Principles of Selection of Plasticizing Barrel Assembly and Design of Injection Molding Nozzle Components
- Considerations: Conveying section, compression section, metering section, three-section ratio, compression ratio, depth of metering section screw groove, length-diameter ratio, number of teeth.
- Selection principles
a.For good mixing effect, a design with a large length-diameter ratio, more teeth, high compression ratio, and shallow metering section screw groove should be used, such as PA, PE, PP, and POM.
b.To prevent shear overheating, a design with a small length-diameter ratio, fewer teeth, long compression section, low compression ratio, and deeper metering section screw groove should be used, such as PC, PMMA, hard PVC, glass fiber reinforced or flame-retardant materials.
c.For high plasticization rate, a design with a smaller compression ratio and deeper metering section screw groove should be used.
- Design of Injection Molding Nozzle Components
A good check valve should have:
a.Ability to stop quickly.
b.Complete check function to maintain minimum plastic flow back.
c.Smooth material flow without dead corners to avoid local shear heat, which can cause plastic degradation.
d.Wear resistance and corrosion resistance.
e.Ability to adapt to a variety of plastics.