The thickness uniformity of industrial antistatic PET rolls is a core indicator affecting their performance stability and application reliability. During production, thickness fluctuations can lead to uneven surface resistivity distribution, differences in mechanical strength, and even breakage or poor bonding in downstream processing. Therefore, a closed-loop control system must be established from five dimensions: raw materials, equipment, process, environment, and testing, to ensure that thickness deviations are controlled within acceptable limits.
Raw material stability is fundamental to thickness uniformity. Industrial antistatic PET rolls typically use PET resin as a base material, achieving functionalization through the coating of antistatic coatings. Large differences in melt flow index between batches of raw materials can cause fluctuations in melt flow, thus affecting the coating thickness. Therefore, it is necessary to strictly screen suppliers, ensure that the melt flow index deviation of each batch of raw materials is within a controllable range, and conduct sampling inspections before feeding to avoid thickness abnormalities caused by raw material issues.
The precision of the equipment directly affects the feasibility of thickness control. In coating equipment, the uniformity of the die lip gap is crucial. Localized wear on the lip or loose adjusting bolts can lead to inconsistent melt flow, resulting in thickness deviations. Therefore, the mold lip needs to be inspected regularly, and multiple measurements should be taken using a laser gap gauge or feeler gauge to ensure that the gap error is within the allowable range. Simultaneously, the elasticity, wear resistance, and heat resistance of the coating roller must also meet requirements to avoid uneven contact pressure caused by roller deformation, which would affect the coating thickness.
Matching of process parameters is crucial for uniform thickness. During coating, parameters such as screw speed, melt pressure, and traction speed must be controlled in tandem. Screw speed directly affects the melt output; excessive speed fluctuations will lead to inconsistent coating thickness. Therefore, a frequency converter is needed to precisely control the screw speed and maintain stable operation, avoiding frequent start-stop cycles. Melt pressure needs to be monitored in real time by a pressure sensor; if pressure fluctuations exceed the range, the screw speed or mold lip gap must be adjusted promptly. Traction speed must match the melt output; excessive traction will thin the coating, while insufficient traction will cause the coating to thicken. Therefore, a PLC system is needed to achieve synchronous control of traction speed and screw speed to ensure stable thickness.
Environmental factors significantly impact thickness uniformity. Fluctuations in workshop temperature and humidity can cause raw materials to absorb moisture or alter melt viscosity, thus affecting coating thickness. For example, excessive humidity can cause antistatic coatings to absorb moisture, reducing their fluidity and resulting in a thinner coating; conversely, excessively low temperatures can increase melt viscosity, increasing coating resistance and leading to a thicker coating. Therefore, it is crucial to maintain workshop temperature within a reasonable range and install an air purification system to maintain cleanliness and prevent dust and other impurities from adhering to the coil surface, affecting thickness measurement accuracy.
Online detection and feedback adjustment are the final guarantee for thickness uniformity. Installing laser or infrared thickness gauges on the production line allows for real-time monitoring of coil thickness changes and feedback of data to the control system. If the thickness exceeds the set range, the system automatically adjusts coating parameters, such as screw speed, traction speed, or die lip clearance, to restore the thickness to the normal range. Simultaneously, the online detection equipment must be calibrated regularly to ensure its measurement accuracy meets requirements and prevent thickness control failure due to equipment errors.
