How to adjust the offset press when printing thick

How to adjust the offset press when printing thick paper

the thick paper used for offset printing is generally white cardboard, gold and silver cardboard, kraft cardboard, etc., which can print various packaging cartons. Generally, the thickness of the commonly used paper of the offline machine is 0.04 ~ 0.3mm, and the offset press should be properly adjusted when printing thick paper. The following takes the domestic J2108 offset printing machine as an example. The maximum thickness of paper that can be printed by this machine is 0.9mm

first, adjust the paper feeding part

1. When printing thick paper, the air volume of the suction nozzle and blowing nozzle of the paper feeding part should be increased correspondingly

2. The paper separating blowing nozzle and the paper delivery suction nozzle should be replaced with rubber rings with larger diameter and thickness, and the tension gauge compression spring can be replaced with steel wires with a diameter of 1.5mm. Remove the connecting pin between the feed roller cam and its shaft, or remove the roller on the swing rod, so that the feed roller does not swing

3. When printing thick paper, increase the distance between the safety bar and the paperboard, and between the paper tongue of the side gauge and the front gauge and the paperboard, and make the distance equal to twice the thickness of the paper. At the same time, pay attention to adjusting the gap of the double tension controller

4. Adjust the distance between the paper feeding tooth pad and the surface of the embossing cylinder, as well as the distance between the paper feeding tooth pad and the paper feeding board. The distance between the safety bar and the paper feeding board should be increased correspondingly, and make this value about 0.3mm larger than the thickness of the printing sheet

II. Double sheet and multi sheet control adjustment

when printing thick paper, because the paper is thick, multiple thick papers are stuffed between the embossing cylinder and the rubber cylinder, which is very easy to cause "stuffy" failure, which is very dangerous. Therefore, before printing, we must carefully adjust the electrical devices such as double sheet control, skew control, and pre punching control

the distance between the double sheet control wheel and the paper feed roller should not be less than 2 sheets of paper thickness, but not more than 3 sheets of paper thickness, otherwise the curved paper will stop when passing through the double sheet controller, or the double sheet has passed through the controller, and the two contacts of the controller power supply have not been contacted, so the purpose of controlling the double sheet cannot be achieved

it is also necessary to timely clean the surface of the double sheet control wheel and the paper feed roller, as well as the dust on the surface of the two contacts at the power control place. There are a large number of new "smart" electrical appliances, dirt or insulation, so as to prevent the double sheet control system from malfunctioning and avoid the "stuffy" fault

third, adjust the printing pressure

theoretically, the lining thickness of the embossing cylinder is zero, but in the actual work process, the embossing cylinder is lined with printing paper, so the thickness of the paper is also the thickness of the lining. Because the impression cylinder has a certain thickness of lining, the pressure between the impression cylinder and the rubber cylinder is required to be slightly greater than the pressure between the plate cylinder and the rubber cylinder. And most of them are about 0.1mm thick. 3. According to the cycle of stress (strain) when the sample breaks, it can be divided into low cycle fatigue test and high cycle fatigue test. The pressure that the paper withstands is its ideal pressure

if the thickness of the whiteboard reaches more than 0.6mm, the pressure will increase with the increase of the thickness of the whiteboard. As we all know, the gradual increase of pressure, in a sense, will mean that the printing fatigue testing machine is not accurate in measuring yield strength. What are the reasons for the poor quality of products, the decline of printing plate endurance, the point increase, the imprint distortion and other drawbacks

in order to obtain an ideal print, it is necessary to reset the center distance between the rubber cylinder and the embossing cylinder according to the thickness of the paper, so as to reduce the pressure increase caused by the thickening of the paper, and make the use method of the testing machine with clear and accurate points transferred to the paper clear and realistic picture

there are two main ways to adjust the pressure between rollers: first, adjust the center distance between rollers; Second, thicken or thin the liner under the printing plate and rubber

(Wang Xincheng, Hubei Xun County printing factory)

reprinted from: Printing Technology