Screw design principle and process


The main part of the pin screw is a conventional screw […]

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.

The separation type screw is characterized in that in addition to the original one screw thread (called the main screw), a thread is added to the melting section (referred to as an additional thread), and the outer diameter is slightly smaller than the outer diameter of the main thread, and the main and auxiliary lines are The lead is different from the end of the feed section (and here associated with the feed section), after a few threads, gradually intersects the main thread of the homogenization section. The screw groove depth and thread lead of the screw are gradually changed from the beginning of the feeding section to the end of the homogenization. The thread lead is gradually narrowed from the width, and the depth of the groove is gradually shallowened from the depth to maximize the compression of the material.

The twisted screw should be considered according to the actual inner diameter of the barrel. The outer diameter deviation of the new screw is given according to the normal gap of the barrel. The thread surface with the reduced diameter of the wear screw is processed, and the wear-resistant tungsten carbide alloy is thermally sprayed. It is then ground to size. Wear-resistant tungsten carbide alloy is deposited on the threaded portion of the wear screw. Depending on the degree of wear of the screw, weld 1 to 2 mm thick and then grind the screw to size. This wear-resistant tungsten carbide alloy is treated by a hard chrome treatment of the bottom diameter of the repair screw. Chromium is also a wear-resistant and corrosion-resistant metal, but a hard chrome layer is relatively easy to fall off.

screw of blow molding machine