Process of Plastic casting

Casting, that is, pouring a liquid into a mold without pressure, can be done with several plastics. When there is not sufficient justification for making expensive dies, the casting process is generally used.

Open molds into which the liquid resin , mixed with a catalyst or hardener , is poured can be used for most plastics.

Centrifugal casting, using the same methods can be used with several plastics to such as polyesters.

Shell molding is some what similar to casting in that no pressure is used. In this process, powdered resin is placed in a heated mold until a layer fuses to the desired thickness. The unfused resin inside is taken out of the mold and the hollow molding removed. Sometimes the mold is rotated in what is called rotational molding.

Slush molding is similar to shell molding. It employs a thermoplastic-resin slurry or "slush" which is poured into a preheated mold. The heat causes slurry to set in a viscous layer of the desired wall thickness.

Both shell and slush molding produce thin-walled products such as toys and gloves.

Hand Lay-up is a simple method to form plastic materials into a required shape. Special shapes like boats , tanks and big-sized parts of plastics are produces by this method. First a mold of desirable shape is prepared. The mold is covered by fiber mats of desired thickness and plastic resin (such as epoxy) is draped over the mold and allowed to harden.

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Mechinopedia For Mechanical Engineers

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