Plastic moulds are divided into injection moulds and co […]
Plastic moulds are divided into injection moulds and compression moulds.
Injection moulds are parts that give shape and scale to plastics in moulding. Although the structure of the mould may vary greatly due to the variety and function of the plastics, the shape and structure of the plastics products and the type of the injection machine, the basic structure is common.
Injection and compression moulds
Injection moulds are thermosetting plastic moulds and thermoplastic plastic moulds according to their moulding characteristics; according to the differences of moulding process, they are transfer moulds, blow moulds, casting moulds, hot moulds, hot pressing moulds (compression moulds), injection moulds, which can be divided into overflow moulds, semi-overflow moulds and non-overflow moulds. Injection moulds can also be divided into cold runner moulds, hot runner moulds and hot runner moulds. There are two kinds of moulds; according to the way of loading and unloading, they can be divided into movable type and fixed type. The classification of die is also different according to the different processing technology. Injection mold is to inject molten plastic into the cavity of the mold with a certain speed and pressure. After the plastic is cooled, the injection mold is opened to take out the moulded product.
Compression moulds for short plastics raw materials are directly added to the open mould cavity, the mould is closed, the plastic becomes active and fills the cavity under the action of heating and pressure, and then hardens and finalizes the product through chemical crosslinking or physical cooling.
Compression moulds are formed by restricting plastic sheets with heating moulds, then opening moulds, removing the moulded products and cooling them in cold water. Compression molding is an important technology in forming process, which is widely used in industrial production and processing and plays an important role in people's daily life. Generally, powder, granular, agglomerate, sheet, or even billet with similar shape of the product is made and placed in the cavity of the heated mould, then closed-die pressure is applied to form and cure or vulcanize the product, and then the product is demoulded (see figure). This method is especially suitable for the moulding of thermosetting plastics (see thermosetting resin). The disadvantages are long production cycle, low power and poor product scale accuracy.