Closed Scraper System Installation and Adjustment

In recent years, the application of closed squeegee systems in flexo printing has increased. To help flexo printing operators understand the closed squeegee system in depth, this article will introduce the installation, adjustment, and cleaning of closed squeegee systems. Some tips and suggestions. It must be specified here that, when performing the following operations, it is imperative that you follow the recommendations and guidelines of the supplier of the enclosed squeegee system and refer to the operating manual.

The basic features of the closed scraper system

The scraping method of the closed scraper system is shown in Figure 1. The basic features of the system mainly include the following aspects.

(1) Adopt unique chamber structure and double-layer ink-sealing design to achieve better ink transfer and save ink.
(2) Effectively controlling the large amount of solvent evaporation in the ink, improving the working environment and reducing air pollution. Since most of the area where the ink is located is sealed, only a very small portion that is in contact with the anilox roll is exposed, thereby greatly reducing the amount of solvent volatilization.
(3) The adaptability to the printing speed is good. Regardless of the printing speed, the amount of ink transferred is fixed, so the printing quality is stable.
(4) A combination scraper can be used to replace the scraper quickly and simply.

Of course, closed-type scraper systems still have some problems. For example, the contact angle of the closed scraper and the degree of freedom of the pressure are very small, the requirements for the uniformity of the scraping ink are high, and the tightness is required to be good, otherwise the ink leakage is easy to occur. In addition, the cleaning operation after the printing is troublesome, especially the ink or varnish that remains in the blind spot is more difficult to remove, but the application of the automatic cleaning device solves this problem to some extent.

Scraper and seal installation

1. Cutting scraper

There are many types of squeegee blades. Regardless of the type of squeegee used, it is necessary to first carefully inspect the squeegee blade for small burrs, small notches, or other defects, which may adversely affect the printing or glazing process. Moreover, the blade of the scraper must be clean.

Always wear protective gloves and goggles when cutting the squeegee, and use special cutting tools to ensure that the trim is straight and tidy. More importantly, it is necessary to ensure that the length of the scraper after cutting is appropriate.

2. Install a new scraper

Loosen the screw on the tool holder, wear safety glasses and gloves, carefully remove the old blade from the tool holder and ink chamber, and send it to the designated area for proper disposal.

Next, use a soft cloth, a suitable amount of special cleaning agent or hot water, and gently wipe off the dried ink or varnish remaining in the tool holder. This is done so that the new blade can be installed in the ink chamber. To prevent ink or varnish from leaking during operation.

When installing a new spatula, make sure that it is the correct length and that there are no defects, and then tighten and fix the knife holder. If the blade is bent or loosened, it will not only affect the service life of the blade, but also the seal will leak easily. Leakage at the sealing strip is often caused by excessive pressure on the anilox roller by the doctor blade. Therefore, it is important to ensure that the sealing strip and blade are properly installed.

3. Install the sealing strip

Carefully check the width of the sealing strip is appropriate, some sealing strips often have some small burrs, or have been damaged during the cutting process. Different material sealing strips have different sealing properties. Therefore, you must consult with your supplier and know which type of sealing strip should be used and why the sealing strip should be used. The accuracy of the dimensions of the sealing strip must also be ensured, even a deviation of 1/4 inch can severely affect the sealing performance. Therefore, it must be ensured that the sealing strip matches the closed-type scraper system used.

In addition, the surfaces of both ends of the anilox roller used in conjunction with the closed-type scraper system should be unengraved, that is, the surface of both ends of the net-spinning roller that contacts the sealing strip has a smooth surface, which can minimize the sealing. The strip wears out and can effectively prevent ink or varnish from leaking from the seal during transfer. The main function of the sealing strip is to block the leakage of ink or varnish. Therefore, be sure to check the seal bar and scraper position before starting printing.

Closed Scraper System Operation and Adjustment

1. Install and adjust the ink chamber

According to the instructions of the closed squeegee system manufacturer, the ink chamber is mounted on the flexographic printing press and the upper and lower blades are gently contacted with the anilox roll. In addition, check whether the contact between the upper and lower blades and the anilox roller is even and consistent. In fact, many problems that occur during the printing process are caused by incorrect ink chamber positions or incorrect installation of seals.

Place the ink chamber so that it is parallel to the centerline of the anilox roller and centered relative to both ends of the anilox roller. In this process, be sure to remove the seal and replace the scraper with two stainless steel blades of the same width. After adjusting the position of the ink chamber to the center, the blade can be replaced with an appropriately sized scraper.

Next, start the loading mechanism and, if necessary, readjust the base until the ink chamber is parallel to the anilox roller. If the doctor blade or ink chamber contacts the anilox roller, the system must be re-aligned to prevent irreversible damage.

Finally, if the closed scraper system uses a pneumatic installation method, check that the distance between the doctor blade and the anilox roller is appropriate, otherwise damage may occur when the anilox roller comes into contact with the doctor blade. In addition, if the blade is not in uniform contact with the anilox roller, serious leakage problems may occur.

2. Ink supply and idling

After the ink chamber is adjusted, start the ink pump and start injecting ink into the ink chamber. It is important to keep in mind that the speed of the ink pump cannot be too fast, otherwise it will cause over pressurization and leakage. The amount of ink or varnish pressed into the ink chamber can be as little as the amount required for the job.

Once the ink chamber is filled with ink or varnish, you can activate the idle button. If you use a metal spatula, you may emit a loud buzzing sound. Use some high-quality spatula or use a non-metallic spatula. Effectively reduce and reduce this noise.

3. Visual inspection

After the system has been running for a while, carefully check the posture of the system, the tube, and the ink pump. The operation of the system should be smooth; the pipes cannot be tangled together and cannot fall under the ink pump; the height of the return pipe cannot be lower than the surface of the ink or varnish in the bucket. In addition, check the backflow of the ink or varnish, and adjust the speed of the circulation pump if necessary.

4. Adjust blade pressure

First, reduce the pressure of the ink chamber on the anilox roller. This is the first step in adjusting the squeegee pressure. A strong “ink flow” may appear on the surface of the time-consuming anilox roller. Next, carefully increase the pressure or slowly turn the pressure regulator handle until the “ink flow” on the surface of the anilox roll disappears. At this time, the squeegee pressure reaches the optimum state, the so-called “knuckle pressure” state, not only The best operating performance, but also caused by the least wear and tear.

Closed scraper system cleaning

When using a closed scraper system, cleaning is a very important part and is the most easily overlooked part. The cleaning procedure is roughly as follows.

(1) Close the ink pump and allow the ink or varnish to flow naturally.
(2) Rinse the closed scraper system with clean water or a special cleaning solution. Note that the cleaning solution must not be used repeatedly. Otherwise, the ink and varnish can only be diluted or diluted, but it cannot be thoroughly cleaned.
(3) Remove the ink chamber and clean it off-line. This saves time and money.
(4) The anilox roll should also be thoroughly cleaned, otherwise the residual ink or varnish may be dried on its surface. Ultrasonic or high pressure automatic cleaning system can be used for cleaning, which can reduce the damage to the anilox roller. When using water-based ink or varnish, the effect of cleaning the anilox roller with hot water is also better. If the ink or varnish has dried on the surface of the anilox roll, it can be removed with a soft cloth or a special brush.