Computer Aided Process Planning Research Articles

Product-oriented workflow management in CAPP

A product-oriented process workflow management model is proposed based on the multi-agent technology.The autonomy, inter-operability, scalability and flexibility of agent are used to cooperate the whole process planning andachieve the full share of resource and information. Thus, unnecessary waste of human labor, time and work is reducedand the computer-aided process planning (CAPP) system's adaptability and stability are improved. In the detailed im-plementation, according to the products' BOM (Bill of materials) in structural design, the task assignment, managementcontrol, automatic process making, process examination and process sanction are combined into a unified management tomake it convenient for the adjustment, control and management.

Optimal operation planning using fuzzy Petri nets with resource constraints

Traditional Computer Aided Process Planning (CAPP) systems produce rigid operation plans for each manufacturing feature. As a result, generated process plans lack flexibility and may not be optimal. This paper proposes a modified fuzzy Petri net, named OPN, to model alternative and optimal operation planning. Operation selection knowledge, which is a basis for operation planning, is formalized in OPN. By solving the T-invariants of OPN, alternative operation plans can be obtained for each feature of a machined part. After the execution of OPN, each alternative operation plan is assigned a numerical value that reflects its confidence degree. Based on alternative operation plans, the final optimal operation plan of each machining feature and the corresponding machine tools can be produced using resource-constrained algorithms.

A product-configuration-driven system for assembly planning within a product data management environment

This paper describes the results of a project sponsored by the Engineering and Physics Science Research Council (EPSRC) in collaboration with leading engineering and consultant companies, which is aimed at developing new methodologies for Computer-Aided Assembly Process Planning (CAAPP). The aims of this project were to investigate contemporary industrial requirements for CAAPP, study the feasibility of integrating CAAPP with data management tools via a product model and review current state-of-the-art systems and methodologies. The research has been focused on finding solutions to some of the limiting factors that have kept CAAPP an immature technology for many years. The deliverable of the research project is a novel assembly planning system, which has been developed in a Product Data Management (PDM) environment. The system takes the product configuration model derived from the PDM system as the input. This input is analysed by the system using intensive built-in knowledge to yield detailed assembly plans. The system achieves integration of CAAPP functionality with a PDM tool, providing a data control framework and a high-level data structure to form the basis of planning. The prototype system has an automatic planning module and an interactive planning sub-system that complements it. The interactive planning module also allows the user to capture the assembly knowledge and model it as a flowchart in the system. As fully automatic planning is a new field, comparison of automatically generated results with those of the semiautomatic system help to evaluate the system and build up user confidence.

Constraint-based process planning in sheet metal bending

The majority of research dealing with computer-aided process planning of sheet metal bending approaches this problem as heuristic search. Since relevant engineering knowledge mostly consists of declarations that prohibit collisions and just a handful of generative rules, there are no useful means to drive these heuristics. In order to find a new way, we have made experiments with a constraint-based approach: using predefined constraint types and geometric constraint satisfaction, complex bending problems have been solved. By returning not just a single solution but a Pareto-optimal set of solutions (i.e., operation sequences, with appropriate part orientations and tools assigned) we have left the engineers freedom to apply further, not yet modeled parts of their domain knowledge.

A computer aided process planning system for concurrent engineering

This paper present ProPlanner, a hybrid computer aided process planning (CAPP) system designed to facilitate concurrent product development. ProPlanner automates information acquisition, product design interpretation, manufacturing operation planning, cutting tool selection, set-up planning and operation sequencing. The system employs a hybrid approach utilizing a combination of rule-based reasoning and object-oriented programming. It enables the early detection of design errors during the design stage before manufacturing and incorporates a feedback mechanism for correcting errors and giving suggestions to modify the product design.

Fuzzy Part Family Formation Based on Grey Relational Analysis

Part family formation is one of the most important techniques in computer-aided process planning (CAPP). This paper presents a new method that uses grey relational analysis and fuzzy clustering to form part families. The main objective of this paper is to identify part families based on a new similarity coefficient which considers processing time, lot size, machine usability, etc., by using grey relational analysis. After the similarity coefficient is calculated, a fuzzy clustering method is used to obtain part families. The main contribution of this paper is to provide a rigorous mathematical approach to forming part families. Part family formation can be controlled, for different applications, by setting a resolution threshold, so the approach is flexible, practical and reliable.

Object-oriented knowledge-based computer-aided process planning system for bare circuit boards manufacturing

The manufacturing industry is time, quality and information driven. In the current highly competitive international marketplace, these factors are especially crucial to the electronics industry. In this paper, an object-oriented model of a computer-aided process planning (CAPP) system for the manufacturing of bare circuit boards is proposed. Process constraints and planning knowledge are all represented and modelled by respective constraints objects. The system is then implemented for the automatic process planning of double-sided circuit boards. The performance of the system is then compared with that of experienced process planners. The advantages in the use of the constraint and knowledge objects approach in a computer-aided process planning system are revealed.

Characterization and identification of forming features for 3-D sheet metal components

This paper presents a new classification system for forming operations, and concepts for extracting and recognizing forming feature from the 3-D sheet metal component created in a wireframe model. A set of principles is developed for characterizing forming features geometrically and topologically. Forming features are extracted by identifying 3-D component graph and subgraphs by vector normal method and vertex fusion methodology. Further, various planes and their type in the component graph are identified, and adjacency plane relationship between them is determined. Cross bend features are extracted by identifying common edges. Pattern recognition is then done using isomorphism principle and a set of characterization principles developed for forming features. A flat pattern is developed for the 3-D component and shearing features are identified. Recognized pressworking features help in the integration of Computer Aided Process Planning (CAPP), codification system, mapping of tools, inspection of tools, etc. The system has been tested for live components.

A Case-Based Computer-Aided Process-Planning System for Machining Prismatic Components

This article deals with a process-planning system that uses case-based reasoning methodology. Briefly, case-based reasoning is an intelligent problem-solving technique which works by searching through a database for previously solved problems for one or more cases whose identifying features closely resemble the current problem. The case-based reasoning system used in this article to develop a process plan, typically consists of three modules, i.e. the part input and representation module, the case retrieval, and case adoption module. In this paper, new approaches have been proposed in all three modules. By incorporating a multiparametric and absolute-matching technique, the case retrieval module especially has become more powerful. A practical approach has been suggested in this research to compute the similarity between part input and case. An illustrative example is included to demonstrate the proposed system.

The UK Navy RAMP Project: Improving the spares provisioning process through the rapid acquisition of manufactured parts

This paper reports on a Naval Support Command (NSC) commissioned pilot study into the use of a ‘production-on-demand’ system to reduce the cost of spares provisioning. The system, known as RAMP (Rapid Acquisition of Manufactured Parts) is based around the electronic communication of component information using ISO STEP standards AP203 and AP224. STEP AP224 has been designed to communicate the information required for process plans to be generated for single-item mechanical parts that are to be manufactured by machining, and, given appropriate computer aided process planning (CAPP) software, can be used to automate or semi-automate the process planning task, offering considerable lead time savings to component manufacturers, and enabling ‘production on demand’. The RAMP process has been tested through the manufacture of nearly 600 components, all of which were UK Navy inventory components, with information regarding the speed and completeness of the process recorded at each stage. The scope and results of this pilot study are reported. It is concluded that the adoption of RAMP processes for UK Navy spares procurement is likely to provide a significant cost and time saving over current procurement processes, and that AP224 has the potential to become the standard mechanism for component information to be exchanged where process planning of mechanical parts to be manufactured by machining is required.

A technology-driven architecture for developing highly configurable CAx software

Developing software for computer aided ‘x’ (CAx), where ‘x’ stands for design, manufacturing, engineering, etc., is a programming- and research-intensive process. Over the years, advances in software technology and tools have made the process of development easier, but expectations of the user have also risen accordingly. Software like computer aided process planning (CAPP) and computer aided assembly planning (CAAP) systems require extensive configuration and development by the user. This problem of user configuration and user development of the system poses a challenge to the software developers and researchers. This paper presents a case study of system development, which uses the state-of-the-art software technologies to overcome some of the problems.

A Review of the Evolution of a Graph Theoretic Approach to Computer Aided Process Planning

Abstract This paper describes the development of Computer Aided Process Planning methods at the University of Canterbury and Nanyang Technological University. Three methods are described: a generative system for milling operations, an interactive system for cylindrical parts, and a retrieval system using neural networks. They are based on tolerance analysis and, in particular our technique for tolerance charting using rooted tree digraphs.

A genetic algorithm based process planning system for mould base

With the growing importance of the plastic injection industry, traditional computer aided process planning (CAPP) methods that optimise plans in a linear manner have not been able to keep up with the need for flexible planning. This paper focuses on the development of a CAPP system to concurrently optimise the operation selections and sequences for mould bases. The system first identifies the machining features automatically. All possible combinations of processes (machine, machining direction and cutting tool) are then generated based on available machining resources. By considering the multi-selection tasks simultaneously, a specially designed genetic algorithm searches through the entire solution space to identify the optimal plan. This planner is expected to assist users in optimising process plans for the whole mould base.

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.

A WWW-based integrated product development platform for sheet metal parts intelligent concurrent design and manufacturing

This paper presents a WWW (World Wide Web) based integrated product development platform for intelligent concurrent design and manufacturing of sheet metal parts. In order to achieve this platform, several major modules are discussed. These modules mainly include the structure of the WWW-based integrated product development platform, an information integration framework, a RTCAPP (real time computer aided process planning) module, a customer interface module, and a design/manufacturing knowledge-based module for supporting product design and manufacturing. This paper gives the structure of the information integration framework for concurrent design and manufacturing of sheet metal parts. An information integration framework, called 'step structure information framework' is proposed. The principles, called 'zero thickness and zero bend radius' are put forward, which can be used to abstract the geometric entities of sheet metal parts in order to facilitate product design and modelling. Finally, case studies are given.

Integration of tool selection with design: Part 1. Feature creation and selection of operations and tools

Tool selection is one of the most significant process considerations when deciding how a machined product will be manufactured. The tool selection activity is rooted in feature geometry but it also has a direct impact on machinability and machine tool performance. Consequently, the integration of tool selection with design is a key step towards the goal of a seamless integration between computer-aided design and computer-aided process planning. This integration requires that design be carried out using features. A feature based design environment was created with associated validation methods for updating and managing feature dimensions, type descriptions and dealing with feature interactions. The next stage of automated tool selection involves converting the information associated with each feature into machining operation requirements, which in turn is used to query a database to extract all tools that may be used to complete a given operation. In this paper, which is the first of two parts, the feature creation and validation methods are presented together with the methodologies for operation and tool selection. In Part 2, a method for the estimation of machining times is presented together with results from testing the methods using real components.

Exact Tool Sizing for Feature Accessibility

This paper presents an algorithm for calculating the volume of a 2D-profile, accessible by a given diameter of milling cutter. The method is independent of the generation of cutter tool paths, and exploits facilities commonly found in kernel modellers. Exact results are obtained despite the simplicity of the procedure. As a proof of the concept, the algorithms have been implemented in the Heriot-Watt University feature recogniser as a pre-processor for a part programming system. The aim of these algorithms is to assist and optimise the selection of multiple tools for the machining of complex components. The methodology has applications in process planning research where it is currently common to assume that a single tool will machine each feature. Although cutter selection is a critical step in planning the manufacture of components, computer-aided process planning (CAPP) systems rarely make any attempt to analyse the tradeoffs involved. Perhaps this is because, traditionally, exact tool accessibility calculations have been viewed as a side effect of generating a cutter tool path. Consequently, accessibility calculations are not carried out explicitly but they appear implicitly in the results of a complex geometric algorithm (i.e. cutter path generation). Because this implicit checking of tool accessibility is carried out, downstream from the higher-level reasoning about set-up and sequencing, the results are generally available only after a detailed process plan has been generated.

A Novel Methodology for Computer-Aided Process Planning

A well-constructed generative computer-aided process planning (CAPP) system is suitable for computer-integrated manufacturing systems and intelligent manufacturing systems. Most generative CAPP systems developed in the last decade employed a linear and batch approach as their underlying methodology, but because of low efficiency and quality, many such systems cannot be applied effectively to industrial enterprises. To overcome these weaknesses, a novel methodology, called prototype-based incremental process planning (PIPP), is presented for CAPP in this paper which offers a new approach for increasing the efficiency and quality of process planning, and for fully supporting concurrent engineering. Based on this methodology, an experimental CAD/CAPP concurrent design system (HFCAD/CAPP) has been built, and a case study is presented to illustrate the characteristics of this system.

An Integrated Design and CAPP System for Cold or Hot Forging Products

This paper deals with an automated computer-aided process planning system by which designers can determine operation sequences even if they have little experience in process planning of bulk metal products by press working. The approach to the system is based on knowledge-based rules and a process knowledge base consisting of design rules is built. Knowledge for the system is formulated from plasticity theories, empirical results and the empirical knowledge of field experts. Programs for the system have been written in AutoLISP for the AutoCAD using a personal computer. An attempt is made to link programs incorporating a number of expert design rules to form a useful package for process planing. This integrated design and computer-aided process planning (CAPP) system is composed of two main modules and nine submodules. It is designed considering several factors, such as the complexities of blank geometry, punch and die profiles, the availability of press equipment, and standard parts. Results obtained using the modules enable the designer and manufacturer of cold forging or hot forging dies to be more efficient in this field.

A simulated annealing-based optimization algorithm for process planning

Computer-aided process planning (CAPP) in the past typically employed knowledge-based approaches, which are only capable of generating a feasible plan for a given part based on invariable machining resources. In the field of concurrent engineering, there is a great need for process planning optimization. This paper describes an approach that models the constraints of process planning problems in a concurrent manner. It is able to generate the entire solution space by considering multiple planning tasks, i.e. operations (machine, tool and tool approach direction), selection and operations sequencing simultaneously. Precedence relationships among all the operations required for a given part are used as the constraints for the solution space. The relationship between an actual sequence and the feasibility of applying an operation is also considered. An algorithm based on simulated annealing (SA) has been developed to search for the optimal solution. Several cost factors including machine cost, tool cost, machine change cost, tool change cost and set-up change cost can be used flexibly as the objective function. The case study shows that the algorithm can generate highly satisfying results.