What is the principle of printing machine?
1, working principle of screen printing machine
Taking the commonly used hand-shaped screen plane screen printing machine as an example, the working principle of the screen printing machine can be described as follows: the power is transmitted by the transmission mechanism, so that the ink scraping plate squeezes the ink and the screen printing plate in motion, so that the screen printing plate and the substrate form an impression line; due to the tension of the screen N 1 and N2, the force F2 is generated on the ink scraping plate, and the resilience makes the screen printing plate not contact with the substrate except the impression line, and the ink is scraping.
During the printing process, the screen printing plate moves relative to the squeegee, and the extrusion force F 1 and the resilience F2 also move synchronously. Under the resilience, the screen returns to be out of contact with the substrate in time, so as to avoid rubbing the imprint. That is, the screen is constantly in deformation and springback during the printing stroke.
After one-way printing, the ink scraping plate is separated from the substrate together with the screen printing plate, and at the same time, the ink is returned back, that is, a printing cycle is completed. The distance between the top of the substrate and the back of the screen printing plate after ink return is called the same plate spacing or screen spacing, which should generally be 2 ~ 5 mm. When printing by hand, the skill and proficiency of the operators directly affect the formation of the nip. In practice, silk screen printing workers have accumulated a lot of valuable experience, which can be summarized as six points, that is, to ensure linearity, uniform speed, equiangular, uniform pressure, centering and vertical edge in the movement of ink scraper. In other words, when printing, the squeegee should go straight ahead and not shake left and right; Can't be slow before, fast before, slow after, or slow and fast; The inclination angle to the ink board should remain unchanged, and special attention should be paid to overcoming the common problem that the inclination angle gradually increases; The printing pressure should be uniform; Keep the distance between the ink scraper and both sides of the inner side of the screen frame equal; Keep the ink board perpendicular to the border.
2. Working principle of flat screen curved screen printing machine
Screen printing of flat screen curved surface refers to screen printing with flat screen on cylindrical or conical curved surface. Under certain conditions, it is also possible to screen print curved surfaces such as elliptical surface, drum surface and cambered surface. Dry screen curved surface screen printing machine is a machine that uses flat screen to print the above curved surface.
Working principle of screen printing machine with plane curved surface: A-roller bearing B-shaft bearing C-mosaic bearing. When printing, the flat screen printing plate moves with the substrate, while the ink scraping plate is stationary. The flat screen printing plate is clamped on the screen frame and moved uniformly by the flat screen curved screen printing machine. Because of the friction of the screen plate, the substrate placed on the supporting device rotates accordingly. The linear speed of the curved substrate at the nip is consistent with the moving speed of the flat screen printing plate, thus realizing ink scraping printing.
Theoretically, the nip 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 the convenience of adjustment, the top angle of the ink scraper is generally 6015, which requires the adjustment of the vertical degree and the upper and lower dimensions. Adjusting to vertical is to ensure that the cutting edge line does not shift laterally when adjusting up and down, and always aims at the highest bus A; The scraper with the top angle of 6015 is used to ensure that the inclination angle α of the scraper is formed after vertical installation. In the actual adjustment, in order to ensure that the flat screen printing plate is separated from the curved substrate in time, the nip can be slightly forward, especially when the diameter of the substrate is large. The supporting device for curved printing is a special device of various forms, which is designed and manufactured by users according to product requirements.
Two pairs of roller bearings can be used for curved surface printing of cylindrical containers or conical containers, shaft sleeve bearings can be used for covers and cups with the ratio of length to diameter less than1.5, and soft hollow containers can be supported by inflatable devices. Elliptical surface is approximately a part of cylindrical surface, which can be supported by cylinder 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, but the difference is the graphic shape of the screen printing plate and the motion form of the screen printing plate. When making a screen printing plate for cone surface printing, it is necessary to draw the development diagram of the cone surface first, and calculate the center of the sector according to the development diagram, and then select an appropriate screen frame to make a screen printing plate.
On the version efgh that can completely accommodate the fan-shaped abed, a printing plate consistent with the fan-shaped one is made. A right-angle rod is fixed on the efgh plate, and the plate can rotate in a fan shape with O as the axis. Then, like the surface printing of cylinder, the substrate is supported by four rollers below the plate, and the scraper is fixed. The plate frame is moved in a fan shape, and the surface printing of conical plate can be carried out by pressing the scraper. 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 shape around the axis of the fan-shaped development diagram, the substrate rotates synchronously on the supporting device; Under the pressure of the scraper, the ink leaks onto the surface of the substrate to complete printing.
3, the process of printing machine:
(1) Working Cycle Program of Flat Screen Printing Machine. Take the flat screen platform monochrome semi-automatic hand screen printing machine as an example, its working cycle is: feeding → positioning → dropping → lowering the ink plate, raising the ink return plate → scraping stroke → raising the ink plate → lowering the ink return plate → lifting the plate → returning stroke → releasing the positioning → receiving.
In the continuous loop action, as long as the function can be realized, the time occupied by each action should be as short as possible, so as to shorten each work cycle and improve work efficiency.
(2) the embossing line. In the printing process, the ink and screen printing plate are pressed to the ink plate, so that the screen printing plate and the substrate form a contact line, which is called the nip. This line is at the edge of the ink scraper, and countless impression lines form the printing surface. It is difficult to realize the ideal nip because the printing stroke is a dynamic process.
Detailed explanation of printing machine classification
1, classified by printing plate form
It can be divided into relief printing machines, lithographic printing machines, gravure printing machines and stencil printing machines. The mounting plate and stamping structure are divided into flat-pressing, round-pressing and round-pressing printing machines.
(1) relief printing machine
Reliefprintingpress. A machine that uses relief to complete the printing process. Such as famous machine (resin version), type printing, zinc letterpress, set of numbered words, etc.
(2) Lithographic printing machine
Lithographic printing machine: planographicpress. A machine that uses lithography to complete the printing process. Such as multi-color machine, four-color machine, two-color machine, single-color machine, fast printing machine and so on.
(3) Gravure printing machine
Intaglioprintingpress. A machine that uses intaglio to complete the printing process. Such as glass bag printing of instant noodles and aluminum foil bag packaging of biscuits.
(4) Screen printing machine
Screen printing machine: screen-processprintingpress is a machine that uses screen plates to complete the printing process. Stencil printing: such as screen printing, circuit board printing, the cloth flower printing, can printing, stencil printing, local glazing, etc.
2, according to the printing paper classification
(1) Sheet-fed Printing Machine
Sheet-fedprintingpress: Sheet-fed printing press uses sheet-fed printing press.
(2) Web printing machine
Web printing machine: roll-fedprintingpress using web.
3. Classification by printing method
(1) flattening press
Flat press: platenpress plate support and impression body are both flat presses.
(2) Circular flattening printing machine
Circular flattening press (platform press): flat-bedcylinderpress printing plate support is flat, while the impression body is cylindrical.
(3) Stop the rotary printing machine
Stop rotary printing machine: stop-cylinderpress printing plate cooperates with reciprocating motion. When moving forward, impression cylinder rotates once, and when returning, impression cylinder stops rotating to complete a printing process.
(4) a rotary printing machine
Rotary printing machine: a printing machine that completes a printing process with one impression cylinder revolution every time the single-revolutionprintingpress printing plate table reciprocates.
(5) Two rotary printing machines
Two-rotary printing machine: a printing machine that completes a printing process every time the two-revolutionprintingpress plate table reciprocates.
(6) Reciprocating rotary printing machine
Reciprocating rotary press: reversibleprintingpress A printing press that completes a printing process every time impression cylinder rotates back and forth.
(7) Rotary press
Rotaryprintingpress: Rotary printing press, the printing plate support and transfer body are all cylindrical, and the printing process is completely rotated.
4, according to the printing ink color classification
(1) monochrome printer
Single-color printing press: a printing machine that prints an ink color on one side of a paper during printing.
(2) Two-color printing machine
Two-color printing press: a printing machine that prints two ink colors on one side of paper during printing.
(3) Multicolor printing machine
Multi-color printing press: a printing machine that prints more than two ink colors on one side of a paper during printing.
(4) Double-sided monochrome printing machine
Double-sided monochrome printer: perfectingpress A printing machine that prints on both sides of paper during printing.
(5) Double-sided multicolor printing machine