Spark plug insulator

More complex shapes can be made by cold isostatic pressing (CIP). CIP uses deformable mbber molds of the required shape to contain the powder. The appHcation of isostatic pressure to the mold suspended in a pressure transfer media, such as oil, compacts the powder. CIP is not as easily automated as uniaxial pressing, but has found wide appHcation in the preparation of more complex shapes such as spark plug insulators (26). 

The particle injection studies also indicated that lead sulfate alone was more harmful than lead oxide or lead chloride, suggesting that in the absence of catalytic activity on carbon combustion, higher melting compounds are more harmful than materials of lower melting point. Flakes of iron oxide from a corroded exhaust valve and bits of ceramic material from a broken spark plug insulator are very potent sources of surface ignition... 

It has proved relatively easy to manufacture a dry bag machine for automatic operation whereby production rates of up to 90 components per minute are claimed. In Figure 299 the compaction, ejection, and filling are demonstrated for a spark plug insulator. The actual production rates depend on maximum pressure, size of component, powder properties, and number of tool cavities. 

Aluminium silicate Spark plugs, insulating tubes... 

Aluminum oxide is by far the most widely used compound with this structure. As a single crystal it is used in watch bearings and pressure-resistant windows. Hot-pressed powders are employed as electrical insulators, windows or radomes transparent to microwaves, envelopes for lamps, and electrical devices. In polycrystalline form it is also the basis of refractory bricks, crucibles, and spark-plug insulators. 

FIGURE 23.4 Schematic of a die for dry-bag isostatic pressing of a spark plug insulator. 

The dry-bag CIP has been used for many years to press spark plug insulators. The steps in this process are shown in Figure 23.5. Notice the insertion of the inner pin in the mold. The world s largest producers of spark plugs produced by this method are Champion and AC Spark Plug. 

In the processing of spark plug insulators the final processing step prior to firing involves green machining as shown earlier in Figure 23.5. 

Which method would you choose to form each of the following shapes briefly justify your choice, (a) A cylinder (b) a tube (c) a cube (d) a teapot (e) a rotor blade (f) a spark plug insulator (g) an insulator for a power cable. 

Class 1 or NPO capacitors have k < 15 and are mainly used for electrical insulation such as substrates, power line insulators, and spark plug insulators. Medium k class 1 capacitors are used in the following ... 

F. 4.17 Schematic of a die for dry-bag isostatic pressing of a spark plug insulator. Reproduced with permission from [115]. Copyright 2007, Springer... 

Small batches and large articles are made. The automatic dry bag process is used to mass-produce small articles such as spark plug insulators. The pressure medium is a gas. Isostatic pressing avoids problems of die-wall friction but does not provide as accurate tolerances as die-pressing. The process was invented by H. D. Madden (US Pat. 1081 618, (1913). 

Skiving. US term for a finishing process, on a lathe, of partially dried ceramic ware such as H.T. insulators, ribbed formers or sparking-plug insulators. 

Mullite was used originally as a spark plug insulator. In recent years it has found extensive use in kiln furniture applications, and as liner material in tube-type furnaces. 

Process Industries Furnaces used for the fabrication of spark plug insulators, catalyst supports for automobile emission control systems, dinnerware, magnetic ceramics, and electrical ceramics are lined with ceramics. Ceramic high-temperature furnace linings and thermal insulation are used in petroleum and chemical processing, cement production, heat treatments, and paper production. 

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