How to adjust the offset machine water delivery mechanism
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The quality of offset printing products is inseparable from the consistency of ink and water. In the printing process, the water supply is too large or too small is often easy to occur, because the size of the printing plate is from the dirty surface of the printing plate. However, the so-called dirty is not only caused by the small amount of water, the operator often mistakes the water supply amount to cause the ink and water to lose balance and form a vicious circle. What kind of printing consequences does the moisture release have?
1. Dilute the ink color to make the ink color lighter and dull, affecting the color of the printed product. If the method of increasing the amount of ink is used to save the ink color, the ink will be large and the water will be large, and the image will be thick, smeared, and unclear.
2. Deinking the ink roller. In severe cases, there will be accumulated moisture on the entire ink roller, so that the printing plate can not get the normal supply of ink, causing the printing plate to "fake".
3. Affect the drying of the blot. If excessive moisture is mixed into the ink, the drying of the ink is inhibited. In addition, the paper absorbs more water, and the drying speed of the product is slower.
4. The paper fiber absorbs too much water, which will cause deformation and cause overprinting. It will also make the paper texture loose, easy to shed, and accumulate on the blanket or printing plate, which seriously affects the quality of the printed product.
5. The ink is emulsified to make the ink lose its viscosity. After the ink is emulsified, it can not protect the printing plate, which is easy to cause "flower plate" and reduce the printing durability of the printing plate.
Through the above analysis, it shows that the mastery of ink and water balance is a key link in offset printing. In addition to experience, the operator is more important to master the correct use and adjustment of the offset machine water delivery mechanism.
In order to adapt the water supply capacity of the water delivery mechanism to the requirements of printing production, the water delivery mechanism is provided with means for controlling moisture and adjusting the amount of water. This can be divided into three parts according to the nature of their work: one is the water supply device; the other is the water distribution device; the third is the water supply device.
The water supply device is mainly composed of a water tank, a water bucket roller and a water transfer roller. The water tank is used to store water, and there is a water bucket roller (also called water outlet roller) on the upper part. The lower half of the bucket roller is immersed in the water bucket solution, and they are not in contact with each other and do not support each other. In addition to the automatic watering device to add water (many manufacturers do not have to use), you can also add water manually. Manual watering requires the operator to constantly add the previously prepared solution to the sink. Since the water supply volume in the water fountain roller is related to the height of the water bucket solution, the water supply solution in the water tank must be kept at a certain water level in order to make the water supply uniform. The operator should not be impatient when adding the water hopper solution. Slowly add the water hopper solution to the water tank. The solution in the water tank cannot be swayed. If it sways, the first is that the local moisture suddenly becomes larger during normal printing, which affects the quality of the product. Second, the water bucket solution will drip into the front part of the sink, causing the paper feeding and clutch pressure to be abnormal (this is because the solution Drip into the front part of the electric tooth to form conductive); Third, drip onto the printed product, causing water droplets on the paper, and it is easy to appear double when printing the next color.
The water transfer roller, also known as the draft roller, is a rubber roller that is placed between the water bucket roller and the water roller and transmits water to and from the swing. The surface is covered with water roller. The adjustment requirement of the water transfer roller is that the water is kept parallel with the water fountain roller and has appropriate pressure, which is adjusted by the tension springs on both sides. When adjusting, the tension of the tension spring must be consistent to ensure that the water transfer roller works in parallel with the water fountain roller during drafting. When feeding water, rely on the cam. When adjusting, the water transfer roller must be placed on the water roller and have proper pressure. There is an adjusting screw and a positioning anchor on each side of the lower side of the water roller. The adjustment also requires that the water transfer roller and the water roller be parallel. The water transfer roller also has a clutch device for drafting water. When the printing is combined, the normal draught water supply is oscillated back and forth through a 220V 0.7kg iron. Stop swinging back and forth when the pressure is off, that is, no longer on the water discharge roller. The button for water supply opening and water supply stop on the console is to control the suction, and they work according to the production situation. In some cases, we sometimes find that the pressure on the plate is increased after the pressure is released. why? This is because after the iron stops working, the pulling force of the top claw pulling spring next to the suction iron is not enough, causing the roller to pass the water from the pressing and conveying roller. The machine stops eating after one or two cycles, and the copper head is sucked by the top claw. The strength of the tension spring is not enough, causing the iron to retract slowly one or two shots, which is the cause of the water surface of the plate. It is very easy to solve this problem, just change a new tension spring or shorten the old tension spring by one or two.
The water leveling device is mainly a water roller. It is usually made of a corrosion-resistant metal material. In order to achieve uniformity of moisture on the water roller, the water roller not only has a rotational motion but also an axial movement. The surface speed of the water roller is equal to the surface speed of the printing plate to keep the plate water roller moving at an equal speed. The axial movement of the water roller is adjusted by the eccentric link, which is relatively simple, and generally does not need to be adjusted during the printing process.
The water supply device can be called a plate water roller or a plate water roller. Generally, they are two, and the surface of the water roll is similar to the water transfer roller. The effect of the plate water roller is to uniformly transfer the aqueous solution from the water transfer roller and the water roller to the printing plate. Its surface speed must be equal to the speed of the surface of the printing plate. It does not allow axial turbulence and radial runout, otherwise it will easily cause damage to the printing plate. The requirements for adjusting the water roller are relatively high and must be adjusted according to the steps. Adjust the eccentricity first so that the pressure between the plate water roller and the water roller is just right. Then adjust the cone so that the pressure between the platen roller and the plate is appropriate. The above method should be described that when the eccentricity is adjusted, not only the pressure between the plate water roller and the water roller but also the pressure between the plate water roller and the printing plate is affected.
When the cone is adjusted, only the pressure between the plate water roller and the printing plate is changed, and the pressure between the plate water roller and the water roller is unchanged. When adjusting the water roller, the water roller should be adjusted first, and then the water roller should be adjusted. The pressure of the upper water roller is lower than the pressure of the lower water roller, because it is possible to use the upper water roller to collect the excess water. This is an experience gained from practice. When adjusting the pressure of the plate water roller, pay special attention to the adjustment eccentric position of the two ends. If the difference is too large, the position of the plate water roller and the printing plate and the water roller will not be parallel, which is easy to cause the problem of looseness and tightness between the two ends. . Therefore, when adjusting the water roller, the method of correcting the center distance must be used to measure the tightness between the two ends and the middle. Therefore, when adjusting the water roller, the method of correcting the center distance must be used to measure the two ends and the middle three points to prevent the contact pressure between the water roller and the printing plate from being too heavy. Otherwise, the state can cause the friction of the printing plate to increase. Greatly worn, the printing plate "flower plate", the printing resistance is reduced, and it will cause the water roller and the printing plate to make a jump when it comes into contact with the printing plate, so that the jumped part is dirty, and the re-falling part has a "water bar". "(ie the white bar). However, the contact pressure between the plate water roller and the printing plate should not be too light, which may cause the smear to be caused by insufficient water supply to the plate. If the water supply is improperly increased, it will cause excessive moisture in the layout. So how do you determine if the contact pressure is at the best adjustment position? According to experience, it is to identify whether there is a beating phenomenon during the operation by pressing the plate water roller and the printing plate to start the machine and then touching the bracket of the plate water roller by hand. Since the plate cylinder has a printing surface that is separated by a gap, the pressure of the contact pressure of the plate roller is easily felt. Under normal circumstances, there is a slight beating feeling. Under normal circumstances, the feeling of slight beating is the most appropriate. If the beating is very serious, indicating that the pressure is too high, then the adjustment should be made again.
To adjust the water delivery mechanism, you need to do the following work: First, the liner of the printing plate should be compounded; second, the aqueous solution in the water tank should be free of impurities; third, the water roller should be changed frequently; fourth, the water roller and the water The rollers should be wiped clean and must be kept clean.