Hobbies And Interests
Injection
Injection molding is one of the major methods of molding plastics. Plastic is fed through a screw and heated. The melted plastic at the end of the screw is injected into a cooled mold. When the plastic is cool and solid, the halves of the mold are opened and the product removed. This allows for the formation of very complex items, and so injection molding is used for the formation of a wide variety of products.
Extrusion
In the extrusion process, liquid plastic is continually forced through a die to form simple shapes. The shaped plastic is moved onto a conveyor belt for cooling, and is then cut into smaller pieces. This process is typically used for items such as fibers or pipes.
Blow Molding and Rotational Molding
Blow molding is very similar to injection molding. A key difference is that once the plastic enters the mold, air forces it towards the outsides of the mold. Blow molding makes hollow items, such as bottles. In rotational molding, the mold contains powdered plastic. The mold is then heated and rotated continuously so that the plastic melts and coats the inside of the mold evenly. This method produces results similar to blow molding, but makes larger parts more easily.
Thermoforming
In thermoforming, plastic does not reach a liquid state. Instead, it is heated until it is soft and pressed into a mold. The plastics used for thermoforming are typically already formed into pieces via extrusion.
Compression and Transfer Molding
In compression molding, plastic or plastic powder fills the mold. The mold halves are heated and pressed together to mold the plastic into the desired shape. This method is often used for automobile parts. Transfer molding is a very similar process, but uses plastic that is partially heated before molding. This allows for more detailed and intricate parts.
Casting
Casting is a method used for simple objects. There are many different casting processes, as casting is essentially any method of forming plastic in which liquid or powdered plastic is used in a mold, but no pressure is added to form the plastic item. The most common method is mold casting, which consists of simply pouring molten plastic into an open mold. Slush casting and static powder casting are both similar to rotational molding, with slush casting using liquid plastic and static powder casting using powdered plastic. Cell casting uses a mold formed from two parallel plates, and is used to make sheets of plastic. Continuous casting is similar to cell casting, but the plastic is poured between two belts to form a continuous sheet.