(PRINTING UNIT) The embossing cylinder feeds the paper into the printing unit and applies pressure to transfer the image on the blanket to the paper by bringing it into contact with the blanket cylinder. The impression cylinder also has gears and grooves with grippers attached to the grooves. At the beginning of printing, the tusks on the shank pinch the paper and begin to register. Then, as the drum rotates, the inked part of the squeegee is partially transferred to the paper. The surface of the impression cylinder has no sinking groove, and its diameter is similar to that of the other two cylinders. In fact, to say that sinking, the roller of the impression cylinder should be regarded as an internal sinker, because it is slightly smaller than the diameter of the drum. It is just an indication mark when setting the machine to align the impression cylinder. In order to adapt to the different thickness of the printing material, the gap between the blanket cylinder and the impression cylinder adopts two basic mechanical designs to achieve adjustment: The first design is that the impression cylinder is mounted on an eccentric sleeve through the cylinder The crossbar controls the movement of the eccentric hub, which in turn moves the impression cylinder toward or away from the blanket cylinder. In the second design, two sets of eccentric bushings are used to adjust the gap between the impression cylinder and the blanket cylinder, but they are all achieved through an eccentric sleeve mounted on the blanket cylinder. The inner set is used to adjust the pressure between the printing plate and the blanket cylinder, and to automatically separate or contact the printing plate and the blanket cylinder. The outer set of eccentric bushings is purely used to adjust the distance between the impression cylinder and the blanket cylinder. After the transfer roller is printed, the transfer roller transfers the paper to another roller, which is responsible for transferring the paper between the printing units or feeding the paper to the delivery device. The roller that conveys the paper between the printing units is called the paper feed roller. The paper feed rollers installed between the two printing units are all odd and its surface is coated with various materials to avoid ink contamination. One of them is to apply a smooth, ink-repellant material to the substrate, and then attach the coated material to the existing roller so that the roller is equivalent to a loose layer. The ink releasable material can be moved freely between the already printed paper and the transfer roller. Smooth materials reduce scratches, and oil-repellent ink-repellent surfaces also reduce the chance of overlapping printing inks. As a temporary measure, some printers also applied a 1/8-1/4 inch (3-6 mm) wide foam release tape to the transfer roller to correspond to the imageless area of ​​the print cylinder. Foam barriers help prevent scratches on the roller surface. For different printing jobs, the location of the foam barrier is different and each time it needs to be recoated. Some printing plants are equipped with air-conveying rollers, or helium-elastic air cushions, instead of the traditional paper-feed rollers. The function of the air cushion is to help the printed part from being contaminated by the ink. For example, there is a kind of air-cushion roller, its inside is an aluminum bar round frame, covered with breathable leather. When the air flow passes through this breathable sleeve, it can hold up the printed paper. In typical double-sided printing, it is usually necessary to place three paper feed rollers between the two printing units. One is a conventional paper feed roller, which follows the printing cylinder of the front printing unit; the other is a large-diameter storage roller, which is large enough to hold two sheets of paper; the other one is with two sets of Turning roller for tooth decay. On the storage roller, the trailing end (final) of the sheet is gripped by the gripper of the reversed roller, and the gripper on the storage roller is opened, and the sheet is conveyed from one roller to the other. At this point, the trailing end of the paper becomes the top, and the freshly printed page is located opposite the impression cylinder of the next group of printing presses, and the other side is then colored against the blanket cylinder. In single-sided printing, the three rollers work in the same way as the conventional feed rollers, that is, the position of the top of the paper in the print transfer does not change. The take-up roller Although technically it is a paper feed roller, we are accustomed to refer to the delivery roller connected to the last printing unit as the delivery roller. It is responsible for driving the transport conveyor and coordinating the transfer of paper between the impression cylinder and the transfer conveyor gripper. Each transport conveyor has two sets of take-up teeth. The commonly used transfer roller is a shaft roller equipped with a series of discs or skeleton wheels. The skeleton wheel can hold the paper in the non-print area and move the print horizontally. If the wheel is not installed correctly, ink will be contaminated. A system called "Super Basket" produced by Printing Research, Inc. (Printing Research Inc.) can replace the above conventional feed rollers. It replaces the roller with a solid cylinder. The cylinder is first coated with a smooth layer of ink-repellent material, and then covered with a loose, oil-repellent, loosing screen that can move freely between the printing paper and the take-up roller. Reduces or eliminates the chance of the print being contaminated. Another set of alternative systems is the Print Research Corporation's BacVac system. In this system, the unprinted ones of the paper face the BacVac vacuum device and a series of roll-overs. They enable the paper to leave the skeleton wheel to prevent ink contamination and provide sufficient support. The BacVac system satisfies most of the printing and glossing operations, but it cannot be used for double-sided printing because the printing surface will roll against the vacuum, causing serious ink contamination. Drum setting The drum setting is part of the protective maintenance work, not already set work. In the following we discuss the procedure for setting up roll-contact and non-roll contact printing cylinders. Roller contact printing press settings: Roller contact printing refers to the printing cylinder and the rubber roller's roll pillows remain in contact during printing. Roller pressure is an important part of the adjustment of the contact press cylinder. Roller function is as follows: It is a calibration device. When the rollers are in contact with each other at the end of the two rollers, it means that the blanket cylinder and the plate cylinder are just in a line; it can prevent excessive gear wear. When the pillows are in contact, the roller gears are just completely meshed and the teeth are pressed to operate according to the mechanical design. If the occlusion exceeds the depth of the teeth, the gears will be worn. When the printing press is running at no load, the pressure disappears, the pillows are separated, and the teeth do not mesh with each other. At this time, the printing press does not load, and there is almost no stain on the gears. As a reference point for measuring the actual thickness of the plate and rubber pad. Rollers represent the effective size of the roller and can be used to determine the depth of the sink sink if necessary. Helps smooth transfer of power between rollers. Because all running gears have gaps between them and wear out, a smooth transfer of power between gears is not possible. Reasonable adjustment of the roll pillow enables the drum to work in harmony and overcome the radial runout between the drive gear and the driven gear. If the pillows are not firmly in contact, gear bite marks will appear. In order to make the pillow really work, it is necessary to force the two pillows to come into close contact under the pressure of the bearing. This is called preloading. Reliance on the pressure of the upper roller to keep the rollers in close contact is not enough. The pressure between the pillows must be greater than the pressure between the printing plate and the rubber step so that the bite marks of the gears can be prevented.