Flexo Printing 1000 Questions (137-150)

137 series of flexo printing machine which connected after the printing function?

The unit type flexographic press has a variety of connection and post-press processing forms, mainly including: single sheet cutting, rewinding, round press die cutting, embossing, flat and flat die cutting, scrap rewinding, film lamination, punching, Stamping and so on.

138 cut single unit by what part?

Cut sheet is one of the ways to collect the finished product of a flexographic printing press. The cut sheet unit is generally located at the end of the machine's tension control zone, which is behind the meter-out roller. It consists of a single sheet roll, an anvil roll and a conveyor table. As with single cylinders and plate cylinders, both axial and circumferential register adjustments can be made.

139 Why do printers also need to prepare multiple sets of single-sheet cylinders of various specifications?

As with the plate cylinder and the round press die cutting roller, the cut single cylinder also cuts out different repetitive length prints by replacing the gears with different numbers of teeth and their corresponding diameters. Therefore, every manufacturer who has such a flexographic printing machine with on-line processing capabilities should prepare multiple sets of singe-sheet cylinders that are compatible with the print specifications of its own daily production.

140 What are the characteristics of single-cut drum?

The cut sheet roller of the flexographic printing press is a key component. It consists of a cylinder body, two roll pillows (also known as shoulder iron) and a gear. Because there is a set of components fixed on the machine wall plate to apply and adjust the pressure on the single sheet cylinder, the roll pillows are generally machined from forged high alloy steel ingots, and the surface has high hardness and strength. The cutting blade is mounted in a narrow groove under the tightness of a row of screws. This groove can have only one, two, or many grooves. The deep groove dimensional accuracy, the equal division accuracy of the angle between the grooves, the parallelism of the groove bottom and the axis of the drum, and the dynamic balance accuracy directly affect the quality of the printed product and the accuracy of the reprocessed register after the printed product goes offline.

141 How to calculate the diameter of the cut sheet roller?

In order to accommodate the different lengths of the printed product, many different diameter single-cut cylinders must be fitted. Its repeat length can be the same as the plate cylinder, it can also be a multiple of the repeat length of the plate cylinder. The following is the method of calculating the diameter of a single sheet cylinder:

Roller diameter D1=PD+0.6mm

Roller body diameter D=D1-2.5=PD-1.9mm

Among them, PD is to cut the diameter of a single cylinder.

In this way, as long as the cutting blade is 1.5 mm above the surface of the cylinder body, the substrate can be cut to a thickness of less than 0.3 mm. In the premise of a certain size of the cutting blade, it is better to determine the depth of the blade groove according to the thickness of the commonly used printing material. Because the blade is too much out of the cylinder body, it will aggravate the wear of the blade; on the contrary, it will cause the failure of cutting the substrate.

142 Anvil Roll What are the characteristics?

The anvil roller used for die cutting and cutting of the sheet is also a key component. Its dimensional accuracy, shape accuracy and dynamic balance also directly affect the quality of printed products. The anvil roll is generally made by forging the alloy steel ingot. In order to meet the requirements of the contact with the blade, the surface of the roller needs to be heat-treated to increase the hardness and strength.

143 rewinding device What are the characteristics?

Rewinding is a finished tape collection method for web flexographic presses. The rewinding device is generally equipped with 1~2 reels. The control of each reel is basically independent. The tension control can use magnetic powder clutch or DC motor to control the torque to ensure that the material is evenly wound and the material roll The neat end face is conducive to reprocessing after going offline.

144 How to choose the different types of rewinding when choosing a machine?

When the width of the material is 420 mm or less, a cantilevered rewinding method can generally be considered. When the material width is more than 500 mm, the rewinding mode with double wallboard support should be considered.

145 Why is it necessary to have 2 reels in a cantilever rewind unit when selecting a flexo printer with a slitting function?

When the post-press processing needs to be cut in line, the cantilever rewind unit should select two reels to rewind the material so as to avoid overlapping of the cut edges and affect the flush end of the material roll.

146 How to prevent the slitting edges of the strips from overlapping with the rewinding unit with double wallboard support?

In order to avoid overlapping of the cutting edges of the tape, a special roller, an arched roller, is now used. The axis of the drum is arcuate and does not substantially rotate. When the web passes, it can pull apart the distance between the cut edges to prevent the cut edges from overlapping. In general, this type of drum is included in the option.

147 circular press die-cutting unit of the flexo printing machine consists of which parts?

A flexographic printing press is generally provided with 3 die cutting stations, of which two are circular press die cutting units and the other is a cut single unit. Each die-cutting station includes a drive roll-anvil roll, a groove for holding the round press die-cut roll and the anvil roll, and a set of fixed-on-machine wallboards that are applied to the round press die-cut roll Pressure and components used to adjust pressure. If a shear die cut is used, there is a support roller below the lower die cut roller, which is also the active roller. The circular press die cutting roller, like the plate cylinder, can perform axial registration and circumferential register adjustment.

148 round circular die cutting roller can be divided into 3 kinds of forms?

Circular die cutting rolls can be divided into three types: magnetic die cutting roller, integral die cutting die cutting roller and shear die cutting roller.

149 What are the advantages and disadvantages of magnetic circular die cutting roller?

The die cutter plate is processed into a thin iron plate. The surface of the magnetic roller is magnetic, and the die cutter plate is magnetically attracted to the surface of the magnetic roller. The advantage is that without changing the repeat length of the roller, it is possible to adapt to the requirements of different die cutting patterns by replacing the die cutter plate, relatively speaking, the capital invested is less. The disadvantage is that it is not suitable for cutting thicker materials, such as paper jams. Magnetic round circular die cutting roller is mainly used for die cutting of self-adhesive labels.

150 What are the characteristics of the overall pressure-cutting circular compression die cutting roll?

Integral die-cutting circular die-cutting circular die cutting rolls machine the surface of the drum to conform to the desired die-cut pattern, and the knife-edge has high hardness and strength. An anvil roll is installed under it. During the cutting, the printing material passes between the cutting roll and the anvil roll, and the printing material is cut by adjusting the cutting pressure. Since it is only necessary to arrange the knife in the desired pattern on one roller surface, its investment lies between the magnetic die cutting roller and the shear die cutting roller. The disadvantages of this die cut form are: the flexibility is not as good as the magnetic die-cutting roller; the life is lower than the shear die-cutting roller.

Shanghai Ziguang Machinery Co., Ltd. Shi Jianping

Source: "Printing Technology - Packaging and Decoration Printing"