silk-screen printing

letterpress printing is one of the oldest printing methods. It is printed using a relief with a raised surface. When printing, the ink is coated on the surface of the font and then imprinted on the paper, and the ink on the surface of the font is transferred to the surface of the paper to form an imprint. Hand-typesetting printing, Leno full-line caster printing, letterpress printing, electrotype printing and photographic letterpress printing all belong to letterpress printing.

Gravure printing is a printing method in which lines are scratched off by manual or mechanical engraving, so that the printing plate forms a concave word or image. When printing, the lines or grooves are first filled with ink, and then the prepared paper is pressed on them, and the paper sticks the ink away to form an imprint. Etching, needle engraving and gravure printing all belong to gravure printing.

Lithographic printing is sometimes called chemical printing, which means that the printed image is on the same plane as the printing plate. It is based on the principle of "oil and water do not mix" to realize printing. This printing type is to present the image on the surface of stone or metal mechanically or manually, and then chemically treat the surface to make part of the image ink-loving, while other blank parts are not ink-loving. When printing, only the ink-loving image part is transferred to the paper to form an imprint. Photographic printing, photocopying lithographs and offset printing all belong to lithography.

Modern screen printing is not only technically different from the other three printing types, but also the most widely used of the four printing types. Its printing objects can be paper, cardboard, wood products, plastics, textiles, ceramics, metals, furs and synthetic materials of the latter materials. It can be used not only for printing flat objects, but also for printing circular, convex, concave and irregular objects. For this reason, screen printing is an inevitable product. However, because the technical details about it are a kind of trade secret, its development is only going on quietly. But in any case, it is constantly improving and developing, and it has broad prospects.

in the development of image transmission, although there are no obvious different stages of development, screen printing, as an important and creative process in international industry, is based on simple mimeographed wax paper copying. Waxed paper copying is an ancient civilization and the oldest image copying method. But it is different from the old mimeographed wax paper copy, just as the modern letterpress printing is different from the letterpress printing in Gutenberg era.

Although the Japanese first used tension-free templates made of hair or silk to print, the development of modern screen printing originated in the United States. Starting from the pioneers of screen printing, Harry Leroy Hiett and Edward A.Owens, screen printing began as early as the early 2th century (191-196). The first attempt of screen printing was made by Francis Willette in Detroit, Michigan, USA. It was screen printed on a woolen pennant.

screen printing is to attach a template with an image or pattern to the screen for printing. Usually the screen is made of nylon, polyester, silk or metal mesh. When the substrate is directly placed under the screen with the template, the screen printing ink or paint passes through the mesh in the middle of the screen under the extrusion of the scraper and is printed on the substrate (there are two types of scraper: manual and automatic). The stencil on the screen seals a part of the screen holes so that the pigment can not pass through the screen, but only the image part can pass through, so only the image part is imprinted on the substrate. In other words, screen printing is actually printed by ink permeating the printing plate, which is why it is called screen printing instead of silk screen printing or silk printing, because not only silk is used as screen material, but also nylon, polyester fiber, cotton fabric, cotton cloth, stainless steel, copper, brass and bronze can be used as screen material.

In the field of screen printing, equipment, materials, technology and technology are all necessary prerequisites for being a worker. This paper will start with the most basic screen knowledge, so that readers can have a comprehensive understanding of screen printing.

screen frame

the screen frame is an integral part of the screen plate, which is often made of wood and plays the role of supporting the screen. As a component of screen printing, screen frame has wooden screen frame and iron screen frame, and there is a combination of the two materials. Although many screen printing plates have been made by screen printing factory, screen printing operators should know how to make their own screen frames and what type of screen frames are most suitable for their job requirements. The type and shape of the screen frame are determined by the live parts to be printed. When making the screen frame, the single best material should be used as much as possible, which is conducive to ensuring and improving the printing quality.

the most common screen frame is flat screen frame, which is mainly used for printing flat substrates. Most screen printers use dried white pine or basswood to make screen frames. These materials have no knots and other uneven defects. When buying battens, it is best to choose materials that can meet the requirements of the four sides of the net frame. When making a mesh frame with a size of 36inch×36inch(81cm×81cm), the wood strips of the mesh frame should be 2 inches thick and 2 inches wide (5cm×5cm). For a larger screen version, the size of the wooden bars of the screen frame should be thickened and widened in proportion. If the screen frame is too thin, the screen will be bent and deformed after use, storage and template stretching. White pine is the most commonly used screen frame material, but sometimes printers also use mahogany, spruce, celery leaf hook and boxwood to make screen frames.

there are many ways to combine grid frames. As long as it is carefully made, each method can meet the requirements of screen printing. The four corners of the screen frame should be fastened together with nails and glue or screws and glue, and the excess glue should be wiped off with a wet cloth immediately after being glued. Nails must be used, and the position of the nails should be lower to avoid scratching the template fabric. No matter which combination method is used for the mesh frame, the four corners of the mesh frame should be reinforced with angle plates or angle irons to ensure its durability. All the corners of the screen frame must be ground into a slightly round shape with sandpaper, and all the edges of the screen frame should also be polished with sandpaper to ensure that there are no rough points that may damage the screen. If necessary, before stretching the net, it can be coated with shellac or linseed oil to improve the smoothness of the net frame. There are four common methods to stretch the net. They use pins, pressing grooves, automatic net stretching machine and commercial patent net stretching technology.

stretching the net

When stretching the net with a pin, use a flat carpet pin with a length of .5 inch (1.2 cm). The warp direction of screen cloth should be consistent with the long side of the screen frame, because most screen cloth has good tension in this direction and can withstand the drag of the squeegee back and forth. In addition, it is necessary to make the cloth pattern consistent with the dragging direction of the ink scraper to reduce the deformation of the image in the printing process. When nailing the screen cloth to the screen frame, firstly, nail should be started at the center of one side of the screen frame, and the distance between each nail is about .75~1 inch, and the nail is 3/8 inch (.95 cm) away from the screen frame. Tighten the screen cloth, first nail a row of nails on one side of the screen frame. First of all, the row of nails is on the outside, and it must be tightened so that the flat head nails are in close contact with the wooden frame. After nailing one side, nail the opposite side. Be careful to tighten the nail by hand. Similarly, nail the other two sides of the net frame. Finally, nail a circle of nails at the staggered position between the inner side and the outer side of the screen frame to ensure that the screen cloth is tightly stretched on the screen frame.

after the screen cloth is nailed to the screen frame, it should be carefully cleaned with cold water or cold water or water containing soap, which can not only remove any possible glue, but also help to tension the screen. When the screen cloth is dry, check whether the tight screen is smooth. If the tension is not tight enough at a certain place, you can carefully remove the nail at that place with a screwdriver, re-tighten the screen at that place, and then re-nail the nail. Screen cloth must be stretched very tightly, otherwise it will be difficult to attach screen printing film or apply emulsion. Some screen printers gently roughen the fibers of nylon, polyester and other silk fabrics with fine pumice or clay balls before coating screen cloth to facilitate firm bonding. But be careful not to weaken the elasticity of the screen. In addition, there are many other methods of screen cleaning and degreasing in actual production.

some screen printers paint the bottom of the screen frame, that is, where nails are nailed, to prevent ink from leaking between the screen and the screen frame.

the grooved mesh frame has a groove on the bottom edge of the mesh frame, which can be dug with a circular saw or a special special trenching tool or a wooden chisel. The depth of the groove should be slightly deeper than the thickness of the splint. If the plywood is made of hard wood such as maple or birch, its service life will be longer and it can be reused. About 3/8 inch (.93 cm) is a good size for plywood. Its shape can be square wood strips or round tips, and it should be suitable for pressing into the groove.

when the screen is stretched, the screen is forced into the groove by the splint. The edges of the groove and splint should be polished smoothly with emery cloth to avoid scratching the screen during extrusion. Use a 4/4 inch (1.9 cm) flat-headed or 5-gauge wooden nail for fixing. The screw holes in the splint should be countersunk holes to ensure that the screw head can be closely combined with the splint when nailing. The hole clearance is about two to four inches.

when stretching the screen, first press one side of the screen into the slot, and add screws, but not too tightly. Fix the splint on the opposite frame to the same extent, and tighten the screen as much as possible when fixing, but it doesn't matter if it is loose at one end of the splint, and it can be adjusted at last. Fix the other two sides in the same way. When all the clamping plates are fixed, tighten the screws step by step in sequence, a little at a time, so as to achieve uniform tension at all points of the screen.

it is a very quick and simple method to stretch the net with automatic machinery. Stapler should be in the same way as nailing, and located at about the same position. If the stapler pulls in the direction parallel to the screen cloth, it will tear the screen cloth. In practical work, a piece of cardboard can be used to pad the screen cloth, and the stapler can clamp the screen cloth and pull it together with the cardboard without pulling the screen cloth directly. This can not only avoid tearing the screen, but also easily remove the stapler by pulling out the cardboard.

The following provides a simple method of commercial screen stretching, which can be quickly used by both beginners and advanced screen printers. This method is suitable for screens of various sizes, but the screen frame should have the same groove as the screen frame stretched by the pressure groove. When stretching the net, put the screen cloth on the groove, and press a rope with a diameter of about 1/8~3/16 inches (.31~.47 cm) together with the screen into the groove with a tool. The rope can be used repeatedly for multiple tightening. At any time, when the screen cloth must be tightened again, the groove can be dug deeper, and then the screen can be pressed into the groove again with the same rope.

In the actual screen making process, there is a screen stretching system. The system is characterized by an independent aluminum frame with four sides automatically tightened. The screen frame can tighten the screen to the required tension. And after printing, the screen can be removed, rolled up and reloaded for use.

no matter which method is used to stretch the net, there are all kinds of already made net frames for use. However, in order to be used for special product printing, such as circuit printing or chemical machinery or special screen printing machine, it is best to use patented screen stretching equipment, which is conducive to ensuring the quality of printed products.