Effect of Printing Speed ​​on Print Quality in Offset Printing (Chinese)

The premise of ensuring the accuracy of overprinting of printed products is to minimize the deformation of the paper during each transfer and imprinting process, especially the deformation of the front edge of the paper. Although there are compensators in Heidelberg multicolor offset presses, this compensation does not have any practical significance for the larger swing angles and the deformation of the dot ends of the paper tails. There are many reasons for the phenomenon of print rejection, and most failures are difficult for the compensator to compensate.

1. The “one line” problem of paper transfer to the first color impression cylinder

For example, in the phenomenon of one of the reasons for rejection, due to the difference in the state of transfer of each piece of paper, when the rules cannot be completely coincided, along with the beating of the cable, the handwriting of the previous colors (especially the first color) is blurred, Dots were distorted, and the color of prints was light and heavy.

To determine if the printer has a slanting angle, first check that the paper delivered to the first impression cylinder is flat. If the paper is wavy at the mouth, that is, the front edge of the paper is not in a "one line" state, the machine must have a problem of rejection. To ensure the "one line" state of the paper on the first-color impression cylinder, the following conditions must be met.

(1) "Line" status when paper is positioned at the front gauge

The paper on the front gauge is at the last link before all the dentition wipes. The ideal condition is that each sheet is the same and remains absolutely flat. If the front edge is not in a “line” state, after the paper passes through the transfer teeth to the impression cylinder row, the front edge of the paper is still not on a straight line. Under the effect of the printing pressure, the paper is deformed and converted into a print rejection angle. In order to maintain the “one line” state that the paper is intended to handle, the following conditions must be met.

1 The paperboard must have a strict flatness

The paperboard is not even, and the front edge of the paper cannot be "one line". When the equipment is overhauled, the flatness of the paperboard should be corrected to within 0.05mm.

2 All previous regulatory positioning planes must be on "one line"

This is especially important when printing thin paper. The deviation of the position of one of the front gauges will cause the paper to partially deviate from the straight line formed by the previously specified plane, thus destroying the “one line” state of the paper.

3 Paper can be correctly positioned at the front gauge

If the tongue pressure of the individual front gauge is low, the paper will not be able to smoothly enter the positioning plane of the front gauge, causing the straightness of the front edge of the paper to decrease. Therefore, the operator should adjust Feida's time for paper-cutting, the position and pressure of the paper-roller and brush wheel on the paper-feeder, and the tightness of the paper-feeding belt in accordance with the specifications, so as to ensure the accuracy of the former specification.

4 Paper is affixed to the paperboard smoothly

Different models are equipped with different devices to ensure the flatness of the paper in the front specified position. In the old Heidelberg 102 series offset press, a suction device is installed below the paper feeding plate, and a flat paper spring plate is installed above. In the new type of machine, an air blowing device is installed at the front paper feeding board, and the paper is attached to the paper feeding board by the negative pressure formed by the air blowing process. Therefore, the operator should carefully adjust the air suction or blowing device on the paper feeding board, the gap between the flat paper spring and the paper. On the paperboard, paper must not be subject to warping problems, otherwise there will be a more serious rejection of angle failure.

For thin paper, no matter what kind of equipment, it can not completely solve the problem of flatness of the paper. Therefore, paper should be carefully knocked before printing to ensure the stiffness of the paper. The author suggests that when designing and printing, a device can be installed at the front predetermined position so that the paper can bear the pulling force in the direction of the paper in the front gauge to level the paper.


(2) Paper Feeding Paper “Line” Status at Paper Feeding

When maintaining or manufacturing the equipment, ensure that the paper-feeding tooth is in a "one line" state when it is pulled on the paper-feeding board. For this reason, the following conditions must be satisfied.

1 The bite plane of the paper pad is standard plane

After long-term use, the transfer paper pad is deformed, and the spray layer at some occlusal planes falls off, making the occlusal plane of the paper transfer pad unstandard, and the front teeth of the delivery paper are not even after the paper is caught. Therefore, the paper must be repaired or replaced. Tooth pads.

2 The ideal gap between the paper handing pad and the paper feeding board is the thickness of the printed paper. In this way, when the paper handing paper is taken out, the deformation of the paper is minimal.

(3) "One line" status after paper feed

1 paper delivery time is accurate

The ideal paper-feeding position of the paper-feeding tooth is the vertical position of the paper-feeding pad and the paper-feeding plate, and the angle reading on the dial is 11.5 degrees. Due to the paper-feeding chip, the wear of the tooth pad and the adjustment reasons, the time for picking each tooth piece on the paper-feeding tooth row is not uniform. When the paper handing paper is taken at the front gauge, the paper handing mat is not absolutely stationary, but there is slight rotation, which is a problem that the rotary paper handing tooth cannot solve. Inconsistent pick-up time results in inconsistent paper conditions for each tooth chip during pick-up and deformation of the front edge of the paper. Some tooth chips only picked up after the paper teeth began to rotate, causing serious deformation of the front edge of the paper. Some tooth chips close the teeth too early, and then hit the paper at the moment when the dental pulp is rubbed. This causes the entire paper or the area of ​​the dental sheet to recede. After the other teeth are picked up, the front edge of the paper is deformed.

Due to the wear of the feed shaft, the shaft bearing, the copper socket and the open ball, the paper take time of the paper feed chip will change every time the paper is taken, making the paper feed time inaccurate. There is no guarantee of the rationality of each paper taking time and the consistency of the closing time of the dental piece, resulting in deformation of the paper.

2 Correctly adjust the paper transport position

When printing, the operator should be accustomed to adjust the position of the paper according to the position of the front rule, and should not center the paper without thinking. When the paper is transported, if the edge of the paper is close to the front rule of the edge on the side of the pull tab (the nearest front edge of the edge of the paper), when the pull pulls the paper, the front gauge will hinder the pulling action of the pull gauge and cause the edge of the paper. Deformation. In this state, the paper feed state of the paper feed is not ideal, and the front side of the paper is not in a "one line" state.

For Trick Dice we have 7/11 dice and loaded dice. Our 7/11 dice is 18MM, they look like regular dice, but they roll seven or eleven on every single throw. 7/11 Trick Dice come in pairs that feature one die that has six dots on all sides and a second die that has three sixes and three twos on the sides.

For loaded dice we put in metal piece, to make dice tend to stop at appointed side. Custom loaded dice is welcomed.

Bescon-Trick Dice 18MM

Trick Dice

Directly Magic Trick Dice,Trick Bomb Dice,Small Magic Trick Dice,Fashion Trick Dice

BESCON INDUSTRIAL CO., LIMITED , http://www.besconcn.com

Posted on