The electrodes must be mounted solidly on the welding machine. The workpieces are correctly positioned in one electrode and all the welds are made at one time in one operation of the machine. The workpieces may be positioned and aligned with one another by punching holes in one and semi-punching the other to match. The projections usually can be embossed or forged in the same operation. In some designs, insulated pins or sleeves may be used in the electrode to position and align the workpieces. Basic examples are shown in Figures 2.11 and 2.12. When the small component of an assembly can be placed on the bottom and the large component on top, it is a simple matter to hold the small component in a recessed lower electrode, as shown in Figure 2.13. However, a problem is created when the design requires placing a small part on top of a larger part. Sometimes the small component can be located and held by a removable device and then welded with a flat upper electrode. Components that nest into the upper elec
trode may be held by spring clips attached to the electrode. Figure 2.14 shows a spring-loaded retainer entered through the side of the electrode holding a bolt for welding. A vacuum also may be used to hold small components in the upper electrode when component design permits.