Abstract: This paper studies the differences and connections between MES production planning management and ERP production planning management. It identifies the production planning management data content for welding, painting, final assembly, and engine assembly workshops in automotive manufacturing enterprises and designs various data transmission implementation methods to meet the application needs of different production processes in different workshops. Furthermore, the production planning management system designed in this paper includes a fault handling module to ensure the complete operation of the production management system. Keywords: MES, Production Planning Management , Implementation Plan I. Overview of MES Production Planning Management Production planning management is crucial in MES systems. We know that, generally, enterprise production planning is completed by the upper-level management system ERP. The differences between MES production planning and ERP production planning are: ERP production planning is based on the order sequence, taking time factors into account, using days as the unit of arrangement. The order is calculated based on factors such as sales order and sales forecast time, manufacturing lead time, raw material procurement lead time, and inventory, using MRP logic; it is an unlimited capacity plan based on orders. MES production planning takes production materials and equipment as objects and schedules according to production units; it is execution-oriented, considers constraints, breaks down ERP production orders, and re-plans production schedules; it is a time-based finite capacity plan. We can see that MES production planning management and ERP production planning management together constitute the production planning management of the entire production process of the enterprise. In order to better realize production, MES production planning management and ERP production planning management must be effectively combined, so that MES and ERP together form a complete closed-loop system of planning, control, feedback, and adjustment. Through the interface, plans and commands are transmitted and actual results are received, so that production plans, control instructions, and actual results information are transparently, timely, and smoothly transmitted in the entire ERP, MES, process control system/basic automation system. MES production planning is the foundation and guarantee for ERP production planning to be implemented. [1] Based on our understanding of MES production planning, when designing MES production planning management, we must ensure that this system can achieve the following functions:  Receive production plans transmitted from the upper management system ERP.  Ensure that the actual results information of workshop production is transmitted to ERP in real time so that ERP can understand the execution of the plan, backflushing, and scheduling.  Break down the production plan created by ERP into smaller parts based on production materials and equipment, and then reschedule production. II. Composition and Transmission Method of Production Planning Management Data Based on the design functions of production planning management mentioned above, the data for production planning management mainly includes the following four aspects:  Production plan data transmitted from ERP;  Actual production performance data transmitted to ERP;  Production information transmitted to equipment and producers;  Production information obtained from equipment or producers. These four types of data will be described separately below. 2.1 Production Plan Data Transmitted from ERP to MES To ensure the needs of workshop production, ERP needs to transmit production plan data for one week ahead to MES daily, which is the sequential plan file. The transmitted sequential plan file should contain all production information involved in the production workshop. Since the MES system and ERP system belong to two different layers of information systems, and typically the ERP system application platform is UNIX while the MES system application platform is Windows, to ensure the smooth and complete transmission of production plan files between the two platforms, we designed an FTP method. That is, an FTP server is established on the MES server, and the ERP system uploads a unique plan file daily at set times. The plan file uses a common text file format. To avoid potential data integrity issues during upload, an identifier line needs to be added to the plan file. When the MES receives the plan file, it decomposes the file and can obtain integrity information from the identifier line. An example of a plan file format is as follows: #####Begin##### Plan Content######END###### 112 The first line serves as the start identifier line of the plan file, and the last line is the end identifier line, indicating the number of records issued in the plan file at the end of the end identifier line. This allows the MES system to compare the file's integrity. 2.2 Production Plan Execution Data Transmitted from MES to ERP To form a closed loop between the MES and ERP production plans, the MES production management system needs to transmit the actual execution performance information of the plan to the ERP. This ensures that the ERP can perform the following functions:  Production plan tracking: Tracking the production status of each vehicle;  Material backflushing and finished product warehousing;  Production query and statistics: Performing statistics from multiple dimensions and angles. The content and quantity of information transmitted vary greatly across different workshops. Therefore, the data content transmitted from the MES production planning management system to the ERP system should be designed separately for the different production processes in welding, painting, final assembly, and engine assembly workshops. 2.2.1 Production Information Transmitted from the Welding Workshop to the ERP System 2.2.2 Production Information Transmitted from the Painting Workshop to the ERP System 2.2.3 Production Information Transmitted from the Final Assembly Workshop to the ERP System 2.2.4 Production Information Transmitted from the Engine Assembly Workshop to the ERP System  Engine rolling off the production line  Engine rolling off the production line, engine unit rolling off the production line  Transmission rolling off the production line  Engine and transmission assembly 2.2.5 Methods of Transmitting Actual Production Information from the MES System to the ERP System The production performance information collected by the MES system is stored in the MES system's database. The ERP system directly retrieves this information from the MES system's database. The ERP system needs to constantly monitor changes in the data in the designated tables of the MES system's database and promptly transmit the production information to the ERP system to achieve the ERP production planning management function. 2.3 MES Transmitting Planning Information to Equipment and Producers To execute the production plan and guide production equipment and producers, the MES needs to transmit the following information. Welding workshop: produces vehicle series code, model code, and vehicle VIN code; Painting workshop: produces vehicle model code, color code, and vehicle VIN code; Final assembly workshop: vehicle VIN code, model code, body color, body number, interior color, body deformation, engine type, transmission type, air conditioning system, seats, interior grade, audio system, braking system, and tires; Engine assembly workshop: engine type, transmission type, and engine and transmission combination information. Depending on the type and content of information transmitted in different workshops, our data transmission methods vary. The main methods are as follows: 2.3.1 Vehicle Model Display Board: Primarily used in the welding workshop, this equipment displays the vehicle model information or parts information for each workstation, guiding producers to manufacture according to the production plan. The vehicle display panel uses a two-digit eight-segment code to display numerical content, as shown in Figure 1 below. 2.3.2 Touchscreen: Touchscreens can display a relatively large amount of information about planned production vehicles. However, due to their small size, they are not suitable for use when producers are far from the touchscreen. Therefore, they are best suited for welding and engine workshops. The MES production planning management system transmits production planning information to the touchscreen and displays it in a specific format to inform producers and facilitate the completion of corresponding production activities. 2.3.3 LED: LEDs can display a relatively large amount of content and are highly visible, making them the most widely used technology. They can be applied in all production workshops and can dynamically prompt producers to perform the correct production activities. 2.3.4 Configuration Sheet: The configuration sheet is printed out using a computer. This method allows the printed configuration sheet to be pasted onto the vehicle awaiting production, providing producers with more information about the vehicle. However, this method is not suitable for relatively harsh working conditions and therefore cannot be used in welding and painting workshops. Figure 2 below shows an example of a configuration sheet designed for the final assembly workshop. 2.3.5 PLC Data Transmission PLC data transmission utilizes the network connection between the PMC system in the MES system and the PLC of the production equipment to transmit production plan information to the production equipment, guiding or correcting the equipment to complete production. This method is suitable for workshops with a high degree of automation. When there are few operators, the production process is usually automatically determined by the production equipment. Therefore, this data transmission method can effectively transmit production plans. Painting workshops typically use this method for data transmission. 2.3.6 Intelligent Material Rack Intelligent material racks use illuminated buttons to indicate the corresponding production activities. On the material racks storing parts for assembly, indicator lights are installed in different compartments according to different types of parts. During production, the indicator lights in the corresponding parts compartments are illuminated according to the production plan requirements, informing the producer. Intelligent material racks are suitable for applications where there are many types of parts at the same workstation, the parts are not large, and manual operation is required. The intelligent material rack design is as follows: 2.4 MES Collection of Equipment and Producer Planning Information To transmit production performance information to the ERP system, the MES system needs to collect performance information from production equipment and producer work processes. The collected data content is the information data transmitted by the MES to the ERP. There are two main ways for the MES to collect production performance information from production equipment and producers: 2.4.1 PLC Data Acquisition PLC data acquisition involves data transmission between the MES system and the PLC controller of the production equipment. It collects the basic information of the production workpieces and production status information of the production equipment in real time, stores it, and after processing, can transmit it to the ERP in a proprietary format. 2.4.2 Producer Input This method uses barcode scanners and computers or touchscreens to provide producers with a fixed-format input interface for production performance information. Producers input the basic information of the production workpieces by recognizing the equipment or manually, and input the production status information into the computer or touchscreen, thus completing the MES system's collection of production performance information. III. Fault Handling MES production planning management serves as a bridge for communication between the upper and lower levels of production processes. It includes communication not only with the lower-level production equipment but also with the upper-level management system ERP. Under normal working conditions, MES obtains the production plan from ERP, makes corresponding adjustments, and then transmits it downwards to guide production. However, in order to ensure that the normal operation of workshop production activities is not affected when the ERP system fails, it is necessary to design certain fault handling procedures to continue to guide production equipment and producers to carry out production when the ERP cannot transmit the production priority plan. We have designed a manual production plan issuance function in production planning management. With this function, production managers can manually issue production plans. This function can play the same role as the production priority plan generated by ERP when the ERP system is not in use or when the ERP system fails. [References] [1] Zhang Tao, Chen Xiangyang, Division of Labor and Integration of MES and ERP in the Steel Industry, China Manufacturing Informatization