Film wrinkling is a common quality defect in the blowing process, especially in the production of ABA three-layer extrusion blowing machine. Based on industry practice and equipment principle, this paper analyzes the causes of wrinkling of equipment systematically from four dimensions: installation of equipment, process control, raw material management and cooling system optimization,and puts forward practical solutions to provide technical guidance to production enterprises.
Equipment Installation and Mechanical Structure Optimization
1.1Die Head Leveling CalibrationMisalignment of die head is the direct cause of uneven thickness of transverse film. When the axes of the die head form an angle to the direction of traction, asymmetric melt flow occurs during die extrusion, resulting in an initial defect of "thicker on one side and thinner on the other." These thickness variations magnify as the bubble inflation and eventually manifest as periodic folds.
Solutions:
Use a laser leveller to inspect die installation surfaces to ensure levelness error ≤0.05mm/m
Adjust die head support bolts for progressive calibration using the "diagonal alternate tightening" method
Periodically check the sealing property of the die head fastening bolt to prevent production vibration from producing displacement.
1.2 Collapse Board Geometric Parameter Optimization for cave-in plates
The angle, surface roughness and symmetry of the folding plate directly affect film flatness. One case study demonstrated a 62% reduction in wrinkles by lowering the angle of the folding plate from 60 degrees to 45 degrees.
Optimization Points:
Angle selection: Calculate bubble diameter with theta = 2artan (D/2L), of which D is bubble diameter and L is distance from die to fold plate
Surface treatment: Hard chromium plating with surface roughness ≤ 0.2 μm
Symmetry calibration: Validation of spatial position deviation ≤ 0.1 mm between left/right plates using a coordinate measuring machine
1.3 Haul-off Roll System Maintenance
The parallelism, pressure uniformity and surface condition of the unloading roller have important effects on the film tension control of the film. A factory case revealed that roll bearings rolling bearings 0.3mm radial runout, causing significant longitudinal wrinkling.
Maintenance Specifications:
Check daily for scratches on adhesive or roller surfaces
Weekly radial runout measurement using dial indicators and bearing replacement as soon as the limit is exceeded
Monthly pressure distribution tests were conducted to ensure that the left-right ≤ 5% pressure difference
Precise Process Parameter Control
2.1 Blow-up Ratio and Draw Ratio Matching
Synergy between magnification and tensile ratio determines the orientation of the films. When BUR>3.5 and DDR<4.0, excessive transverse stretching results in wrinkles. DOE experiments determined optimal parameters LDPE/LLDPE blends: BUR=3.0±0.2, DDR=4.5±0.3.
Control Essentials:
Establish a process parameter matrices to determine the range of different materials/thickness
Installation of an online thickness gauges for real-time monitoring of MD/TD thickness
Realization of Implement PID control algorithms for steady traction motor speed (fluctuation range ≤0.5%)
2.2 Melt Temperature Profile Optimization
Excessive melt temperature reduces the entanglement of molecular chains and decreases the strength of the melt; insufficient temperature can lead to poor plasticization --both of which can lead to bubble instability. Studies have shown that for every 10°C increase in temperature, bubble oscillation amplitude increase by 23%.
Temperature Control Strategies:
Zonal temperature control: 160-180°C in feeding area, 180-200°C compression zone area, 200-220°C in metering area
Precision die head temperature control: oil cycle heating ≤ 1°C fluctuation
Screw speed-temperature linkage: when the screw speed is greater than 80 rpm, the temperature of the measuring area is automatically increased by 5°C to compensate for shear heating
2.3 Cooling System Efficiency Enhancement
Wrinkles are usually caused by inadequate cooling or uneven circulation of air rings. In one enterprise case, CFD simulation-optimized air ring designs resulted in an 18% increase in cooling efficiency and a 41% decrease in crease.
Cooling System Optimization:
Gas ring modification: doublelip design, stable flow of inner lip, outer lip control bubble oscillation
Wind volume control: Install Install variable frequency blowers and adjust bubble diameter in real time (Recommendations: 0.8-1.2m3/min.kg)
Temperature management: Configure a cooling water system to maintain cool air at 15-20°C
Raw Material Quality and Formulation Management
3.1 Raw Material Preprocessing
Water, impurities and low molecular weight materials in raw materials can lead to poor plasticization and bubble rupture. One enterprise's preprocessing protocol reduced wrinkles associated with raw materials by 76%.
Preprocessing Standards:
Drying treatment: LDPE/LLDPE was dried at 80°C for 4 hours to reach ≤0.02% moisture content moisture content
Screening filtration: Particles > 180 microns removed using an 80-mesh filters.
Homogeneous mixing: weightless feeder to ensure layer ratio fluctuation ≤0.5%
3.2 Formulation Optimization
Differences in melt flow rate (MFR) directly affect the properties of films. Orthogonal experiments identified the most optimal parameters: A layer (surface MFR = 2.0g / 10min min, and B (core core) MFR=0.8g/10min as the best comprehensive properties.
Formulation Design Principles:
Interlayer MFR Matching: Maintain difference between surface and core layers ≤ 1.5 g / 10 min
Containment dose: Adjusted to film thickness (< 20 micron film 0.3-0.5%)
Resistant choice: nano-silica has better dispersion than traditional talc
Production process monitoring and Exception Handling
4.1 Online Quality Monitoring
To establish a three-dimensional monitoring system of ``thick and tenuous phase"to carry out wrinkle early warning. One enterprise's intelligent monitoring system was 92 percent accurate in predicting wrinkles 15 minutes in advance.
Monitoring System Configuration:
Laser thickness gauges: 1000 samples/min frequency, ± 0.5μm accuracy
Tension sensors: 0-500N range, 0.1N resolution
High-Speed Camera: Microwrinkle Detection with 2000fps frame rate and image processing algorithms
4.2 Exception Handling Procedures
Develop standardized SOPs for rapid fault response. Typical wrinkle removal handling workflow:
Observe wrinkle characteristics → Measure wrinkle periodicity → Inspect corresponding equipment components → Adjust process parameters → Verify effectiveness → Document records
Case Analysis:
periodic transverse wrinkles with a production line cycle of 1.2m:
Adjust angle from 50 to 40 degrees to eliminate wrinkles
Record the most angle parameters parameters for the raw material lot number
Preventive Maintenance and Continuous Improvement
5.1 Equipment maintenance plan
Implementation of preventive maintenance based on TPM, focusing on:
Die head cleaning: Ultrasonic cleaning every 500 hours to remove carbon deposits.
Screening: Screening of screw tube clearance every 2000 hours (replaced ≥ 0.3mm)
Electrical system checks: quarterly verification of the accuracy of inverter/sensor accuracy
5.2 Process Database Building
Accumulate production data and establishment of process quality related models. One enterprise's database shows:
Optimal die head temperature range: 215-220°C with lowest wrinkle rate
Optimal towing speed to screw speed: 1.8 -2.2 for optimal film flatness
Conclusion:
Solving ABA blown film machine wrinkle issues requires systematic thinking, from equipment precision and process control to raw material management and process control. Implementation of the proposed solution enabled an enterprise to:
Wrinkle rate reduction was reduced from 8.2% to 1.5%
The first-pass yield rose 27 percentage point
19% improvement in Overall Equipment Effectiveness
The manufacturer should adjust the solution according to the characteristics of its own equipment, establish continuous improvement mechanisms, evaluate solution effectiveness periodically, optimize production parameters continuously, and finally achieve the goal of zero wrinkle production.
