The narrow web self-adhesive material used in label printing enterprises is cut from wide web rolls of self-adhesive material by suppliers. Therefore, the accuracy of the slitting rewinding equipment, the arrangement of the slitting process, and the quality of the large rolls of self-adhesive material to be cut all directly affect the quality of the small rolls of self-adhesive material after slitting.
After opening a roll of self-adhesive material packaging, the relevant personnel first need to check the following aspects:
Whether the end face is neat and whether there are cracks or cuts in the edge
If the end face of the self-adhesive material is not neat, it will cause "snake" phenomenon in feed paper, causing inaccurate overprinting. If the edge of the self-adhesive material has cuts or cracks, the paper will break during machine printing, causing waste.
Whether the core part of the self-adhesive material is loose
If the core part of the self-adhesive material is loose, the end face will be uneven when placed in the paper feeding position. During printing, the edge of the self-adhesive material will gradually deform, causing drifting or snake-like phenomenon and resulting in inaccurate overprinting.
Whether both ends of the self-adhesive material are equally tight
If the self-adhesive material on both ends is not equally tight, it is because the tension of the two ends of the rewinding is different or one end of the self-adhesive material is deformed by moisture absorption. If there is a deviation correcting device on the equipment or it is adjusted manually, this deficiency of the self-adhesive material can be improved. However, if the precision of the equipment is low or the self-adhesive material has severe defects, it is difficult to avoid problems such as deviation and inaccurate overprinting.
The accuracy of the slitting machine and the arrangement of the slitting process have a great impact on the quality of the self-adhesive material after slitting.
Slitting tools
Dull or swinging slitting tools, too deep inlet, insufficient lateral pressure, poor lubrication, and too much glue on the bottom knife can all cause problems with the end face quality of the self-adhesive material after slitting, including glue seepage, unclean end face, and material feeding swing.
Glue seepage on end faces
If the tool is not sharp, the self-adhesive material is not completely cut but instead is folded. The adhesive bonds to the surface of the tool and the self-adhesive material, making it easy to stick to dust. The adhesive can also adhere to the surface of the printing machine's guide roller, causing trouble for the operator.
Unclean end faces
The unclean end face of the self-adhesive material often leads to white spots during printing. This is because the paper fibers and coating edges of the self-adhesive material have loosened, and these substances suspend on the surfaces of the self-adhesive material, printing plate, and glue roller, forming periodic white spots. The operator needs to clean the printing plate frequently, which causes significant waste.
Material feeding swing of the self-adhesive material
If the slitting tool swings left and right during the slitting process, the edge of the self-adhesive material will be uneven. The uneven edge not only causes the end face of the self-adhesive material to be uneven but also makes the self-adhesive material display periodic left and right swing on the printing machine, which is easy to confuse with the "snake" phenomenon, making it difficult for the operator to determine the overprinting problem.
Rewinding shaft
The rewinding shaft is the most critical part of the slitter, and its accuracy is easily affected by the accuracy of movement and the accuracy of the internal parts.
Movement accuracy of rewinding shaft
Rewind shaft in the winding can not swing, swing will cause the paper roll end face uneven, self-adhesive material tension cyclical loosening and tightening changes, and the shaft of each paper roll is not the same impact.
The reasons for the change of rewinding axis movement accuracy are: the influence caused by mechanical processing (such as large radial runout, inconsistent depth of keyway on the circumference); poor stiffness of self-adhesive material, natural deformation by gravity: bearing damage at the end of the shaft, resulting in jumping when rewinding axis movement.
Mating accuracy of internal parts of rewinding shafts
Rewind shafts are usually divided into two types: air expansion shafts and slip shafts. These two kinds of shafts have keyways on the circumference, and the keyways are equipped with airbags, friction plates and other parts. The ideal state is that these parts remain concentric and do not produce radial runout. If these parts are not concentric in maintenance, it will cause the paper take-up shaft to jump when it rotates (sometimes it is a local jump in the axial direction). This runout can cause quality problems after rewinding the self-adhesive material.
In addition to the rewinding shaft accuracy, the rewinding shaft stiffness, material and length also have a great impact on the slitting quality. The faster the speed of the rewinding shaft, the larger the diameter of the rewinding self-adhesive material, the longer the length of the rewinding shaft, the greater the deflection deformation of the rewinding shaft. Deflection deformation is easy to make the rewind shaft bending, and this bending deformation in the axial direction is not the same, the middle peak is the largest, the two ends gradually become smaller.
The dynamic deformation of this deflection of the rewinding axis is with the slitting speed, winding diameter and become larger, resulting in the rewinding axis on each roll of self-adhesive material rewinding tension is not the same, which is a batch of slitting self-adhesive material register situation is not the same reason.
Slitting machine technical parameters set
Slitting machine technical parameters set is a very practical work, different slitting products, different types of equipment, different equipment state input technical parameters are not the same, only familiar with the performance of different self-adhesive materials and the principle of equipment to reasonably set the data to ensure the quality of slitting.
Slitter rewinder machine technical parameters mainly include unwinding tension, rewinding initial tension, slitting speed and rewinding taper.
Unwinding tension
Large volume of unwinding requires constant tension of self-adhesive material, so that the quality control of the slitting behind the guarantee. Different self-adhesive materials, different widths, the set unwinding tension are not the same.
The initial tension of rewinding
The initial tension determines the elasticity of self-adhesive material rewinding. If the tension is small, the finished roll will be loosely deformed and the edge is not neat; if the tension is large, the paper core tube will be deformed and the self-adhesive material will bleed.
Slitting speed
Slitting speed determines whether the edge of the self-adhesive material is neat and flat after rewinding, whether there will be printing "snake" swing phenomenon. The general rule is: slitting the finished product diameter of small paper self-adhesive materials, slitting speed can be faster; slitting the diameter of large self-adhesive materials or film self-adhesive materials, slitting speed can be slower, the specific situation should be determined flexibly according to the site.
Rewind taper setting
Taper setting directly affects the finished paper roll tightness, especially for some large diameter self-adhesive materials. The so-called taper is actually the ratio of the initial tension of the rewinding and the final tension of the rewinding.
The ideal taper setting is to ensure that the finished self-adhesive material is tight at the center of the roll, and as the diameter increases, the rewinding tension gradually decreases, and the final roll will not appear tight on the outside and loose on the inside. Because the self-adhesive material roll center is loose, the printing of self-adhesive material end face will be axially deformed, affecting the registration accuracy, label printing companies can not use.
Usually high-grade slitting machine in the software will be the above data designed into different menus, data packages, so the operator to match the material of self-adhesive materials, specifications to select the menu to achieve the best slitting effect.
