## 3 Object Investigation
### Shaping Area  
The shaping area is mainly used to manufacture helical springs and leaf springs, which are used for the suspension systems of trains. The manufacturing processes of these two springs, as well as the relevant machines and objects in the forging workshop, are briefly introduced, as follows. 1. Helical springs  
The raw material of helical springs (Figure 7) is spring steel wire, and the manufacturing process mainly includes six steps. The relevant machines at all steps in the workshop are shown in Figure 11.  
The first step is billet shearing, where the shapes of both ends of the wires used as the billets are adjusted with an inclined rolling mill (A27) after being heating in the furnace (A26). The wires are sheared to the appropriate length with a shearing machine (A22). The machines for billet shearing are shown in Figure 12.  
Figure 10: Locations of working blocks in the forging workshop. Figure 9: Classification of exhibition areas. The second step is heating, where the sheared steel pieces are placed on a material rack (A20), and then, put into a large heating furnace (A14). The full length of the large heating furnace is about 85 m, and the furnace temperature is about 500-800 \({}^{\circ}\)C. Many motor-driven rollers are equipped in the furnace to convey the billets forward to the outlet to be heated until softened. The third step is coiling and shaping, where the required spring diameters are selected according to the appropriate spring coiling fixture (A17), in order to wind the softened wires after heating into a spiral shape through a spring coiling machine (A13). If there is any error in the spacing of the shaped springs during manufacturing, hand tools are used to make detailed adjustments. The machines for coiling and shaping are shown in Figure 13.  
Figure 11: Flowchart of helical spring production line. Figure 12: Billet shearing and heating. (**a**) Inclined rolling mill (A27), (**b**) shearing machine (A22), material rack (A20), large heating furnace. The fourth step is quenching, where the shaped helical springs are immersed in a quench tank (A11) to rapidly cool the spring steels, in order to change the crystallization mode. According to the oral descriptions of the retired workers, peanut oil was once used as the quenchant for helical spring quenching in the Taipei Railway Workshop. The machines for quenching are shown in Figure 14a,b. The fifth step is tempering, where the atoms of iron, carbon, and other alloying elements in steel are quickly diffused, rearranged, and recombined, in order to stabilize the steel structure. Hence, reheating the quenched helical springs in a spring heater (A10) for tempering is intended to bring the springs to an appropriate temperature below the lower critical temperature, and then, the spring ends are trimmed. The cooling tank for tempering is shown in Figure 14c. The sixth step is post-processing, which includes grinding and rust prevention, and the finished springs are tested. Large springs are polished by an end grinding machine (A06), while small springs are directly hammered by hand, and the finished products are tested by a spring testing machine (A04). A hardness tester (A07) was also found in the field; however, as orally described by the retired workers, while this machine was originally intended for spring testing, it was found to be inapplicable. The machines for this step are shown in Figure 15.  
Figure 14: Quenching and tempering. (**a**) Quench tank (A15), (**b**) quench hook, (**c**) cooling tank (A11-2). Figure 13: Coiling and shaping. (**a**) Spring coiling machine (A13), (**b**) spring coiling fixtures (A17), (**c**) spring coiling tools (A17). 2. Leaf springs  
The production process of leaf springs (Figure 8) is similar to that of helical springs, as shown in Figure 16, with the same rust prevention, testing, and other post-processing devices. The first step is the billet shearing, where the billets are sheared to the appropriate length with a steam hammer (A32).