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Applying RFID technology to the design of discrete manufacturing execution system can greatly shorten production preparation time and production cycle, improve product quality, more effective use of workshop resources, rapid improvement of workshop management capabilities and management efficiency, and speed and accuracy of product traceability Significant improvement and management of working hours will be more scientific and reasonable.
1MES system and RFID technology
Manufacturing execution system (manufacturing execution system, referred to as MES) was put forward by American AMR company (Advanced Manufacturing Research, Inc.) in the early 1990s. It aims to strengthen the execution function of MRP plan, and control the MRP plan with the workshop operation site. Link the system. The field control here includes PLC program controller, data collector, bar code, various measuring and testing instruments, manipulator, etc. The MES system has set up the necessary interfaces to establish a cooperative relationship with manufacturers that provide on-site control facilities. MES can optimize and manage the entire production process from order placement to product completion through information transmission. When real-time events occur in the factory, MES can respond to them in time, report them, and use the current accurate data to guide and process them. This rapid response to changes in status enables MES to reduce non-value-added activities within the enterprise, and effectively guide the production and operation process of the factory, so that it can not only improve the timely delivery ability of the factory, improve the circulation performance of materials, but also improve Production rate of return. MES also provides mission-critical information about product behavior within the enterprise and throughout the product supply chain through two-way direct communication.
RFID (Radio Frequency Identification, abbreviation RFID), radio frequency identification technology is an automatic identification technology that began in the 1990s, radio frequency identification technology is a use of radio frequency signals through spatial coupling (alternating magnetic field or electromagnetic field) to achieve no The technology that contacts information transmission and achieves the purpose of identification through the transmitted information. From the basic principle of information transmission, the RFID technology is based on the transformer coupling model (energy transfer and signal transmission between the primary and secondary) in the low frequency band, and based on the spatial coupling model of the radar detection target in the high frequency band (the radar emits electromagnetic wave signals). After hitting the target, carry the target information back to the radar receiver). In 1948, Harry Stockman published “Communications Using Reflected Power”, which laid the theoretical foundation for radio frequency identification technology.
2 demand analysis
As market competition intensifies and product life cycles shorten, discrete manufacturing has become more and more sensitive to the market’s response speed. The most representative parameters related to reaction speed are reaction time and delivery date. For this reason, enterprises must adopt information technology and advanced manufacturing technology to improve their production efficiency while guaranteeing quality. This requires managers to strengthen the production process management between the enterprise resource planning layer and the process control layer.
The application of RFID technology to the design of discrete manufacturing execution system makes up for the information management gap and information feedback delay in the enterprise resource planning and control layer, and realizes the smooth transmission of workshop production data. It can greatly shorten production preparation time and production cycle, improve product quality, use workshop resources more effectively, rapidly improve workshop management capabilities and management efficiency, greatly improve the speed and accuracy of product traceability, and work-hour management will be more scientific and reasonable.
3 System design goals
Discrete MES system can make full use of the technical advantages of RFID, solve the problem of information and management between the enterprise planning layer and the workshop site control layer, and realize the visualization and digital management of manufacturing and quality.
(1) Production capacity analysis: It can analyze the workshop, team, equipment and personnel in many aspects at the same time, so that managers can understand the on-site production progress, dispatch resources, and improve production efficiency.
(2) Real-time tracking of the entire production process: accurately track the production status of each work-in-process, understand the completion status of different orders, and provide strong support for managers to make decisions.
(3) Improve product quality: establish a computer-aided quality assurance system to realize computer management of quality inspection records and quality statistical analysis, which can quickly find hidden quality hazards and effectively reduce the incidence of product quality accidents. The establishment of the quality system and the strengthening of management will further improve product quality and production quality, greatly reduce loss costs, and effectively save costs.
(4) Provide the basis for report printing: the calculation and summary of various production data and the generation and printing of various reports are all managed by a computer, replacing the previous manual calculation, accounting, and manual report work. Reduce the work of related staff.
(5) Solve the problem of overstock of semi-finished products: The online quantity and online time of different stations can be provided at any time. Help enterprise managers to find out the links that affect the production schedule in advance, and provide help for balancing production.
4MES system application scheme
Because RFID electronic tags are relatively expensive and have a low penetration rate in fields such as manufacturing, at the same time, there is no uniform standard in various industries. The core idea of the discrete manufacturing MES application RFlD technology design program proposed in this paper is to use RFID tags to track the product manufacturing process within the enterprise. When raw materials are processed, RFID electronic tags are bundled, and all the information of the work-in-progress is written in the electronic tags. The electronic tags can be reused. An RFID electronic tag reader is installed at each production process station to track the production of the work in progress. The product at the station controller reads the electronic tag information through an RFID reader, and enters key information such as product model specifications and production time into the factory computer to track product production information.
The RFID card reader on the workshop station reads the electronic label information of the work-in-process, and returns to the database through the connection to the controller. Managers can not only track the quality and quantity of key parts in real time, but also issue corresponding production instructions through the electronic billboard of the factory workshop based on real-time changing information, and give workers corresponding production operation plans. At the same time, the quality of each product component can be analyzed later.
5 Overall structure of the system
5.1 System network topology diagram
Based on the RFID-based discrete MES data collection network topology, the bottom-level station card reader is connected to the control connector to the server, and downstream to various products in progress on the production line. Realize the application integration of bottom-level production data collection and server communication. The parking space card reader collects workshop site data in real time. The data is fed back to the server through the control connector. Managers use factory computers to analyze field data in real time, make reasonable decisions, and inform factory employees in the form of factory electronic billboards. Factory employees can complete the work in process according to the new instructions. The RFID card reader reads the electronic label information of the work-in-progress. On the one hand, it is sent to the factory computer as the basic information for production monitoring, and on the other hand, it is sent back to the parking card reader, and the workers are given corresponding production operation guidance through the electronic billboard.
5.2 System architecture diagram
The system adopts a three-tier structure of ERP/MES/PCS. Among them, the system integration interface realizes the data and business integration between the MES system and the ERP system. The communication middleware adopts the C/S structure to extend the wireless data collector to the client of the system. The collector can directly connect to the human database for real-time data exchange. In this way, the amount of information exchanged between the data collector and the server is small, the communication efficiency is high, the response speed is fast, and it has a strong data collection function, which can meet the needs of the factory for data collection and communication, and the burden on the server side is also Lighter.
5.3 System Features
On-site paperless operation avoids manual data copying errors. The data is quickly collected and sorted, which reduces the overall cost of users. The Internet can be used for remote data query. Real-time grasp on-site production quantity and quality status, and accurately grasp the information of raw materials, products in process, equipment and employees. The use of electronic billboards provides on-site visual management so that employees can accurately grasp the production schedule. Maintenance personnel can determine the production employees of the product based on the collected information, clarify the responsibilities, and establish production and quality data reports.
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