Devolopment of precision forging

Closed type forging with symetrically-split lower and upper die was developed for cross pins for automotive universal joint. In comparison to conventional flashed-forging, it could make a remarkable cost down by reducing machining work and saving material.
Closed die-set installed on existing press machine was developed to further increase productivity. It became popular worldwide in this industry.
However cross pins produced on current closed forging can not avoid a parting line caused by the split-dies. Furthermore unbalanced elastic deformation of punching shaft tends to result in deteriorating roundness of journals.
Machining process then becomes innevitable after forging process.

New die-set on our study enables all journals to be flash-free and to retain the roundness by controlling elastic deformation so that journal area produces net-shape without requiring machining. Our study will help contribute to further cost-down.

Structure

Using hydraulic bilateral style closed type die-set, upper side holds 4-split die moving in axial direction and lower side holds pressing cam as well as pull-back cam.

Characteristics of this method

• (1) Flash free in the journal area where accuracy is required.
• (2) Enables improved roundness at the journal area
• (3) Die mold does not requres any adjustment work , since the deformation level of die-mold can be controlled by the pressing force.