The blow molding screw is a core component of plastic blow molding equipment, primarily used for plasticizing, melting, and conveying plastic raw materials. The following is comprehensive information about blow molding screws:
I. Main Types and Features
Conventional Screws These are structurally divided into a feeding section, a gradient section, and a metering section, but they consume a lot of energy and are gradually being replaced by newer screws.
Separable Screws Replacing the gradient section with a separate section and featuring a dual-thread design for primary and secondary threads provides improved melt stability.
Barrier Screws Adding a barrier section enhances shearing and improves mixing capacity.
New Screws CTM Screws: Improve mixing efficiency through a spherical hole structure.
Split-Flow Screws: Adding pins or splitter blocks improves mixing.
The moisture contained in the plastic has a certain effect on the wear of the screw surface. If the plastic is relatively damp, the moisture is not completely removed before extrusion. When the residual moisture enters the compression section of the screw, it forms “steam particles” with high temperature and pressure that are previously melted and mixed in the molten plastic. As the screw advances during the extrusion process, from the homogenization section to the screw head, these “steam particles” are decompressed and expanded during the extrusion process, like fine impurity particles, which have a frictional and destructive effect on the wall surface, and also have a great impact on the quality of the extruded product, and unstable feeding will also occur.