A corner-looping based tool path for pocket milling

In milling around corners, cutting resistance rises momentarily due to an increase of cutter contact length. NC tool path generation in dealing with sharp corners thus requires special consideration. This paper describes an improved NC tool path pattern for pocket milling. The basic pattern of the improved tool path is a conventional contour-parallel tool path. Bow-like tool path segments are appended to the basic tool path at the corner positions. When reaching a corner, the cutter loops around the appended tool path segments so that corner material is removed progressively in several passes. By using the corner-looping based tool path, cutter contact length can be controlled by adjusting the number of appended tool path loops. The procedures of creating the improved tool path for different corner shapes are explained. The proposed tool path generation was implemented as an add-on user function in a CAD/CAM system. Cutting tests were conducted to demonstrate and verify the significance of the proposed method.     

Development of a collaborative CAD/CAM system

This paper presents the development of a collaborative CAD/CAM system (COCADCAM). COCADCAM extends an existing single-location CAD/CAM system to a multi-location CAD/CAM application so that two geographically dispersed CAD/CAM users can work together on a three-dimensional CAD-geometry coediting and CAD-related tasks collaboratively and dynamically. COCADCAM dynamically supports CAD data communication that are not available in traditional single-location CAD/CAM. The dynamic data communication is achieved through the development of networking algorithms and CAD/CAM functions in this paper. The networking algorithms based on UNIX Interprocess Communication (IPC), the Network File System (NFS), and a connection-oriented client and server model under the Transmission Control Protocol/Internet Protocol (TCP/IP) suite. The CAD/CAM functions included surface modelling, simulation of a milling toolpath, and post-processing of an NC program following collaborative CAD-geometry coediting, which are directly or indirectly supported by the Application Programming Interface (API) of the CAD/CAM software. The networking algorithms and CAD/CAM functions together can facilitate an environment for CAD-geometry coediting and related tasks such as design, analysis and manufacture. COCADCAM has been successfully implemented through local area network (LAN) and the Internet; a remote machining cell is also linked so that the generated NC program based on a coedited free-form surface can be used for the physical machining operation. The algorithm proposed by COCADCAM can be referenced for the extension of other single-location CAD/CAM systems to multi-location applications.     

基于激光快速原型的CAD网络浏览器的研制

把CAD/CAM中快速成形建模技术与TCP/IP网络套接字技术相结合 ,并以脚医学中的脚支撑模型为应用领域 ,研究开发CAD网络浏览器 ,该浏览器能在Internet网络上提供CAD模型浏览和脚支撑铣削加工刀具轨迹及其数控G码的生成。     

Process planning for Floor machining of 2½D pockets based on a morphed spiral tool path pattern

This work proposes a process planning for machining of a Floor which is the most prominent elemental machining feature in a 2½D pocket. Traditionally, the process planning of 2½D pocket machining is posed as stand-alone problem involving either tool selection, tool path generation or machining parameter selection, resulting in sub-optimal plans. For this reason, the tool path generation and feed selection is proposed to be integrated with an objective of minimizing machining time under realistic cutting force constraints for given pocket geometry and cutting tool. A morphed spiral tool path consisting of G¹ continuous biarc and arc spline is proposed as a possible tool path generation strategy with the capability of handling islands in pocket geometry. Proposed tool path enables a constant feed rate and consistent cutting force during machining in typical commercial CNC machine tool. The constant feed selection is based on the tool path and cutting tool geometries as well as dynamic characteristics of mechanical structure of the machine tool to ensure optimal machining performance. The proposed tool path strategy is compared with those generated by commercial CAM software. The calculated tool path length and measured dry machining time show considerable advantage of the proposed tool path. For optimal machining parameter selection, the feed per tooth is iteratively optimized with a pre-calibrated cutting force model, under a cutting force constraint to avoid tool rupture. The optimization result shows around 32% and 40% potential improvement in productivity with one and two feed rate strategies respectively.     

Automation in the design of EDM electrodes

Plastic parts, especially those designed for consumer electronics products, are becoming more compact and freeform in shape. This requires the construction of compact and delicate geometric features in the injection moulds that produce these parts. It is now common practice to employ electric discharge machining (EDM) whenever the conventional machining process fails to machine such delicate features. Although CAD/CAM systems are widely used in mould design and manufacturing, and specific commercial CAD/CAM systems that are customized for injection mould applications are also available, there are still no intelligent CAD tools that address the specific requirements of EDM electrode design. The aim of this research is to develop an intelligent CAD tool that supports EDM electrode design. This CAD tool uses a new technique that recursively splits the EDM region into sub-regions until machinable electrodes can be constructed. The CAD tool has been implemented and integrated into a commercial CAD/CAM system, and 40 different real designs has been used to test its capability in handling a wide variety of geometric shapes. Performance data show that the efficiency of the design process can be improved by at least 50%, with a potential to achieve 85% through improved implementation and further research.     

CATC — A Computer Aided Tolerance Control system

Computer utilization in manufacturing systems is increasing at a rapid rate. Developments thus far have been disjointed. Much work needs to be done in the area of integrating computer aided design and computer aided manufacturing (CAD/CAM). Tolerance control is an important component in the integration of CAD and CAM. Selection of design tolerances affects the build-ability of a product. The selection of manufacturing processes and sequence of processes affects process tolerance stacking. Unexamined process tolerance stacking leads to scrap and rework. A computer aided tolerance control (CATC) system is presented in this paper. This system is based on the tolerance chart technique. The CATC system is interactive and uses computer graphics for information display. The system can be used for computer aided process planning (CAPP) and for CAD/CAM integration.     

CAD/CAM技术在脚医学中的应用

将CAD／CAM技术与脚医学结合，研究开发脚支撑设计制造系统，包括脚底曲面数据的读取及处理，根据医疗规划完成三维脚支撑模型的构造，平衡及光滑处理，激光快速原型文件和铣削加工刀具轨迹的自动生成等。     

Process planning for Floor machining of 2½D pockets based on a morphed spiral tool path pattern

This work proposes a process planning for machining of a Floor which is the most prominent elemental machining feature in a 2½D pocket. Traditionally, the process planning of 2½D pocket machining is posed as stand-alone problem involving either tool selection, tool path generation or machining parameter selection, resulting in sub-optimal plans. For this reason, the tool path generation and feed selection is proposed to be integrated with an objective of minimizing machining time under realistic cutting force constraints for given pocket geometry and cutting tool. A morphed spiral tool path consisting of G¹ continuous biarc and arc spline is proposed as a possible tool path generation strategy with the capability of handling islands in pocket geometry. Proposed tool path enables a constant feed rate and consistent cutting force during machining in typical commercial CNC machine tool. The constant feed selection is based on the tool path and cutting tool geometries as well as dynamic characteristics of mechanical structure of the machine tool to ensure optimal machining performance. The proposed tool path strategy is compared with those generated by commercial CAM software. The calculated tool path length and measured dry machining time show considerable advantage of the proposed tool path. For optimal machining parameter selection, the feed per tooth is iteratively optimized with a pre-calibrated cutting force model, under a cutting force constraint to avoid tool rupture. The optimization result shows around 32% and 40% potential improvement in productivity with one and two feed rate strategies respectively.     

Intelligent Programming of CNC Turning Operations using Genetic Algorithm

CAD/CAM systems are nowadays tightly connected to ensure that CAD data can be used for optimal tool path determination and generation of CNC programs for machine tools. The aim of our research is the design of a computer-aided, intelligent and genetic algorithm(GA) based programming system for CNC cutting tools selection, tool sequences planning and optimisation of cutting conditions. The first step is geometrical feature recognition and classification. On the basis of recognised features the module for GA-based determination of technological data determine cutting tools, cutting parameters (according to work piece material and cutting tool material) and detailed tool sequence planning. Material, which will be removed, is split into several cuts, each consisting of a number of basic tool movements. In the next step, GA operations such as reproduction, crossover and mutation are applied. The process of GA-based optimisation runs in cycles in which new generations of individuals are created with increased average fitness of a population. During the evaluation of calculated results (generated NC programmes) several rules and constraints like rapid and cutting tool movement, collision, clamping and minimum machining time, which represent the fitness function, were taken into account. A case study was made for the turning operation of a rotational part. The results show that the GA-based programming has a higher efficiency. The total machining time was reduced by 16%. The demand for a high skilled worker on CAD/CAM systems and CNC machine tools was also reduced. Received: September 2004 / Accepted: September 2005     

B/S结构标准全文数据库设计与验证技术

基于B/S结构数据库的设计技术,开发可靠性与质量管理标准超文本全文数据库,研究新的超文本链接测试验证方法和测试工具,验证了该数据库的设计.该技术可扩展应用到CAD、CAM、ERP等企业信息化系统的标准技术支持系统.     

Something to smile about: 3D graphics are revolutionizing oralhealth care

Computer graphics and all the computer-aided drawing and manufacturing (CAD/CAM), scanning, and imaging technology is changing dentistry. Invisalign is a technology that straightens adult teeth using a series of clear, plastic, nearly invisible aligners. Though proprietary CAD/CAM software that does 3D modeling, the company creates the fixtures for orthodontists. For dental implants dentists make a study cast of the area where the abutment will be placed. They then scan the cast into the computer using a 3D optical scanner, creating a 3D point cloud. Technicians create a polygonal surface from the point cloud. They use proprietary software to virtually assemble the digital teeth data with an unmodified (or template) version of their product. This template is a 3D model of an ideally shaped dental abutment. The computer generates the tool path and sends it to the milling machines that create the titanium abutment. Maxillofacial surgery repairs physical malformations resulting from disease, injury, burns, birth defects, or aging. In these cases, a maxillofacial surgeon must make changes that often include removing bone and replacing it with modeled implants. A surgeon uses computer graphics to solve these problems in his practice. The common thread among the examples of oral health care techniques discussed is the CAD/CAM software they use from Raindrop Geomagic     

TORNADO: a DBMS for CAD/CAM systems

TORNADO is a database management system developed for CAD/CAM application systems. It is a CODASYL-type network system written in FORTRAN, with a very powerful tool for handling complex data structures.There are no restrictions on combinations of object classes and relationships, and it directly handles many-to-many relationships and compound object classes. TORNADO also handles variable object length and dynamic length table records. A second paper will discuss the implementation details.     

NEW INSIGHTS INTO PRINCIPLES FOR DESIGNING ARCHITECTURE OF ENVIRONMENT SYSTEM FOR TOOL INTEGRATION ─IN THE CASE OF PRODUCTION MACHINES DESIGN

ＮＥＷＩＮＳＩＧＨＴＳＩＮＴＯＰＲＩＮＣＩＰＬＥＳＦＯＲＤＥＳＩＧＮＩＮＧＡＲＣＨＩＴＥＣＴＵＲＥＯＦＥＮＶＩＲＯＮＭＥＮＴＳＹＳＴＥＭＦＯＲＴＯＯＬＩＮＴＥＧＲＡＴＩＯＮ─ＩＮＴＨＥＣＡＳＥＯＦＰＲＯＤＵＣＴＩＯＮＭＡＣＨＩＮＥＳＤＥＳＩＧＮＺｈａ...     

基于UG的五轴数控机床加工仿真

目前多数五轴数控机床仿真系统,一般只提供二维的动画仿真,而且仿真系统的几何造型功能十分有限,零件和机床模型需要在其他CAD软件中进行建模,然后导人数控仿真系统。由于文件格式的转化,零件的CAD模型将会产生误差,降低了仿真精度。该文利用UGCAD／CAM软件造型功能建立五轴数控机床和零件模型,读取数控代码对机床各部件进行三维运动仿真,并对加工过程中机床运动部件之间的干涉及工件过切进行检查,建立干涉实体,为刀具轨迹的修改提供依据,同时免除了文件格式的转化产生的误差。     

Computer aided design of form rolls for NC manufacture

Computer aided design (CAD) and computer aided manufacture (CAM) are two modern areas of computer application which have decisive influence in the manufacturing industries. The recognition of the potential of CAD/CAM is worldwide and many have taken advantage of the new technology. The design and manufacture of form rolls and the special tooling used in cold roll forming of thin walled metal sections are areas where the CAD/CAM approach can make a positive computer aided tool for creating form roll designs suitable for NC (numerical control) manufacturing. This work was undertaken by the Department of Production Technology and Production Management at the University of Aston in Birmingham in collaboration with a leading manufacturer of thin walled sections. Significant improvement of lead time and productivity in both design and manufacturing of form rolls have been accompanied.     

A system for CAD/CAM software development and implementation

Some approaches to CAD/CAM software are presented based on the experience gained by the authors from the development and implementation of several such systems. The metamonitoring system MEMO and two examples of its implementation in mechanical and civil engineering are described. MEMO implies the family of complex multi-task software which can be used as a tool for building integrated packages and as a monitoring system for controlling the problem solution processes. MEMO can be considered a kernel of the supporting environment for CAD/CAM systems software development and implementation.     

协同开发环境中的CAD/CAM集成系统研究

本文探讨了计算机网络技术下的CAD／CAM集成系统．提出了一种协同环境下的CAD／CAM集成系统，并构造了其网络体系结构和其系统的框架结构。     

An optimal approach to multiple tool selection and their numerical control path generation for aggressive rough machining of pockets with free-form boundaries

To machine pockets, especially ones with closed free-form boundary curves, roughing is crucial to part productivity, for this operation alone could take more than 60% of the total machining time. At present, there is a high demand from industry for a new machining technique that can efficiently cut pockets. Aggressive rough machining, in which the largest possible cutters are always employed and are fully immersed in workpieces, can be a solution. Although aggressive roughing is by far the most efficient machining strategy, compared to prior pocketing methods, no computer numerical control (CNC) programming technique has been developed to support it, resulting in few applications in machine shops. To address this urgent industrial need, based on the medial axis transform of a pocket, this work proposes an optimal approach to multiple tool selection and their numerical control (NC) path generation for aggressive roughing of the pocket. First, the NC paths of a specific tool are quickly generated using the pocket’s medial axis transform. Thanks to the unique characteristic of the medial axis transform, the paths can ensure the tool the largest accessible space for pocketing. At the same time, they can guarantee the tool to be free of gouging and interference. Then, an optimization model of selecting multiple cutters and generating their NC paths is built in order to achieve the highest efficiency of the aggressive rough machining. To demonstrate the advantages of this innovative approach, two examples are rendered, and their results are compared to those obtained by the existing methods. This approach can be directly implemented into current CAD/CAM software to promote aggressive rough machining of pockets in industry.     

Robust uniform triangulation algorithm for computer aided design

This paper presents a new robust uniform triangulation algorithm that can be used in CAD/CAM systems to generate and visualize geometry of 3D models. Typically, in CAD/CAM systems 3D geometry consists of 3D surfaces presented by the parametric equations (e.g. surface of revolution, NURBS surfaces) which are defined on a two dimensional domain. Conventional triangulation algorithms (e.g. ear clipping, Voronoi-Delaunay triangulation) do not provide desired quality and high level of accuracy (challenging tasks) for 3D geometry. The approach developed in this paper combines lattice tessellation and conventional triangulation techniques and allows CAD/CAM systems to obtain the required surface quality and accuracy. The algorithm uses a Cartesian lattice to divide the parametric domain into adjacent rectangular cells. These cells are used to generate polygons that are further triangulated to obtain accurate surface representation. The algorithm allows users to control the triangle distribution intensity by adjusting the lattice density. Once triangulated, the 3D model can be used not only for rendering but also in various manufacturing and design applications. The approach presented in this paper can be used to triangulate any parametric surface given in S(u,v) form, e.g. NURBS surfaces, surfaces of revolution, and produces good quality triangulation which can be used in CAD/CAM and computer graphics applications.     

An integrated manufacturing planning assistant — IMPA

In this paper, we describe our development of a fully integrated manufacturing planning assistant (IMPA) system, which is able to: (1) interpret the finished part requirements directly from the designer's CAD systems or solid modelers without user intervention or special feature coding; (2) check the machinability of a designed part; (3) automatically generate a process plan, a tool path and an NC (numerically controlled) code, and (4) support interactive user modification of the resulting plans, tool paths and NC code. A demonstration version of the system was designed to provide automated assistance for the planning of machining processes on three-axes NC machine tools. The underlying architectural concepts and reasoning algorithms can be extended to more complex machines such as four-or-more-axes NC machines. CAD, CAE, and CAM including robotic, FMS (flexible manufacturing system) and NC machines are widely used in industry today. There is increasing interest in automation of factory control software Merchant, (1988); this includes automating the generation of the control programs — that is, in developing systems which will automatically produce the NC code for machining the part, given a model of the part, the shape of the raw material, and the machine specifications. With such systems, there are several difficulties in the manual preparation of an NC program code such as, long and tedious calculations, high risk of error in data preparation, etc., which need to be eliminated. This is a critical step toward the integration of CAD and CAM into a truly concurrent engineering and manufacturing environment.