Gravure squeegee, gravure, ink use problem analysis

With the development of China's tobacco industry, the gravure printing method is characterized by its thick ink layer, good color reproducibility, strong print resistance, and the consistency of hue consistency in product mass production is relatively easy to control, quality is stable, and production efficiency is high. It occupies an extremely important position. According to my many years of experience in gravure printing, I would like to make a simple exchange with my colleagues about the use of squeegee, gravure and ink in the production process.

1 Scraper

There is a saying in the industry that if gravure is good or not, it will look like a squeegee. The quality of squeegee assembly in gravure printing directly determines the number of printing problems and the level of consumption.

1) Squeegee assembly

Before assembly, both ends of the squeegee blade are pinched with fingers and the light is inspected for wrinkles, bulges, and defects. After confirming that there is no defect, put the blade into the squeegee holder, lightly tighten the screw, measure with a ruler and adjust it to the required height; tighten the screws from the middle to both ends in turn (also from left to right or from right to left Tighten the screws).

Use 600# fine water sandpaper to apply the oil, grind it gently on the sand surface to remove the coarse sand particles on the surface of the sandpaper, then use your fingers to pinch the sandpaper to rub the edge of the squeegee blade back and forth more than ten times to remove the burr from the squeegee blade itself ( It is worth noting that the stroke of each sanding must be on both ends of the squeegee blade; then, the two sides of the squeegee blade are lightly polished with sandpaper to remove the burrs generated by grinding the edge of the squeegee blade; wipe the solvent with a tissue paper. Clean the doctor blade.

Raise the squeegee holder and check the squeegee blade to ensure that the squeegee blade is straight, free of ripples, and wrinkles on the ink holder. The machine must be refitted until straight. If the squeegee blade is not straight, wavily and wrinkle-free, the uneven squeegee will appear after the squeegee, and it will also bring printing quality problems such as ink pull, ghosting and so on.

2) Squeegee on the machine debugging

Put the assembled squeegee into the printing color group, lock the fastening screw, and adjust the balance device so that the edge of the squeegee blade is parallel to the platen and slightly evenly contacted.

Rotate the plate with ink and slowly increase the pressure of the squeegee. Observe and adjust the squeegee until the ink is even. Then add the pressure to the required parameters.

Raise the speed to 130 m/min to 160 m/min, fully run the squeegee with the layout for 5 minutes to 10 minutes, and use a bamboo swab to clean the squeegee and the contact plate to avoid the burr caused by the squeegee Lamo and ghosting and other printing problems.

3) The effect of the squeegee angle on printing

Under normal circumstances, the best contact angle of the squeegee shaft with the plate layout is 60°. This angle can ensure that the squeegee scrapes the excess ink on the surface of the plate cylinder and does not easily scratch the plate. When the squeegee angle is too large, a large number of coarse ink lines that are not damaged by the squeegee are likely to be generated. When the squeegee angle is too small, the squeegee phenomenon of the printed product occurs. In the course of production, if there are printing problems such as cable pulling and ghosting, the angle and pressure of the squeegee can be adjusted in due course.

2 Treatment before gravure

Most of the plate-making factory in the printing plate production in the polishing process is completed by the machine, the surface is relatively smooth, the machine is used when the squeegee moves along the plate in the axial contact with the plate, not easy to scrape the non-printing graphics Some inks are prone to problems such as pull lines and ghosting. Through years of practice and verification, the surface of the printing plate has a faint, cross-twill-like appearance, but it is not easy to produce pulling lines, ghosting, etc. Therefore, after the printing plate can be soaked with 600# fine water sandpaper, the sand surface is lightly ground. Remove rough sand, two hands on sandpaper pressed on the plate, so that the surface of the printing plate is cross-twill, this method can effectively control the printing problems such as cable and ghosting. In the production run, the printing problems such as cable pull and ghosting can be applied with 600# fine water sandpaper. After the sand surface is lightly ground to remove the coarse sand particles, the corresponding parts of the printing problem on the printing plate are lightly polished.

3 ink control

At present, the inks used by cigarette label printing enterprises are basically spot color inks. The following points should be noted when using them:

1) The original ink should be fully stirred, and then the corresponding thinner should be added evenly, and the mixture can be evenly stirred and adjusted to the viscosity required by the upper machine, and the hue can be used after fine adjustment.

2) In the process of use, it should be noted that the viscosity of the ink must be regularly detected every 15 minutes to 30 minutes, and the consistency of the ink viscosity should be adjusted in time. Since most of the ink dilution solvents are volatile, the ink viscosity will increase continuously after prolonged use, and the ink viscosity is too high, which often leads to printing quality problems such as blocking plates and cable pulling. Conversely, low viscosity can cause poor ink leveling, ink bleeding, and water-grain-like phenomena.

3) The ink needs to be sealed and stored in a timely manner if the ink is not used for a long time because of the end of production or mechanical failure.

Through the above adjustment of the squeegee, printing plate, ink before the machine and during the use of the machine can greatly reduce or even avoid printing problems such as pull lines, ghosting, etc., reduce the number of replacement squeegee, effectively reduce consumption, improve productivity .