Precision Extrusion Using Tool for Counter Pressure

2000 Fiscal Year Final Research Report Summary

• Project/Area Number: 11650126
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 機械工作・生産工学
• Research Institution: Osaka University
• Principal Investigator: OSAKADA Kozo Osaka University, Engineering Science, Professor, 大学院・基礎工学研究科, 教授 (50031109)
• Co-Investigator(Kenkyū-buntansha): OTSU Masaaki Osaka University, Engineering Science, Research Associate, 大学院・基礎工学研究科, 助手 (20304032) ; SHIOMI Masanori Osaka University, Engineering Science, Lecturer, 大学院・基礎工学研究科, 講師 (90263227)
• Project Period (FY): 1999 – 2000
• Keywords: Precision Forging / Forward-Backward Extrusion / Gear / Counter Pressure / Control of Extruded Velocity

Research Abstract

Extrusion of forward bar or gear, and backward can or bar by combined extrusion is studied. To attain the specified length of the gear just at the end of the process, the forward extrusion velocity is controlled with a counter tool. By controlling the forward extrusion velocity, a product with given extruded length are obtained with a low extrusion pressure. In this process, the counter-pressure caused at the die exit can be utilized to reduce the defects.
1.Forward-backward combined extrusion with control of forward extrusion velocity
When the counter pressure is raised to the order of flow stress of the billet at the strain of 1.0, the end surface becomes completely flat and no post machining is needed.
2.Forward-backward combined extrusion with alternate control of forward and backward extrusion velocities
Since the end surfaces do not always contact with tools, the end surfaces cannot be flat completely. Although the flatness of the back end surface is 0 % without controlling backward extrusion velocity, it becomes 80% when the alternate control of extrusion velocities is employed.
3.Forward gear-backward bar or can combined extrusion with control of forward extrusion velocity
The under-filling defect at the side of teeth in the case of backward bar is less than the case of backward can. In the case of backward can, the defect is disappeared when the counter pressure becomes the 75% of flow stress of the billet at the strain of 1.0, and the completely flat end surface is obtained when the counter pressure is 140% of the flow stress.
4.Inverse extrusion after controlled forward-backward combined extrusion
Although the extrusion pressures for only forward-backward combined extrusion and inverse extrusion are almost equal, the longer forward extruded part is obtained by the inverse extrusion.