Reasons and solutions for the bite of the edge of the offset bite

After a sheet-fed offset press runs for a period of time, the various parts have different degrees of wear, especially the open cams, bumps, tooth pads, and tooth bases. When the paper is printed, the transfer cannot be performed normally, and it is often easy to bite. The edge of the paper was bitten, causing overprinting inaccuracies. The bite of the paper edge was not allowed in the front and the quality of the printed product was affected.

1. During the process of the delivery of the offset printing press, the failure of the bite of the edge of the paper should be comprehensively analyzed. The difference should be treated differently. Carefully check the position of the delivery teeth and the teeth of the roller too close to each other, and make the paper in the printing paper transfer process. The bite of the mouth bite broken, the solution is to properly cross open.

2. Under normal circumstances, the embossing cylinder of the size printer and the transfer paper bite the paper edge to about 12mm, so that the distance between the cylinder and the delivery paper cannot be too large, so that the bite distance of the delivery teeth is too large. If the edge of the paper is broken, the position remains constant. Found that such failures are to find the cause in the paper-feeding teeth and drum teeth, will slow the offset press, carefully check the paper-feeding teeth and the transfer of paper teeth, the process is accurate in place, the teeth are too slow or the angle of the teeth Large, but easily lead to paper edge bite broken, check the paper feed teeth cam teeth wear, if the cam wear is serious, repair welding or replacement of new parts may be required. It is required that the paper feeding teeth and the large roller teeth control the paper at the same time when the paper feeding teeth hand the paper to the impression roller.

3. The bite of the mouth caused by improper adjustment of the teeth of the bite line in the offset part of the offset sheet is mainly due to the inconsistency of the level of the teeth of the teeth, or the unevenness of the teeth, so that the individual teeth may not be stretched enough, or Zhang closed. Therefore, papermaking paper bite the edge of the paper. Solution: Reposition the tooth pads of the delivery bite row to make it straight and uniform, and then carefully adjust its bite force. Adjusting the bite force of each bite can use a 80g/m2 kraft paper, extend into the teeth, pull it out by hand, and test the size of the bite force.

4. The adjustment of the front gauge position is not good, so that the roller bite bite the paper too much, so that the bite distance of the delivery teeth is too much, so the paper bite the edge of the paper during the handover process. Solution: Adjust the distance between the front regulation paper and control the 3-5mm bite distance.

5. The edge of the offset nip paper is bitten and the paper breaks irregularly, and the tear is wide for a while and becomes narrow again. This phenomenon is generally due to the inconsistent elasticity of the tape on the offset of the offset printer. In addition, when the paper is turned on, it can be seen whether the pressure roller of the feed line can rotate flexibly. Turn the offset press to slow, and see if the time for the paper to reach the front gauge is appropriate. Under normal circumstances, when the current gauge reaches the receiving position, the distance between the front margin of the paper margin and the 8-10mm distance is appropriate. If it is not appropriate, it needs to be performed. Adjustment.

6. The most important point is that the edge of the mouthpiece is bitten. The delivery position of the delivery teeth and the roller teeth is not on the public line, or the delivery time of the delivery teeth and roller teeth is too long. Solution: First, adjust the position of their transfer, use the hands to move the machine during the adjustment, check and give corrective action; second, shorten the delivery parallel time of the delivery teeth and roller teeth.

7. The edges of the paper are broken due to paper. In the papermaking process, the paper is formed of fibers that are intertwined with each other, resulting in uneven density. There are many trachomas and voids in the structure, and the paper surface is uneven. Therefore, a certain amount of fillers, rubber compounds, color materials, etc. must be added to improve the surface of the paper. Smoothness, reduce paper transparency, reduce paper absorbency, increase paper whiteness, weight, water resistance, toughness and so on. If the paper is too dry, poor fiber toughness, crisp, loose paper, poor flatness and other reasons, it will easily cause the paper to break in the process of paper feeding, short gauge, and embossing.

In summary, there are three types of failures that occur when the edge of the bite is bitten during the offset printing process:

1 The paper bite was broken continuously and the location of the damage was not changed. This is due to incorrect delivery of the transfer teeth and drum teeth or improper adjustment of the delivery teeth and drum teeth.
2 Not every piece of paper is bitten by the edge of the paper, but is partially separated from the printed sheet by a number of pieces that have not been bitten, and is of a regular nature. This is mainly due to the reason that the paper collection system is receiving the paper. Pay attention to adjust the biting force of the take-up tooth row. 3 When the mouth of the paper bite, it will break when it is big or small, it will be good, it will be bad, and it will not be regular. This phenomenon is generally due to the improper adjustment of the offset press feeder, or the improper adjustment of the height of the front gauge. These two parts must be adjusted separately.

In the daily work, offset printing, rules, stamping, and paper collection must be properly adjusted. The edges of the seams are punctured and related to the components. The worn open teeth require welding and replacement. Accessories, do not blindly tamper with the emergence of problems, to avoid disturbances, bring a series of process failures, according to the data required by the maneuvering instructions of the offset press manual to make reasonable adjustments, delivery paper teeth, drum teeth, delivery teeth The level of the three big bite paper conveying parts of the pad must be adjusted to be consistent. The closing time and the closing size of the three parts of the paper handing tooth, the roller tooth and the receiving tooth pad must be the same, and the handing over is accurate and in place. Some problems that should be paid attention to during the adjustment process should be taken care of.