Dry bag isostatic pressing

Fig. 8.148 Operational sequence ofa dry bag isostatic press for the manufacturing of spark plug blanks [B.12a, B.42].

Fig. 6.7-27 Operational sequence of a dry-bag isostatic press for the manufacture ofspark-plug blanks [B.13a, B.48, B.97]...

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

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... 

RTS System. Radial Trocken Strangpresse. In this dry bag ISOSTATIC press (q.v.) for the continuous production of ceramic tubes, a length of tube is isostatically pressed in a vertical cavity between pressure tube and mandrel. The top of the tube is widened into a short cone. The formed tube length is then extruded downwards, leaving the cone at the bottom of the mould. A second length of tube is then isostatically pressed above the first, and the cone closes over its lower end to form a continuous tube. The process may be repeated to make tubes of any... 

Isostatic pressing is a compaction technique through the application of a uniform hydrostatic pressure to the powder confined in a flexible rubber container. There are two modes of isostatic pressing (i) wet-bag pressing and (ii) dry-bag pressing. In wet-bag isostatic pressing, the powder is filled in a flexible rubber mold, which is then submerged into a pressure vessel filled with oil as fluid, as shown... 

Many of the difficulties encountered in dry-pressing can be avoided by some form of isostatic-pressing. Ideally, this simply involves the application of hydrostatic pressure to powder in a flexible container. Powder movement is minimal and side-walls are absent. In practice shapes are often produced by the use of rigid mandrels as illustrated in Fig. 3.4. Powder is weighed into a rubber bag with a rigid mouth and a mandrel is then inserted and makes a seal with the mouth. Pressures of 20-280 MPa ( 200-2800 atm) can be applied through either liquid or gas media. The pressure must be released slowly since the air originally... 

Fig. 6.7-28 Operational sequence of an automatic isostatic press with round, timed (sequenced) tooling table [B.13a, B.48, B.97] Fig. 6.7-29 Photograph and diagram of a dry-bag CIP system (courtesy Dorst, Kochel am See, Germany). 1, protective enclosure 2, control cabinet 3, hydraulic unit 4, high-pressure intensifier pump 5, loading device 6, hopper 7, dosing device ...

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). 

An extremely useful attribute of the isostatic pressing process is its ability to be able to form unusually shaped green bodies. For example it has found an application in the mass production of the insulator part of spark plugs. In this instance the dry bag technique is used for mass producing bodies. 

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