ویرایشگر مدل ویژگی و برنامه ریزی فرایند سیستم برای محصولات ورق های فلزی

Sheet metal is widely used for industrial and consumer products because of its malleability into complex shapes. However, in the aerospace industry manufacturing planning of sheet metal products is still mainly carried out manually. Most of the previous research in this field has been primarily devoted to computer aided process planning for rotational and prismatic parts. This paper describes the development of an advanced software toolset used for the automation of sheet metal fabrication planning for aircraft components. The system is specifically designed to be implemented and maintained by manufacturing engineers, rather than computer programmers. Therefore a systematic user requirement capture has been carried out, and the planning knowledge has been captured within a leading aerospace company, which was the main sponsor of the project. The prototype system was then developed in collaboration with a software consultant company and finally evaluated and benchmarked through industrial case studies which proved that the system provides an efficient and effective approach to sheet metal fabrication process planning, when compared with other commercially available systems.

It has been recognised that process planning is the crucial link in the manufacturing cycle, as it determines how a product is to be manufactured. Traditionally process planning is carried out manually by experienced engineers who interpret engineering drawings of products and determine the ‘best’ route and manufacturing methods based on available materials, processes, the time scale and cost restraints. Manual planning is time consuming, labour intensive and may involve human errors [1]. It is also not unusual for different planners to specify different routes for the same part, which do not always incorporate the optimal solution to the problem. Standardisation, best practice and the company’s knowledge are difficult to maintain. As a solution, computerisation of process planning has evolved. Early planning systems were primarily for documentation generation, storage of bulk information and retrieval of generated plans [2]. The most maturely developed area so far has been focused on the machining applications [3] and [4]. Research and development in fabrication applications such as heat treatment, forging, injection moulding, and sheet metal fabrication is still premature, and the reported systems for sheet metal fabrication rely on a high level of interaction by the expert who provides decision-making at different stages of planning [3], [5] and [6]. The main aim of this research is to develop a user-oriented planning system for sheet metal fabrication in the aerospace sector. The idea is not to replace the role of expert process planners, but instead, to provide an advanced tool to assist them to be more efficient and consistent in their work. This project was set up in collaboration with an aerospace manufacturing company, and a software consultant company. In the aerospace company sheet metal forming processes are used to manufacture various components, such as bending and straight flanging, surface contour sheet, linear contouring, deep recessing and flanging, and shallow recessing. About 80% of the process plans being produced are mass produced components consisting of standard details and features with certain differences, whilst the remaining 20% are complex components which are small in quantity, but high in detail and quality. The first version of the prototype CAPP system developed was to generate process plans for bending and flanging of the mass produced components [7]. A further development allows the user to enter the product data as a feature tree for simple sheet metal components. Future developments of the system will be able to cope with the remaining more complex components and possibly be modified for prismatic and rotational parts as well. The initial stage of the research was conducted on-site at the aerospace company, to understand the manufacturing processes and process planning tasks, and to capture user requirements for computer aided process planning functions [8]. The second stage was carried out on-site with the software consultant company. The results gained from the requirements capture enabled a more realistic planning system to be developed. Although the prototype system is dedicated to the aerospace manufacturing sector, the underlying methodology can also be tailored to general sheet metal fabrication. The manufacturing logic as well as the data about the tools, work centres and manufacturing practices is kept in a database. The CAPP system draws on this database at run time to generate the process plan. This data-code separation allows the system to be generic and flexible

A new computer aided process planning system has been developed based on the latest software engineering technology and a comprehensive literature survey, a professional user requirements and knowledge capture within a leading aerospace manufacturer. The combination of many planners’ knowledge into the Master Plan has made the developed system more competent than those which only use one or few people’s knowledge. The system has been tested with typical data from the collaborator and the results obtained and feedback received from engineers in the company has shown that the system is much quicker, more efficient and consistent in producing sheet metal fabrication process plans than existing systems reviewed. The architecture of the system separates the manufacturing data and logic from the code. This makes the system flexible and generic as it can be configured for individual customer’s needs without making any changes to the code. The system has an intuitive and user-friendly interface. The productivity enhancement in using this interface has been established by comparison studies with other CAPP systems. The system has a low gradient learning curve allowing both, novice and experienced process planners, to use the system with equal ease. It should be noted that although the number of forming processes available in the system is limited, further development of the system will include other types of forming processes such as shearing, stretch forming, super-plastic forming, rubber forming and deep drawing. The addition of a standalone feature modeller allows an alternate and more graphical method of component information input to the system. It also allows quick and easy alterations to be made. Preliminary evaluation studies indicate that not only does the system perform as per the specifications set by user requirement capture but surpasses them.