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Author: MULAN –Plastic Molding Manufacturer
Injection molding is a specific cycle, and there are five elements that affect injection molding: temperature, speed, pressure, position, and time. These five process elements determine the quality of injection molding. The quality problems often encountered in injection molding are mostly caused by the abnormal quality caused by the failure to control the five points. Temperature is the primary factor in injection molding, and temperature can be divided into several key factors: drying temperature, material temperature, mold temperature and so on.
The drying temperature is the pre-drying of the plastic material to ensure its molding quality and ensure that the dry humidity of the plastic is within a certain range; the material temperature is the normal plasticization of the plastic and smooth filling and molding; the mold temperature is taken into account during the injection molding process Factors such as the size of the injection mold temperature, appearance, and molding cycle affect the cooling rate of the product in the mold cavity and the appearance quality of the product. The second element speed: speed is divided into injection mold speed, molten material temperature, ejection speed, mold opening and closing speed, and thimble advance ejection speed. The increase of injection speed affects the increase of mold pressure. Increasing the molding speed of injection molding can increase the flow rate, and the product quality is uniform to ensure product quality. High-speed injection is suitable for long-process products, and low-speed injection speed to control product size affects plasticizing ability, which is the plasticizing quality The higher the speed, the higher the melt temperature, the stronger the plasticizing ability. The loosening speed is an important condition to ensure the operation of the machine in order to reduce the specific capacity of the melt, reduce the internal pressure of the melt, and prevent its outflow.
The third element is pressure: pressure is divided into injection pressure, holding pressure, back pressure, clamping pressure, mold base protection pressure, and ejection pressure. Injection pressure is used to ensure the pressure loss of the melt from the nozzle-runner-gate-cavity to ensure that the cavity is filled; the pressure-holding method is used to reduce the sticking of the part due to excessive injection pressure, cracking or bending The pressed method is used to prevent the mold from being broken due to foreign matter in the high-speed and high-pressure state; the top-pressed method is used to prevent the product from leaving the mold surface and damage the mold. The fourth element is position: position can be divided into mold opening position, ejection modulus, measurement modulus, injection modulus, and cushioning modulus.
The mold opening position is to ensure the normal work of the demoulding and picking parts; the top return stroke is to protect the ejection limit by the spring partial reset; the top return stroke is to ensure that there is enough plastic to fill the mold to ensure product quality; the top return stroke is to make the melting The specific capacity of the body in the metering chamber increases, and the internal pressure decreases to prevent the melt from flowing out of the cavity; the top return stroke is to prevent mechanical damage caused by the contact between the screw head and the nozzle. The fourth element is time: time is divided into cooling time of plastic products, plastisol time, plastic drying time, cooling time of plastic products, melting time, drying time, cycle time, and holding time. Molded products need a specific cycle; injection time determines the size of injection molding products; holding pressure is to prevent the melt from flowing back; cooling shrinkage effect; cooling time is to ensure that plastic products are solidified and prevent product deformation; injection time is to ensure The product is sufficient; the drying time is to ensure that the product will not become longer, poor quality and other factors.