Injection Mold Structure Deep Dive - Longterm Manufacturing Solutions Limited

The Operational Mechanism of Injection Molding Molds

Core Components and Installation

The fixed mold half is rigidly mounted on the stationary platen of the injection molding machine, while the movable mold half attaches to the reciprocating platen. This configuration is fundamental for precision systems like precision plastic injection molds, multi-cavity hot runner molds, gas-assisted molds, and collapsible core molds.

collapsible core molds

Mold Closing and Alignment

Guide System: During operation, the hydraulically driven movable mold half is guided by precision ground guide columns (diameter: 20–50mm, straightness ≤0.01mm/m), ensuring alignment accuracy critical for precision plastic injection molds.
Locking Force: Hydraulic or toggle clamping systems generate 500–5000 tons of force to secure the mold halves, preventing flash in high-pressure applications like multi-cavity hot runner molds.

Plastic Injection Process

Material Flow Path:

For multi-cavity hot runner molds, heated manifolds maintain melt consistency across all cavities (temperature variation ≤±3°C).

Plastic melt (temperature: 180–320°C) is injected from the machine nozzle
It travels through the sprue, runner system, and gates into the mold cavity

Gas Assisted Injection: In gas-assisted molds, nitrogen (pressure: 5–20 MPa) is introduced post-injection to hollow out thick sections, reducing weight by 15–30% and eliminating sink marks.

Specialized Mold Functions

Collapsible Core Molds:

Hydraulic or pneumatic actuators retract collapsible cores (tolerance: ±0.02mm) to release parts with undercuts, essential for complex geometries in automotive components.

Precision Plastic Injection Molds:

Tolerances as tight as ±0.005mm are achieved via hardened tool steels (HRC 50–55) and fine-finished surfaces (Ra <0.8μm).

Cooling and Demolding

Cooling System:

Conformal cooling channels (diameter: 8–12mm) maintain uniform mold temperature (ΔT ≤5°C), critical for cycle time reduction in multi-cavity hot runner molds.

Ejection Phase:

After cooling (10–40s), the mold opens, and ejector pins (diameter: 4–10mm) powered by hydraulic cylinders push parts out.
In gas-assisted molds, residual gas pressure assists in part release.

Operational Parameters for Specialized Molds

Mold Type	Key Considerations	Typical Applications
Collapsible Core Molds	Core retraction speed (0.1–0.5m/s)	Pipe fittings, appliance handles
Gas Assisted Molds	Gas injection timing (0.5–1s post-injection)	Automotive bumpers, office chairs
Precision Plastic Injection Molds	Temperature control (±1°C), vibration dampening	Medical devices, electronics
Multi-Cavity Hot Runner Molds	Runner balance, thermal uniformity	Consumer goods, packaging

Safety and Efficiency Enhancements

Interlock Systems: Proximity sensors ensure mold halves are fully closed before injection, preventing material leakage in precision plastic injection molds.
Process Monitoring: IoT sensors track clamp force, melt pressure, and temperature in real-time for multi-cavity hot runner molds, reducing scrap rates by 20%.

Conclusion

The coordinated operation of fixed and movable mold halves, combined with specialized features in collapsible core molds, gas-assisted molds, precision plastic injection molds, and multi-cavity hot runner molds, enables the production of complex plastic parts with unmatched precision and efficiency. This mechanism forms the backbone of modern plastic manufacturing, driving innovation across industries.