Quality is the lifeblood of enterprise's survival and development. In the actual operation process, a little carelessness will cause the printed matter to be dirty, which will directly affect the printing quality. The following I will sum up in the long-term practice in the face of these failures can be timely and accurate troubleshooting.
1. Water spots. According to the principle of oil-water incompatibility, if the paper with water droplets, printed matter will leave a water spot. Cause analysis: (1) if the air pump is in the high temperature and humidity environment, the offset press is placed in the air conditioning workshop, and the moisture in the humid air is blown to the cool environment by the air pump, and the salty water will be condensed and blown to the paper by the presser foot and the paper separation nozzle. (2) Many offset press water buckets are made of iron sheet or copper plated iron sheet. As the acidic wetting solution is corrosive, over time, the water bucket will be gradually corroded to form sand holes. Some sand holes are very small, and only two or three drops of water can be dropped per minute. In this way, there will be water spots on the printing products from time to time. Therefore, it is necessary for the operator to carefully inspect the water bucket in the light, and solder the sand holes with tin. (3) Some offset press maintenance is not perfect, the operator never cleans the bucket. In addition, when cleaning the ink roller, the ink on the ink roller splashes around with the cleaning agent, and the water roller fluff forms scale together with the water roller fluff. With the rotation of the bucket roller, it accumulates between the bucket roller and the bucket wall, forming hard slag over time. When the bucket roller rotates, the hard slag will take the water on the bucket roll along the bucket wall from time to time, forming water spots on the print. (4) When the printing plate needs to be filled with water urgently because of the small paste plate, the water bucket roller will transfer a large amount of water to the water transfer roller. During the transfer and extrusion process of the water roll, the excess water will drip down. There is a water baffle under the water bucket of J2108, which has a good effect, but it is necessary to avoid dropping water due to too much water. However, J4104 and other models have no water baffle, so it is necessary to stop the emergency water supply. 2. Oil stain. As the viscosity of the oil is much lower than that of the ink, the oil droplets will expand on the surface of the blanket after being pressed, and make the ink produce a reverse set impression, and form a round oil spot on the printing crystal. The causes are as follows: (1) lubrication of paper feeding head is important and necessary. When you add oil, you should wipe less frequently. After refueling, start the machine and the paper feeder to let the oil drip down during the movement, and then wipe it again to ensure that there will be no excess oil dripping on the paper during normal printing. (2) Focus on the inspection of the air pump. If the air pump injects oil, the presser foot and the paper separation nozzle will blow out a lot of oil mist like oil droplets splashing on the paper trailing tip. Touch the oil filling cap on the oil chamber of the air pump with your hand (there is a small hole on it) to check whether there is gas ejected. If not, it means that the oil return effect of the air pump is not good. (3) The transmission rod and umbrella gear at the lower part of the gauge also need to be lubricated. Of course, only a little less or a little butter can be applied on it. If you add too much oil, the drawing gauge will stick to the paper during the paper drawing process. (4) If the lubrication effect is not good, it is easy to cause wear and tear, resulting in bad paper holding and inaccurate overprint. Therefore, when adding lubricating oil, be very careful, while adding oil, wipe, transport, turn for a period of time, and then wipe with cloth. But many operators often do not add oil because they are afraid of polluting the paper, resulting in the wear of spring rod and pin. (5) In the process of oiling, the paper transfer roller and the paper receiving guide rod are easy to stick with oil, so pay special attention to oil filling, and regularly check and clean if necessary.
3. Eichhorned spot, color spot or white spot. If there are spot spots on the plate, it will leave eye like spots on the crystal. If there are spot spots on the blanket, there will be spot like spots or white spots on the printing crystal. Cause analysis: (1) when the paper with poor surface strength is in contact with water and ink, it is easy to produce De dusting and scuffing, and adhere to the blanket or plate. (2) When taking the ink from the ink tank, the dry ink skin and ink residue should be removed, because the ink skin. Once the ink residue falls into the ink hopper, the ink will be transferred to the plate. (3) There are a lot of fluff on the water roller velvet. When printing the field plate, it is easy to leave burr and silk marks on the printed matter. Now there is a kind of nylon water glue velvet which is not easy to fall off. If you wrap it on the water roller, the effect will be very good. Sometimes, a water roller velvet several colors are used, it has been covered with ink residue, in the water transfer process, the ink residue will be transferred to the plate. (4) The cleaning and maintenance of COTS is very important, but some operators do not pay attention to this work and do not take them off one by one for cleaning. As a result, cots are subject to high temperature friction and ink. The corrosion of solvent causes cracking, especially at both ends of cots. During printing, the ink residue from the cracked cots sticks to the plate and is difficult to clean. (5) In order to prevent sticking and dirty and the printed matter for dusting, considering that some papers have more paper powder, when printing, the paper is sprayed with powder. The paper powder will adhere to the blanket with the paper imprinting, and then transfer to the plate. So should try to spray in the last color, if you have to spray powder also pay attention to the size of the powder, in the premise of not sticky dirty, the smaller the better, if necessary, can be air printed.
4. Dough. Spray powder splashed on the printed matter, due to the ink is not completely dry and make the printed matter appear a ball of powder. Cause analysis: (1) if the machine that needs to spray powder is not cleaned and maintained for a long time, the paper suction support, chain and pressing fan will be full of powder. When printing, due to the machine shaking or press fan rotation, the powder will fall on the newly printed product. (2) When spraying powder, if the heating switch is not turned on, the dry powder will condense into a lump in the humid environment. In some machines, the powder injection valve is installed in the hood (such as J4104 machine). When the machine hood is filled with oil automatically, the oil will drip on the powder spraying valve and form oil sludge with the powder in the valve. These pieces of powder and sludge are blown down by the air pipe, leaving a powder ball on the printed matter, so the powder spraying channel must be kept in a clean and dry environment.

5. Due to improper operation and other reasons caused by printing dirty. Cause analysis: (1) in order to improve the quality of printed matter, the paper must be flat, straight and easy to separate. So the operator needs to knock the paper. After printing some large area full-scale dark ground (such as bright red, purple), the paper is easy to curl downward, and these curly paper can not be transported normally. Therefore, we should be careful when handling these paper. If you beat too hard, the paper will inevitably produce creases, where there will be a crease white stripes. The correct way is to press up gently to make the paper's mouth and trailing tip flat. (2) Operators often need to take a stack of just printed products to the sample table to check the color registration. For some full version, large area prints to take less, otherwise it is easy to cause printing sticky dirty. Because of the large amount of ink on these prints, it will curl downward on the receiving table, so it is not easy to sample from the machine. In addition, the machine speed is fast, so pay attention not to scratch the printed matter. (3) After the product is printed, wait a little while to wake up or discharge the material to prevent the printing material from sticking when carrying the paper by hand.

6. Rub dirty. In the process of paper feeding, embossing and receiving, there will be scratches and scratches. Throw injury. Cause analysis: (1) the paper receiving wheel on the paper receiving roller presses the paper after blowing air from the paper delivery suction nozzle. If the ink is not 1000, two color spots will be left on the paper. For example, the stroke of the paper receiving wheel of J2108 machine is large, and the control cam is steep. As the paper receiving wheel is pressed down rapidly and heavily, there will be two spots on the paper. (2) When the paper passes through the paper feeding table, the paper receiving wheel, pressing wheel, brush wheel and paper weight ball will drag two or three ink marks out of the ink, especially when the paper delivery teeth speed up the paper delivery, the brush wheel and paper weight ball are easy to drag out traces. (3) There is a twist roller in the drawing gauge of J2108 and J4104 machines. When printing the front and back sides, especially the dark ink on the back, a few "teeth marks" will be found. Therefore, when opening the material, try to leave a little white edge to pull the gauge paper, and also pay attention to the direction of the mouth when printing, and put the light color (such as light yellow, light blue, etc.) ink on the drawing gauge. Therefore, it is necessary to fully consider the defects of domestic tension gauge. (4) When delivering paper, the paper is easy to be scratched when the front gauge is tilted upward, such as J2108 and J4104 machines, because of the straightness of the paper with a fixed weight of more than 350g / m2. In the paper delivery drum, due to the small swing angle of the lower front gauge, it is easy to scratch on the back of the printed matter, resulting in the negative side scratch dirty, such as pz2660 machine. (5) In the process of paper transfer, the printing surface of the multi-color machine is wrapped on the roller. Due to the insufficient cleaning and maintenance of the machine, the residual ink on the roller will leave silk marks on the printed matter. Therefore, it is better to place the large-area imprinted layout in the last color printing to avoid getting dirty on the paper transfer roller. (6) After being imprinted by the imprinting drum, the printed matter is held by the paper receiving teeth and transported to the paper receiving station by the paper turning wheel. Since there is no anti rubbing cloth on the domestic tipping wheel, traces will be drawn on the printed matter, which are mainly at the paper trailing tip. Therefore, it is necessary to adjust the tipping wheel reasonably according to the specific situation. If a trademark is printed, two spaces should be left at the joint of the trademark; if the instruction manual is printed, the paper turning wheel should be adjusted at the spine of the book; if a painting is printed, the paper turning wheel should not be placed at the same color block, but placed in a bright color place, even if there is a scratch, it is not obvious. (7) The roller diameter of j2104 and pz2660 machines is small. When printing papers with a fixed weight of more than 200g / m2 (wh47-np prints more than 105g / m2), because of the stiffness of the paper, it will not be wrapped on the surface of the drum. In the process of movement, it will be affected by the centrifugal force in n direction, wrapped on the bar and embossing shaft. According to the specific situation, the paper guide rod should be reasonably distributed and installed , or on the bar or embossing shaft pad Shanghai cotton and other packages, holding the paper will not be thrown out and scratch. (8) When printing large area dark and spot color ink, if the slow paper suction is too large. Open teeth too early, the paper will fall too early, a print friction, resulting in print scratches.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.
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