7 common faults and solutions for PI film slitting

Vertical stripes

Vertical stripes refer to the circumferential rib like stripes formed on the surface of the film roll. The main reasons for the generation of longitudinal stripes during the slitting/rewinding process are the large amount of air trapped and the poor accumulation of thickness tolerances. Once severe stripes appear, they are difficult to eliminate. One of the reasons is that the cutting speed is too fast. Generally speaking, quality issues such as longitudinal stripes and staggered layers are most likely to occur at high speeds.

split-level

The phenomenon of some thin films being misaligned on the end face of the film roll is caused by the sliding of the film or changes in the width of the film during the winding process. The misalignment is also related to the cutting speed. If the acceleration and deceleration are too fast, it is easy for smooth films to slip and cause misalignment. Therefore, the speed change should be slowed down. If the film roll is taken too tightly, it will also cause lateral slippage of the film. If the film roll is too loose, it will cause air to be sucked in, which will cause the end face of the film roll to be staggered. The winding tension should be adjusted.

Bottom wrinkles

Bottom wrinkles only occur in a certain length at the beginning of film winding, manifested as numerous and deep wrinkles and stripes, which are caused by various factors. In terms of process parameters, different types of slitting machines have different ways, methods, and values for setting process parameters.

For example, old-fashioned slitting machines control the winding tension by manually adjusting the voltage of the winding motor and use mechanical friction resistance to obtain the unwinding tension, while modern slitting machines use computers to control the winding and unwinding motors based on input process parameters to obtain the most suitable winding and unwinding tension. The parameter settings between the two are fundamentally different.

The performance of the equipment itself and the inherent properties of the film have a significant impact on the quality of film cutting and winding, but appropriate processes can improve quality issues such as longitudinal stripes and bottom wrinkles. Appropriate slitting processes should be used for films of different equipment and specifications. When the equipment condition changes, process adjustments can also be made to compensate, but process adjustments must be made carefully.

In addition, the most important raw and auxiliary materials for the slitting process are paper cores and large axis film rolls. The quality of these materials not only affects the slitting speed, but is also closely related to longitudinal stripes, wrinkles, and other issues. A combination of process control, incoming inspection, and final inspection is needed to strengthen monitoring and stabilize the quality of large axis film rolls and raw and auxiliary materials.

Bent edge

The edge curling occurs at the edge of the film winding, which is caused by the stacking of thicker film edges through winding, resulting in the edge area curling up. The usual reason is that the cutting blade is too blunt, causing stretching at the incision during slitting, resulting in the edge of the film roll curling outward after rewinding, causing edge curling. At this time, the cutting blade should be replaced in a timely manner to avoid edge curling problems. Incorrect installation of cutting tools, too fast winding speed, and too tight winding can also easily cause edge curling.

Violent tendons

Stretching is a significant protrusion formed on the surface of a PET film roll due to the accumulation of thickness tolerances. This is mainly due to the quality of the film itself. The quality of the film itself refers to the quality of the already formed large axis film roll that has been cut or the finished product that has been cut again, such as the thickness tolerance of the film, the winding state of the film, etc., all of which have a significant impact on the apparent quality of the cut film roll. Poor quality films cannot achieve satisfactory apparent quality even after cutting/rewinding.

Slitting only improves local problems and cannot change all problems. To achieve good product appearance and winding quality, on the one hand, appropriate adjustments must be made during slitting, and on the other hand, the quality of the previous film-forming process must be improved.

Insufficient length and excessive width deviation

This is caused by errors in roll counting or insufficient length of the cut film, as well as incorrect positioning of the equipment. To meet the user's need to obtain a certain length of film roll, in general, the operator can obtain the winding length from the data displayed on the winding machine.

However, in production, it is common to encounter situations such as breaking the film and cutting off some of the thin films on the surface of the main shaft film roll. If the calculation and cutting are carried out according to the marked length, and it is only discovered at the end of the cutting that the length is not enough and cannot be spliced, then the entire vehicle product cannot become a genuine product, especially for slitting machines with a width of more than 1 meter, the economic loss is even greater.

To avoid this situation, the length of the large axis film roll with the same model, specification, and process should correspond to the diameter of the film roll to a certain extent. As long as the measured diameter data is compared with the winding length after being installed on the machine, it is possible to roughly determine whether the roll length of the film roll meets the requirements. If there is a significant difference between the two, attention should be paid to the splicing length during cutting to avoid the occurrence of insufficient length.

There are dust and even small flying insects and other foreign objects inside the film roll

During the slitting process, PI film needs to be reopened and then rewound, which creates conditions for the entry of external foreign objects. Due to the fact that many thin film products require direct contact with the products themselves, strict hygiene requirements are imposed. A clean production workshop is crucial to ensure good product cleanliness.