Flexo Printing 1000 Questions (4)

100. What is the structure of the coil rectifying device?
The coil rectifying device is constructed by installing two paper guide rollers on the upper side of the coil rectifying device support, one side of the support is equipped with a guide rail for sensors, and one or two sensors are mounted on the guide rails, and are installed under the supports. There is a servo motor.
There are two types of structure of the correcting device: using one sensor's correcting device, correcting only one edge of the coil; using two sensor's correcting device to simultaneously monitor both sides of the coil to make the center line of the material. Always in "centered" working condition. The sensor is divided into photoelectric detection and ultrasonic detection. The former is only suitable for detecting opaque materials such as paper, while the latter is suitable for detecting various materials, including transparent materials such as: BOPP, PET, PVC and so on.
101. What is the working principle of coil rectifying device?
When the running belt passes through the two paper guide rollers and enters the gap in the sensor, it is monitored. As long as the tape is skewed, the sensor will send a signal, the servo motor will immediately deflect the bracket, and the two paper guide rollers installed on the bracket will be deflected at the same time to adjust the running direction of the material belt to the correct paper path.
102. What is the use of corona treatment device?
In order to increase the surface tension of printing materials such as films or aluminum-plated paper, the ink can be firmly adsorbed on it, and a corona treatment device needs to be added to corona treatment the surface of the printing material. This type of device is divided into two types: one that can only handle aluminum-plated paper or one that can only handle film, that can handle both aluminum-plated paper and film, and that can only be treated on one side and can be double-sided. .
103. What other material handling equipment can be installed in the unwinding and dosing unit?
In the unit type flexographic printing press, most of them are equipped with a pneumatic loading coil device to reduce the operator's labor intensity; at the same time, in order to ensure that the reel does not make the tape slack and avoid repetitive wear, it is generally The platform equipped with splicing paper; To avoid paper hairs entering the ink or sticking to the plate, affecting the quality of the printed matter, consider adding a paper-hair cleaning device (it has a brush type, vacuum suction type, single-side processing type and double Surface treatment type and other forms); In order to make the roll paperboard not to be over-crimped during the printing process, it is also possible to consider increasing the paper flattening apparatus.
104. What are the parts of the flexo unit?
The flexo printing unit is mainly composed of a plate cylinder, an impression cylinder, a plate cylinder clutch mechanism, a printing register device, an ink fountain roller, an anilox roller, and a doctor blade.
105. How does the flexo unit work?
The working principle of the flexo printing unit is that the ink stored in the ink fountain is uniformly transferred to the surface of the printing plate by the uniform ink distribution of the anilox roller and the doctor blade; the continuously running tension-controlled material is continuously fed into the printing plate. Between the plate cylinder and the impression cylinder, when the plate cylinder is in the combined pressure state, the ink of the plate graphic part is transferred to the printing material under very light pressure; the overprint adjustment of each printing unit is operated manually or by electric The printing register device completes the printing; after the tape passes through the hot air drying box or the UV curing device installed on each printing unit, the ink layer is dried or solidified.
106. What are the key components of the flexprint unit?
The plate cylinder and the impression cylinder in the flexo printing unit are all key components. Their dimensional accuracy, shape accuracy and balance accuracy all directly affect the printing quality. In addition, laser-engraved ceramic anilox rollers are called “the heart of a flexographic printing press”. In addition to ensuring the size, shape, and balance accuracy, the correct number of screens, ink storage (BCM), and a strong web wall are also required. All are very important factors.
107. What should be the characteristics of the plate cylinder?
The characteristics of flexo plate cylinders are: printing of different reprint lengths is achieved by replacing different gears and plate cylinders of corresponding diameters. Therefore, every manufacturer who uses a flexographic printing press should prepare multiple sets of plate cylinders that are compatible with the various types of prints that are commonly used by them. In order to facilitate the assembly and disassembly of the drum, the drum body is generally made of aluminum alloy material to form a hollow tubular structure.
108. What is the structure of the plate cylinder?
The common plate cylinder has two structural forms: two-end insert head type and spindle insert type. The former is inconvenient because it is not easy to change the fashion, and it is rather troublesome to change the pressure once it is changed. Therefore, it is seldom applied to imported flexographic equipment or domestically-made flexographic equipment; the latter can only be taken out at the time of changing the mandrel. Under the printing plate cylinder, the printing plate cylinder with the same repetitive printing length is not required to readjust the printing pressure, so it is widely used in most imported or domestic advanced equipment, and as long as the printing machine manufacturer controls the processing of the roller bearing. Accuracy and assembly quality do not produce axial and radial runout of the drum.
109. Sleeve type plate cylinder What are the characteristics?
In recent years, flexo printing technology has developed rapidly and sleeve technology has begun to be applied. Compared with the traditional plate cylinder, the sleeve has a lighter weight and can be assembled and disassembled by one person; it can be conveniently positioned on the air-bearing roller; it can be repeatedly pasted and can be changed at any time on the sleeve; the biggest advantage is that Only one air-lift roller can be used to fit a variety of sleeves with the same hole diameter and different wall thickness, so as to obtain a series of printing cylinders with repeated printing length.
110. How to calculate the diameter of the plate cylinder?
In order to adapt to the different repeat lengths of the print specifications, the printing plant needs to be equipped with a number of plate cylinders of different diameters. At present, many printing companies are looking for manufacturers to process plate cylinders themselves. Therefore, it is particularly important to learn how to correctly calculate the plate cylinder diameter.
1 If printing with aqueous ink, 0.38mm double-sided tape and 1.7mm printing plate are recommended to calculate the diameter of the plate cylinder. Calculated as follows:
D=PD-2×(0.38+1.7)mm+0.1mm
=PD-4.06mm
The diameter of the D-printing cylinder body is 0.1 mm (0.004 inch) in the index circle diameter of the PD-plate cylinder gear, which is 2 times the deformation of the printing plate under a certain pressure.
The size of the flexographic press imported from the United States, the United Kingdom, and Canada is in inch. The formula can be rewritten as:
D=PD-2×(0.015+0.067)inch+0.004inch
=PD-0.16inch
Among them, 0.015 inch is the thickness of the double-sided tape, and 0.067 inch is the thickness of the plate.
2 If using UV ink printing, it is recommended to use 0.51mm double-sided tape and 1.14mm printing plate to calculate the diameter of the plate cylinder. The calculation formula is:
D=PD-2×(0.51+1.14)mm+0.1
=PD-3.2mm
The 0.1 mm (0.004 inch) in the above formula is 2 times the deformation of the plate under a certain pressure.
The size of the flexographic press imported from the United States, the United Kingdom, and Canada is in inch. The formula is rewritten as:
D=PD-2×(0.02+0.045)inch+0.004inch
=PD-0.126 inch
Among them, 0.02inch is the thickness of the double-sided tape, and 0.045inch is the thickness of the plate.
This formula has been confirmed in the processing and application of the plate cylinders of web flexographic printing machines produced by most imported flexographic printing machines and Shanghai Ziguang Machinery Co., Ltd. The calculation method provided by some flexo press manufacturers is different from the above formula. As the use unit of a flexo press, the plate cylinder should be processed according to the drawings provided by the printer manufacturer.
111. What kind of structure of the impression cylinder has?
In addition to the large-scale and complex working conditions of satellite type flexographic printing presses, laminating or flexographic printing presses are generally manufactured by forging ingots. In order to meet the requirements of using water-based ink, the surface of the drum needs to be chrome-plated.
112. Which 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 transmission of ink pressure?
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 retreats, 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, screen) 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, this pressure caused the flexo plate to have a deformation of 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.
119. How does the 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 separated from the anilox roller and the impression cylinder at the same time. 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 slider of the plate cylinder is pressed, so that the printing circular arc cylinder is in the pressing position; when the compressed air is switched When entering the cylinder and retracting the piston rod, the clutch shaft is driven to rotate, and the milling plane on the shaft is downward. The supporting slider of the printing plate cylinder slides up under the action of another spring cylinder, so that the plate cylinder is at the pressure-releasing position.
120. What are the characteristics of the flexographic ink supply system?
Flexo sheet

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