Closed-Loop Control for Flawless PET Production
Stability is essential for high-quality continuous production. Our production line implements closed-loop control systems at all critical process points, enabling real-time monitoring and instant adjustments. From drying temperature and extrusion zone temperatures to stretch roll speeds and winding tension, sensor signals are continuously fed back to controllers and compared with setpoints to dynamically adjust actuators. This real-time error-correction mechanism effectively counters external disturbances, ensuring process parameters remain within optimal ranges to guarantee consistent product thickness, width, strength, and significantly reduce scrap rates.
Key Features
- Control Principle: Full closed-loop automatic feedback control on key quality variables, minimizing manual intervention and parameter drift
- Temperature Closed-Loop: All heating zones utilize PID closed-loop control with robust anti-interference capability
- Tension Closed-Loop: Tension sensors at stretching, haul-off, and winding stages with servo motors or magnetic powder clutches for real-time adjustment
- Speed Synchronization: All drive points synchronized via master speed chain or bus system with precise, adjustable ratios
- Thickness Control (Optional): Integration with online thickness gauge for Automatic Thickness Control (ATC)
Technical Specifications
| Parameter Category |
Parameter Item |
Specification / Description |
| Temperature Control |
Control Method |
PID Closed-Loop with Auto-tuning |
| Control Accuracy |
±1.0 °C (heating zones) |
| Response Time |
Correction to disturbance < 2 seconds |
| Tension Control |
Control Stages |
Stretching, Haul-off, Winding |
| Sensor Type |
Tension Dancer or Load Cell |
| Control Accuracy |
±1% FS (Full Scale) |
| Speed Synchronization |
Synchronization Method |
Electronic Gearing/Camming (Bus-based) |
| Optional Configuration |
Automatic Thickness Control |
Closed-loop based on beta-ray or infrared gauge |
Frequently Asked Questions
What's the difference between closed-loop and open-loop control in actual production?
Open-loop control is similar to setting a stove's flame and leaving it, where ambient changes might cause heating fluctuations. Closed-loop control functions like an intelligent oven with a thermostat, constantly monitoring internal temperature and automatically adjusting heat to maintain the set point. In production, closed-loop automatically compensates for disturbances like voltage fluctuations, ambient temperature changes, and minor raw material variations, whereas open-loop requires frequent manual checks and adjustments and cannot achieve the same level of stability.
Why is tension closed-loop so important?
Constant tension is crucial for preventing product deformation, breakage, wrinkles, or uneven tightness during PET stretching, haul-off, and winding. Tension fluctuations can cause unstable draw ratios affecting strength uniformity, haul-off slippage causing thickness variations, and poor winding patterns like "telescoping" or "ribbon" winding. A tension closed-loop system instantly responds to and corrects any tension change, making it essential technology for achieving neat roll formation and excellent product appearance.
