Principle and type of screw barrel of injection molding machine
The principle of the screw barrel of the injection molding machine:
The main part of the pin screw is a conventional screw which can be placed in the groove of the melting section or the metering section of the screw or the smooth cylindrical surface without the groove at the end of the metering section. The pins are arranged in a certain arrangement, and the density can vary from one to another. The cylindrical pin is formed by fitting the pin into the hole of the screw; the square or diamond pin is formed by milling the pin directly on the screw.
If the pins are arranged in the melting zone, the pin can break the solid bed, destroy the two-phase flow, stir the solid and liquid phases together, and increase the contact area between the final dissolved solid phase fragments and the contained materials, and promote Melt. If the pin is placed in the melt transfer zone, its primary function is to split the flow, increase the interface, change the direction of the flow, and rearrange the flow. Dividing and converging multiple times, changing the flow direction to homogenize the melt composition and temperature.
The mixing section is an inwardly slotted structure disposed at the end of the normal screw homogenization section, and the outer diameter is equal to the outer diameter of the screw. The grooves are divided into groups, each of which is a confluence area of materials. The material is divided by the groove, merged into the confluence area, and then divided and merged. The principle is similar to the pin type.
Injection molding machine screw barrel type:
1. Gradient type Gradient type screw features: long compression section, energy conversion during plasticization is moderate, and it is mostly used for plastics with poor thermal stability such as PVC.
2, mutant type of mutant screw features: shorter compression section, more energy conversion during plasticization, mostly used in polyolefin, PA and other crystalline plastics
3, general-purpose general-purpose screw features: general-purpose screw with strong adaptability, can adapt to the processing of a variety of plastics, avoid frequent replacement of the screw.