Specification lithographic offset printing process

Adhere to the correct process operations and strengthen quality management measures are important factors in ensuring print quality. The standardized operation method in the process of lithographic offset printing is: First, the calibration is “Sanping”, and the so-called “Sanping” refers to: blanket flat, drum flat, ink roller, and water roller flat; followed by adjusting “2 small”, so-called “ “Small” refers to: Small amount of water and low pressure; Third, it means “three hardworking”. The so-called “three-diligence” refers to diligently checking printed sheets, mixing ink fountains, and diligently checking layout moisture.

One, calibration "Sanping"

Flat blanket

Blanket flat refers to the blanket roller surface to be flat. Lithographic offset printing uses blanket printing, mainly because the blanket not only has good elasticity, but also has good ink transfer performance. Therefore, the quality of the blanket and its proper use are directly related to the printing quality of the offset printing product. The surface of the blanket is the surface characteristic of the blanket to be used correctly. Specifically, the flatness of the blanket is the overall quality of the blanket. Process performance. The smoothness of the surface of the blanket is a necessary condition for realizing complete contact of the printing surface and ensuring the uniform transfer of the dot ink.

Nowadays, printing materials have been rapidly developed. The errors in the flatness of the blankets have been greatly reduced due to errors in manufacturing and processing. The flatness of the blankets is mainly caused by underlays under the blankets. The backing must be flat. When installing the blanket, it is important to prevent foreign matter from being caught in the pad and to prevent it from wrinkling. Use the "paint map" method to fill the depressions of the blanket. The specific method is as follows: The ink on the ink roller is evened out, and the yellow ink is generally used, and the ink roller is leaned on the plate, so that the printing plate is coated with a uniform ink and then pressed. If the ink on the blanket is uniform, the surface of the blanket is flat; if the uneven surface of the blanket resembles the shape of the map, it means that the surface of the blanket is uneven; it can be described in pencil on the liner or blanket fabric, and then With different thickness of paper directly attached to the fabric backing to make it flat.

2. Roller flat

Roller flat means that the axes between the drums should be parallel to each other and the pressure between the drums must be balanced. Roller pressure is the primary condition for finishing offset printing. If the axes between the drums are not parallel, the roller contact pressure will be directly inconsistent, the ink transfer effect will be unsatisfactory, and the ink color of the printed products will be uneven. Therefore, adjusting the center distance of the rollers to make the axes of two adjacent rollers parallel is a crucial task. It is necessary to do a good job and it is worth spending more time in this respect.

Detecting whether the rollers' axes are parallel to each other is generally to measure whether the roller gap is equal. The most commonly used method for detecting the gap between the rollers is to clean the rollers and compress the rollers to roll the soft lead wire with a diameter of about 0.5 mm between the rollers. And through the pressure adjustment mechanism to adjust, the final thickness of the measured soft wire is the clearance of the pillow; can also measure the use of micrometric feeler (or thick gauge), with a flat iron ruler, and the roller axis balance Raise the thickness at the two ends of the pillow, and then gradually increase the thickness with a micrometric feeler. Insert the test piece between the drum shell surface and the iron ruler until the gap between the feeler thickness and the iron rule is filled and equal. Calculate the total thickness of the feeler gauge. , is the gap between the pillows. In order to be as accurate as possible, several measurements can be made and several measurements taken. Measuring the gap between the two ends of the roller must be consistent, so as to ensure that the axes between the rollers are parallel. When measuring, it is generally based on the impression cylinder. Measured by only using the same roller gap, often can not guarantee the axis parallel, but also must be in the end of each roller shell, the middle three points to determine the equidistant, in order to achieve axis parallel.

3 ink roller, water roller flat

1 ink roller flat. The ink roller flat mainly means that the roller cylinder cylindricity is uniform, the axis of the plate cylinder, the axis of the ink roller (also called the reticle roller) and the axis of the ink roller are parallel lines. The function of the inking mechanism is to supply the ink uniformly, stably, and continuously to the surface of the printing plate. Only the ink roller level can ensure the contact relationship between the printing plate and the ink roller, the ink roller and the ink roller. Therefore, the ink roller level is a necessary condition for the ink conveying mechanism to function normally.

In production practice, we often use the uniformity of the pressure of the printing plate and the ink roller, the ink roller and the ink roller to express the ink roller level. The adjustment method is as follows:

Adjustment principle: ● The pressure of the four inking rollers should be 1>2>3>4, that is, the pressure of the first inking roller is the largest and the fourth is the smallest. Ink roller usually has four, in front of the first contact with the printing plate, close to the water transfer mechanism of the two ink roller called the ink roller, the role is mainly for the ink, the pressure is slightly heavier, in order to supply sufficient ink for the printing plate; after contact with India The two ink rollers of the printing plate are called collector rollers, and they mainly function to collect ink. The pressure is slightly lighter, which makes the collection of ink clean, which is beneficial to the smoothness and clearness of the dots. ● The pressure of the inker roller and the tandem roller is slightly lighter or equivalent to the pressure of the ink roller and the plate. This is to ensure that the normal ink transfer and the linear speed of the ink roller are equal to the linear speed of the printing plate.

Adjustment order: first inside and outside. The first set of ink rollers and the latter set of collector rollers. First, the ink roller and the ink roller, the ink roller and the printing plate.

Adjustment process: ● After installing the second ink roller (one inside) of the ink roller group, jog the machine to the ink roller at the blank part of the printing plate. ● Measure the pressure of the ink roller and the ink roller with a micrometer (thickness of 0.15-0.25mm) (lift the undercarriage), select both ends and the middle as the test point, and use three fingers to hold the thousands when measuring. The plug end of the plug is slightly pulled out, and it is slightly slower when pulled out. It feels resistance when it is pulled out. It can be adjusted to feel both frictional resistance and it can pull the steel sheet smoothly. This feels more appropriate. Check the pressure with the embossing method, make the ink roller to ink, rotate at a low speed or jog the machine, stop it for a few seconds, then reverse a little, and the contact stripe can be seen on the surface of the screed roller. The generally obtained contact stripe is uniform and has a width of about 6 to 8 mm. • Measure the ink roller and plate pressure (falling the ink undercarriage), and use the feeler to measure the adjustment as described above. Check the pressure with the embossing method, make the ink roller evenly inked, make it coated with a certain ink layer thickness, then "jog" the machine, rotate the plate graphics part to the position corresponding to the ink roller, The ink roller handles can be repeated several times to leave ink streaks on the plate. The generally obtained contact stripe is uniform and has a width of about 8 to 10 mm. ● Other ink roller adjustment methods and so on. It can also be measured by a paper pull test.

2 water roller flat. Water roller flat mainly refers to the axis of the plate cylinder, the axis of the water roller, and the axis of the water roller. The role of the water transfer mechanism is to provide a uniform, stable and continuous water supply to the surface of the printing plate. Similar to the ink roller, water roller level is a necessary condition for the water supply mechanism to function normally. The level of water roll can also be expressed by the pressure uniformity of the printing plate and the water roller, the water roller and the string water roller. The adjustment of the water roller and the adjustment of the ink roller are basically the same, but it should be noted that the mutual influence between the upper and lower water rollers. To control the pressure on the adjusting roller and the string roller, the pressure should not be too large. The excessive pressure of the water will be squeezed on the upper roller, which can neither supply water to the plate nor transfer the water to the lower roller.