The temperature of the plastic mold has a great influence on the molding quality of the product. It is one of the three major process conditions of injection molding. For precision injection molding, there are not only the problem of high and low temperature, but also the problem of temperature control accuracy. Obviously, it is in precision injection molding. In the process, if the temperature control is not accurate, the fluidity of the plastic melt and the molding performance and shrinkage rate of the product will not be stable, so the accuracy of the finished product cannot be guaranteed. Usually, a system combination method such as a temperature control box and a heating ring is used to control the temperature of the phantom.
1. There are several ways to heat or cool the mold body of a plastic mold to adjust the temperature. Steam, hot oil circulation, hot water circulation and resistance can be used to heat the mold body. Cooling circulating water or cooling water can be used to cool the mold body. Air is carried out. For the temperature adjustment of the mold used in the injection molding machine, resistance heating and cooling water circulating cooling are more widely used. When the mold is heated by resistance, the flat part is heated by a resistance wire, the cylindrical part is heated by an electric heating coil, and the inside of the mold is heated by an electric heating rod. The mold needs to be cooled by arranging a circulating water pipe for cooling. Resistance heating and cooling water circulation, the two work alternately according to the temperature conditions of the mold body, so that the mold temperature is controlled within the temperature range required by the process.
2. Precautions for mold temperature control:
(1) The temperature of each part of the forming mold after heating should be uniform to ensure that the melt has a better filling quality, so that the molding quality of the injection molded product is guaranteed, and the pass rate of the injection molded product is improved.
(2) The process temperature adjustment of the mold body should be determined by the viscosity of the melt. For higher viscosity melts to be injected into the mold, the mold body temperature should be adjusted slightly higher; while for lower viscosity melts to fill the mold, the mold body temperature can be appropriately lowered. When preparing for injection production, the temperature of the mold body is within the range of process requirements. In order to ensure the uniform temperature of the mold body, the mold body whose temperature is required by the heating process should be kept at a constant temperature for a period of time.
(3) When injection molding large plastic products, due to the large amount of melt used for molding, the melt flow channel is relatively small, and the large mold body must be heated and moisturized at the melt flow channel to prevent the melt flow channel from being too long. Cooling while flowing increases the viscosity of the melt, which slows down the material flow, affects the quality of melt injection and mold filling, and causes the melt to cool down and solidify in advance, making the injection molding machine impossible to perform.
(4) In order to reduce the temperature of the melt due to the long melt flow channel and increase the heat energy loss, a heat-insulating and moisturizing layer should be added between the low temperature part of the mold cavity and the high temperature part of the melt flow channel.
Post time: Oct-22-2021