Research and development of integrated CAPP system for automotive wire harness manufacturing enterprises

The automotive wiring harness is known as the car nerve, and is the transmission carrier of the vehicle power and various signal distribution systems PASDS (Power and Signal Distribution System). As far as the current state of the art is concerned, the stronger the function of the car, the higher the technical content and complexity of the wire harness. At present, a large number of wire harness manufacturers still use AutoCAD hand work harness diagrams by process designers and then pass them to the workshop for production. Undoubtedly, such a series of processes from planning wire harness to production are inefficient, difficult to guarantee quality, and it is difficult to realize wire harness design informationization and process automation. The integrated CAPP system for automotive wire harness manufacturing enterprises combines process knowledge base to integrate wiring harness planning, process information generation and export, and wire harness production, effectively solving the problems of low production efficiency and unqualified product quality. 

1 Automotive wiring harness production enterprise process file features

There are various types of process documents. From the nature of the documents, they can be divided into static and dynamic types. The main sources are the standardized process specifications and process design manuals. For automotive wiring harness manufacturers, static files are mainly composed of wire harness production specifications and enterprise production specifications. The dynamic file consists of the process task allocation card, which is the product of the comprehensive detailed process file and the wire harness design process prepared before production for production management and scheduling. Most of the processes are carried out in strict accordance with the characteristics of the product and the process documents, and a few processes are determined by the workers themselves. After the completion of various processes, the quality inspection personnel shall check the conformity of the products according to the requirements of the inspection card. The technical documents of such enterprises are characterized by: multi-type, file-by-order product archiving. The coordination and communication between various departments of the enterprise is limited to the paper document mode, which seriously affects the improvement of the company's benefits. These are mainly reflected in: 1) manual process task distribution card design based on the harness pattern drawn on AutoCAD; The product data is not shared, the experience and knowledge of the process experts are not realized; 3) the product design process lacks management and control; 4) the process resources are not optimized.

2 Computer-aided process design CAPP system functional analysis

Through the actual research and analysis of automobile wire harness manufacturing enterprises, it is determined that the functional requirements of CAPP system of automobile wire harness manufacturing enterprises should solve the technical design and production problems of enterprises from various aspects such as design, management and integration. The function of the functional flow chart system mainly has the following aspects:

(1) Based on the structure of automotive wiring harness products: In the enterprise, all production activities are carried out around the product. Process design based on wire harness product structure can find and manage process documents intuitively, conveniently and quickly, and effectively guide assembly and assembly of wire harnesses in the workshop.

(2) Automotive wiring harness process design: This is the core work of the process work. CAPP should ensure the completion of process design with high efficiency and high quality, mainly including wire harness process flow preparation, drawing of automobile wire harness diagram, and standard working hour calculation.

(3) Utilization of harness resources: In the process of process design, it is necessary to apply process technology to support data (wire harness production specifications, national/enterprise technology harness standards), and refer to process technology basic data. The resources of each company are different and the way they use resources is different.

(4) Wire harness process file generation: It is the final step of the process work. It summarizes the wire drawing material consumption and working time calculations, and the wire crimping data and the single drawing are effective guarantees for assembling the wire harness.

(5) Wire harness process design management: This is the management part of the process work, including wire harness diagram version management, material code management, wire harness process file security management, etc., which is of great significance for enterprise specification management.

(6) Wire harness diagram and process file network: In the LAN, the wire harness diagram and part of the process files are displayed in the production workshop and warehouse terminal by the Web method, and the preparation of the warehouse and the warehouse materials are guided.

3 CAPP system structure

The development of automotive wire harness CAPP system is based on the premise of the automotive wire harness enterprise itself, while fully considering the design object, that is, the characteristics of the wire harness and the actual needs of the wire harness manufacturing enterprise, practicality and advancement simultaneously.

The system is effectively combined with a typical C/S (Client/Server) structure and a B/S (Browse/Server) structure. That is, the design graphics and various wire harness components such as plug-in parts, cover parts and other parts graphics, process information and basic material information are stored in the back-end database, and the conventional process harness diagram design is carried out at the process designer side, in the warehouse and workshop terminals. Display information such as process documents to guide production.

3.1 System Management

This module is the key to ensuring that the system operates in a safe and reliable environment. The specific work is: divide the user into multiple categories such as designer and administrator, judge and set the use rights of various functions of the system according to the authority, confirm the check-in and check-out of the wire harness document, unified print output, process document information, etc. Product data is safe.

3.2 graphic design

This module is an integral part of the system core and completes the task of drawing harness diagrams for various models. By drawing the main harness, and then designing the necessary harness parts such as covering parts, surface cladding, and connectors, a real image harness is generated to guide production.

3.3 Process Information Module

Generate the appropriate process files and perform the necessary management based on the harness map drawn on the system. It is part of the core of the system, including the order and direction of the assembly of the various harnesses and the required man-hours in the production harness, in the format of the excel file.

3.4 Material Management Module

Its function is to manage the various basic material data of the production harness. For example, the basic information of wires, coverings, connectors, and surface coatings is added, deleted, modified, and screened.

3.5 wire harness diagram management module

Mainly to achieve the terminal production workshop, warehouse and other terminals, Web-based presentation of relevant materials to guide production and material management.

4 key technologies of CAPP system

4.1 Design of wire harness graphic database

The graphic database realizes the static description of the designed wire harness graphic features, and plays the role of "supporting the upper and lower" in the integrated CAPP, mainly including information of various wire harness parts such as wires, covering parts and inserts. For designers and administrators, they have a clear understanding of harness material consumption and layout during assembly. For business managers and assemblers, they can guide their work through the carrier of graphical information, that is, process information. According to the characteristics of AutoCAD's own database, the graphic handle and the custom graphic mark are extracted as the mark of the recognition graphic. Figure 3 shows the main wire harness of the CAPP system, where j0, jl, j2, j3, and j4 represent the node numbers on the main harness. There should be these fields in the graph database to explicitly represent it: harness product diagram number, node number, parent node, distance, node handle, node number handle, distance handle, line handle, where the handle is the iconic attribute of the AutoCAD record graphic Through it, the graphics can be modified, deleted, moved, etc.; the wire harness product number represents the figure number of the entire wire harness diagram, the node number, the parent node, and the distance represent the characteristics of the nodes in the wire harness diagram. Summarize the information in Figure 3, the various handle information is generated by AutoCAD, j0 has no parent node, j1's parent node is J0, the distance is 200 units, j2's parent node is jl, the distance is 300 units, j3's parent node kitchen 2 The distance is 400 units.

4.2 Process generation

Most CAPP systems use a simple "linear batch" process model No1, which divides the entire process design process into several sub-tasks that are executed sequentially (ie, linear processes), such as material entry. Harness part design, wire harness design, process generation and process data export, etc. There is very little feedback and iteration between subtasks, and the design analysis in each subtask is designed for the wire harness design once (ie batch processing) Equation). Since this model does not reflect the nature of the process design, there are many problems with the CAPP system developed.

For experienced designers, the design process is not performed in a fixed order. On the contrary, sub-tasks often cross in parallel, which is an iterative process. The process design process shows concurrent intersections, which is an iterative process. The process design process shows concurrency. For example, the general design of the wire harness is carried out according to the wire stripping, riveting, inserting, single-matching, and final matching sequence. For the familiar designer, the connector can be inserted first according to the wire harness diagram, and then the stripping, riveting, and Single matching and other processes. Secondly, the craftsman does not analyze and consider all the steps of drawing the wire harness diagram at one time. Instead, first read the sample of the wire harness image printed or faxed, determine the main process, then carry out the part design and other auxiliary processes, and finally carry out the whole process. The overall design of the graphic.

Here the harness design uses a progressive model. Starting from analyzing the information of the wire harness parts, the prototype of the process is first established, that is, the material information, the wire harness part information and its graphics are first established, and the wire harness graphic design is carried out through the process rules, thereby gradually completing the process specification design of the entire part.

4.3 Process output and integration with Web information systems

(1) Process database. The process database is a database of process design results generated by the storage system, including a process schedule, a bill of materials list, and a total process card table. The system puts the process data inventory on the server and shares the P1 for the work site on the local area network. The user can call the query and output the harness part information, the harness map information and the bill of materials at any time through the network at the working sites of various running line CAPP systems. .

(2) Integration with Web Server. Use the Web Server to store harness maps and process data to share resources with the server of the harness design system. But the difference is that it is designed primarily for the factories and warehouses of wire harness manufacturers, providing the necessary information to ensure the efficiency of wire harness production and wire harness material management.

5 system implementation

5.1 system technology platform selection

The choice of the system development environment should not only consider the needs of system development, but also the economic conditions and actual operating environment of the enterprise. According to the characteristics of the automobile wiring harness manufacturing enterprise and the requirements for the confidentiality of the process information, the system uses AutoCAD 2006 as the secondary development platform, combined with the characteristics of the mixed mode of C/S and B/S, using ObjectARX2006 to drop 1 in Visual C++. . Developed under the Net environment. The CAPP system client platform uses Windows XP Professional and the server uses Windows 2000 Server. There are a large number of process data and graphic files in the CAPP system. These files are circulated among network users, which puts high requirements on network performance, and therefore requires support of large-capacity databases and hard disk space.

5.2 Database Design and Access

In the database design, because of the many relationships involved in the process specification, it is necessary to establish an ER diagram. In data processing, the consistency and integrity of the data must be ensured, and the table must be reasonably constrained. In order to achieve access to database data by the CAPP system, OLEDB technology is adopted. The system establishes a database for basic material information, harness assembly process cards, harness system management, harness graphics, and process files.

6 system application

The system was applied in a wire harness factory in Hubei with good results. The factory is a medium-sized wire harness and auto parts manufacturing plant, with a process technology department, parts design department, quality inspection department, data department, network center, production workshop, warehouse and other departments. The system database is deployed in the network center, the C/S and B/S modules are deployed in the process technology department and the parts design department, the B/S modules are deployed in the production workshop, and the C/S modules are deployed in the warehouse. The process technology department uses the system design and the wire harness diagram and process to obtain the process information; the part design department uses the parts in the system design harness diagram for the process technology department; the production workshop uses the browser to observe the wire harness diagram and process data designed by the process technology department. To guide the production; the warehouse uses the system to observe the process data and prepare the wire harness materials. After many months of use, the process design efficiency of the plant has been greatly improved, from 73% to 93%, and the product failure rate has dropped from 19% to 6%. Most importantly, the factory's wire harness production cycle has been shortened to 213, which greatly increases the efficiency of the company's orders and external competitiveness.

7 Conclusion

Through the actual investigation of the wire harness enterprise, the characteristics of the process documentation of the automobile wire harness manufacturing enterprise are summarized, the functional analysis of the CAPP system of the automobile wire harness manufacturing enterprise is carried out, and the overall structure and function modules of the CAPP system conforming to these enterprises are designed, research and discussion. The design and implementation of each functional module of the CAPP system. The system has been applied in a wire harness manufacturing limited liability company and has achieved good application results. Practice has proved that it plays an important role in the wiring harness process design and production of automotive wire harness manufacturing enterprises.