Moulding processes rotational

In recent years rotational casting methods have made the slush moulding process virtually obsolete. In these processes an amount of material equal to the weight of the finished product is poured into a mould. The mould is then closed and rotated slowly about two axes so that the paste flows easily over the cavity walls in an oven at about 200-250°C. When the compound has gelled, the moulds are cooled and the moulding removed. Compared with the slush moulding process there is no wastage of material, little flash, and more even wall thickness. Completely enclosed hollow articles such as playballs are most conveniently made. 

Fig. 4.61 illustrates that the mould temperature is quite different from the set oven temperature (330°C) or indeed the actual oven temperature, throughout the moulding cycle. An even more important observation is that in order to control the rotational moulding process it is desirable to monitor the temperature of the air inside the mould. This is possible because there is normally a vent tube through the mould wall in order to ensure equal pressures inside and outside the mould. This vent tube provides an easy access for a thermocouple to measure the internal air temperature. 

A process for making hollow articles from latex. A heat-sensitised compounded latex is poured into a hollow non-porous mould which is then rotated about several axes until the latex has gelled on the surface of the mould. See Rotational Moulding. Similar to slip casting of ceramics. Ketones... 

ECTFE can be processed by conventional molten-state methods such as extrusion, injection, compression, transfer, rotational and blow-moulding processes. 

Figure 5.6 Moulding process on a rotating table, viewed from above...

Rotational moulding process for forming hollow plastics bodies in which a measured quantity of polymer is placed inside a split female mould, the mould is heated and rotated in at least two planes dispersing the polymer over all parts of the mould, and then cooled whilst still rotating. 

ROTATIONAL MOULDING PROCESS CAPABILITY CHART (ALL THERMOPLASTICS)... 

Grade Selection Criteria Food contact approval. Medical approval. Processing characteristics for transfer moulding, compression moulding, extrusion, injection moulding and rotational moulding. 

Grade Selection Criteria Process characteristics for extrusion, blow moulding and rotational moulding. 

The efficiency of coupling internal cooling into the rotational moulding process has been numerically studied and depicted in Figure 1 for part thickness up to 12mm. 

A preliminary study shows that the onset of part warpage at different degree of part solidity is independent of the total cycle time for the rotational moulding process with external-internal cooling. For the external cooling process, this warpage formation for thicker parts does have a considerable influence on prolonging the total... 

K.K. Lim and A. lanakiev. Modelling of Rotational Moulding Process Multi-Layer Slip Flow Model, Phase-Change and Warpage, Polym. Eng. ScL, 2006, 46, 7 pp. 960-969. 

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