Plasticizing Unit for Precision Injection Molding
The plasticizing unit is a critical component for enhancing plasticizing quality, injection repeatability, and product integrity. Current developments focus on achieving high speed, high pressure, and rapid response capabilities.
High-speed plasticization is a defining feature of precision injection molding machines. Standard injection speeds range from 300–1000 mm/s, with advanced systems reaching 2000 mm/s.
For speeds ≤500 mm/s: Single-stage coaxial units can simultaneously handle injection and plasticization.
For speeds >500 mm/s: Single-stage coaxial units struggle with precision due to melt backflow, causing metering inaccuracies and material degradation.
Solution: IMC (Injection Molding Compounder) System
Separates plasticization (extruder screw) and injection (plunger) functions.
Plunger-barrel clearance is significantly smaller than screw/check-ring clearance, preventing backflow.
Independent plasticization improves quality and capacity, unrestricted by molding cycles.
All-electric systems enhance control accuracy for parameters like:
Plasticizing displacement, screw speed, backpressure
Injection stroke and holding pressure
Widely adopted in precision molding for superior repeatability.
Compared to conventional screws, precision screws feature:
Lower compression ratio
Higher L/D ratio (24–30 vs. standard 20–23)
Enhanced wear resistance
Material selection prioritizes stiffness/strength to withstand injection pressures of 216–243 MPa (up to 392 MPa for ultra-high-pressure machines), preventing bending or torsion failures.
Precision Clamping Unit
Essential for mold protection and product quality. Precision units offer:
10–15% higher rigidity vs. standard
30–40% stricter parallelism (0.05–0.08 mm) between moving/fixed platens
Innovations:
High-precision ball guideways for platen stability.
Dual-function servo valves (speed control + closed-loop pressure) enabling low-pressure mold protection.
Wear-resistant friction pairs (pins/bushings) to maintain parallelism.
Precision mold-height adjustment mechanism.
Hydraulic cylinders act on the center of the moving platen, eliminating mid-plate deflection and ensuring long-term parallelism.
Upgraded with ball guideways for enhanced stability.
Eliminates tie-bar deflection, improving parallelism accuracy.
Reinforced "C" frame design (e.g., Milacron’s Freedom series with U-structure and dual bottom tie-bars).
Patented balancing cylinders stabilize platen alignment.
Separates force-bearing and mold-mounting functions into interconnected blocks.
Force is concentrated on a central ring, isolating deflection to the ring area and preventing full-platen deformation.
Enhances clamping precision.
Precision Hydraulic Control Technology
Key Developments:
Integrated smart systems combining digital hydraulics and electronic processing for closed-loop control of flow, speed, position, and pressure.
Multi-functional proportional valves (e.g., Atos’ servo-proportional cartridge valve) replacing 3–5 conventional valves, enabling simultaneous speed/pressure control.
Precision Control Systems
Advancements:
Nissei’s TACT system: Reduces product weight variation from 0.022g to 0.006g.
Hongxun Tech’s all-electric system: CPU speed increased to 400 MHz (±0.1°C temperature control).
JSW’s J-EⅡ-P series: Features 6-stage injection/holding pressure control, 3-stage screw speed/backpressure control, and adaptive servo circuits for temperature consistency.
Application Case: HDJM-100 All-Electric Precision Molder
(Ningbo Haida Plastic Machinery)
Key Capabilities:
Injection: 300 mm/s (standard), 500 mm/s (high-speed); 235.2 MPa pressure.
Holding pressure: 196 MPa for micro-shrinkage control.
Plasticizing: Melt density repeatability improved to 0.5–0.6% (vs. 3–5%).
Temperature control: ±0.1°C via PID.
Clamping: Ball guideways + reinforced platens/tie-bars eliminate deflection.
Positioning: 0.05 mm accuracy via closed-loop displacement sensors.