Molding methods rotational casting

In rotational casting a predetermined amount of liquid plastisol is placed in a heated, closed, two-piece mold. The liquid is uniformly distributed against the walls of the mold in a thin uniform layer (Figure 2.43c) by rotating the mold in two planes. The solidified plastisol in the mold is cured in an oven the mold is then opened, and the part is removed. The method is used to make completely enclosed hollow objects. Doll parts, plastic fruits, squeeze bulbs, toilet floats, etc. can be made by rotational casting of plastisols. 

Typical processing methods blown film extrusion, cast film extrusion, coating, coextrusion, extrusion, Injection molding, molding, lamination, rotational molding ... 

In the Watertown Arsenal method, the metal is melted in batch lots of the required weight in high-frequency induction furnaces and poured into a horizontally mounted mold rotating at 1300rpm while it is cooled on the outside with water. The mold is made of heavy cast iron and machined inside to the desired shape of the exterior of the gun to be produced. The finished casting has a hollow core and can be easily bored out to the desired internal diam of the gun(Ref 3)(See also Ref 2a)... 

Zeiss [48] describes a method for measuring sections of milled ferrite powder. The powder was mixed in 40 60 volume ratios with epoxy resin using a homogenizing head rotating at 25,000 rpm. The mixture was then poured into a 0.5 in diameter mold and cured at 60°C and 1000 psi to eliminate air bubbles. The casting was then polished in a vibratory polisher using 0.3 and 0.5 pm alumina in water. A photomicrograph of the polished section was used for subsequent analysis. 

This method is ideally suited to the casting of spherical shapes, but the outer shape may be modified with the use of special techniques. Normally, metal molds are used and plastic is poured into the rotating mold that may spin about a horizontal, inclined, or vertical axis. The centrifugal force, even though minor relative to gravity, improves both homogeneity and accuracy. 

Practically all resins (TS and TP) are used in RPs, but a few predominate (Tables 7-2 to 7-5), with TS polyesters being the major type. Typical polyesters are summarized in Table 7-4. The polyester RPs are used in all processes, but their principal use is in the low pressure methods (spray-up, hand lay-up, pressure bag molding, casting, pultrusion, rotational molding, filament winding, and compression molding. 

TEEEs can be processed successfully by low-shear methods such as laminating, rotational molding, and casting. Standard TEEElastomers are usually modified with viscosity enhancers for improved melt viscosity for blow molding. ... 

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