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Application of QR code technology in engine parts processing line
In 2012, Nanjing Automobile Group Co., Ltd. introduced Direct Part Marking (DPM) technology into its manufacturing process, marking a significant step toward achieving accurate traceability for critical engine components such as the cylinder block, cylinder head, and crankshaft. While the connecting rod and camshaft were not suitable for QR code printing due to limited marking space, they still benefited from batch-level traceability. The implementation involved setting up nine scanning and marking stations along the cylinder, cylinder head, and crankshaft production lines. At these stations, a two-dimensional code containing part identification, part number, and supplier code was printed directly onto the workpieces. These codes were then scanned using a QR code reader, with data uploaded via the PT-MES system to the Q-DAS database for further processing.
DPM, or Direct Part Marking, is a specialized method of marking components directly on their surfaces without the need for labels or tags. This approach ensures durability and reliability, especially in harsh industrial environments. In our factory, the QR code marking process is automated. Once a workpiece is positioned and clamped, a proximity sensor sends a signal to the PLC controller. Based on pre-defined logic, the controller transmits the necessary data—such as component ID, part number, and supplier code—via an RS232 interface to the marking machine. The machine then prints the information in a two-dimensional format. Scanners later read the QR codes, ensuring that each part can be tracked throughout the production cycle.
As shown in Figure 1, pneumatic marking is used at the upper line of the cylinder and cylinder head lines, while laser marking is applied at the final inspection stage of the crankshaft line. This combination ensures high-quality and consistent marking across different stages of production.
The two-dimensional code marking and scanning stations are strategically placed along the production line. For example, on the cylinder head line, a marking station is located at OP10, a middle scanning station at OP50, and a final quality gate scanning station at OP150. Each station plays a crucial role in capturing and verifying the QR code data. The marking process involves several steps: starting the cycle, detecting the workpiece, clamping it, checking the model, positioning the marking machine, printing the code, scanning, and verifying the result. If any issue arises during scanning, the system alerts the operator, who can either rescan or manually input the data.
At the offline scanning stations, similar procedures are followed. When a workpiece arrives, the scanner automatically captures the QR code and sends the data to the PLC. If the scan fails, the operator can manually enter the information. The system also includes a bypass function to release a workpiece if needed. These features ensure smooth and reliable operation even in challenging conditions.
To achieve full product traceability, the PT-MES and Q-DAS systems are used for querying product information and measurement data. For instance, users can log into PT-MES to view details about a specific crankshaft, including its serial number, steel stamp number, status, and location. Similarly, Q-DAS allows operators to access detailed measurement data, such as leakage test results, providing a complete record of each part’s performance.
Common issues like low scanning rates or inconsistent readings have been addressed through adjustments such as improving lighting, adjusting camera angles, deepening the print depth, and regularly replacing marking needles. These efforts increased the scanning success rate to 99.9%, meeting the project's expectations. Additionally, problems with data synchronization between the Andon system and scrap handling were resolved by modifying the manual scanner settings and implementing background processing in PT-MES.
In conclusion, the use of two-dimensional code technology in engine manufacturing has proven to be highly effective, offering precise traceability and improved production management. However, successful implementation requires seamless integration of processes, equipment, and software systems. With proper coordination and continuous improvement, this technology will continue to play a vital role in modern manufacturing.