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

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 spindles when bears asymmetric radial force during spinning.

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

1-Upper spindle 2-Preformed part 3-Lower spindle 4,5,6,7-Rollers **Figure 3.** Radial thickening by spinning
