In the eyes of customers, the quality of BOPP film depends not only on the quality of the stretching film but also onthe quality of the slitting machine.In other words, the quality of the film, besides thickness deviation and film performance related to the stretching process, also depends on the impact of the slitting process, such as: the setting and control of process parameters, slitting environment, quality of the slitting machine, quality of the paper core, packaging, transportation, etc. The slitting process is a crucial link in determining film quality, and the quality of slitting plays a vital role in maintaining the film's competitive advantage in the market.
The quality of slitting is a comprehensive reflection of various factors, and the various factors involved interact with each other, making quality issues in slitting more complex. To provide everyone with a comprehensive understanding of slitting quality issues, I have summarized common quality problems that occur during our company's slitting production process, analyzed and discussed the causes of various slitting quality issues and their impact on usage quality, as a platform for everyone to communicate and learn, and I hope everyone can provide valuable opinions to continuously enrich its content, aiming for mutual promotion and improvement.

1. Winding too loose/tight
Among the many factors affecting product usage quality, the tightness of the film roll is crucial. Proper control of tightness not only ensures slitting quality but also compensates for quality defects generated during the film-making process. However, improper control of winding tightness will inevitably directly affect the appearance and usage quality of the product.
(1) Several common methods for judging winding tightness
1. Finger pressure inspection method: This method involves the inspector using their hand to press on the surface or end face of the film roll to determine whether the winding tightness is appropriate. This is a commonly used inspection method, with the advantages of being quick, intuitive, and highly reliable, but it requires some experience and lacks data support, making recording difficult.

2. Instrument measurement method: This method uses a hardness tester to measure winding tightness, providing data support. The advantages are scientific, quantitative, and easy to record, reducing disputes over judgment differences. However, it can only detect the surface condition of the film roll and cannot reflect the complete internal facts of the film roll. The relationship between the tightness and hardness of the film roll is not completely linear; the most sensitive reading is between 87 and 95. When the hardness drops to 85, further loosening the winding has little effect on hardness. Similarly, when the hardness rises to 97, further tightening the winding has less and less effect on the hardness of the film roll.
3. Visual analysis method: This method involves visually analyzing the color change or end face shape of the film roll to judge the winding condition. For the same product, a darker end face color indicates tighter winding, especially near the paper core, where overly tight winding often appears black. Regarding end face shape, a star shape is the best judgment basis; a single star may indicate one side of the film is loose or tight, while a double star indicates that the film roll is tight on the outside and loose on the inside. The advantage of the visual method is that it is quick and accurate, but it can only analyze some individual winding issues and is not comprehensive.

4. Process tapping method: During the slitting and winding process, using a stick-like object or finger to tap the film surface can help judge the tightness of the film roll based on touch and sound. This method can track the tightness of the film roll throughout the entire process, with high accuracy and reliability. However, improper use may damage or contaminate the film surface and poses certain operational risks, so it is not recommended for frequent use. However, in our daily slitting process, we can accurately judge the winding tightness by combining the finger pressure inspection method, hardness measurement method, and visual analysis method.
Winding hardness is a reference indicator for quantifying winding tightness, reflecting only one quality characteristic of the film roll's surface and not the entire tightness of the film roll. Therefore, the key is effective control of the film roll's tightness to ensure the product's usage quality.