Theoretical Analysis and Numerical Simulation of Ejection Demolding Process Parameters for Large Cylindrical Helical Gears After Die Forging

To address the critical technical issue of difficult demolding following the die forging process of large cylindrical helical gears, a systematic theoretical analysis and process parameter investigation of the demolding technique for such forgings was conducted in the present work. Firstly, a mechanical theoretical model was established for the forging ejection and demolding procedure, and the influence mechanisms of friction coefficient and ejection velocity on ejection load, effective strain, and damage characteristics of the forging were quantitatively revealed. The results indicated that an increase in friction coefficient led to a remarkable growth in frictional resistance between the forging and the tooth-profile die cavity, which consequently elevated the maximum ejection load, effective strain, and damage value of the forging synchronously. Similarly, the maximum ejection load, peak effective strain, and maximum damage value of the forging increased sharply with the rise in ejection velocity. Therefore, it was proposed that in practical industrial production, the friction coefficient should be controlled within the range of 0.25 to 0.30 by adopting suitable high-temperature lubrication measures, and a relatively low ejection velocity should be preferentially adopted to guarantee the overall quality of the forged gear. This study provided a reliable theoretical basis and technical support for engineering applications. The optimized parameters (friction coefficient 0.25–0.30 and low ejection velocity) could be directly adopted in industrial production to reduce ejection load, lower strain and damage, and stabilize the forging quality of large cylindrical helical gears in actual die forging and demolding processes.