Flexo Printing 1000 Questions (151-168)

151 How is the overall pressure-cutting circular compression die cutting roll machined?
The general cutting process of the overall pressure cut round circular die cutting roller is: according to the technical parameters of the printing material and the requirements of the processing pattern, different grades of tool steel are selected, and the surface is processed into a shape of a blade after high-precision CNC cutting. Then, heat treatment was performed to harden the surface of the material. Finally, the blade was finished under a microscope, and the die was cut on the machine.

How long is the life of the 152 full-bore circular roll die cutting roll?
Circular die cutting roll can be die cut about 1 million times. After the blade is blunt, as long as there is no large gap, it can be sent to the factory for grinding. A round press die cutting roll can be grinded 3 to 5 times, and can be die cut 800,000 times or so after each grinding. If used and maintained properly, the life cycle of circular die cutting rolls is 3.5 to 5 million times.

What are the characteristics of 153 up and down shear type circular pressure die cutting roller?
The up-and-down shearing round die-cutting die roll also shapes the surface of the drum to conform to the desired die-cut pattern, and the knife-edge has high hardness and strength. It uses a pair of rollers as cutting edges. When the die is cut, the printing material passes between the two rollers and die cutting is done using the principle of scissors. This type of die-cutting roller has a long service life, but has a large one-time investment and is suitable for die-cutting long-run prints, and is particularly suitable for die-cutting of a paper box.

154 Why is it that circular die-cutting will be popularized in China?
The round press die cutting process has the characteristics of high accuracy and high production efficiency of "die cutting pattern" and "printing pattern". It has been widely used abroad. In China, due to the round circular die cutting roller is currently mainly processed abroad, the cost is relatively high. However, with the involvement of domestic processing companies and the reduction of input costs, this form of processing will surely gain popularity in our country.

155 what is the pressure bumps and indentations?
The embossing and embossing are generally done on the circular press die cutting station of the machine. The roller form is similar to that of the upper and lower shear rollers except that the printing material does not need to be cut through. A pair of rollers are respectively made into a negative and a positive figure, and the printing material is allowed to pass between the two rollers during die-cutting, and an appropriate pressure is applied by a manual pressure adjusting device to complete the embossing or indentation.

156 flat die-cutting die-cutting unit is mainly composed of which parts?
The advanced flat die-cut die-cutting unit is an electromechanical integrated device consisting mainly of a swing arm and die-cutting device. They are driven in two different ways: the power of the swing arm comes from the main drive of the machine; the die-cutting device is driven by a computer-controlled servo motor.

157 flat pressure die-cutting unit which advantages and disadvantages?
Flat die-cut die cutting is another form of die-cutting. It also has the features of high accuracy of die-cutting pattern and printing pattern. Due to the low cost of making a die-cut version, it is suitable for short-lived version and is more popular in our country. However, since the die-cutting form is limited by the mechanical structure and the die-cutting speed is not very high, it is not able to show the high production efficiency of the flexo printer.

158 There are several types of waste after die-cutting?
No matter whether it is round die cutting or flat die cutting, scrapping must be done. There are two types of waste discharge methods for flexographic printing presses: one is the waste rewinding process; the other is the vacuum waste disposal process.

159 What type of scrap is suitable for rewinding with scrap?
Scrap rewinding is suitable for waste scraps and scraps that can be continuously fed after die-cutting or slitting. It requires the scrap edge to be symmetrical with respect to the centerline of the width direction of the printing material, and has a uniform width, so that the scrap can be prevented from breaking on a narrow width side, resulting in shutdown.

160 How to control tension when rewinding a scrap?
Since the tension value of the waste material is much lower than the tension value of the printing material before die-cutting, the control of the tension of the waste material is very important at this time. There are generally two types of tension control: one is the use of mechanical friction clutches, the use of increasing or reducing the positive pressure to change the size of the friction, so as to achieve the purpose of changing the tension value; the other is the use of pneumatic clutch, through Change the air pressure to change the tension value.

161 What is the working principle of vacuum exhaust?
The vacuum waste form is suitable for waste edges that are not suitable for curling, and shredded paper scraps produced by die cutting. It is equipped with a rotating hard bristle brush, close to the round side of the circular die-cutting roll to discharge the paper side, brush the scrap paper off, and then sucked away by the vacuum cleaner under the printing material. There is also a vacuum exhaust device which is internally provided with a rotary knife, and the waste edge cut by the slitter knife is sucked into the interior and discharged after shredding.

162 film covered by what constitutes?
The film laminating apparatus is generally mounted on a wallboard of a round press die-cutting unit on a side close to the printing unit, and a rubber roller is mounted on the round press die cutting station. It also has a set of components fixed to the machine wall plate that apply and adjust the pressure on the rubber roller.

163 film coating device works?
When the printed product arrives at the circular press die cutting station, the sticky coating material that is unwound from the liner and is peeled off comes from above, and the film material is pressed under the pressure of the rubber roller and the anvil roller. It is integrated with the substrate to complete the laminating process. Coated material liners are collected using a waste rewind device. At present, most of the coating materials used are pre-coated films, which can be combined with printing materials after hot pressing, which is more economical and convenient. If the film material does not have a liner, it does not need to peel off the liner and collect the liner.

164 film tension control What are the characteristics?
The film tension control is similar to the unwind tension control, and the tension control of the rewind is similar to the rewind tension control. There are also two types of tension control in the film. One is the use of mechanical friction clutches, which are used to increase or decrease the positive pressure to change the magnitude of the friction force so as to achieve the purpose of changing the tension value; the other is to use pneumatic clutches. Change the tension value by changing the air pressure.

What is the working principle of 165 round hot stamping?
The round hot stamping device includes a hot stamping roller, a set of components fixed on the machine wall plate to apply and regulate the pressure to the hot stamping roller, and electrical components specially used for the heating of the hot stamping roller. The hot stamping foil is mounted on the laminating device and controls the unwinding tension. The hot stamping roller and the printing material are in line contact during hot stamping, and the time is short. Therefore, it is required that the material for the hot stamping roller must have good thermal conductivity and withstand a certain strength, and the material will not be deformed under high temperature conditions. Therefore, the current hot stamping device in our country still needs to rely on imports.

What are the advantages and disadvantages of 166 round hot stamping?
The advantage of hot stamping is that the accuracy of hot stamping is high. However, as mentioned earlier, round hot stamping is line contact, which greatly limits the speed of use of the machine and can only reach 20 to 30 meters per minute; in addition, this type of hot stamping method is affected by the thermal conductivity of the line contact, and the large area is hot. The quality of India is not ideal.

167 What are the parts of the punch?
The punching device is composed of a pair of punched discs and confetti discs respectively having recessed pins and protruding pins. It is also installed in the round press die cutting station.

168 How to choose punching pins for different printing materials?
For the punching of thin paper, a soft pin like a computer form printer can be used, so that the machining error of the punched plate has little effect on the life of the pin; for the punching of the paper jam, shearing must be used. Hard-selling, so that the processing requirements of the punched disk is very high. If it is used for punching of self-adhesive liners, since it does not need to punch the adhesive paper, the paper scraps stick to the adhesive and can be rolled away together with the waste edge.

Source: "Printing Technology"