Injection molding is an important processing method in manufacturing industry. It is widely used in machinery, chemical industry, automobile, instrument, household appliances, toys and other fields. In addition to mold and process, the control accuracy of injection molding machine is also an important factor affecting the processing accuracy of injection molding. Linear displacement sensor used for speed and pressure control of injection molding machine can improve the control of injection molding machine Precision, improve the quality and production efficiency of plastic products.
Injection molding is to control the movement of the screw of the injection molding machine, and indirectly control the feeding speed and pressure of the mold cavity. Traditional injection molding machine uses travel switch for control system, which is suitable for some plastic products with low requirements. For the products with complex structure, it is necessary to improve the accuracy of injection volume in the whole injection stroke, multi-stage injection and stepless speed regulation in each stage to obtain better quality. The linear displacement sensor can convert the mechanical displacement into the resistance change of proportional relationship and output DC voltage signal. Because of its simple structure, small size, low price, high precision, stable performance and less affected by environmental factors, it is widely used in injection molding machine industry.
The linear displacement sensor is used to control the position of injection material quantity (including the position of melt glue), the position of opening and closing mold and the position of ejector pin ejection. The installation method is simple, just install the sensor on the non moving end of the fixed part of the machine tool, fix the pull rod end at the moving end of the measured part, stretch and compress the pull rod distance at the moving end to control the measured part.
Through the use of linear displacement sensor and other sensors, the position of sol back pressure, injection speed and pressure maintaining condition can be accurately controlled in the injection molding process. During injection, the linear displacement sensor controls the amount of molten material by controlling the displacement of injection screw, so as to ensure the accuracy of precise injection measurement. If the injection speed is too slow, the products will have cold joints, uneven density, high stress and other defects; if the injection speed is too fast, it will cause poor air intake and exhaust, and affect the surface quality of the products. For the complex structure of plastic products, high molding requirements, often choose multi-stage injection molding. When the screw injects melt glue into the mold, it is required to control the process parameters such as different injection speed and injection pressure at different positions. Multi stage injection molding is to achieve different injection speed and pressure by linear displacement sensor to fully improve the uniformity of melt temperature, thus improving the filling process, so as to obtain injection parts with good appearance, stable size and small internal stress.
