Control of Cast Film Thickness: Multi-Dimensional Factors Driving Industry Technological Innovation

Industry Background and Core Challenges

As a core material in packaging, electronics, medical and other fields, the thickness uniformity of cast film directly affects product performance and subsequent processing quality. According to industry statistics, approximately 30% of global film production waste is caused by uneven thickness. In recent years, with the increasing demand for high-speed and intelligent production, how to accurately control film thickness has become a key direction for industry technological research.  

Analysis of Core Factors Influencing Film Thickness

1. Equipment Factors: Precision Design and Intelligent Adjustment

Die Lip Clearance Control: Die lip clearance is the primary factor affecting transverse thickness. Traditional thermal expansion bolt adjustment technology achieves fine-tuning by heating/cooling bolts, but the automatic adjustment range is limited to ±1.5μm, requiring manual intervention beyond this range. Dongguan Tenghe New Materials' latest patent uses arc-shaped adjustment plates combined with cylinder linkage technology, significantly improving adjustment accuracy and flexibility.  

Air Knives and Vacuum Boxes: The angle of air knives (typically 30°), position, and air volume directly affect the effect of melt film adhering to rollers. Excessive air volume causes film jitter and thickness deviation, while insufficient air volume leads to transverse fluctuations. The exhaust air speed of vacuum boxes must match production speed and film thickness; otherwise, holes or bubbles are likely to occur.  

Cooling Rolls and Traction Systems: The stability of cooling roll linear speed determines longitudinal thickness uniformity. If the extrusion volume is fixed, a 10% increase in linear speed reduces film thickness by approximately 5%. Roundness deviation of traction rolls causes periodic thickness fluctuations.  

2. Process Parameters: Dynamic Balance of Temperature and Speed

Temperature Gradient Design: The barrel temperature increases along the material flow direction, and the transverse temperature of the die head presents a "saddle shape" (lower in the middle and higher at both ends) to compensate for differences in melt flow paths. For example, the die lip temperature during polypropylene processing needs to reach 210-240°C, and a deviation exceeding ±5°C will cause transverse unevenness.  

Matching of Traction Speed and Extrusion Volume: Screw rotation speed and cooling roll linear speed need to be dynamically coordinated. Taking PET film as an example, a 1% fluctuation in screw rotation speed can cause a 2% deviation in film thickness.  

Distance Between Die Lip and Cooling Roll: Excessive distance (usually required to be <10cm) is prone to environmental disturbances, causing melt film jitter and increasing the risk of thickness fluctuations.  

3. Material Properties: Resin Performance and Formula Proportions

Resin Melt Index and Density: Resins with high melt index (such as MI > 12g/10min) have significant shrinkage effects, with edge thickening rates reaching 15%-20%. Every 0.01g/cm³ increase in density increases crystallinity by 3%, affecting cooling uniformity.  

Additives and Recycled Material Blending: Deviations in the blending ratio of additives such as(slip agents) and antistatic agents exceeding 5% will change melt viscosity, leading to uneven flow in the die cavity. When the recycled material blending amount exceeds 20%, it is prone to causing melt pressure fluctuations and increasing thickness deviation.  

Technological Innovations and Industry Solutions

Intelligent Measurement and Control Systems: The automatic measurement and control system developed by Timaco Company uses an X-ray thickness gauge (accuracy ±0.1μm) to provide real-time feedback data, combined with a three-axis motor-driven adjustment of bolt angles, reducing the scrap rate by 40%.  

R&D of Environmentally Friendly Materials: The application of bio-based PE and degradable resins is gradually becoming popular. For example, PVDF piezoelectric films have improved thickness control accuracy to ±0.5μm through optimizing the film-forming solution concentration (4%) and polarization processes.  

Process Integration and Optimization: The laboratory casting machine launched by Guangdong Xihua Machinery uses multi-zone independent temperature control (±1°C) and an air-cooling system, suitable for high-precision requirements of nanocomposite materials, improving film uniformity by 30%.  

Industry Trends and Future Prospects  

1.Deep Penetration of Intelligence: Digital twin and AI algorithms will enable predictive adjustment of thickness fluctuations, shortening the debugging cycle by 70%.  

2. Upgrading of Green Manufacturing: The proportion of degradable resins is expected to exceed 25% by 2030, with carbon footprint tracking technology embedded in production lines.  

3. Expansion of High-End Applications: The aerospace industry's surging demand for high-temperature resistant (>150°C) and radiation-resistant films will drive the iteration of ultra-precision extrusion technology.  

Controlling cast film thickness is a complex systems engineering involving the collaborative interaction of equipment, processes, and materials. In the future, with the deep integration of intelligent technologies and environmentally friendly materials, the industry will break through traditional production bottlenecks and inject new momentum into high-end manufacturing and sustainable development.