Injection molding machine injection molding process thermal performance and cooling rate
Various plastics of injection molding machines have different specific heat properties such as heat, thermal conductivity and heat distortion temperature. When the plasticization is higher than the heat, it requires a large amount of heat, and an injection molding machine with a large plasticizing capacity should be used. The hot deformation temperature is high. The cooling time of the plastic can be short, and the mold release is early, but the cooling deformation is prevented after demolding. Plastics with low thermal conductivity have a slow cooling rate (such as ionic polymers and other cooling rates are extremely slow), so they must be sufficiently cooled to enhance the mold cooling effect. Hot runner molds are suitable for plastics with lower heat and high thermal conductivity. Plastics with higher specific heat, lower thermal conductivity, lower heat distortion temperature and slower cooling rate are not conducive to high-speed molding, and proper injection molding machines and mold cooling must be used.
Various plastics of injection molding machines are required to maintain an appropriate cooling rate according to their type characteristics and shape of plastic parts. Therefore, the injection molding machine mold must be set to the heating and cooling system according to the molding requirements to maintain a certain mold temperature. When the temperature of the material increases the mold temperature, it should be cooled to prevent the deformation of the plastic parts after demolding, shorten the molding cycle and reduce the crystallinity. When the residual heat of the plastic is not enough to keep the mold at a certain temperature, the mold should be provided with a heating system to keep the mold at a certain temperature to control the cooling rate, ensure the fluidity, improve the filling conditions or control the plastic parts to cool slowly. Prevent uneven cooling inside and outside of thick-walled plastic parts and improve crystallinity. For good fluidity, large forming area and uneven material temperature, it may be heated or cooled alternately or partially heated and cooled according to the molding condition of the plastic parts. For this purpose, the mould should be equipped with a corresponding cooling or heating system.
Injection molding machine injection molding process hygroscopicity
Plastics have various additives to make them have different degrees of moisture. Therefore, plastics can be roughly classified into two types: moisture absorption, adhesion moisture, non-absorbent water and non-stick moisture. The water content in the material must be controlled within the allowable range. In the case, the water becomes gas or hydrolyzes under high temperature and high pressure, causing foaming of the resin, deterioration of fluidity, and poor appearance and mechanical properties. Therefore, hygroscopic plastics must be preheated as required by appropriate heating methods and specifications to prevent re-absorption during use.