系统进行生产设计船体外壳建模时应注意线型的光顺质量要尽量提高。     

基于AutoCAD的冷冲模系统设计

在AutoCAD基础上利用VBA进行二次开发的冷冲模系统,采用交互式和参数化设计的方法,实现了计算机辅助冷冲模设计的全过程。文章主要从参数确定和系统开发两方面详细介绍了冷冲模的设计过程,为压力机的选择提供了依据,可大大缩短模具的生产周期,减少设计中的主观错误,使模具的生产效率明显提高。     

Detecting re-design area for increasing manufacturability of drilling and three-axis pocketing operations

The intensive competition has forced the manufacturing industry to improve product quality and production efficiency, and meanwhile reduce production cost. Detecting potential manufacturability problems in early design stages would prevent unnecessary cost involved in re-work and/or re-design activities at later manufacturing stages. This paper presents an algorithm for determining re-design areas to feedback the designer when the design model involves machining holes and pockets using a three-axis computer numerical control machine. The algorithm takes into account the various sizes of tools and tool holders, and therefore allows a designer to test the manufacturability of their available cutters on their design models. A color-based obstacle-detecting method, based on layer-slicing of re-design areas, helps a designer to re-evaluate a design model for increasing manufacturability. Practical examples are provided as the output of the process.     

基于J2EE的模具制造过程管理系统研究与开发

在深入分析了分布式计算系统的主流解决方案J2EE技术特点及体系结构的基础上，针对现代模具企业信息化管理的特点与要求，应用J2EE技术研究开发了适于模具企业应用的制造过程管理系统，使复杂的模具制造过程信息管理更加规范有序，进而保证了模具质量，缩短了模具制造周期。     

面向并行工程的模具制造设备建模

在分析模具生产并行工程的特点及模具生产中的主要设备的结构和功能特性的基础上 ,指出满足并行工程要求的、完整的设备定义模型 ,必须同时包含生产必需的设备动态信息和静态信息 ,并提出了一种适合模具并行工程环境的设备定义模型的数据结构和计算机程序实现方法     

复杂曲面加工中干涉问题的研究

提出用干涉区域自动生成系统来识别不容易被加工的关键区域。根据给定的刀具尺寸参数,本系统通过分析曲面几何形状,自动识别不易被加工的区域并将零件表面自动划分为关键区域和可加工区域。该系统已经应用到作者开发的CAD系统并在几种复杂表面零件的生产中使用,明显减少了刀具路径生成时间,提高了加工效率。