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When cutting thin paper, the easiest and most common problem is that the paper produces “wrinkles” on the machine in the direction of paper feeding way. The wider the machine (i.e., the wider the paper) and the thinner the paper, the easier it is to wrinkle.
Fault cause: Excessive tension
In general, if the tension in a certain part of the machine is too high, wrinkles will occur in that area and affect the subsequent parts. For example, sometimes if the unwinding tension is set too high, wrinkles will occur in the unwinding section, and the more severe the wrinkles will be at the back, and even the paper will break. Some users originally ordered a thick paper sheeter machine, which is easy to wrinkle when used to cut thin paper. At this time, wrinkles usually occur in the middle and rear of the paper sheeter machine.
Reducing the tension setting of each part can solve this problem, but the most fundamental solution is to replace a set of rollers suitable for thin paper, including slotted traction rollers, gears, and independent drive systems.
Fault cause: The deflection angle of the correction device is too large
The tension of the paper at the deviation correction device is tight on one side and loose on the other side, making it prone to wrinkles. If it is the uncoiling part, there will be a phenomenon of “bark” wrinkling on the feed tension roller, of course, on the loose side of the paper.
Let the web guiding device “straighten itself” (by press the “Center” button on the controller), slow down for a section of paper, adjust the appropriate horizontal position of the paper and stabilize it, stop the web guiding device’s drive motor, and then adjust the electric eye sensor of the device to align with the current position of the paper edge that needs to be monitored. At this time, switch the web guiding system to “automatic” mode of operation. This can minimize the deflection angle of the correction device during the “automatic” working process, minimizing the possibility of wrinkles. At this point, a clear mark should be made on the horizontal position of the paper processing roller, and the position will be easy to align when changing to a new roll of paper.
Fault cause: There are foreign objects (such as large paper scraps or ink blocks) or dents on the surface of the paper guide roller; The parallelism of individual rollers is out of tolerance, etc.
To adjusting the tension and checking the machine, if necessary, electrical tape can also be wrapped on the inner side of the paper guide roller at the location, approximately 15 millimeters away from the two paper edges, to prevent the paper from moving laterally inward. A paper guide roller with slotted spiral lines can also be used to extend the thin paper outward. But when the stiffness of thin paper is too small and the tension is relatively high, it will actually wrinkle due to the spiral line, so it needs to be analyzed in a specific case.
In addition, when cutting thin paper, after the original paper roll cover is removed from the packaging, the paper near the outer packaging surface will absorb moisture from the air and then wrinkle. When the outer wrinkled paper enters the machine, it will definitely cause problems.
Of course, this situation is only temporary. As long as this part of the paper is passed or simply cut off and reconnected at a lower speed, normal production can be started. As for how to avoid the above problems, we suggest strictly ensuring that the packaging of the paper roll is intact during transportation and storage, and removing the packaging when it is about to be cut on the machine to minimize the time it takes for the paper roll to absorb moisture from the air
The term ‘warping’ here refers to the warping of paper in a direction perpendicular to the paper feed. When looking in the direction of the feed, one can see that both sides of the paper or finished product are warping upwards. Due to the increasing speed of modern packaging machinery, the requirements for product quality are inevitably becoming higher. Once the cut product warps, it will bring some trouble to the packaging assembly line operation.
Fault cause: To explain in a simple sentence, the occurrence of warping is caused by the difference in tension (stress) between the front and back sides of the thin paper, and the vast majority is caused by changes in humidity on the surface of the paper. Thin paper has a certain thickness even when it is thin. If one side (or both sides) of the paper is affected by moisture (humidification), resulting in inconsistent tension between the front and back sides, and the stiffness of the paper in the fiber direction is generally better than that in the transverse direction, then under the combined action of the two, the paper will inevitably warp. Thick paper is less prone to warping because its overall stiffness is good.
Observe the situation of the paper in the uncoiled section, simply pull the paper out of the roll for a period of time and place it for comparison. At this point, the general single copper paper will slightly warp, because the moisture content of the original paper roll is generally only about 5%. Achieving equilibrium in a workshop with a relative humidity of about 50% can increase the moisture content to about 7%. During the moisture absorption process, the coating on the front of the paper will hinder some moisture from entering the paper from the front, while the back will be relatively damp, causing the paper to slightly warp. Of course, the coating on the front will also have certain limitations on the deformation of the paper fibers.
The cut product is flat, but the finished product warps after being placed in the packaging workshop for a period of time. So the sliced tissue should be packaged and stored as soon as possible. To avoid warping caused by dampness.
Static electricity “refers to the static electricity generated during high-speed start-up production. Once thin paper products generate static electricity, it can cause some trouble for orders that need to be received on the paper receiving table when cut into individual sheets. After the paper is cut, the finished product often moves down tightly against the bottom roller, sometimes falling off, and sometimes just getting stuck between the bottom roller and the front end of the paper receiving table. When it falls, it only causes a small amount of waste, which does not affect the overall situation. If the paper gets stuck, it needs to be shut down for cleaning, resulting in greater waste.
Fault cause: static electricity
Install effective anti-static devices in front and behind the cutting unit. For example, electrostatic eliminators, specialized conductive copper wires, etc.
Fault cause: The workshop is too dry, and the paper loses too much water, especially in the dry desert areas of the Middle East.
Install a water spray device beside the machine to increase the paper humidity. Hang a wet towel on the roll out unit to increase humidity and reduce static electricity. The degree of humidification is based on not causing paper curling.
Fault cause: Poor stiffness of the thin paper itself
Install an “L” shaped spring steel plate or brush at the upper edge of the transverse cutting knife, with the aim of forcefully pressing down the product that is moving upwards or sticking to the knife edge, allowing it to enter the normal paper receiving stage.
Fault cause: Sometimes, when cutting thin paper with a cross cutting machine, it is easy to break the paper, which is more serious than when feeding paper jams. There are three main reasons for this: firstly, the tensile force of the paper is set too high, and secondly, there are defects such as cracks at the edges of the paper. Another issue is the quality of the paper itself, such as low fiber content (recycled paper) or poor longitudinal tension during pulp making. In the vast majority of cases, the first two reasons work together to cause paper breakage. Once a break occurs at the edge of the paper, it is easy to break the paper at the deflector, and then at the middle and rear of the machine, due to the increasing tension of the paper, it is easy to break the paper.
During the transportation and loading and unloading of paper rolls, it is necessary to avoid damage to the paper edges as much as possible. Once any damage is found on the paper edges, it should be dealt with in a timely manner before starting the machine for cross cutting. For example, if there are only one or two paper edge breaks, adhesive tape can be used to stick them properly. For a multi-layer break, an art knife can be used to make a longer transition fillet along the longitudinal direction to avoid fracture due to stress concentration. For those severely damaged outer layers of paper, it is best to remove them all.
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