Industrial control systems encompass programmable logic controllers (PLCs), supervisory data acquisition and monitoring (SCADA) systems, and distributed control systems (DCS). PLCs are typically used as crucial low-level control components in SCADA and DCS systems to implement specific operations and process control of industrial equipment, while SCADA focuses on monitoring data from various subsystems. DCS, primarily used in process industries, emphasizes distributed control but also incorporates SCADA functionalities.
To improve the management and control level of the workshop, the application of Manufacturing Execution Systems (MES) has become increasingly common in manufacturing enterprises in recent years. MES is a production management system based on planning, execution, and control. It is located at the execution layer between the planning layer and the on-site production. It needs to process production and management information in the production process, and it also needs to transform, process, and transmit production process information. Therefore, it needs to achieve connection and data acquisition with the lower-level production equipment.
On the workshop floor, interconnecting with equipment through MES can make the production process transparent, seamlessly link the enterprise execution layer with the workshop control layer, eliminate information silos at the equipment level, and obtain real-time status information of CNC equipment for dynamic management of control equipment.
However, at present, traditional manufacturing enterprises have a large number of equipment, which are not only a mix of old and new equipment and different brands, but also have diverse communication methods and large data collection volume, making data collection for MES extremely complex and difficult.
So, how does MES connect to existing devices? What are the methods for MES data acquisition?
MES uses PLC to acquire data.
Generally speaking, MES collects data from the device PLC in two ways: proactive and interactive. Proactive means that the MES actively accesses the CPU-related memory area of the device PLC (this memory area serves as a data storage through communication between the two parties); the other way is that the MES sends a data communication request, and the PLC sends the data to the MES according to a specified format.
The MES is directly connected to the equipment and needs to communicate with the PLC. The main focus is on ensuring proper hardware and software interfaces. Data can be transmitted from the PLC to third-party devices, or a SCADA (Supervisory Control and Data Acquisition) system can be added between the MES and the PLC. The communication protocol of the MES needs to be considered. For automated production lines or equipment with network interfaces, the MDC (Metadata Controller) can directly exchange data with the PLC of the equipment through the network, and can collect the working status of the production line or equipment.
Through MES (Manufacturing Execution System), upper-level production management can monitor lower-level equipment, making workshop management more transparent and enabling the acquisition of relevant production information, such as production quantity, speed, number of downtimes and duration. This information can be presented in a clear and intuitive graphical interface, providing managers with real-time on-site information and effectively assisting maintenance engineers in quickly locating and analyzing on-site faults and determining solutions.
Without a PLC, how can an MES (Manufacturing Execution System) acquire data?
1. Data acquisition through the installation of sensors on the equipment
For equipment that cannot connect to a PLC, speed and quantity sensors need to be installed to collect operational status data. Process-oriented production environments have strict requirements for temperature and humidity; their primary data collection method is temperature and humidity sensors. Auxiliary data collection for equipment requires the addition of sensors for dampening solution pH and conductivity. Wireless data acquisition cards and gateways typically use reflective or through-beam infrared sensors.
2. Collect data using barcode scanners or RFID tags.
Barcode scanning is commonly used in warehouse management in manufacturing enterprises. In a WIFI network environment, it is frequently used for managing production materials such as product name, quantity, batch, production date, and warehouse location. RFID is generally used in on-site logistics management, such as the quantity of semi-finished products, the warehouse location of finished products, the name of semi-finished products, the processing material number, the location of semi-finished products, the start time, and the end time.
