Design principle of barrel screw of injection molding machine:
The main part of the pin screw is an ordinary screw, the pin can be set in the fusion section of the screw or the drop groove of the metering section or a smooth cylindrical surface without a screw groove at the end of the metering section. The pins are arranged in a certain arrangement, and the density and the number can be varied. The cylindrical pin is formed by assembling the pin into the hole of the screw; the square or diamond-shaped pin is formed by milling the pin directly on the screw.
If these pins are set in the melting zone, the pins can break the solid bed, disrupt the two-phase flow, stir the solid and liquid phases together, increase the contact area between the undissolved solid phase fragments and the contained materials, and promote Melting. If the pin is set in the melt conveying area, its main function is to divide the stream, increase the interface, change the direction of the stream, and rearrange the stream. Split and merge multiple times, change the flow direction, and homogenize the melt composition and temperature.
The mixing section is an inwardly slotted structure set at the end of the homogenizing section of the ordinary screw, and its outer diameter is equal to the outer diameter of the screw. The groove is divided into several groups, and between each group is the confluence area of materials. The material is divided by the groove, and then meets in the confluence area, and then divides and converges. The principle is similar to the pin type.
The characteristic of the separable screw is that in addition to the original screw pattern (called the main screw), there is also an additional thread (called the additional thread) on the melting section. Its outer diameter is slightly smaller than the outer diameter of the main thread. The lead is different, the secondary thread starts from the end of the feeding section (and is connected with the feeding section here), and after several threads, it gradually intersects with the main thread of the homogenization section.
The screw groove depth and thread lead of this kind of screw are gradually changed from the feeding section to the end of homogenization. That is, the thread lead gradually narrows from the width and the groove depth gradually becomes shallower, which can maximize the compression of the material.More about:screw barrel for Injection molding machine