The program control of injection speed is to divide the injection stroke of the screw into 3 ~ 4 stages, and use their own appropriate injection speed in each stage. For example, slow down the injection speed when the molten plastic first passes through the gate, use high-speed injection during mold filling, and slow down at the end of mold filling. — belt carrier molding machine

This method can prevent overflow, eliminate flow marks and reduce the residual stress of products. During low-speed mold filling, the flow rate is stable, the product size is relatively stable, the fluctuation is small, and the internal stress of the product is low, The internal and external stresses of the product tend to be consistent (for example, when a polycarbonate part is immersed in carbon tetrachloride, the part molded by high-speed injection has a tendency to crack and does not crack at low speed). Under relatively slow mold filling conditions, the temperature difference of the material flow, especially the temperature difference between the material before and after the gate, helps to avoid shrinkage and depression. However, due to the long duration of mold filling time, it is easy to cause delamination and poor fusion of the part Marks not only affect the appearance, but also greatly reduce the mechanical strength. During high-speed injection, the material flow speed is fast.— belt carrier molding machine

When the high-speed mold filling is smooth, the molten material quickly fills the mold cavity, the material temperature decreases less, and the viscosity decreases less. Lower injection pressure can be used, which is a hot material mold filling situation. High speed mold filling can improve the gloss and smoothness of parts, eliminate the phenomenon of seam and delamination, small shrinkage depression, uniform color, and ensure fullness for most parts of parts. However, it is easy to cause products to get fat and blister or parts to turn yellow, even burn and zoom, or cause difficulty in demoulding, or uneven mold filling. For high viscosity plastics, it may lead to melt fracture and cloud spots on the surface of the parts.— belt carrier molding machine

High speed and high pressure injection can be considered in the following cases:

(1) The plastic has high viscosity and fast cooling speed. The long process parts adopt low pressure and slow speed, which can not completely fill all corners of the cavity;

(2) For parts with too thin wall thickness, the molten material is easy to condense and stay when reaching the thin wall. One high-speed injection must be adopted to make the molten material enter the mold cavity immediately before a large amount of energy consumption;

(3) For plastics reinforced with glass fiber or containing a large amount of filling materials, due to poor fluidity, high-speed and high-pressure injection must be used in order to obtain smooth and uniform parts. For high-grade precision products, thick wall parts, parts with large wall thickness changes and parts with thick flanges and ribs, multi-stage injection is best used, such as level 2, level 3, level 4 or even level 5.