茂名How to control temperature, time, pressure and speed when making injection molding products

Barrel temperature, mold temperature

The screw barrel temperature is set according to the properties of different plastic materials. The barrel temperature is generally 10 ℃ - 30 ℃ higher than the plastic melting point. When manufacturing injection molding medical device products in Dalian, it must be noted that the melting point and allowable residence time in the barrel of materials provided by different manufacturers will also vary due to different synthetic methods or types of additives.

The mold temperature is generally cooled by circulating water when it is set, but when producing products with high precision size or surface quality requirements, the mold temperature machine that can be accurately controlled should be used according to the process requirements.

Pressure holding time and cooling time of injection molding

The injection time, pressure holding time and cooling time must be set according to the product thickness, mold temperature, material properties, etc. The injection time is generally set to be slightly longer than the time for the screw to complete the injection stroke movement. Too long injection time will not only produce negative effects such as mechanical wear and increased energy consumption, but also prolong the molding cycle. The pressure holding time is set according to the thickness of the product. The pressure holding time is not required for thin-walled products during molding;

When setting the pressure holding time, as long as there is no obvious depression on the surface of the product, it can also be determined by weighing method. The time when the pressure holding time is gradually extended until the product quality no longer changes can be determined as a better pressure holding time. The cooling time also needs to be determined according to the product thickness, mold temperature and material properties. Generally, the cooling time of amorphous polymer is longer than that of crystalline polymer.

Injection pressure and speed

The injection pressure setting should follow the principle of low rather than high, as long as it can provide enough power to achieve the required injection speed, so that the melt can smoothly fill the mold cavity, too high pressure is easy to produce internal stress in the product; However, when molding products with high dimensional accuracy, in order to prevent excessive shrinkage of products, high pressure injection molding can be used to reduce the shrinkage of products after demoulding.

The injection speed will affect the appearance quality of the product. Its setting should be based on the geometric structure and exhaust condition of the mold. Generally, on the premise of ensuring a good appearance, the injection speed should be increased as much as possible to reduce the filling time.

In injection molding, when the melt flows in the mold, the mold wall will form a curing layer, thus reducing the thickness of the flowable channel. Generally, according to the mold structure and injection speed, the mold wall will have a curing layer of about 0.2mm. Therefore, faster injection speed is usually used in molding.