**1.2. Classification of SFP**

30 Metal Forming – Process, Tools, Design

**Figure 1.** Diagram of axial thickening SFP

**2. SFP principle of radial thickening process** 

1- Upper die 2-Blank 3-Lower die **Figure 2.** Perform by stamping

3

2

1

spindles when bears asymmetric radial force during spinning.

a) Hydraulic pressure assistant upsetting b) Small gap upsetting with rigid support

In the hydraulic pressure assistant upsetting, the sidewall will be thickened greatly because the stabilities of sidewall of the blank can be guaranteed effectively by the assist of hydraulic pressure. The die for this upsetting process is complicated and its application is greatly restricted by high sealing requirements of the whole structure. Whereas, the instability of the parts wall in a small gap upsetting with rigid support can be controlled by increasing the upsetting step or decreasing the amount of thickening. Compared with the hydraulic pressure assistant upsetting, the dies of small gap upsetting with rigid support are simpler, in which, only a mandrel is needed to put in the center hole of part, and the gap between

The principle of radial thickening process is shown in Fig. 2 and Fig. 3. Firstly, a conventional drawing is used to form a lower boss in the center of the preformed part (Fig. 2). Then the preformed part is clamped in the center by the upper spindle and lower spindle of spinning machine (Fig. 3). When the preformed part rotates together with the spindles, the rollers feed in radial direction and thicken the rim one by one. The lower mandrel inserted into lower spindle can stop the part sliding in the radial direction between the

punch and mandrel could be changed by changing the diameter of the tooling.

In terms of the combination mode of stamping and forging, the SFP process can be classified as compound SFP and sequence SFP. In the compound SFP, the stamping process and local bulk forming are carried out in one die-set. In the sequence SFP, the stamping process and subsequent local bulk forming are carried out in different die-sets.

In terms of the tool movement, the SFP can be also classified as linear SFP and rotational SFP. In the linear SFP, the tools move along a line and thicken the local feature wholly in one or more axial upsetting steps. In the rotational SFP, the tools feed along a radial direction and thicken the rim of the blank incrementally.
