HYDRAULIC SYSTEM FOR INJECTION MOLDING MACHINES
The hydraulic system serves as the core power and control unit of injection molding machines, with its performance directly impacting equipment stability, molding efficiency, and product quality. Below is a detailed technical analysis of system components, operating principles, key features, and optimization directions.
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I. SYSTEM CORE COMPONENTS
1. Power Source Module
• Variable/Servo Pump Units: Achieve demand-based flow control via displacement adjustment or speed regulation, offering 30-60% energy savings over traditional fixed-displacement pumps.
• Motor Drives: Servo motors (response time <10ms) outperform asynchronous motors with millisecond-level dynamic pressure/flow adjustments.
• Oil Reservoir Assembly: Includes temperature sensors, air breathers, and level indicators to maintain hydraulic oil temperature (40-55℃) and cleanliness (below NAS 7).
2. Control Execution Layer
• Directional Control Valves: Proportional directional valves (±0.5% repeatability) enable precise timing control for mold opening/closing and injection.
• Pressure/Flow Valve Groups: Stacked pressure-compensated valves + proportional flow valves allow independent adjustment of pressure (0-350bar) and speed (0-300mm/s) per process step.
• Servo Proportional Valves: High-frequency response (200Hz) with spool displacement feedback meets transient response requirements for thin-wall products (0.1mm) during high-speed filling.
3. Actuator Layer
• Injection Cylinders: Dual-cylinder synchronous control (position sync error <0.05mm) ensures melt uniformity during plasticization.
• Clamping Cylinders: Four-cylinder differential fast-lock structures achieve 2000-ton clamping force loading within 3 seconds.
• Ejection/Core-Pull Cylinders: Cylinders with displacement sensors (0.01mm resolution) support sequential demolding for complex molds.
4. Auxiliary Function Units
• Cooling Circuits: Plate heat exchangers + temperature control valves maintain hydraulic oil temperature within ±1℃.
• Filtration Systems: Three-stage filtration (100μm suction filter → 25μm return filter → 5μm high-pressure filter).
• Accumulator Banks: Nitrogen cylinders + piston accumulators absorb pressure pulsations and store 50% of peak energy.
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II. TYPICAL PROCESS-STEP HYDRAULIC PRINCIPLES
【表格】
Process Step Pressure Control Flow Control Response Characteristics
Mold Closing Rapid low-pressure → high-pressure clamping (segmented pressure) Variable pump + proportional valve dynamic adjustment Fast closing <0.5s, high-pressure loading <2s
Injection Adjustable back pressure (0-50bar) Multi-segment injection speed control (3-5 segments) Injection speed fluctuation <±1%
Packing 0-350bar closed-loop feedback Adjustable packing time (0.1-999.9s) Pressure deviation <±2bar
Cooling Low-pressure maintenance (10-20bar) Minimum flow maintenance (5L/min) 40% reduction in standby energy consumption
Mold Opening Segmented pressure relief (shock avoidance) Differential fast opening + slow positioning Mold opening repeatability ±0.02mm
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III. TECHNOLOGICAL BREAKTHROUGH DIRECTIONS
1. Full Electro-Hydraulic Hybrid Drives
• Injection units adopt servo motors + ball screws (±0.005mm repeatability), while clamping units retain hydraulic servos (fast dynamic response) for 65% energy savings.
2. Digital Twin Monitoring
• Multi-sensor networks (pressure/flow/temperature/vibration) construct hydraulic system digital models, enabling predictive maintenance to reduce downtime by 70%.
3. Micro/Nano-Level Control
• Nanometer-resolution displacement sensors (0.001mm) + 500Hz high-frequency response valves meet ultra-precision molding requirements for optical lenses.
4. Green Hydraulic Technologies
• Water-glycol-based eco-friendly hydraulic oils (flash point >200℃) paired with magnetic oil filters achieve 99.5% iron debris removal for oil regeneration.
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IV. INDUSTRY APPLICATION CASES
• Automotive Sector: A new energy vehicle manufacturer adopted dual-pump parallel flow technology, reducing bumper molding cycles from 45s to 32s for a 35% annual capacity increase.
• Medical Devices: A consumables producer implemented closed-loop pressure control, reducing dimensional tolerances of IV connector Luer taps from ±0.05mm to ±0.02mm.
• Packaging Industry: High-speed thin-wall packaging machines achieved 16-cavity PET preform molding (2.8s cycle, defect rate <0.3%) via servo hydraulic + multi-cavity molds.
