Sheet metal punching flexible manufacturing system (FMS) production management


Abstract: Combined with the development of domestic sheet metal punching FMS, the information flow of the sheet metal FMS production management system is analyzed. The production management system is divided into five modules: system settings, data management, planning and scheduling, communication interface, and CAD/CAM management. The functions and implementation of the planning and scheduling modules are studied, based on the relational database SGL Server and Client/ Server structure has developed corresponding production management software.

  Independent sheet metal CNC processing equipment has shortcomings such as low efficiency, high cost, chaotic logistics management, and difficult quality control, which have become restrictive factors for the development of related enterprises. The sheet metal processing flexible manufacturing system (FMS) can overcome the above shortcomings and represents an important development direction of sheet metal processing equipment. Combining with the production needs of a certain factory, based on the domestic CNC punching machine, related units have developed a sheet metal punching FMS. The production management system is an important link to realize the effective integration of FMS, which determines the reliability, flexibility and automation level of FMS to a large extent. This paper studies the information flow and realization of the sheet metal punching FMS production management system from the perspective of application.

Figure 1 Schematic diagram of sheet metal punching FMS configuration

1 Sheet metal punching FMS control system composition
  The production management system is an integral part of the FMS control system. Based on the modular idea, the sheet metal punching FMS is divided into three units: central control, punching and warehouse. The central control unit is a workshop-level controller, which is composed of a planning and management server, a CAD/CAM programming workstation, and a dispatching and monitoring workstation. It is responsible for the FMS planning, production management, scheduling and monitoring functions. The punching unit controller and the warehouse unit controller are responsible for the production activities of their respective units. The structure of the FMS control system for sheet metal punching is shown in Figure 2.
Figure 2 Block diagram of the FMC control system for sheet metal punching

  The control and production management system of sheet metal punching FMS adopts Client/Server structure, based on Windows NT platform, the front-end program is developed in Visual Basic language, the back-end server database is based on MS SGL Server, and the local machine data such as user password and authority setting is based on MSAccess97 Development. A good control structure and development platform ensure the security and scalability of the system, and create conditions for the system to expand into sheet metal FMS and access to corporate CIMS.
2 Function analysis of sheet metal punching FMS production management system
  The development of the sheet metal punching FMS production management system should not only consider the integration of CNC punching machines, but also provide necessary interfaces for the integration of CNC shearing machines and bending machines, and be able to respond to system configuration changes within a certain range, such as the number of punches. , Increase in the number of warehouses, etc. In addition, the production management system should provide multiple operating modes to ensure that the operation plan can be adjusted in time when some equipment fails, and the system will not be paralyzed due to a single equipment failure.
  The FMS production management system is a process of controlling the information flow of the FMS with management software and formulating the optimal operation strategy of the FMS on the basis of information integration. Information flow control is the main difference between FMS and traditional automated production systems. To realize the effective management of sheet metal FMS, it is necessary to make a comprehensive analysis of the functional modules and information flow of the FMS production management system. According to the system function, the production management system is divided into five modules, and the relationship between the modules is shown in Figure 3.

Figure 3 Sheet metal punching FMC production management system module composition

  Among them, the system setting module completes the setting of basic system parameters, such as database capacity, single-shift production time, etc.; the data management module is mainly used for the management and maintenance of system operating data; the planning/scheduling module completes production plan entry, job queue generation, and daily Job queue optimization and sorting ~ static scheduling and dynamic scheduling; the communication interface module is the contact interface between the production management system and the real-time monitoring system, CAD/CAM system, etc., and is the basis for the effective integration of FMS. Considering the difficulty of integrating the sheet metal CAD/Nesting/CAM software ProCAD/CAMOR, a CAD/CAM management module was developed to manage the CAD/CAM task data and product data, and realize the communication with the host system.

  In fact, each module does not exist independently, and the module division is only for the needs of system analysis. During the operation of the FMS, there is continuous data exchange between modules and between modules and equipment, CAD/CAM systems, and monitoring systems.

3 Information flow analysis of sheet metal punching FMS
  Information flow analysis is the prerequisite for the development of FMS production management system. The research content of information flow analysis includes: what data needs to be collected; where the data is generated and where it flows; data processing, exchange and utilization, etc. Analyze the information flow in the sheet metal punching FMS, and divide the data into three types: basic data, control data and status data.

  (1) Basic data is data related to FMS settings, including: ①System configuration data, such as machine tool number, machine type, punch die position number, daily working hours, etc.; ②Material data, such as sheet metal specifications and dimensions, punch die specifications Etc.; ③User data, such as user name, authority, password, etc.

  (2) Control data is data related to the processing process, including: ①Product data, such as part number, part drawing and layout drawing, NC program, etc.; ②Plan data, such as plan number, delivery date, theoretical total working hours Etc.; ③processing task data, such as the number of parts, NC program number, execution times, etc.; ④job queue list, such as job number, priority, etc.
  (3) Status data is data used to describe resources, including: ①Equipment status data, such as stacker operating time, downtime, etc.; ②Material status data, such as mold status, etc.; ③Processing progress, such as job working status, etc. .

  During the operation of FMS, there is an internal connection between various data, which is mainly manifested as:

  ① Data connection When different modules or tasks require the same kind of data, data connection occurs. Data sharing should be considered in database design to ensure that modules exchange information in a timely manner.

  ② Decision-making connection When the decision-making of each functional module influences each other, a decision-making connection occurs.

  ③Organization contact Organizational contact is the prerequisite for the efficient operation of FMS, which can ensure the real-time and flexibility of FMS operation.

  Sheet metal punching FMS has a complex data structure and data types, including structured data (such as part numbers, part names) and unstructured data (such as geometric figures, CNC programs); the data has diverse and dynamic connections And real-time characteristics. These all increase the difficulty of data management. Relational databases have the characteristics of good data description consistency, logical structure and physical structure independent of each other, and are widely used. However, relational databases also have the following disadvantages:

  ① It is difficult to manage unstructured data (such as graphics, NC codes, etc.);

  ②Unable to express complex structure types such as nesting and recursion, and lack deduction and reasoning ability;

  ③The real-time performance is poor.

  The data server of the sheet metal punching FMS is developed by the relational database SOL Server; some partial data in the client is developed by the relational database Access97. The client/server structure is formed between the production management system and the real-time monitoring system, the CAD/CAM system, and the unit controller. In view of the shortcomings of relational databases, the following measures are taken in database design:

  ① Use files as an auxiliary tool to manage unstructured data such as graphics and NC codes, set the storage path of graphics and NC code files in specific fields of the database, and access the file content through the address.

  ②First, the monitoring system processes the high real-time status and control data in the FMS, and then the local database completes operations such as access in the background.

  ③For some local data (such as job plan and scheduling data), the Access database is stored on the local machine to speed up the response speed and reduce the burden of network transmission.

  ④For historical status data (such as production plan history, equipment status history), set the data capacity and control the amount of data.

4 Production planning and scheduling in sheet metal punching FMS
  Planning and scheduling is an important part of FMS production management. The planning module is responsible for accepting the master production plan (MPS) and formulating the FMS medium and long-term plan and short-term plan. The task of the scheduling module is to rationally configure and use resources to optimize system performance.

  The scheduling before FMS processing is called static scheduling. The task is to group, sort and refine the current operation plan to reduce the system adjustment time and realize the load balance of the machine tool. To facilitate the solution, static scheduling is often expressed as a single-objective optimization problem. As far as sheet metal punching FMS is concerned, because the planning and layout process has taken the delivery date into consideration, and the system configuration is relatively simple, the number of die changes and machine tool adjustment time can be minimized as static scheduling goals.
5 concluding remarks
  From the application point of view, the module composition of the sheet metal punching FMS production management system is studied, and the data flow form, internal connection and processing measures in FMS are analyzed. Taking the FMS planning and scheduling module as an example, the FMS static scheduling algorithm and the FMS dynamic scheduling solution based on rule simulation are given.