자동변속기용 헬리컬 피니언 기어의 냉간 압출 공정 개발

This paper shows some achievements at bending of extruded aluminum profiles during the extrusion process. Bent profiles are used in the manufacture of many kinds of products such as transport apparatus and mechanical parts for reduction of production cost and weight. The conventional process chain for the production of bent profiles involves a successive extrusion, stretching, and bending of the profiles. Conventional bending methods can not meet demands for precision and cost-effective production in some cases, due to cross sectional deformation, irregular decrease of tube wall thickness and a complication of the process design. An estimation of spring-back required for precision of the bending radius can not always be achieved by the over bending of the profile. Since the profile is warm during the bending process, the spring-back phenomenon can be avoided. This means that an additional bending process is not necessary. Consequently, flexible bending can be achieved with cost reduction and quality improvement. Experimental tests were completed to study the relationship between curvature radius of profile and position of guide on the extrusion for vehicle bumper. Modified 7108 Al alloy is applied as a billet material in order to increase strength. The overall correlation between the experimental and numerical results is good. It is therefore concluded that the present method provides an efficient means for the variable curvature extrusion process.