METHOD TO MANUFACTURE HOLLOW LONG TRANSMISSION INPUT SHAFT BY TWO-STAGED COLD FORGING/EXTRUSION AND MANUFACTURING APPARATUS THEREOF

摘要

The present invention relates to a method to manufacture a hollow long transmission input shaft by two-staged cold forging/extrusion, which provides a dense structure, and excellent surface roughness and strength, and a manufacturing apparatus thereof. According to the present invention, a vertically penetrated hollow molding product (S20) is primarily cold-extruded and forged to form a first extrusion product (S30) having a large-diameter thick wall part (31) and a small-diameter body part (35) formed in upper and lower parts, respectively. The first extrusion product (S30) is secondarily cold-extruded and forged to manufacture a second extrusion product (S40) having an extended thick wall part (41) and a small-diameter shaft part (45) formed in upper and lower parts, respectively. Due to first cold-extrusion/forging, the height (H30) of the first extrusion product (S30) is greater than the height (H20) of the complete hollow molding product (S20) by 1.5 to 2.5 times. Due to second cold-extrusion/forging, the height (H41) of the extended thick wall part (H41) is less than the height (H31) of the large-diameter thick wall part (45) and the height (H45) of the small-diameter shaft part (45) is greater than the height (H35) of the small-diameter body part (35) by 1.5 to 3 times.;COPYRIGHT KIPO 2018