Relevant process requirements for injection molding

Injection molding is a specific cycle. 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 Automotive Injection Molding are mostly caused by the abnormal quality caused by the failure to control the five points.

Temperature is the primary factor of injection molding, and temperature can be divided into several key factors such as drying temperature, material temperature, and mold temperature. The drying temperature is the pre-drying of the plastic material to ensure its molding quality, and to ensure that the plastic’s dry wetness is within a certain range; the material temperature is the normal plasticization of the plastic and the smooth filling and molding; the mold temperature is considered during the injection molding process The important factors of the injection mold temperature, appearance, molding cycle and other factors affect the cooling rate of the product in the cavity and the appearance quality of the product.

The second element speed: speed is divided into injection mold speed, molten material temperature, mold withdrawal speed, mold opening and closing speed, ejector pin advance and withdrawal speed. The increase of injection speed affects the increase of mold pressure. Increasing the injection molding speed can increase the flow rate, uniform product quality, and ensure product quality. High-speed injection is suitable for long-process products. Low-speed injection speed control product size affects plasticizing ability, which is plasticizing quality The higher the speed, the higher the melt temperature, and the stronger the plasticizing capacity. The loosening speed is an important condition for ensuring the operation of the machine. The opening and closing speed in order to reduce the specific capacity of the melt, reduce the pressure in the melt, and prevent its outflow.

The third element is pressure: pressure is divided into injection pressure, holding pressure, back pressure, mold clamping pressure, mold base protection pressure, and ejection pressure. The injection pressure is used to ensure the pressure loss of the melt from the nozzle-runner-gate-cavity to ensure that the cavity is full; the pressure holding method is used to reduce the part due to excessive injection pressure that causes the sticky mold to rupture or bend ; The pressing method is used to prevent the mold from rupturing due to foreign matter in the high-speed and high-pressure state; the top pressure method is used to prevent the product from detaching from the mold surface and causing the mold to be damaged.

The fourth element is position: position can be divided into mold opening position, ejection modulus, measurement modulus, injection modulus, and cushion modulus. The mold opening position is to ensure the normal operation of the demolding parts; the top return stroke is the spring partial reset to protect the ejection limit; 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 for melting The specific capacity of the body in the metering chamber is increased, and the internal pressure is reduced to prevent the melt from flowing out of the cavity; the top return stroke is to prevent the contact between the screw head and the nozzle and cause mechanical damage.

The fifth element is time: time is divided into cooling time of plastic products, plastisol time, plastic drying time, plastic product cooling time, melting time, drying time, cycle time, and pressure holding time. Molded products require a specific cycle; the injection time determines the size of the injection molded product; the pressure holding is to prevent the melt from flowing back; the effect of cooling shrinkage; the cooling time is to ensure the solidification of the plastic product and prevent the product from deforming; the injection time is to ensure The product is sufficient; the drying time is to ensure that the product does not become longer, poor quality, and other factors.