Extruder Screw Barrel Design Considerations
Plastic extruder screw barrel, and screw tightly, in normal operation, should pay attention to the following important characteristics.
1. barrel straight.
2. barrel shall be designed to withstand pressure of extruder. These pressures may be as high as 70-140MPa (10000-20000psi), in the injection or higher.
3. screw in the cylinder wall surface should be more wearable than the extruder screw, screw barrel is easy to replace, rework is cheaper than a barrel.
4. screw sliding tube back-end support should be used to support, when the barrel is heated to allow expansion. Rigid supports can cause the bending of the barrel may result in serious damage screw and barrel.
5. in order to improve the Group conveying, feeding screw tube segments can be slotted. Slots plus solution should guarantee good cooling capacity, to take away the high friction heat generated and prevents tank melting of bulk materials. In addition, the grooves should be tilted open, gradually to shallow depths, minimizes the chances of material structure hung within the bad.
6. If you do not take the air intake should be offset, and tangent to the inner wall of the barrel opening side wall to reduce plastic melt hung vents leading-edge opportunities, as shown in Figure 2. 20. Compared with the traditional design of symmetrical exhaust vents, constantly at the bottom of the items in the vents can be easily blocked. Vent openings can be designed into a downward-sloping to avoid cooling logistics one extruder screw barrel.