Flexo printing machine maintenance and printing operation skills

In recent years, flexographic printing has become widely used as a new printing method in the packaging industry in China. It has the advantages of fast printing speed, high resistance to printing force, easy operation, on-line production of printing and post-processing, short production cycle, etc., and environmental protection, which has attracted more and more attention.

Flexographic printing materials are widely used in printing, high production efficiency, the use of environmentally friendly ink, UV ink, the printing process can be integrated offset printing, gravure, silk screen printing units, on-line production, has become the focus of people's attention today.

The development of China's flexo edition is relatively late, its development speed is slow, and its application level is low. Compared with European and American countries, there is a big gap. However, in recent years, more and more applications have been made in the packaging of milk packages, adhesive labels, cigarette labels, wine labels, toothpaste tubes, and paper boxes. Due to the lack of understanding of flexographic technology and the limitations of objective conditions, people cannot print products that rival those of offset printing.

For the maintenance and maintenance of different flexo presses, we talked about how to master the flexographic process and regulate the pressure.

First, maintenance and maintenance of flexographic printing machine

The synchronization of the power of the flexo printing unit, the balance of the ink supply, and the balance of the printing roller have certain requirements in the printing process.

The power of the flexo printing machine is transmitted from the main motor to the reduction gear box of each unit, and the color groups are operated synchronously. To make the overprinting of the printed product stable, the gear box should be well maintained. The reducer is one of the key components of the entire printing press. Pay attention to the amount of oil and the temperature of the oil when it is turned on (the oil must be replaced when it is turbid). Do not start the machine at high speed without lubrication to avoid damage. When it is necessary to make a circle to the plate, the circumferential plate-version motor is started so that the planetary out-of-plane frame can produce forward and reverse revolutions, and the speed of the printing roller can be superimposed or overlapped at the synchronous speed, thereby completing the registration requirements in the circumferential direction.

The ink balance is achieved by an anilox roller and a doctor blade. Anilox roller supply is accurate and reliable. There is a ceramic network line roller, the base roller is coated with ceramic, laser engraving. Its precision, surface roughness, shape and position tolerance, hardness and corrosion resistance are all very demanding and expensive, and it is produced by a professional factory. When using this type of anilox roller, special care must be taken to prevent bumping, keep it clean and prevent ink clogging, and clean immediately after printing. The accuracy of the anilox roller is one of the important factors for ensuring the printing quality of the flexographic printing press.

Anilox rollers are precise transfer ink rollers. The amount of ink transferred is determined by the number of network cables per inch. The higher the number of lines, the more the number of network pits and the lower the amount of ink. The smaller the number of network lines, the smaller the number of network pits and the greater the amount of ink. The number of screen lines in the printing process of the anilox roller is reasonable, which is determined by the color requirements of the printing product. Screen screening, screen printing should be selected high number of lines, low ink volume; field printing should be selected low line, large amount of ink.

The squeegee is used to ensure uniform ink supply to the plate. If no scraper is used, the roller is used to transfer the ink, the anilox roller is pressed tightly, and the ink transfer is fast and the speed is slow. Anilox roller with a large difference in the amount of ink, rotating faster and more ink, slow rotation is less. For this purpose, a squeegee is provided on the flexo press. With the squeegee, the amount of ink transferred from the anilox roller to the printing plate is limited to the ink storage volume of the anilox roller. This ensures the balance of the printing plate ink regardless of the speed of the machine. Therefore, there are high requirements for installing scrapers. The scraper should also have a certain degree of elasticity, toughness and strength. The knife edge should be straight and free of burrs and wrinkles. The commonly used steel scraper is 0.15mm or 0.2mm.

Squeegee installation, there are positive and reverse mounting, and now more use of reverse squeegee, and combined into a scraping ink chamber.

Second, the use of anilox roller and scraper to pay attention to the problem

The use of anilox rollers for a long time can cause wear of the bearings at both ends, resulting in a defective printed ink. At this time, the bearings at both ends must be replaced. Before any problems are found in the printed matter, the operator can also check that the dial of the anilox roller can be tested with the dial indicator, or that it is normal to feel steady on the blade holder by hand. If there is jitter, replace the bearing in time. In order to ensure the printing accuracy and the quality of printed products, the three-roll run-out value of the anilox roller, plate roller, and printing roller shall not exceed 0.02 mm.

After the squeegee has worn out, it must be replaced promptly. Usually pay attention to disassemble the knife holder and clean it, and clean the ink in the blade and the knife bar. The ink in the knife holder has not been cleaned for a long time. After the ink squeegee is installed, the knife edge will be curved and not straight. The amount of ink scraped on the anilox roller forms a circumferential ink mark, which is difficult to adjust during printing.

Squeegee material is divided into stainless steel scraper and polyester plastic scraper. Plastic scrapers are generally used for field layout printing, preferably. Due to the high-speed operation of the flexo printing machine, the knife edge wears quickly, which often causes the scrap of the polyester plastic scraper to fall into the ink or between the scraper blade and the anilox roller, and then passes it on the printing plate, which affects the quality of the printed product. Because of the small wear of the steel scraper, the reverse mounting is generally used for scraping, and the angle is 30° to 40°. The angle and pressure of the blade depends on the adjustment of the blade spring (cylinder).

The long-term operation of the flexographic printer makes the doctor blade wear faster, so the correct installation of the doctor blade is especially important for printing. When the squeegee is worn out, pay attention to cleaning the ink in the knife holder and the knife bar. For example, there are dry inks in the knife holder and the press blade, which will cause the blade to be bent on the back of the knife, which is not straight. It will also cause the anilox roller to produce circumferential ink marks, which are difficult to adjust during printing and affect the quality of printed products.

To clean the squeegee each time printing is finished, be sure to wipe the blade with alcohol to evaporate the moisture on the blade so as to prevent the blade from rusting and affect the unevenness of the squeegee during printing.