Flexo printing 1000 questions (111-120)

What is the structure of the 111 impression cylinder?

In addition to satellite type flexographic printing presses, because of their large size and special working conditions, there are various and complex structural forms. Stacked or unit type flexographic printing presses are generally machined from forged steel ingots. In order to meet the requirements of using water-based ink, the surface of the drum needs to be chrome-plated.

112 What kind of pressure can be adjusted on the flexo unit?

The pressure on the flexo unit is divided into the pressure of ink transfer, the pressure of inking and the pressure of printing. They all directly affect the quality of printed products. Adjusting these pressures reasonably is very important for flexographic printing.

113 What is the pressure of ink transfer?

The ink transfer pressure refers to the pressure between the ink fountain roller and the anilox roller, that is, the compression deformation of the ink fountain roller. The greater the pressure of ink transfer, the smaller the amount of ink transferred; on the contrary, the greater the amount of ink transferred.

114 How to adjust the pressure of ink transfer?

The mechanism for adjusting the ink transfer pressure is mounted on the ink fountain holder and is performed using a manual fine screw. The screw is installed horizontally. It applies pressure to the support seats at both ends of the ink fountain rubber roller in the direction of the anilox roller. The gap between the ink fountain roller and the anilox roller can be changed to change the thickness of the ink layer. At the same time, the pressure is applied. The anilox roller was provided with ink from a fountain roller.

115 What is the pressure of inking?

Inking pressure refers to the pressure between the anilox roller and the plate cylinder. Its role is to transfer the ink on the anilox roller to the plate, so that the graphic part of the plate gets the required ink layer.

116 How to adjust the ink pressure?

The manual fine-screw screw for adjusting the inking pressure exerts a horizontal force on the adjustable plate equipped with the plate cylinder support slider, and the adjustable plate uses the anilox roller as the center to make a slight rotation, thus changing the anilox roller and the Plate center distance between rollers. When the screw is retracted, the spring can ensure that the adjustable plate is always in contact with the screw, so that the distance between the two ends is the same, and the surface of the ink layer on the anilox roller is just tangent to the arc surface of the printing plate.

According to a study by a flexographic machine manufacturer in the United States, this pressure caused the flexo plate to have a deformation of about 0.05 mm (0.002 inch).

117 What is printing pressure?

One of the characteristics of flexographic printing is that it requires only minimal printing pressure (smaller than offset, emboss, gravure, and screen printing) to transfer the ink on the plate to the substrate. The adjustment of printing pressure is one of the keys to determine the quality of printed products.

The flexographic printing pressure can be adjusted in a small range. According to the study of the flexographic press manufacturer in the United States, the pressure caused by the flexo printing plate is generally about 0.05 mm (0.002 inch).

118 How to adjust the printing pressure?

In order to meet the need for fine-tuning the printing pressure, manual fine-screw screws are also used in the flexo printing unit. It applies a pressure in the direction of the impression cylinder to the supporting sliders at the two ends of the printing plate cylinder, and at the same time generates the pressure between the plate cylinder and the impression cylinder. With this pressure, the thin ink layer on the printing plate can be uniformly transferred to the surface of the printing material. When the screw retreats, under the action of the cylinder, the support sliders at the two ends of the plate cylinder are pushed upward so that the slider is always in contact with the screw.

The progress of flexo printing technology has put forward a quantified concept for the fine adjustment of printing pressure. A dial gauge was installed on the Jalast Flexo press produced in Switzerland to display data on printing pressure. In American Andy's Model 4200 flexographic printing press, servo motors are used to control the cylinder motion to adjust the printing pressure. At the same time, the pressure data of different prints can be memorized and saved on a magnetic disk.

How does the 119 flexo unit achieve the plate cylinder clutch pressure?

The flexo printing unit is generally used to change the position of the printing plate cylinder so that the printing plate cylinder is pressed or pressed together with the anilox roller and the impression cylinder. Because the displacement of the plate cylinder is a constant value, there is no need to repeatedly adjust the pressure after each plate cylinder pressure.

The pneumatically controlled clutch pressure mechanism is the most commonly used clutch pressure device in a narrow flexographic printing press. The cylinder and the clutch shaft are connected by a connecting rod, and a plane is locally milled on the arc surface of the clutch pressure shaft. It is the level difference between the plane and the arc surface that allows the plate cylinder supporting the slider to slide up and down. When the compressed air enters the cylinder and pushes out the piston rod, the clutch shaft is driven to rotate, the arc of the shaft faces downwards, and the supporting roller of the plate cylinder is pressed to make the plate cylinder in a pressure-compressing position; when the compressed air is reversed, When the cylinder rod is retracted and the piston rod is retracted, the clutch shaft is driven to rotate, the milling plane on the shaft is downward, and the support roller of the plate cylinder slides upwards under the action of another spring cylinder, so that the plate cylinder is in a pressure-releasing position.

What are the characteristics of the 120 flexo ink system?

The ink supply system of the flexo printing unit is much simpler than the ink supply system of the offset printing machine and the convex printing machine. It is generally composed of an ink fountain, an ink fountain roller, an anilox roller and a doctor blade. The ink in the ink fountain is transferred to the anilox roller by the rotation of the ink fountain roller immersed in the ink fountain, and the amount of ink transferred by the anilox roller is controlled by the squeegee, and the cooperation of the anilox roller and the squeegee causes the ink to flow. Flexographic presses achieve excellent transfer of ink quality at high speeds. Of course, there are also ink fountain rollers used to dip the anilox roller directly into the ink fountain. The squeegee is used to quantitatively transmit the ink to the ink supply. For example, the Agaflex flexo press uses such a system.

(Shanghai Ziguang Machinery Co., Ltd. Shi Jianping)