China PVC Injection Molding Machine 100ton-800ton - Reliable Suppliers & Factory for Quality Production
01 Injection Unit
Injection Unit — View 1
Injection Unit — View 2
Injection Unit — View 3
Frequently Asked Questions
Q1
What is the injection unit in an injection molding machine?
The injection unit is the core component responsible for melting plastic material and injecting it into the mold cavity under controlled pressure and speed. It typically consists of a hopper, barrel, screw, and nozzle working together to ensure consistent material flow.
Q2
What are the main functions of the injection unit?
The injection unit performs three primary functions: plasticizing (melting and homogenizing the raw material), injecting (pushing the melt into the mold at precise speed and pressure), and holding (maintaining pressure during cooling to compensate for material shrinkage).
Q3
How does the screw design affect injection unit performance?
The screw geometry — including its length-to-diameter ratio, compression ratio, and flight depth — directly impacts plasticizing efficiency, melt uniformity, and output consistency. Different screw designs are optimized for specific materials such as PVC, PE, or engineering-grade resins.
Q4
What materials can be processed by the injection unit?
Modern injection units are designed to process a wide range of thermoplastic and thermosetting materials, including PP, PE, ABS, PC, nylon, POM, and various engineering plastics. Material compatibility depends on barrel temperature range, screw design, and corrosion-resistant coatings.
Q5
How is injection pressure controlled in the injection unit?
Injection pressure is precisely controlled through the machine's hydraulic or servo-electric drive system. Advanced closed-loop control systems monitor real-time pressure and velocity, automatically adjusting parameters to ensure consistent shot weight and part quality throughout production.
Q6
How should the injection unit be maintained for optimal performance?
Regular maintenance of the injection unit includes periodic purging of the barrel to prevent material degradation, inspection and replacement of screw and barrel wear surfaces, checking nozzle tip condition, lubricating moving components, and verifying temperature sensor calibration. Following a scheduled preventive maintenance program extends service life and ensures stable production quality.