Engine cylinder head leak detection production capacity improvement solution

China FAW Group has planned to expand the production capacity of its vehicle assembly line. To support this growth, it is essential to enhance the efficiency of the cylinder head assembly line, particularly the leak test machine, which currently operates at a slow cycle time of 60 seconds per unit. This slow performance has become a bottleneck, hindering the overall improvement of the assembly line's cycle time. As a result, technical upgrades and process optimizations are being implemented to increase production efficiency.  *Figure 1: Production line* **Working Principle of the Leak Test Machine** In industrial settings, the "leak rate" is commonly used to assess the sealing performance of a component. If the actual leak rate is below the allowable limit, the part is considered acceptable. The leak tester uses compressed air or vacuum to detect leaks in the tested component. It inflates the component or evacuates it, then isolates the test chamber from the pneumatic system. The pressure change in the chamber over time is measured. If there is a leak, the pressure will gradually drop (in the case of pressurization) or rise (in the case of vacuum testing). The flow detection leak tester is primarily used for checking engine cylinder head valves, oil seals, and similar components. It automatically inflates, balances, saturates, measures, and discharges the dry air medium, displaying the gas leak rate. This method is simple, reliable, and widely used in production. Key parameters for the test include the material and geometry of the workpiece, its condition, test pressure, test duration, allowable leak rate, temperature, and ambient conditions. When the results meet specifications, the part is vented and moved to the next stage. **Equipment Status Survey** **1. Measurement of the Test Time of the Leak Tester** The cylinder head leak tester requires five units to test four inlets, four exhausts, three oil passages, and one waterway. Each test has specific timing: - Project 1: Three inlets, each taking 10 seconds for 30 seconds total. - Project 2: Three exhausts, each taking 10 seconds for 30 seconds total. - Project 3: Two oil circuits, each taking 12 seconds for 24 seconds total. - Project 4: One waterway and one oil circuit, with 18 seconds for the waterway and 12 seconds for the oil circuit, totaling 30 seconds. - Project 5: One inlet and one exhaust, each taking 10 seconds for 20 seconds total. After the five testers are positioned, they operate simultaneously, with a maximum test time of 30 seconds. Switching between tests takes an additional 4 seconds, resulting in a main test time of 34 seconds. **2. Calculation of Auxiliary Action Time** The auxiliary actions, such as loading and unloading parts, plugging, and releasing, take a total of 26 seconds (see Figure 2).  *Figure 2: Auxiliary time* **Improvement Plan** Three options were considered to improve the cycle time: 1. **Option 1:** Reduce the leak test time (inflation, balance, testing). However, this could lead to inaccurate results, so it was not adopted. 2. **Option 2:** Increase the number of leak testers. Due to high costs and balanced test times, this option was also rejected. 3. **Option 3:** Shorten the auxiliary time by optimizing the movement of the workpiece into and out of the station, as well as the plugging and closing process. **Scheme 3 Implementation** - **Project Plan 1:** Synchronize the entry and exit of the cylinder head during testing, reducing the time by 2.5 seconds. - **Project Plan 2:** Seal the intake, exhaust, and fuel rail holes simultaneously before testing, reducing the blocking time by 2.5 seconds. - **Project Plan 3:** Close the intake, exhaust, and fuel rail holes at the end of the test, synchronizing the opening and closing process, reducing the time by 1.5 seconds. After implementing these changes, the total time was reduced by 6.5 seconds. The original cycle time was 60 seconds (34s + 26s), and after optimization, it became 53.5 seconds (34s + 19.5s). This improvement brought the process closer to the target of 54 seconds per unit. **Program Implementation** - **Stage 1:** Optimized the synchronization of workpiece movement, sealing, and removal. After implementation, six consecutive tests took 324.4 seconds, averaging 54.07 seconds per unit, just 0.57 seconds above the ideal 53.5 seconds. - **Stage 2:** Further improved the speed of plugging and reduced the table lowering time. After optimization, ten consecutive tests took 514.8 seconds, averaging 51.48 seconds per unit.  *Figure 3: Production beat improvement* **Conclusion** Through the optimization of the cylinder head leak test process, the issue of slow test cycles was successfully resolved. This improvement ensured that the production cycle of the cylinder head assembly line was enhanced, meeting the company’s requirements for increased assembly capacity. The author believes that similar challenges are common in the use of related equipment globally, and the methods applied here offer valuable insights for improving productivity and reducing manufacturing costs in the automotive industry.

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