01. The effect of increasing back pressureIn order to obtain high-quality adhesive, the plastic needs to be uniformly heated or melted and thoroughly mixed. Using the correct screw is necessary for proper melting and mixing, and there is sufficient pressure (or back pressure) in the feeding cylinder to achieve consistency between mixing and heat.Increasing the resistance of the return oil can generate back pressure in the injection cylinder. But the screw takes longer to reset, so there is more wear and consumption in the drive system of the injection molding machine. Try to maintain back pressure as much as possible, isolate from air, and ensure consistency in melt adhesive temperature and mixing degree
02. Stop valveRegardless of the type of screw used, its tip is usually equipped with a stop valve. To prevent plastic from flowing out of the nozzle, a pressure reducing (reverse) device or a special nozzle may also be installed. If a check valve is used, it must be regularly inspected as it is an important part of the injection cylinder. At present, switch type nozzles are not commonly used because the nozzle equipment is prone to plastic leakage and decomposition. At present, each type of plastic has a list of applicable nozzle types.06. Screw retreat (reverse cable)Many injection molding machines are equipped with screw retraction or suction devices. When the screw stops rotating, it is retracted by hydraulic pressure to suck back the plastic at the tip of the nozzle. This device allows the use of an open nozzle. Reduce the amount of suction as much as possible, as entering the air can cause problems for some plastics.
03. Rotation speed of screwThe rotational speed of the screw significantly affects the stability of the injection molding process and the heat acting on the plastic. The faster the screw rotates, the higher the temperature. When the screw rotates at high speed, the frictional (shear) energy transmitted to the plastic increases the plasticizing efficiency, but at the same time, it also increases the unevenness of the melt adhesive temperature.Due to the importance of screw surface velocity, the screw rotation speed of large injection molding machines should be lower than that of small injection molding machines, because at the same rotation speed, the shear heat generated by large screws is much higher than that of small screws. Due to different plastics, the speed of screw rotation also varies.
04. Injection volumeThe evaluation of syringe molding machines is usually based on the amount of PS that can be injected in each injection, which may be measured in ounces or grams. Another ranking system is based on the volume of adhesive glue injected by the injection molding machine
05. Plasticizing abilityThe evaluation of injection molding machines is usually based on the amount of PS material that can be uniformly melted within 1 hour or the amount of PS heated to a uniform melt adhesive temperature (in pounds and kilograms), which is called plasticizing ability
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