Laser Cleaning Machine for Anilox Roller

Laser Cleaning Machine for Anilox Roller

1. Background of the anilox roller laser cleaning.

In flexographic printing, the anilox roller evenly transfers a certain amount of ink to the printing plate. It is both an ink transfer roller and an ink metering roller, and the amount of ink is used to achieve accuracy. The anilox roller is called the heart of the flexo printing machine by people in the flexo printing industry. The final printing effect depends to a large extent on the quality and operation results of the anilox roller.

Ceramic anilox rollers have shined in the development of flexographic printing due to their advantages such as high ink transfer accuracy and long service life. They have gradually replaced metal anilox rollers and become the standard configuration of flexo printing equipment and printing companies. In this process, the problem of cleaning the ceramic anilox roller has actually always existed along with the various advantages of the ceramic anilox roller. The reason why the cleaning problem of ceramic anilox rollers is emphasized is that compared with metal anilox rollers, ceramic anilox rollers are more difficult to clean. There are mainly the following reasons:

(1) The ceramic layer of the anilox roller is coated on the surface of the base roller of the anilox roller through a thermal spraying process. The material characteristics of most ceramics and the characteristics of the thermal spraying process determine that the ceramic layer has naturally existing pores, but the texture is different. The porosity of the roller ceramic layer varies from large to small. The presence of pores increases the surface energy of the ceramic layer, which causes the residual ink to adhere more stubbornly within the cells.

(2) The cells on the surface of the anilox roller are formed by laser engraving. The inner wall of the cells and the edge of the screen wall are relatively rough. This situation also increases the adhesion fastness of the residual ink in the cells.

(3) The line count of the anilox roller can reach up to 1600LPI, which means that the cell opening size on the surface of the anilox roller may be less than 15 μm. The cells with such small openings are blocked by the cured ink, making it difficult to clean.

(4) Some anilox rollers blindly pursue high screen lines and large ink volumes, and design cells with extremely irrational depth opening ratios. Small cell openings, coupled with irrational cell depths, result in many anilox rollers not being used. Broken, but damaged by washing or scrapped due to inability to apply ink evenly due to incomplete cleaning.

(5) The performance of flexo printing inks has also been rapidly improved in recent years, especially in terms of increasing printing speed and improving weather resistance. The better these performance properties of the ink, the more difficult it is to clean off the remaining dry solid ink using conventional methods.

Therefore, since the birth of ceramic anilox rollers, how to clean and maintain them safely and efficiently and extend their effective service life has been a topic of great concern.

Commonly used cleaning methods for anilox rollers are as follows:

a. Solvent manual cleaning

b. Ultrasonic cleaning

c. High pressure water cleaning

d. NaHCO3 jet cleaning

e. Dry ice blast cleaning

f. Plastic particle spray cleaning

The above methods can be classified into: solvent method (a.), solvent + medium injection (b.c.), medium injection (d.e.f.). Each of these methods has its own advantages and disadvantages. If used properly, it will have a very good cleaning effect; if used improperly, it will also have serious consequences. For example, improper selection of solvents can cause bulging of the anilox roller, irregular ultrasonic cleaning can cause cracks in the anilox roller screen wall, and media injection is not suitable for high line count anilox rollers, etc.

Because the benefits and risks of these cleaning methods coexist, and the requirements for users are relatively high. This reality provides an opportunity for the birth of laser cleaning methods. 

2. Basic principles of laser cleaning.

First, what is laser cleaning?

To put it simply, a specific laser beam is used to scan the surface of the anilox roller, so that the ink in the cells absorbs the laser energy and vaporizes, thereby achieving the purpose of cleaning without causing any damage to the cells of the anilox roller.

To understand the basic logic of laser cleaning, you must first understand the target object to be cleaned. During the anilox roller cleaning process, the cleaning target is undoubtedly the dried ink in the cells.

Simply put, the ingredients in the ink are divided into toner, binder, and additives. The binder determines the adhesion fastness and the film-forming performance of the ink. It is also the main component other than the toner after the ink dries. In other words, if you want to clean up the dry ink in the cells of the anilox roller, the core issue is to effectively handle the dry ink connecting material in the cells.

Therefore, the selection and adjustment of the laser should be set according to the ink binder. It can vaporize the ink binder without changing the ceramic layer.

We can understand laser cleaning by dividing it into the following steps:

(1) After laser scanning, the laser energy is absorbed by the ink remaining in the cells of the anilox roller;

(2) Instant high-energy injection causes the binder (resin) component in the ink to rapidly expand to form plasma;

(3) The highly ionized unstable gas formed in the fine cells of the anilox roller will instantly increase the air pressure in the cells, and form a strong impact airflow toward the opening of the cells, flushing the pollutants out of the mesh hole;

(4) The power and energy threshold of the laser are selected and adjusted according to the resin component of the connecting material. During the scanning process, only the resin component (or similar components) can fully absorb the energy of this type of laser, while ceramic components and most colors The material composition cannot be changed by absorbing laser energy;

(5) As the laser scans, there will be an exhaust port next to the laser head connected to the outer vacuum pump, which will continuously remove the flushed out pollutants (mostly plasma gases and toner that cannot be vaporized) draw away;

(6) A small amount of toner that has not been extracted will be scattered on the surface of the anilox roller and can be blown clean with compressed air. To avoid the generation of dust, you can use a lint-free cloth dipped in alcohol to wipe the surface of the anilox roller.

3. Safety of laser cleaning.

(1) Safe for people and the environment

Laser cleaning does not use any chemical solvents or other media other than laser, and the cleaning waste will be extracted in time for further processing. During this cleaning process, the only contaminant is a very small amount of toner scattered on the roller surface, and this emission is almost negligible. Therefore, it is undoubtedly very friendly to the health of operators and is sufficient to cope with increasingly stringent environmental protection requirements.

(2) Safety for anilox rollers

Laser is essentially a beam of light with highly consistent phase and frequency, but this light has excellent directionality and concentrated energy. Different objects have different absorption rates of light, and lasers are no exception. We can change the absorption rate of laser light by a certain type of substance by adjusting the type of laser and the threshold values of various laser indicators. In the topic of laser cleaning of anilox rollers, in fact, as long as you find a laser and adjust the threshold reasonably, the absorption rate of the resin component in the ink for this light reaches the peak level, and the absorption rate of the ceramic layer for the laser reaches the valley value. Level, it can achieve ink cleaning while protecting the ceramic anilox roller from damage. This is the basic logic of laser cleaning.

4. Advantages of laser anilox roller cleaning.

(1) Easy to operate

Laser cleaning equipment is precise and stable. During the early testing, the parameters obtained by the test can be saved in the control system of the equipment, and can be selected according to the corresponding working conditions during actual application.

(2) Security

1) Due to the improvement of intelligence, the control system can have many built-in protection mechanisms to ensure the safety of people, the environment and the anilox roller.

2) No solvent is required, effectively reducing the probability of corrosion of the anilox roller.

Especially for sleeve anilox rollers, we have seen many sleeve anilox rollers corroded. Most of them are caused by improper cleaning and the penetration of solvent or water from the interface between the glass fiber and the aluminum core at the end of the anilox roller.

3) Avoid the collapse and cracking of the anilox roller screen wall caused by other physical cleaning methods.

(3) Clean thoroughly to extend the life of the anilox roller.

Laser cleaning can ensure that the anilox roller is clean without causing damage to its surface, ensuring consistent and highest printing quality. This maximizes the service life of the anilox roll

(4) Reduce labor time costs and reduce downtime

Laser cleaning operation is simple and convenient. Place the anilox roller in a suitable position in the equipment and click the start button until the anilox roller is cleaned. No manual intervention is required during this period. The time saved can be used to do other things or rest. And the cleaned anilox roller can be used directly. Significantly reduces labor time costs and downtime.

(5) Environmentally friendly

The whole process of laser cleaning does not involve any solvents and other media. There will be no irritating smell in the workshop, and there will be no wastewater of various colors discharged, which can ensure the cleanliness and tidiness of the workshop.

Wuhan Doya Optic & Electric Equipment Co., Ltd. is a more than 15 years professional laser equipment manufacturer with our own factory and professional R&D team. We are the only manufacturer in China that independently develops laser cleaning for anilox rollers. At present, we have exported to Europe, the United States, Mexico and other countries.

Welcome to contact us for details of laser cleaning machine for anilox rollers.