1. Working principle of flat screen printing machine.
The working cycle program of flat screen printing machine. Taking the flat screen platform type monochrome semi-automatic hand screen printing machine as an example, its working cycle is: feeding → positioning → plate dropping → lowering to the ink plate, lifting back to the ink plate → scraping stroke → raising to the ink plate → lowering back to the ink plate → lifting the plate → ink return stroke → releasing positioning → receiving the workpiece.
In continuous loop actions, as long as the function can be achieved, the time occupied by each action should be as short as possible to shorten the synchronization of each work cycle and improve work efficiency.
Impression line. In the printing process, the ink and screen printing plate are pressed onto the ink plate, forming a contact line between the screen printing plate and the substrate, which is called the embossing line. This line is located at the edge of the ink scraper, and countless embossing lines form the printing surface. It is difficult to achieve an ideal embossing line because the printing process is a dynamic process.
Working principle of screen printing machine. Taking the commonly used hand shaped 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, causing the ink scraper plate to press the ink and screen printing plate in motion, forming an imprint line between the screen printing plate and the substrate. Due to the tension N1 and N2 of the screen, a force F2 is generated on the ink scraper plate, and the rebound force prevents the screen printing plate from contacting the substrate except for the imprint line. Under the pressure F1 of the ink scraper plate, the ink leaks from the moving imprint line to the substrate through the mesh holes.
During the printing process, the screen printing plate and the ink scraper move relative to each other, and the squeezing force F1 and the rebound force F2 also move synchronously. Under the action of the rebound force, the screen returns to its original position in a timely manner and is out of contact with the substrate to prevent the imprint from getting dirty. The screen is constantly undergoing deformation and rebound during the printing process.
After completing one-way printing, the ink scraper separates from the substrate together with the screen printing plate and performs a return ink cycle, completing one printing cycle. The distance between the top of the printed material and the back of the screen printing plate after ink return is called the same plate distance or screen distance, which should generally be 2-5mm. During manual printing, the operator's technique and proficiency directly affect the formation of the embossing line. In practice, silk screen workers have accumulated a lot of valuable experience, which can be summarized into six points: ensuring the straightness, uniformity, equiangular shape, pressure equalization, centering, and verticality of the ink scraper during movement. That is to say, during printing, the ink scraper should move in a straight line and cannot shake left or right; Cannot be slow in the front and fast in the back, fast in the front and slow in the back, or sometimes slow and sometimes fast; The inclination angle of the ink plate should remain constant, and special attention should be paid to overcoming the common problem of gradually increasing inclination angle; The printing pressure should be kept uniform and consistent; Keep the distance between the ink scraper and the inner sides of the frame equal; Keep the ink board perpendicular to the frame.

2. Working principle of flat and curved screen printing machine.
Flat screen printing on curved surfaces refers to the use of flat screens for screen printing on cylindrical or conical surfaces. Under certain conditions, it is also possible to screen print curved surfaces such as ellipses, drums, and arcs.
A dry mesh curved surface screen printing machine is a machine that uses a flat screen to print the above-mentioned curved surfaces.
Working principle of flat and curved screen printing machine: a - roller support b - axial support c - embedded support. During printing, the flat screen printing plate moves with the substrate, while the ink scraper remains stationary. The flat screen printing plate is clamped on the screen frame and moved uniformly by the flat screen curved screen printing machine. Due to the friction of the screen, the substrate placed on the support device rotates accordingly. The line speed of the curved substrate at the embossing line is consistent with the movement speed of the flat screen printing plate, achieving ink scraping printing.
In theory, the embossing line should be located at the highest generatrix of the curved substrate to increase the off grid angle and ensure printing quality. For the convenience of adjustment, the ink scraper generally adopts a top angle of 60 ° ± 15 °, and it is required to be able to adjust the verticality and upper and lower dimensions. Adjusting 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 busbar A; The use of a scraper with a top angle of 60 °± 15 ° is to ensure the formation of a scraper inclination angle α after vertical installation. In practical adjustments, in order to ensure timely detachment between the flat screen printing plate and the curved substrate, the embossing line can be slightly offset forward, especially when the substrate diameter is large. The embossing line must be offset forward, and the supporting device for curved printing is a specialized device in various forms, designed and manufactured by users according to product requirements.
The curved surface printing of cylindrical or conical containers can use two pairs of roller supports, and cover and cup types with a length to diameter ratio of less than 1.5 can use shaft sleeve supports. Soft hollow containers can be supported by inflatable devices. An ellipsoidal surface is approximately a part of a cylindrical surface and can be supported using cylindrical embedding 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, except for the shape and motion of the screen printing plate. When making a screen printing plate for printing on the surface of a cone, it is necessary to first draw a unfolded diagram of the cone surface, and then calculate the center of the sector based on the unfolded diagram, and then select an appropriate mesh frame to make the screen printing plate.
Produce a printing plate that matches the fan-shaped abed on the efgh that can fully accommodate the fan-shaped abed. Fix the right angle rod on the EFGH plate and install it as a fan-shaped rotating plate with O as the axis. Then, just like printing on the surface of a cylinder, four rollers are used to support the substrate below the plate, and the scraper is fixed. The plate frame is moved in a fan-shaped manner, and the scraper is pressurized to perform surface printing on the conical plate. During printing, the conical support 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 unfolded image, the substrate rotates synchronously on the support device; Under the pressure of the scraper, the ink leaks onto the surface of the substrate, completing the printing process.