Steel drum screen printing technology question and answer (1)
Shanghai Xugong Coating Technology Co., Ltd. Xu Guoxing
Our steel drum industry often needs to print text or graphics on the surface of steel drums. Nowadays, the widely used method of engraving is to engrave the metal foil or polyester sheet according to the required words or patterns, and then cover the surface of the steel drum to paint. The method of stereotype painting is simple and practical, so it is widely used in our steel drum industry. However, since the surface of the metal sheet or the polyester sheet and the steel drum cannot be completely covered tightly, or the engraved pattern and the corners of the typeface are lifted up, it is easy to cause the hub to be blurred when painting. In addition, the paint mist is easy to splash when painting, and other places where printing is not required. Also, in order to avoid the falling off of the hollow, it is necessary to leave a "contact strip" in the pattern or font, which at least makes the original pattern or typeface slightly different. Moreover, when the paint is sprayed, the paint mist is flying in the space, and the influence on the environment and the operator is also not negligible. For beautiful patterns and small words, the engraving method is even more powerless. These are all defects that cannot be avoided by the stencil painting method. Therefore, screen printing with superior printing quality and construction conditions has gradually been recognized and applied by the steel drum industry.
Here, some screen printing techniques are discussed in a question and answer manner, and it is hoped that the screen printing of steel drums will be helpful.
First, what is screen printing?
Screen printing, also known as silk lacquer printing, belongs to the orifice printing category, and is a four-color printing method with lithography, embossing and gravure printing. Screen printing uses silk, nylon or metal filaments as the base of the board, and is tensioned on a wooden frame or metal frame by a stretcher or by hand. Screen printing plates are formed by hand-engraving film, photochemical plate making method or by photolithography using a photolithographic method. During printing, the ink is passed through a scraper to pass the desired surface of the formed image hole on the screen to form a desired image. This is screen printing.
Second, what is the principle of screen printing?
The principle of screen printing is to use a screen as a board base, a screen printing plate with a graphic by photolithography or a photosensitive material. Most of the current practice is to apply a photosensitive adhesive on the screen board base, and then expose the negative film with the graphic and typeface on it, and the exposed photosensitive film cannot be washed due to photochemical reaction, and the image and The part of the lettering is not sensitive due to their blocking of light, and these unsensitized films are easy to wash. ! go with. After washing, a screen printing plate was produced. The text and the part of the image become a through hole (the ink can pass through the printing) because the photosensitive film is washed away, and the other parts are closed cells (the ink cannot pass through the printing). At the time of printing, ink is placed at one end of the screen printing plate, and a certain pressure is applied to the ink on the screen printing plate by the squeegee, and the squeegee is uniformly moved toward the other end of the screen printing plate, and the ink is moved during the movement. The squeegee is squeezed from the mesh of the graphic and typeface portions onto the object surface to be printed to form a graphic identical to the designed original.
1. It has strong printing adaptability. The screen printing is not long, but it can be printed on the plane. It can also be printed on the curved surface, spherical surface and concave surface. It can be printed on the hard surface or on the flexible surface. It can be printed directly or indirectly (either screen printing on gelatin or silica gel plate and then transferred to the surface to be printed); and the printing area is not limited. Our steel drums not only have a flat surface such as a bottom and a cover, but also a circular arc surface such as a barrel body, and there is a convex curved surface such as a rib, and the printing area also needs to change from time to time. Therefore, it is most appropriate to use the screen printing method to print graphics and typefaces.
2. The ink layer is thick and has a strong three-dimensional effect. The ink layer thickness of the general graphic and typeface printed on the screen printing can be up to 30 microns; the thickness of the graphic and typeface printed by the foaming ink can be up to 300 microns; Film-printed printed circuit boards with film thicknesses up to 1 000 μm; and screen printing for color registration and screen color printing. Therefore, the graphic and typeface printed by screen printing are not only thick, but also strong in stereoscopic effect, and can be printed in multiple colors.
3, can use a variety of inks or even paint printing. Since screen printing is a type of print, it can be printed using a variety of inks as well as pastes, waterborne coatings, adhesives and even paints. Our steel drum industry is screen printed with alkyd enamel, and it is said to work quite well.
4. Compared with the slab painting on the steel drum, the superiority is obvious. First of all, because the plate base of the screen printing is soft and can be well fitted to the surface of the steel drum, as long as the board base is well done, the picture and the words will be distinct, clear and accurate. Secondly, the contact strip added in the stencil painting in order not to cause the smear to fall partially does not exist in the screen brush. Third, the screen-printed printing plate is the original photocopying, so the printed pattern or text is exactly the same as the original. Fourth, screen printing does not produce the phenomenon of color shade caused by the enamel painting, and there is no phenomenon that the paint mist splashes everywhere. Fifth, screen printing mostly uses scratching, brushing or printing, which is beneficial to the health and environmental protection of operators. Sixth, no matter how small the text and the words are, it can print the same effect as the original, which is unimaginable in the engraving method.
4. How is screen printing classified?
Screen printing is highly adaptable, not only for general paper printing, but also for graphic and typeface printing on plastic, ceramic, glass, metal, circuit boards and other objects. It can be said that it can be used in all walks of life, and the printing principle is basically the same. However, because the physical and physical properties of the printed objects need to be different, the requirements of various industries are different, so the screen printing of various industries has its own particularity. Therefore, screen printing can be divided into several categories according to the nature of the surface to be printed: paper printing, plastic printing, ceramic printing, glass printing, metal printing, circuit board printing, textile printing, etc. Our steel drum industry belongs to special metal printing). In this way, in each practical application, a relatively independent screen printing system is formed.
5. How many methods of screen printing are there?
The method of screen printing is actually only manual printing and mechanical printing. Manual printing refers to the need to print the surface of the object, remove, the plate of the persuasion, the scraper of the scraper are manually operated. Mechanical printing can be divided into semi-automatic and fully automatic. Semi-automatic mechanical printing means that the surface to be printed is manually delivered to the position, and manually removed and removed, but the movement and printing process of the printing plate is completed by mechanical; fully automatic mechanical printing It means that the delivery of the object surface to be printed is continued until the printing is removed and removed.
6. What is the main process flow of general screen printing?
The main process of screen printing consists of two parts, namely making plates and printing. The printing part is relatively intuitive and imaginable, and it is usually unfamiliar to the production of printing plates. Therefore, the process flow of making screen printing plates by photolithography using photosensitive materials is mostly introduced here.
See the figure below for details:
Manual or photo-engraving → negative film → lamination → exposure → development → drying → revision → plate
Drying → coating photosensitive glue → drying → washing the net → stretching the net → selecting the net, selecting the box.
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