The difference with the injection mold is that the compression mold has no pouring system, and the mold is equipped with a feeding chamber. There is a heating device in the cavity or feeding chamber. The structure of the compression mold can be divided into the following major parts.
(1) Cavity part. The cavity is the location where the part is directly formed, where the mold cavity is composed of a punch, a core, and a cavity.
(2) The feeding chamber is different from the injection mold. There is a feeding chamber containing raw materials above the compression mold cavity.
(3) Heating and cooling system. Thermosetting plastic compression molding needs to be performed at a higher temperature, so the mold must be heated. Compression molds are usually heated by electric heating.
In addition, like the injection mold, the compression mold is usually also provided with a guide mechanism, a demoulding mechanism, a lateral split core pulling mechanism, etc., which will not be repeated here.
There are many structures of compression molds, and there are many ways of classification. According to the fixed form of the mold on the press, it can be divided into the following three types.
①Movable compression mold. The mold is not fixed on the press. After forming, the mold is moved out of the press, and the mold is opened with a special tool for mold release (such as a mold remover). After the feed chamber is cleaned and the mold is reassembled, production is repeated. This type of mold has a simple structure and is easy to manufacture. It is suitable for compression molding small and medium-sized parts in small batches and plastic injection parts with complex shapes and difficult feeding.
②Semi-fixed compression mold. Generally, the upper mold is fixed on the press, and the lower mold can move along the guide rail (the lower mold can also be fixed as needed). When the lower mold moves, it is positioned with a positioning block, and is guided by the guide equipment when closing the mold. After the forming is completed, the lower mold is removed, and the parts are taken out by hand or a mold remover. When the movable mold is too heavy or there are many inserts, in order to reduce labor intensity and facilitate operation, a semi-fixed compression mold can be used.
③ Fixed compression mold. The upper and lower molds are fixed on the press, and the processes of mold opening, mold closing, and demolding are all carried out in the press. This mold has high production efficiency, simple operation and long mold life. However, the structure is complex and the cost is high. It is suitable for forming parts with large batches or large shapes.
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