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Working principle of printing machine

Update time : 2020-06-30

Source : Zhejiang Deguang Machinery Co.,Ltd

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Working principle of printing machine

  1. Working principle of screen printing machine

  Taking the commonly used hand-shaped screen flat 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 embossing line. Due to the tension N1 and N2 of the screen, the force F2 is exerted on the squeegee. 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, it passes through the mesh hole and leaks from the moving impression line to the substrate.

  During the printing process, the screen printing plate and the squeegee move relative to each other, and the squeezing force F1 and the rebound force F2 also move synchronously with it. Under the action of the rebound force, the screen returns to the substrate in time to avoid contact with the substrate. The imprint is dirty. That is, the screen is constantly deforming and rebounding during the printing process.

  After the one-way printing is completed, the squeegee will be separated from the substrate together with the screen printing plate, and the return ink will be returned at the same time, that is, a printing cycle is completed. The distance between the upper surface of the substrate and the reverse of the screen printing plate after ink recirculation is called the same plate distance or screen distance, and 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, that is, to ensure the linearity, uniformity, equiangularity, pressure equalization, centering and verticality of the squeegee movement. That is to say, the squeegee should be straight forward during printing, and can not be shaken from side to side; can not move forward and backward, fast forward or backward, or slowly and suddenly; the inclination angle to the ink plate should remain unchanged, especially pay attention to overcome the inclination angle Common problems that are gradually increasing; the printing pressure should be kept uniform; 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.

  2. Working principle of flat screen curved screen printing machine

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

  Working principle of flat and curved screen printing machine: a-roller support b-axis meeting support c-inlay support. During printing, the flat screen printing plate and the substrate move 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 uniform speed. Due to the friction of the screen, the printing material placed on the supporting device rotates accordingly. The linear speed of the curved substrate at the imprinting line is consistent with the moving speed of the flat screen printing plate to realize ink scraping printing.

  Theoretically, the embossing line should be at the highest bus of the curved substrate, so as to increase the off-screen angle and ensure the printing quality. For easy adjustment, the squeegee generally adopts a 60°±15° vertex angle, which requires adjustment of vertical degree and up and down dimensions. The adjustment to vertical is to ensure that the blade line does not shift laterally when adjusting up and down, and is always aligned with the highest bus A; the scraper blade with an apex angle of 60°±15° is used to ensure that the wiper blade angle is formed after vertical installation α. In the actual adjustment, in order to ensure that the flat screen printing plate and the curved substrate are separated in time, the impression line can be slightly shifted forward, especially when the diameter of the substrate is large, the impression line must be shifted forward. The support device for the curved surface printing is Various forms of special devices are designed and manufactured by users according to product requirements.

  For curved printing of cylindrical or conical containers, two pairs of roller supports can be used. For the covers and cups with a length to diameter ratio of less than 1.5, bushing supports are used. Soft hollow containers can be supported by inflatable devices. The elliptical surface is approximately a part of the cylindrical surface and can be supported by cylindrical inlays.

  The principle of printing on the surface of the cone is basically the same as the principle of printing on the surface of the 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, find the center of the fan according to the expanded view, and then select an appropriate screen frame to make the screen printing plate.

  On the efgh, which can completely contain the fan-shaped abed, a printing plate matching the fan-shape is made. Fix the right-angle rod on the version efgh, and install it as a fan-shaped version with o as the axis. Then, as with the surface printing of the cylinder, four rollers are used to support the substrate under the plate. The blade is fixed, and the plate frame is moved in a fan shape. The pressure of the blade can be printed on the surface of the cone plate. When printing, the conical bearing printing is in line contact with the screen printing plate under a certain scraper pressure; when the screen printing plate moves horizontally in a fan-shaped manner around the axis of the fan-shaped development, the substrate rotates synchronously on the support device Movement; under the pressure of the squeegee, the ink is missed to the surface of the substrate to complete the printing.

  3. The flow of the printing machine:

  (1) Working cycle program of flat screen flat screen printing machine. Take the flat screen semi-automatic screen printing machine with flat screen as an example, one of its working cycles is: feeding→positioning→set off→down to ink plate, back to ink plate→scraping stroke→up to ink Board → lower back to the ink board → lift the plate → back to the ink stroke → release the positioning → receiving.

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

  (2) Embossing line. In the printing process, the ink plate and the screen printing plate are squeezed to form a line of contact between the screen printing plate and the substrate, called the embossing line. This line is at the blade edge of the squeegee, and countless embossed lines form the printing surface. It is very difficult to achieve the ideal embossing line because the printing stroke is a dynamic process.