The combined sheet and bulk forming process has a high potential for the near-netshape forming of lightweight metal components with thin and multiwall thickness. In this forming process, bulk forming, i.e., a compressive forming process, is applied to sheet or plate workpiece, in combination with the conventional sheet forming (stamping) process to minimize the material waste and manufacturing cost. The current work focuses mainly on “spin forming” and “combined stamping and forging process” which are key technologies in the combined sheet and bulk forming process.

The spin forming process includes the flow forming and shear forming of axisymmetric hollow components. This process has high potential for near-netshape forming of high-strength and lightweight hollow components with thin wall of multi thicknesses. In the flow forming process, the wall thickness of rotating tubular (cylindrical) workpiece is reduced incrementally into intended value between the roller(s) and mandrel. The internal diameter of workpiece remains constant by a mandrel which is installed inside workpiece. In the shear forming, various kinds of conical, semispherical, and cup-shaped hollow components can be formed from flat disk-shaped sheet by using forming roller(s) and mandrel. It is important to optimize major process parameters and the initial workpiece (perform) for successful spin forming.

The combined stamping and forging process utilizes some of the bulk forming modes, i.e., partial compression of workpiece (sheet or plate) in its thickness direction (such as upsetting, coining, pin/boss/rib forming, ironing, etc.) for reducing the wall thickness locally, together with some of the forming modes of conventional stamping of sheet metal (such as deep drawing, bending, expanding, piecing, etc.). In this process, various kinds of thin-walled 2D/3D components with multi thicknesses, ribs, pins, and webs can be formed in near net shape from sheet metal workpiece with uniform thickness. The technical issues in this process are high forming pressure in local compression (upsetting) of sheet workpiece and potential defects caused by lateral material flow. Therefore, the optimization in forming sequence in multistep forming and tooling design is essential for successful forming.

In this chapter, the basic process knowledge are presented to cover the working principles, deformation characteristics, important process parameters, forming process and tooling design, forming machine, case studies for application, etc.