| 摘要 |
PURPOSE:To improve the accuracy of a product, and to improve the production efficiency by forming preliminarily a forging billet being in a cavity by an upsetting compression, raising a back pressure of one punch, also lowering a back pressure of the other punch, and punching and forming said billet. CONSTITUTION:An upper die and a lower die 1a, 1b are diesunk on a mating face in accordance with a cavity 2 which is coincided with an external form of a gear. A forging billet 5a is placed between the upper die 1a and the lower die 1b, the upper die 1a is moved by pressure toward the lower die 1b, and an upsetting compression forming is executed. In this case, a low pressure is operated suitably on a punch 3a, and a part of the billet 5a is formed preliminarily so as to generate a recess in a punch hole 4a. Subsequently, the punch 3a is made to descend by raising a back pressure of the punch 3a and also lowering a back pressure of the punch 3b, punching and forming are executed, and a product gear 5d is obtained. According to this method, a product having a good accuracy can be mass-produced. |
