Spark Plug Single Iridium

Shell
1.The one-piece spark plug shells can be made in several ways. When solid steel wire is used, the steel can be cold-formed, whereby coils of steel are formed and molded at relatively low temperatures. Or, the steel can be extruded, a process in which the metal is heated and then pushed through a shaped orifice (called a die) to produce the proper hollow shape. Shells can also be made from bars of steel that are fed into automatic screw machines. These machines completely form the shell, drill the hole through it, and ream it-a process that improves the finish of the drilled hole and makes the size of the hole more exact.

2.The formed or extruded shells-called blanks until they're molded into their final shapes-require secondary operations to be performed on them, such as machining and knurling. Knurling a shell blank involves passing it through hard, patterned rollers, which form a series of ridges on the outside of the blank. Similarly, machining--in which machine tools cut into the exterior of the shell blank-generates shapes and contours on the outside of the shell. The shells are now in their final shape and are complete except for threads and side electrodes.

Side electrode
3.The side electrode is made of a nickel alloy wire, which is fed from rolls into an electric welder, straightened, and welded to the shell. It is then cut to the proper length. Finally, the side electrode is given a partial bend; it is given its final bend after the rest of the plug assembly is in place.

4.The threads are then rolled on the shells. Now complete, the shells are usually given a permanent and protective silvery finish by an electrolytic process. In this process, the shell is placed in a solution of acids, salts, or alkalis, and an electrical current is passed through the solution. The result is a thin metal coating applied evenly over the shell.

Insulator
5.Insulators are supplied from stock storage. Ceramic material for the insulator in liquid form is first poured into rubber molds. Special presses automatically apply hydraulic pressure to produce unfired insulator blanks. The dimensions of the bore-the hollow part of the insulator-into which the center electrodes will be pressed are rigidly controlled.

6.Special contour grinding machines give the pressed insulator blanks their final exterior shape before the insulators are fired in a tunnel kiln to temperatures in excess of 2,700 degrees Fahrenheit. The computer-controlled process produces insulators that are uniformly strong, dense, and resistive to moisture. The insulators may be fired again after identifying marks and a glaze are applied.

Center electrode
7.The nickel alloy center electrode is first electrically welded to the basic steel terminal stud, a narrow metal wire that runs from the middle of the plug to the lower end (the opposite end from the electrode gap). The terminal stud is attached to a nut, which in turn is attached to the ignition cable that supplies the electric current to the plug.

8.The center electrode/terminal stud assembly is sealed into the insulator and tamped under extreme pressure. Insulator assemblies are then sealed in the metal shell under 6,000 pounds pressure. After reaming to correct depth and angle, the rim or edge of the shell-called the flange -is bent or crimped to complete a gas-tight seal. Spark plug gaskets from stock are crimped over the plug body so that they won't fall off.

9.To form the proper gap between the two electrodes, the center electrode of the now completely assembled spark plug is machine-trimmed to specifications, and the ground electrode is given a final bend.

Packaging
10.After a final inspection, the spark plugs are placed in open cartons that have been automatically formed. The plugs are generally wrapped in plastic film, placed first in a carton, and then prepared for shipping in quantity to users.