How the printing press works

How the printing press works:

1. Working principle of screen printing machine

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, and the squeegee squeezes the ink and the screen printing plate during the movement, so that the screen printing The printing plate and the substrate form an embossing line. Since the screen has tensions N1 and N2, a force F2 is generated on the squeegee, and the rebound force makes the screen printing plate not in contact with the substrate except the embossing line. Under the action of the squeezing force F1 of the squeegee, through the mesh, the printing is missed from the moving embossing line to the substrate.

During the printing process, the screen printing plate and the squeegee move relative to each other, and the extrusion force F1 and the rebound force F2 also move synchronously. Dirty blots. That is, the screen is constantly deformed and rebounded during the printing stroke.

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, the ink is returned to the back, that is, a printing cycle is completed. The distance between the top of the substrate and the reverse side of the screen printing plate after returning to ink is called the same plate distance or screen distance, which should generally be 2 to 5 mm. In manual printing, the operator's technique and proficiency directly affect the formation of the embossing line. In practice, screen printing workers have accumulated a lot of valuable experience, which can be summarized into six points, that is, to ensure the linearity, uniformity, isometric, pressure equalization, centering and verticality in the movement of the squeegee. That is to say, the squeegee should move in a straight line during printing, and should not shake left and right; it should not be slow forward and fast back, fast forward and then slow or suddenly slow and fast; the inclination angle to the ink plate should remain unchanged, and special attention should be paid to overcoming the inclination angle. The common problem of gradually increasing; the printing pressure should be kept uniform; the distance between the squeegee and the inner side of the screen frame should be equal; the ink plate and the frame should be kept perpendicular.

2. Working principle of flat screen and curved screen printing machine

Flat screen curved screen printing refers to screen printing with a flat screen on a cylindrical or conical curved surface. Under certain conditions, screen printing can also be performed on curved surfaces such as elliptical surfaces, drum-shaped surfaces, and curved surfaces. The dry screen curved screen printing machine is a machine that uses a flat screen to print the above curved surface.

3. The process of the printing machine:

(1) The working cycle program of the flat screen printing machine. Taking the flat screen platform type monochrome semi-automatic hand screen printing machine as an example, one of its working cycles is: feeding the piece → positioning → setting off → lowering to the ink plate, rising back to the ink plate → scraping stroke → rising to the ink plate Plate → lower back to ink plate → lift plate → ink return stroke → release positioning → pick up.

In 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 cycle of each work cycle and improve the work efficiency.

(2) Embossing line. During the printing process, the ink and the screen printing plate are squeezed to the ink plate, so that the screen printing plate and the substrate form a contact line, which is called the embossing line. This line is at the edge of the squeegee, and countless embossed lines form the printing surface. Achieving an ideal nip line is difficult because the printing stroke is a dynamic process.