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Flat panel printing technology (Part 2)

the post handover paper feeding part is a key component that affects the registration of printing sheets. The adjustment technology requires high requirements, and some operators often fail to deeply understand the key. It is very necessary for operators to carefully grasp the key

in the paper feeding part of the rear handover, the paper teeth have the most parts and the most direct effect on the printing sheet. From its role, it can be divided into paper delivery, paper biting in the process of imprinting, paper feeding after printing, etc. A monochrome Offset Press can bite up to 13 rows, with more than 10 teeth in each row. Therefore, the operator should first make these more than 100 paper teeth coordinate with each other, coexist in a balanced manner, and play their respective roles independently, which requires the operator to master high skills, be patient and meticulous, and do this work tirelessly. Summing up the experience of some teachers in adjusting paper teeth for many years, it can be summarized as 2. The formula of 4 words can make the spring obtain different stiffness: "focus on the whole, take care of the majority, distribute evenly, bite moderately, advance and retreat, and test repeatedly". In the process of adjustment, the ultimate goal is to require the whole row of paper teeth to bite the paper evenly and uniformly. We must focus on this whole

the so-called taking care of the majority means that during the adjustment process, if it is found that most of the teeth are very tight, and some teeth are not tight, of course, the cold-rolled strip is widely used, and individual teeth can be tightened. However, if most of the teeth are not tight, but only a few or a few teeth are tight, these few teeth should be loosened and lightened. Because the whole row of teeth are installed on the same shaft, and there is the same line of the roller to bite the paper. Therefore, it is very important to adjust the intensity and looseness of some teeth or a few teeth, and the teeth that were not tight will become tight. This is where there is progress and retreat. It is common for some inexperienced operators to adjust their teeth only by tightening those that cannot bite tightly, and only advance but not retreat. Often, one tooth is adjusted too tightly, which will affect the adjacent teeth to become loose, and even the whole row of teeth can not bite the paper tightly. The more the adjustment is, the less ideal it is, the more disordered it is, and the greater the biting force it is, which should be avoided

for the parts of paper teeth, in order to accurately register the print, there are the following requirements:

1 The three bearings of the toothing shaft must be on the same axis line to make it rotate flexibly

2. The toothing shaft and the bearing are matched accurately without obvious wear. It should be lubricated frequently and repaired in time

3. The supporting force of the large spring of the teeth biting shaft is appropriate. When biting paper, all the supporting force acts on the teeth, that is, the positioning blocks do not contact each other

4. The compression of the small spring on the teeth should be uniform and appropriate. If the compression is too large, the bite will be less tensioned, and excessive relative friction will occur between the bite piece and the bite shaft, resulting in the early wear of the shaft or tooth piece

5. The bite shaft is not allowed to move axially

6. The tooth pad should always be straight and aligned with the roller surface. In case of obvious paper concave, it should be repaired or replaced in time. The surface of the tooth pad should have a large friction coefficient, and the surface of the hard tooth pad should preferably be "roughened" appropriately

7. Always maintain proper biting force and adjust the cam joint position

8. The connecting rod, swing rod, roller and other junction points shall not be loose

in the process of adjustment, the bite force of the middle bite should be first corrected as the benchmark, and then extended to the left and right sides to correct one by one. Before finishing the adjustment, it is necessary to repeatedly check whether the bite force reaches the ideal, and then tighten the fastening screws of each bite one by one at a time. After fastening, make a final inspection to check whether the biting force of each paper biting tooth changes

in order to accurately register, the parts and components of the paper feeding system must meet the following three requirements:

1 The paper biting teeth must be evenly distributed and able to bite the paper evenly, with the bite 5mm and consistent balance

2. Paper in the printing process, we must always firmly control the paper

3. In the process of paper handover, in a very short moment, it is necessary to hand over the machine and control the paper at the same time

the third requirement is very important, and every operator must understand this principle. We say that the key to "accurate registration" lies in the handover of the printing sheets, and the key to the correct handover of the printing sheets lies in the handover process. In a very short moment, the paper should be grasped and controlled by the two parts at the same time. In order to make the operator understand, let's make the problem more specific

three times of paper handover process must be achieved:

1 The front gauge leaves the working limit only after the paper is delivered and clenched firmly

2. The paper teeth of the embossing cylinder open only after they bite the paper

3. After the paper feeding row bites the paper tightly, the paper teeth of the imprint cylinder open

of course, the three situations in the detection of the spring fatigue products used in the car safety belt coil spring only occur in an extremely short moment, but the extremely short moment of "two parts jointly control the paper" is absolutely indispensable. Without this extremely short-term "joint control", the paper will lose control. Even if it is extremely short-term out of control, it will cause the consequences of "a millimetre of difference, a thousand miles of loss". Many overprint problems arise because operators lack a deep understanding of this

if the above three points are accurately achieved, the paper handover will not move and the accurate registration will be possible

the above four items are only the basis. There are still many links in the alignment of one color with another and multiple colors, but the reason is the same. Apply the above principles, from here to there, and I believe that good results will be achieved

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