Screen printing technology classification and process
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1 working cycle program of flat screen printing machine. Take the flat screen type flat-type monochrome semi-automatic hand surface screen printing machine as an example. Its working cycle is: feeding piece → positioning → falling plate → falling to the ink plate, rising back to the ink plate → scraping stroke → rising to ink Plate → return to the ink board → lift the plate → return ink stroke → release the positioning → receive the piece.
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 synchronization of each work cycle and improve the work efficiency.
2 embossed lines. During the printing process, the ink is pressed against the ink plate and the screen printing plate, so that the screen printing plate forms a contact line with the substrate, which is called an embossing line. This line is at the edge of the squeegee, and numerous embossed lines form the printed surface. It is very difficult to achieve an ideal embossing line because the printing stroke is a dynamic process.
3 screen printing machine works. Taking the commonly used hand-screen screen printing machine as an example, the working principle of the screen printing machine can be described as follows: the transmission mechanism transmits power, and the squeegee plate squeezes the ink and the screen printing plate during the movement to make the screen The printing plate and the substrate form an embossing line. Since the screen has the tensions N1 and N2, the force F2 is generated on the squeegee plate, and the resilience makes the screen printing plate not contact with the substrate except the embossing line. Under the action of the pressing force F1 of the squeegee, it is leaked from the moving nip to the substrate through the mesh.
During the printing process, the screen printing plate and the squeegee plate are moved relative to each other, and the squeezing force F1 and the resilience force F2 are also synchronously moved. Under the action of the resilience force, the screen is returned to the substrate in time to avoid contact with the substrate. The blot is dirty. That is, the screen is constantly in the process of deformation and rebound during the printing process.
After the squeegee is finished unidirectionally printed, it is separated from the substrate together with the screen printing plate, and at the same time, returning ink is returned, that is, a printing cycle is completed. The distance between the top of the substrate and the opposite side of the screen printing plate after ink return is called the same plate spacing or mesh distance, and should generally be 2 to 5 mm. When hand-printed, the manipulation and proficiency of the operator directly affect the formation of the embossed line. In practice, silk screen workers have accumulated a lot of valuable experience, which can be summarized into six points, namely, ensuring linearity, uniformity, equiangularity, pressure equalization, centering and vertical edge in the movement of the squeegee. That is to say, the squeegee should be straight forward when printing, and can not be shaken left and right; can not be slow before fast, fast before or after slow or slow; the angle of inclination to the ink plate should remain unchanged, pay special attention to overcome the tilt angle Increasingly common problems; the printing pressure should be kept uniform; keep the distance between the squeegee and the inside of the frame equal; the ink board is perpendicular to the frame.
2. The working principle of flat screen curved screen printing machine. Flat screen curved screen printing is a screen printing on a flat or conical surface with a flat screen. Under certain conditions, screens such as elliptical surfaces, drum surfaces, and curved surfaces can also be screen printed.
The dry mesh curved screen printing machine is a machine that prints the above curved surface using a flat screen.
The working principle of the flat net curved screen printing machine a-roller support b-shaft will support c-inlaid support. During printing, the flat screen plate moves with the substrate while the squeegee is stationary. The flat screen printing plate is clamped on the frame by a flat screen curved screen printing machine with a uniform motion, and the substrate placed on the supporting device rotates due to the friction of the screen. The line speed of the curved substrate at the embossing line coincides with the moving speed of the flat screen printing plate to realize the squeegee printing.
In theory, the embossed line should be at the highest busbar of the curved substrate to facilitate the increase of the off-grid angle and ensure the printing quality. For the convenience of adjustment, the squeegee generally adopts a 60°±15° apex angle, which is required to be adjusted for the vertical degree and the upper and lower dimensions. Adjusting to vertical is to ensure that the cutting edge line does not produce lateral displacement when adjusting up and down, always aiming at the highest one of the busbars A; the squeegee with a vertex angle of 60°±15° is to ensure the inclination of the squeegee after vertical installation. α. In the actual adjustment, in order to ensure that the flat screen printing plate and the curved surface substrate are separated in time, the embossing line can be appropriately biased a little ahead, especially when the diameter of the substrate is large, the embossing line must be biased forward, and the supporting device for the curved surface printing is Various forms of special equipment are designed and manufactured by users according to product requirements.
The curved surface of the cylindrical container or the conical container can be printed by two pairs of roller bearings, the cover of the cover type and the cup type having a length to diameter ratio of less than 1.5, and the flexible hollow container can be supported by the inflator. The elliptical surface is approximately a part of the cylindrical surface and can be supported by a cylindrical inlay.
The principle of printing on the surface of a cone is basically the same as the principle of printing on the surface of a cylinder, except for the shape of the screen printing plate and the form of movement of the screen printing plate. When making a screen printing plate for the surface printing of a cone, first draw out the developed surface of the cone surface, and determine the center of the fan shape according to the developed image, and then select the appropriate mesh frame to make the screen printing plate.
On the efgh that can completely accommodate the fan-shaped abed, a plate conforming to the fan shape is produced. Fix the right angle rod on the efgh and install it as a fan-shaped version with o as the axis. Then, like the surface printing of the cylinder, the substrate is supported by four rollers under the plate, the blade is fixed, and the frame is moved in a fan shape, and the surface of the cone plate is printed by pressing the blade. During printing, the conical printing is in line contact with the screen printing plate under a certain blade pressure; when the screen printing plate moves horizontally around the axis of the fan-shaped development view, the substrate is synchronously rotated on the supporting device. Movement; the ink is printed on the surface of the substrate after being pressed by the squeegee to complete the printing.