Hydrostatic molding

Isostatic compaction Powder encased in flexible mold is pressed equally from all directions by pressure transmitted to the mold by a liquid medium. Isostatic molding, isostatic pressing Hydrostatic molding chambers, automatic isostatic presses... 

Hydrostatic molding is a suitable alternative to compression molding techniques for the production of plastics that do not have the usual melt flow behavior, such as previously reviewed in the Plastic section for polytetrafluoroethylene. 

In some specialized applications requiring an isotropic product, an isostatic, or hydrostatic, molding technique may be used. The application of pressure in all directions... 

In addition to the production of high quality charges, hydrostatic pressing and isostatic pressing can be used to consolidate expis which are so sensitive that frictional contact with the walls of a conventional mold creates a hazard. Materials like pure RDX, of which it is difficult to make firm pellets except in small sizes, can often be pressed hydrostatically or isostatically (Ref 9)... 

P molding pressure, external pressure Pco, collapsing hydrostatic pressure... 

The mixer was made by casting, molding and curing [25,93], Then, the channels were covered by glass slides. Two ports were placed at the inlet reservoir feeds. The liquids were pumped by hydrostatic pressure. Platinum electrodes were deposited in the upstream and downstream reservoirs by AC excitation. The EKI then occurs along the entire channel. 

Cold Isostatic Pressing. In isostatic pressing, the powder is filled into flexible molds made of rubber or elastomers and subjected to hydrostatic pressure. The pressure is commonly in the range of 200 to 400 MPa. As a result of the uniform pressure, a much higher uniformity in density is achieved. Isostatic pressing has gained much... 

Catalysts of metal modified amorphous silica are made from the powders by compacting the powder under pressiure. The powder may be evenly flowed into a steel mold or die and compacted with a plunger. Hydrostatic compaction around a mandrel in a mbber mold which is squeezed by hydrostatic pressure can be employed for making cylindrical, hollow objects. Powders can be roll-formed into sheets or bars or can be extruded through a die to form rods. 

There are many variations on using the cold isostatic press (CIP) here we just emphasize some basic themes. Figure 23.3 illustrates the so-called wet-bag CIP process. Powder is weighed into a rubber bag and a metal mandrel is inserted that makes a seal with the mouth of the rubber bag. The sealed bag is placed inside a high-pressure chamber that is filled with a fluid (normally a soluble oil/ water mixture) and is hydrostatically pressed. The pressures used can vary from about 20 MPa up to IGPa depending upon the press and the application. For production units the pressure is usually <400 MPa. Once pressing is complete, the pressure is released slowly, the mold is removed from the pressure chamber, and the pressed component is removed from the mold. 

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... 

In contrast to the effect of shear stress or rate, the hydrostatic pressure enhances the viscosity as it decreases the so-called free volume. This case is mostly relevant for injection molding wherein extremely high pressures prevail. In this case a numerical solution is carried out by computer, describing the fields of temperature and pressure for each point. Graphical or nmnerical solutions may, at best, provide an approximation to real conditions, as the material data are not well known, the parameters apply in a limited range and various assumptions are imdertaken for the sake of simplicity. 

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