Printing faults and troubleshooting of the hottest

2022-08-23
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Troubleshooting of offset printing (Part 2)

the adjustment method is: without instruments and measuring tools, subtract 0.15mm (i.e. the thickness of two 80g/m2 papers) according to the standard pad parameters specified by each machine, install the rubber drum, cut two 40mm wide paper strips with the same paper, place them at both ends of the rubber drum about 10 ~ 15cm away from the end, and then press them on the bench. Pull the note with a little force, but you can't break it. After the tension of the paper strips at both ends reaches the same, remove the rubber and add 0.15mm thick paper. The pressure of the rubber roller and the embossing roller can be solved by pulling the paper strip as described above

the conclusion is that the pressure of the impression cylinder and the rubber cylinder is greater than that of the plate cylinder and the rubber cylinder (i.e. a piece of printing paper). The purpose is to transfer the ink on the leather to the product more effectively

III. printing faults caused by non parallel ink rollers

analysis: non parallel ink rollers, too heavy or too light landing can cause printing faults, but the pressure of the landing roller on the printing plate causes more faults

the ink rollers are not parallel to each other, and the contact surface must be inconsistent, so the ink transfer is abnormal and uneven

the four roller plates against the plate should not be too heavy or too light. The printing plate is too light. The printing plate is not well placed, the plate base is not strong, and the water is a little larger, and the plate will be painted quickly. If the ink floats on the plate with increased ink delivery, the plate will be pasted with reduced water delivery. Generally, there will be large amount of water and small amount of ink, which will eventually lead to ink imbalance

the plate on the plate roller is too heavy, which affects the service life of the printing plate and is easy to lift the ink bar. The regenerated version will also be crushed and broken, and there will be ink accumulation on the edge of the version. The most serious problem is that the plate has a bar. The ink bar appears when the bucket solution is weak in acidity, and the white bar appears when the bucket solution is strong in acidity

Troubleshooting: the pressure between ink rollers must be balanced, and the contact surface should be about 2 ~ 3mm. If the ink roller is olive shaped, it is best not to use it, because it cannot be balanced. The width of the plate setting roller bar: the new rubber roller should be 5 ~ 6mm, and the old rubber stick should be 4 ~ 5mm. Because most of the old cots are aging, the elasticity is weak, and the pressure should not be large. Avoid plate bumping. In addition, the inking roller on the landing plate must be slightly lighter than the inking roller on the landing plate, so that the amount of ink on the plate base is substantial

IV. printing failure caused by non parallel water rollers

achieving water ink balance in printing is the key to improving product quality. If the water rollers are not parallel or one of them is not adjusted reasonably, it will affect the ink balance

the weight of the plate rolled by the plate water will reverse the ink, reducing the amount of ink on the printing plate. The plate rolled by the plate water is too light, there is insufficient water on the printing plate, the water is small, the ink is large, and the blank is easy to get dirty. The water roller of the plate is too tight by the copper roller of water string. There is water on the water roller, but there is no water or insufficient water on the printing plate, and the printing plate is dirty

the water roller by the plate is too light, and the water cannot be transported to the printing plate, which is dry and dirty. If the amount of ink is reduced, the ink color of the product cannot reach saturation

the tightness of the small water roller against the copper rollers on both sides should also be reasonable, which directly affects the supply of water to the large water so that the tensile testing machine can continue to supply water to the tensile roller of the standard tensile sample

Troubleshooting: when filling the water rubber sleeve, try to tighten and flatten it. After wrapping, it is best to measure the circumference with a piece of paper in order to achieve symmetry and consistency

the method to test the tightness of the water roller on the plate is: put the trailing tip of the printing plate against the water roller, and repeatedly insert 0.2mm thick steel sheets at different parts of the water roller against the plate. The steel sheet should be inserted with a certain force, but not too tight. The water can roll the plate about 6 ~ 8mm. The water roller of the plate should be slightly looser than the water roller of the plate, so that the ink scale on the water roller of the plate can be reduced or avoided, and it can be transferred back to the water copper roller and the small water roller

the tightness of the small water roller depends on the copper roller of the water bucket, and 80g/m2 kraft paper strip can be used for tension test. When the small water roller leans against the copper roller of the water bucket, lift and pull the kraft paper strip upward, which is both powerful and continuous. It is better to stop the machine and test with 0.2mm thick steel sheet, and the tightness of the small water roller against the copper rollers on both sides is basically the same

v. printing failure caused by unstable pH value of bucket solution

the pH value of bucket solution is too low to resist the invasion of ink on the blank of the page. The blank is easy to get muddy and dirty, and it is easy to paste the page. Increase the water delivery, the water film on the plate is too large and the ink volume is weakened, and the ink color of the product is not full and lusterless. There are small blister eyes in the solid version, which makes you feel uncomfortable

the pH value of the bucket solution is too high. Although the layout is fresh, it is easy to spend the layout. If the water transmission is reduced, the layout will be dry and dirty. Finally, it leads to both flower and dirty plates, shortening the service life of printing plates

the water bucket solution is too much or too little, causing the water film on the layout to be too big or too small, and the ink cannot be balanced. Ps2101 offset printing...

elimination method: conditional units can use instruments to measure pH, which is about controlled within the range of 3.6 ~ 4.5 of "cheetah" and "pangolin" announced by ninjatek, a 3D printing material subsidiary of finner group in the UK. If there is no instrument detection, according to the author's experience, the water bucket solution can be prepared according to the following proportion (wetting powder) 1:200 (water). But this is not an absolute standard proportion. The specific situation should be treated in a specific way to achieve reasonable preparation. To achieve this, we must look at three aspects: first, the size of the water film on the layout, second, whether the ink color of the product is full and the layout is clean, and third, whether the paper of the product is flat and does not roll corners. Generally, when the new version is put on the machine, the sand eye on the version is not damaged, and the water film cannot be seen. The layout is grayish brown without brightness. Touching the blank with your hand has a moist feeling, and the layout is clean without dirt. The pH value of the bucket solution is a reasonable value. After printing for 20000, the layout gradually appears bright, with water film, but it does not get dirty, the ink color is full, uniform and normal, the paper does not roll corners, and the pH value of the water bucket solution is a reasonable value. On the contrary, the water film on the layout is large, and the pasted version reappears after shutdown for processing. This is because the pH value is too small, so the solution dose should be increased. If there is no water film on the layout, but the ink color of the product gradually decreases from the original saturated state or the stencil, this proves that the pH value of the bucket solution is high, and it must be diluted with clean water. In addition, the water bucket solution should be kept in a certain amount, and the water supply should be uniform, so that the ink can be kept in balance

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