Reverse engineering of machining operation planning

Computer-aided process planning (CAPP) is becoming increasingly crucial to today's computer-integrated manufacturing (CIM) and rapid production. To automate the process planning, feature-based operation planning systems have been suggested and studied extensively. In such a system, given a machining feature, the operator requires practical machining operation data for the feature. In this research, a system of reverse engineering is proposed to extract machining features and their associated machining operation data. Furthermore, a machining know-how database containing the extracted data is created for future operation planning. Since successful NC programs contain the machining know-how of skilled workers, the system is aimed at extracting the machining know-how data from the NC programs through reverse engineering. The extraction of the machining features and feature topologies has been addressed previously. The present paper deals with the extraction of machining operation data, including operation sequence, cutting conditions, machining type and cutting mode. A prototype of the system is developed and a machining know-how database is generated. The extraction of machining features and their associated machining operations has been verified through a variety of NC programs.     

An intelligent feature-based process planning system for prismatic parts

Today, feature-based design has become a core technology for solid product modelling primarily because it can capture the designer's intent and provide the capability to satisfy the informational needs of the down-line application tasks for CAD/CAM integration. This paper reports the development of an intelligent environment, IFPP (Intelligent Feature-based Process Planning), for the feature-based design synthesis and process planning of prismatic parts to be produced on CNC machining centres. IFPP consists of two functional modules, namely Feature Based Modeller (FBM) and Automatic process Planner (AutoPlan). The FBM provides a graphical environment for the feature-based synthesis, validation and representation of the solid model of the part to be produced. AutoPlan maps this feature information to the corresponding machining processes to generate the operation plan and corresponding CNC code. This CNC code is unique in that it is functionally encapsulated with the feature data to provide a 'Variant' strategy utilizing the special parametric programming facilities provided on the controller. IFPP thus demonstrates an integrated part-process environment that enables quick turnaround from design to manufacture.     

Development of an integrated model for process planning and parameter selection for machining processes

The concept of ‘do it right the first time’ in the machining industry not only expects the best quality products but also at the best possible cost. The cost of machining depends on intelligent process planning and selection of machining parameters such as speed, feed, and depth of cut. The problem of machining parameter selection has received great attention by researchers and many techniques have been developed. A review of these techniques reveals that the selection of the machine and cutting tool is done before the process of cutting parameter selection and process sequencing, and often the selection is based on experience. The current research is an attempt to develop an integrated model (ExIMPro: Expert system based Integrated model for Machining Processes) which finds the sequence of operations with set of machines, tools, and other process parameters to minimise the cost of machining for a cylindrical part. This system consists of existing expert system Machining Parameter SELection (MPSEL) for machine and tool selection and a Microsoft Excel® and Visual Basic® based parameter selection model. The present model focuses on turning and cylindrical grinding operations but other processes can be incorporated with little modification to the software.     

Extraction of milling know-how from NC programs through reverse engineering

To automate machining process planning, the acquisition and representation of machining knowledge or know-how in a reusable way is needed. The machining know-how is implied in NC programs made by experienced workers. In this paper, the methodology and system for extracting machining know-how in milling operations have been developed. With the system, machining features, operations and their associated cutting conditions (depth of cut, feed rate and spindle speed, etc.) and machining method can be extracted by analysing NC programs in conjunction with the tools used and workpiece blank model. The milling know-how is represented as a collection of these extracted data that can be used in future machining operations. To verify the system, actual NC programs for milling have been analysed and the milling know-how has been extracted successfully.     

Concurrent analysis of machining sequences and fixturing set-ups for minimizing set-up changes for machining mill-turn parts

In a typical machining process for producing a mill-turn part, milling operations and turning operations are required. If both milling machines and turning machines are utilized, the part may need to be moved between the two types of machines. In addition, the fixturing set-ups may need to be changed when different portions of the part are machined. In this research, a concurrent analysis model for analysing machining sequences and fixturing set-ups is presented. The purpose is to determine a good machining sequence by evaluating the machine changes and the fixturing set-up changes. A feature-based fixturing analysis method is developed for calculating the fixturing parameters for machining prismatic features and rotational features of a mill-turned part. A branch-and-bound method is developed to analyse the feasible machining sequences to find the best sequence with the minimum number of machine changes and fixturing set-up changes. A software system is implemented and example parts are tested and discussed.     

CAD/CAPP/CAM集成系统的研究与开发

文章介绍了可实用的CAD/CAPP/CAM集成系统。该系统是由机械产品设计人员,工艺人员和数控机床NC编程人员共同努力,在商品CAD/CAM软件Pro/ENGINEER平台上开发的。系统由三个子系统组成：零件信息识别子系统,CAPP子系统和自动CAM子系统。零件信息识别子系统从三维零件中提取零件信息,CAPP子系统分析零件信息,自动生成零件加工工序和工步,从刀具数据库中查询刀具及切削用量,并完成各工序的工步排序。自动CAM子系统根据CAPP的结果,自动生成Pro/ENGINEER的NC工步,经过NC仿真后     

Automated feature validation for creating/editing feature-based component data models

In a feature-based design system, it is necessary to check if a feature is valid (i.e. dimensions and class are proper) before adding it to the component model, and to detect if there will be any changes in the existing features which interact with it. The same applies to an existing feature to be modified and its interacting features when editing a feature model. This ensures a precise feature model of component design for the downstream applications. It is a commendable goal to automate the process of feature validation, which in turn increases the system's capability and intelligence, thus reducing the requirement on the designer's effort. This paper presents a Boolean operation-based systematic methodology of automating feature validation by checking feature dimensions and class, respectively. It briefly introduces a feature-based component data model (FBCDM) suitable for process planning and NC programming, and then discusses in detail the problem of feature validation and the algorithms of feature validation for creating/editing FBCDMs.     

Identification of machining features based on available resources of cutting tools

In research on machining feature recognition, the problems of interacting features and availability of cutting tools are considered two major obstacles for developing industrial applications. In this research, a new machining feature recognition approach is developed to address these problems. In this work, a new concept called cutting mode is introduced to associate generic machining surfaces and cutting motions. In the feature recognition process, the machining surfaces of a part are first mapped to cutting modes, and these cutting modes are further mapped to available cutting tools. Among all the created candidate machining processes, heuristic rules are employed to identify the optimal solution that requires the minimum number of setups. When a number of machining surfaces are associated with a cutting tool in the same setup, these surfaces are grouped as a machining feature. Therefore the interacting features are recognised by the different cutting tools to produce these features. A database of available cutting tools is used to avoid the identification of features which cannot be machined in a machine shop. Three mechanical parts with interacting features are selected in the case studies to demonstrate the effectiveness of the developed approach.     

Adaptive and dynamic process planning using neural networks

Although feature-based process planning plays a vital role in automating and integrating design and manufacturing for efficient production, its off-line properties prevent the shop floor controller from rapidly coping with dynamic shop floor status such as unexpected production errors and rush orders. This paper proposes a conceptual framework of the adaptive and dynamic process planning system that can rapidly and dynamically generate the needed process plans based on shop floor status. In particular, the generic schemes for constructing dynamic planning models are suggested. The dynamic planning models are constructed as neural network forms, and then embedded into each process feature in the process plan. The shop floor controller will execute them to determine machine, cutting tools, cutting parameters, tool paths and NC codes just before the associated process feature is machined. The dynamic nature of process planning enables the shop floor controller to increase flexibility and efficiency in unexpected situations.     

An efficient algorithm for automatic machining sequence planning in milling operations

Machining sequence planning can be considered as one of the most important functions of manufacturing process planning. However, less attention has been paid to automation of this function in contemporary computer-aided process planning systems. This paper describes an efficient algorithm for automatic machining sequence planning in 2.5D milling operations. It is programmed in LISP and forms the machining sequence planning module of a CIM system. This module is integrated with a feature-based design system that determines required machining operations and parameters for each machining operation. This information is then sent to the machining sequence planning module for determining proper machining sequence plans for producing the part. The algorithm generates feasible machining sequences based on the bilateral precedence between machining operations. The algorithm results in minimized tool changes.     

Feature-driven,process-based approach to the integration of CAD /CAM in wireframe models

This paper presents a structure for an integrated CAD/CAM system in wireframe models than can be simultaneously used for product design and manufacture of prismatic components. A feature-driven, process-based design methodology, which derives its basis from traditional geometry-based design, feature-based design, deterministic and expert heuristic manufacturing knowledge, is proposed. This methodology provides an integrated modelling environment for automation of downstream manufacturing applications such as process planning and NC code generation. Representation of features in the design database is not limited to geometry alone but includes material, tooling and machine specifications and is based on a process-to-geometry mapping. Research shows that informational completeness of a CAD database depends on application; and for manufacturing tasks, the vocabulary of the process describing the means of making a part should be mapped directly to the feature-based geometry. This effort answers key issues in integrating CAD and CAM in the most widely used wireframe modelling systems.     

Feature-based representation for manufacturing planning

Improved integration using product models in a computer aided design and manufacture environment implies that there is an enhanced need to provide information support across a wide range of applications. In a typical situation concerned with mechanical products, these applications are likely to include detail design, process planning and assembly planning. Features have frequently been used to support these and other applications individually, but single feature representations that simultaneously meet the information needs of a number of applications are unusual. Assembly and process planning are two important aspects of an integrated design and manufacture system, and a formal structure for their representation in a feature-based design system is presented. Features are considered to be machined volumes and are described in a hierarchical taxonomy that is designed to be useful across a range of machined components. The assembly structure is also defined hierarchically with the (machining) features forming the basic entities in the assembly. Assembly relationships among features are defined in the form of mating relationships that are carried by the features. A set of mating relationships between pairs of features has been defined after having studied the literature and a number of engineering products. An integrated data structure containing process planning information from earlier research work and the assembly mating relationships is presented and forms the basis of class definitions for each level in the assembly hierarchy. Object-oriented programming techniques have been used to implement a prototype system using the ACIS solid modelling kernel. The research has illustrated the feasibility of using a single feature representation to support a number of activities within a computer integrated manufacturing environment.     

Manufacturing features: Verification interaction accessibility and machinability

A major problem in CAD/CAM integration lies in the difficulty in representing the component definition adequately for all applications. Features are considered as a main factor in the CAD and CAM link because various design, engineering and manufacturing data can be associated with a feature. However, tagging feature labels onto geometry does not guarantee the geometric correctness of the resultant feature; knowledge of the topology and analysis of the geometry is needed to correctly identify the validity of the resultant feature. This paper discusses a feature-based design system capable of representing 2.5D components in terms of manufacturing features such as holes, slots and pockets, which are associated with distinctive manufacturing processes. The system is capable of verifying all the defined features by comparing the definition of the resultant features against those of the applied features. Feature interactions are considered to investigate the effect of the interaction on the validity, accessibility and machinability of each feature. Individual features can be extracted from the product model, where all the information about the product is held, for analyses. Each volumetric feature corresponds to a solid that can be removed by one or more machining operations; as a consequence of applying volumetric features, surface features are generated. These surface features provide enough information to enable the validity and machinability of the individual features to be determined and to establish the possible routes in which the feature can be accessed, if any. The proposed approach has been explored in a rapid prototyping test bed consisting of product modelling environment coupled with a solid modeller.     

FMS中CAPP与CAM集成技术的研究

介绍了一个适用于FMS的CAPP／CAM集成系统。它由创成法CAPP系统，NC自动编程系统和它们之间的接口等主要部分组成。系统采用基于特征的零件描述方法作为集成环境下统一的零件信息模型。由CAPP系统生成的工艺规程，通过接口文件自动传输给NC编程系统，经过特征识别后，从特征NC程序库中调用相应的特征数控程序，实现NC自动编程，为检验NC程序的错误，系统还具有刀具轨迹仿真功能，系统用户界面友好，经加工验证，可用于生产。     

Algorithms for grouping machining operations and planning workpiece location under dynamic machining conditions

In this paper, algorithms are presented to develop an integrated system to generate machining groups for set-ups and to plan workpiece location layouts for fixture design. The objective of the proposed system is to overcome the deficiencies of existing set-up planning and fixture design approaches. Parts are described in terms of machining features that consist of attributes required for automation and integration. The approaches of machining feature-based design and precedence matrix algorithm are combined to automate the process-planning task and to generate the machining groups for set-ups. An algorithm for selecting the locating and clamping positions of the workpiece is presented to configure the fixture in terms of modular elements. Fixture configuration verification analysis is carried out for time-varying machining forces to ensure that the workpiece will be held against cutting and clamping forces. The chip-removal effect is taken into account for stability analysis using finite-element analysis technique. An example is included to illustrate the application of proposed system.     

箱体零件CAD／CAPP／CAM集成系统的研究与实践

在ＣＩＭＳ环境下，针对箱体零件ＣＡＤ、ＣＡＰＰ、ＣＡＭ信息集成的功能需求，在基于特征的箱体零件信息模型、工艺计划模型与服务于工艺设计的制造环境模型的支持下，开发出了特征造型，工艺设计及加工过程仿真与ＮＣ编程等子系统，从而完成了一个集成化的箱体零件ＣＡＤ／ＣＡＰＰ／ＣＡＭ系统。     

Effect of machining parameters on turning of VAT32® superalloy with ceramic tool

The objective of this research was to study the machining of superalloy VAT32® using alumina-based ceramic tool without cutting fluid, applying different machining parameters to evaluate the surface finish of parts, vibration and main wear of tools. For this, a turning process with a linear trajectory of 30 mm was performed, in which were collected data vibration and surface roughness of the stretch, as well as wear and damage in the tools. The turning tests were performed utilizing cutting speeds of 270, 280 and 300 m/min, a feed of 0.10, 0.18 and 0.25 m/rev and a cutting depth of 0.50 mm. With results, it was identified that the feed influenced significantly both the vibration and the system, since the cutting speed influenced only the vibration. Being that the best results happened for the smaller feed and greater cutting speed. It concludes that the machining of superalloy VAT32® with ceramic tool introduced herself promising.     

叶轮零件集成数控编程与数控加工过程仿真

探讨应用于叶轮类零件的集成数控编程与加工过程仿真技术,给出了其功能结构图与流程图,利用商品化软件SURFCAM和VERICUT构建了集成数控编程与加工过程仿真环境,并利用其实现了一个整体叶轮零件的数控编程与加工过程仿真,实际加工结果表明其能够有效解决叶轮类零件的复杂曲面加工问题.