Exploration Of Common Problems In Printing Press Sink Fluid

Exploring common problems of printing machine sink fluid—The concentration of the appropriate sink fluid is based on the conductivity value. When the conductivity is too high, the ink will not be easy to dry, and if the conductivity is too low, it will be easy to stain or accumulate ink. So you must try to find the appropriate conductivity value. After finding the concentration value, multiply the total tank volume by the percentage to be the first addition. In addition, when the conductivity value changes more than ±50~100, you need to make corrections before you can continue to use it. At the same time, you also need to pay attention to the temperature in the water tank, because the temperature will affect the conductivity measurement value.


Generally recommended ideal printing water conditions are:

(1) The water quality must be soft water;

(2) The conductivity value is 700~1300 (the conductivity value of water must be deducted);

(3) PH value 4.0~5.5;

(4) The temperature of the water tank is 5℃~15℃;

(5) The degree of emulsification is below 35%;

(6) The proportion of alcohol IPA is 5%~15%;

(7) The concentration ratio of the tank liquid is 1.5%~2.5%.


The following are the actual test results of the center in the printing laboratory:

Sink fluid: Magic 150　 Conductivity Meter: Delta OHM Conductivity Meter　Model: HD 8706　PH Meter: HANNA PH Meter　Model: HI 8521

According to the above example, the total amount of 80,000cc*2%=1,600cc of the water tank of the printing press in the central printing laboratory has a conductivity value of 1,000 (1,095-92.5) ± 100 and a pH value of about 5.0. In addition, we found that the pH value does not change significantly after the concentration of the tank solution is 3%, so it is not easy to detect whether the amount is appropriate, and some European tank solutions have more buffers added, and their function is to keep the tank solution stable. The acidity and reduction of the corrosion of the layout will cause problems when using the pH value to measure the concentration of the bath solution.

Printing machine process:
①Working cycle program of flat screen flat screen printing machine. Take the flat screen platform type monochrome semi-automatic hand-surface screen printing machine as an example. One of its work cycles is: feeding → positioning → setting down → lowering to the ink plate, raising back to the ink plate → scraping stroke → raising to the ink Plate → lower the ink return plate → lift the plate → ink return stroke → release positioning → receive.

②In the continuous cycle action, as long as the function can be realized, the time occupied by each action should be as short as possible to shorten the period of each working cycle and improve work efficiency.

③ Embossing line. In the printing process, the ink and the screen printing plate are squeezed to the ink plate to form a contact line between the screen printing plate and the substrate, which is called the impression line. This line is at the edge of the squeegee, and countless embossing lines form the printing surface. Realizing the ideal impression line is very difficult, because the printing stroke is a dynamic process.

How the screen printing machine works. Taking the commonly used hand-shaped screen printing machine as an example, the working principle of the screen printing machine can be described as follows: the power is transmitted through the transmission mechanism, so that the squeegee squeezes the ink and the screen printing plate in motion to make the screen The printing plate and the substrate form an impression line. Because the screen has tension N1 and N2, it generates force F2 on the squeegee. The resilience makes the screen printing plate not contact the substrate except the impression line. Under the action of the squeezing force F1 of the squeegee, the printing is leaked from the moving impression line onto the substrate through the mesh.

During the printing process, the screen printing plate and the squeegee move relative to each other, and the squeezing force F1 and the resilience F2 also move synchronously. The blot is dirty. That is, the screen is constantly deformed and rebounded during the printing process.

The squeegee is separated from the substrate together with the screen printing plate after the one-way printing is completed, and at the same time, it returns ink to complete a printing cycle. The distance between the upper surface of the substrate and the reverse side of the screen printing plate after the ink is returned is called the same page distance or screen distance, which should generally be 2 to 5 mm. In manual printing, the technique and proficiency of the operator directly affect the formation of the impression line. In practice, screen printing workers have accumulated a lot of valuable experience, which can be summarized into six points, namely, to ensure the linearity, uniform velocity, equiangularity, pressure equalization, centering and vertical edge in the movement of the squeegee. In other words, when printing, the squeegee should move in a straight line without shaking from side to side; it cannot be slow in the front and fast in the back, slow in the front and slow in the back or abruptly and quickly; the inclination angle to the ink board should remain unchanged, and special attention should be paid to overcome the inclination angle The common problem of increasing gradually; the printing pressure should be kept even and consistent; the distance between the squeegee and the inner sides of the screen frame should be equal; the ink plate should be perpendicular to the frame.

The working principle of flat screen curved screen printing machine. Flat screen curved screen printing refers to screen printing with flat screens on cylindrical or conical curved surfaces. Under certain conditions, it is also possible to screen print elliptical, drum, arc and other curved surfaces.

The dry mesh curved screen printing machine is a machine that uses a flat screen to print the above curved surface.

The working principle of the flat surface screen printing machine a-roller support b-shaft meeting support c-inlaid support. During printing, the flat screen printing plate moves with the substrate while the squeegee is stationary. The flat screen printing plate is clamped on the screen frame and moved by the flat screen curved screen printing machine to move at a constant speed. Due to the friction of the screen, the substrate placed on the supporting device rotates accordingly. The linear speed of the curved substrate at the impression line is the same as the moving speed of the flat screen printing plate to achieve scraping printing.

Theoretically, the embossing line should be at the highest busbar of the curved substrate to increase the off-screen angle and ensure the printing quality. In order to facilitate adjustment, the squeegee generally adopts a top angle of 60°±15°, and it is required to be able to adjust the verticality and the upper and lower dimensions. The adjustment to vertical is to ensure that the cutting edge line does not shift laterally during up and down adjustments, and is always aligned with the highest bus A; the squeegee with a top angle of 60°±15° is used to ensure that the squeegee inclination is formed after vertical installation α. In the actual adjustment, in order to ensure that the flat screen printing plate is separated from the curved substrate in time, the impression line can be slightly forwarded, especially when the diameter of the substrate is large, the impression line must be offset forward. The support device for curved printing is Various types of special devices are designed and manufactured by users according to product requirements.

Cylindrical container or conical container can be printed with two pairs of roller bearings, sleeve bearings for caps and cups with the ratio of length to diameter less than 1.5, and flexible hollow containers can be supported by inflatable devices. The ellipse is approximately a part of a cylindrical surface, which can be supported by a cylindrical inlay method.

The principle of printing on the surface of a cone is basically the same as that of printing on the surface of a cylinder. The difference is the graphic shape of the screen printing plate and the movement form of the screen printing plate. When making a screen printing plate for printing on the surface of a cone, first draw an expanded view of the surface of the cone, and find the center of the sector based on the expanded view, and then select an appropriate screen frame to make the screen printing plate.

On the plate efgh that can completely contain the fan-shaped abed, a printing plate that matches the fan-shaped shape is produced. Fix a right-angle rod on the efgh plate, and install it on the o-axis to form a fan-shaped plate. Then, just like printing on the surface of a cylinder, 4 rollers are used to support the substrate under the plate, and the squeegee is in a fixed shape. The frame is moved in a fan shape, and the squeegee is pressurized to print on the surface of the conical plate. During printing, the conical bearing is in line contact with the screen printing plate under a certain squeegee pressure; when the screen printing plate moves in a horizontal fan shape around the axis of the fan-shaped expansion drawing, the substrate rotates synchronously on the supporting device Movement; the ink is squeezed by the squeegee and leaks onto the surface of the substrate to complete the printing.