Heating devices and types of injection molds

The heating device and type of the injection mold. During the injection molding process of the injection molded part, the injection mold is in a cold state when the injection starts. Due to the influence of the heat transfer of the melt temperature in the cavity of the injection mold, during the injection molding process, The materials used in the external application are different, and the temperature of the injection mold is also different. In order to obtain good quality, Shanghai Mulan Injection Mold Processing Factory should open slowly as much as possible, and maintain an appropriate and uniform temperature during the injection process. Therefore, when designing the mold, it is necessary to consider setting up a heating or cooling device to adjust the temperature of the mold.




Generally, when the temperature of the injection molding material is insufficient, Shanghai Mulan Injection Mold Processing Factory should consider adding a heating device in order to make the injection mold reach the mold temperature required for molding; when forming thick-walled injection molded parts, a heating device must also be added. When the material temperature makes the mold temperature exceed the injection molding requirements, it should be considered to add a cooling device. In some cases, cooling and heating may be used simultaneously or alternately. Under normal circumstances, injection molds for thermoplastics often need to be cooled, while thermosetting plastics must be heated for injection molding. The mold temperature is determined according to the type of plastic, the thickness of the injection molded part, and the requirements of crystalline plastic.


The heating device and type of injection mold, when molding thermoplastics, for plastics with poor fluidity and fast cooling speed, in order to improve the fluidity of the melt and avoid defects such as sink marks, insufficient filling and stress cracks in thick-walled injection molded parts, at the same time Also in order to improve the hardness, stiffness, wear resistance and certain strength of high crystallinity injection molded parts, heating devices need to be installed; for hot runner molds and injection molds for forming thermosetting plastics, heating devices also need to be installed.


1. The influence of abnormal mold temperature on the quality of injection molded parts


Since injection molds are required to have a certain mold temperature when molding injection molded parts, if the mold temperature is too high or too low, the quality of injection molded parts will be affected.


2. Types of injection mold heating


There are many heating methods for injection molds, such as hot water, hot oil, hot air and steam. However, the most common heating method currently used is electric heating, and the commonly used ones include electric heating plates, electric heating frames, electric heating coils and electric heating rods. Various types of electric heaters, the principle of selecting electric heaters is to choose according to the shape of the injection mold. When conditions permit, the shape of the injection mold is designed to be circular, so that the electric heating coil can be used for heating, so that it can be in good contact. High heat transfer efficiency. For thermosetting plastic injection molds, heating rods should generally be used.





3. Calculation of heating capacity


Injection mold heating is one of the compression molding conditions, and it is necessary to calculate the amount of heating when designing the injection mold. For fixed compression molds, the power should be calculated separately for the upper and lower molds. Generally, the temperature of the upper mold is about 5°C higher than that of the lower mold.


The heating device and type of injection mold, Shanghai Mulan Injection Mold Processing Factory uses electric heating rods to heat the mold. The design of the injection mold needs to be based on the type of plastic, the wall thickness of the injection molded part, the defect of the injection molded part, the size of the injection mold and the cavity The number of selected electric heating rod specifications.