Screen Printing Technology (1)

(Screen Printing Techniques) Image copying or image transmission is a means by which people can visually record information and express thoughts and perceptions, such as painting, oil painting, photography, copying, and printing. Among them, printing is the most important in image reproduction. One form. At present, printing can be roughly divided into four basic categories: (a) relief printing; (b) gravure printing; (c) lithography; (d) screen printing. This article focuses on screen printing. Today, with the rapid development of technology, all industries are inextricably linked, and screen printing is also the same. Therefore, before learning about screen printing, understand it and other types of printing. Relations and differences are very necessary. Here we will briefly introduce the other three kinds of printing. Letterpress printing is one of the oldest printing methods. It is printed using a relief with a raised surface. During printing, the ink is applied to the surface of the pattern and then imprinted on the paper. The ink on the surface of the pattern is transferred to the surface of the paper to form a print. Handprint printing, Leno's full-line caster printing, lead printing, electro-printing and photo-engraving are all relief printing. Gravure printing is a printing method in which the printing plate forms a concave character or image by manually engraving the line or engraving it mechanically. When printing, the line or groove is first filled with ink, and the prepared paper is pressed against it. The paper sticks the ink away to form a print. Etching, acupuncture and gravure are gravure printing. Lithography is sometimes called chemical printing, meaning that the printed image is on the same plane as the printing plate. It is based on the "oil and water is not mixed" principle to achieve printing. This type of printing is performed by mechanically or manually presenting the image on a stone or metal surface, and then chemically treating the surface such that the image portion is ink-receptive and the other portions are not ink-repellent. When printing, only ink-infected parts of the image are transferred to the paper to form a print. Photographic printing, photolithography and offset printing are all lithographic printing. Modern screen printing is not only technically different from the other three types of printing, but it is the most widely used of the four printing types. It can be printed on paper, cardboard, wood products, plastics, textiles, ceramics, metals, furs, and composites of several later materials. It can be used not only for printing flat objects, but also for printing round, convex, concave and irregular shaped objects. Because of this, screen printing is an inevitable product. However, since the technical details about it are a trade secret, its development is only going on quietly. But no matter what, it is continuously progressing and developing, and it has broad prospects. In the development of image transmission, although there are no distinctly different stages of development, screen printing, as an important part of the international industry and a creative process, derives its principle from simple stencil printing. Wax paper copying is an ancient civilization and one of the oldest methods of image reproduction. But it is different from the old stenciled stencil copy, just as modern letterpress printing is different from letterpress printing from the Gutenberg era. Although the Japanese first used the loose, tension-free stencils made of silk or silk to print, the development of modern screen printing originated in the United States. From screen printing pioneers Harry Leroy Hiett and Edward A. Owens, screen printing began as early as the beginning of the 20th century (1901-1906). . The first screen-printing attempt was made by Francis Willette of Detroit, Michigan, which screen-printed on the felt pennants. Screen printing is the attachment of a stencil with an image or pattern to a screen for printing. Usually the screen is made of nylon, polyester, silk or metal mesh. When the substrate is placed directly under the screen with the stencil, the screen-printing ink or paint passes under the squeegee of the squeegee and passes through the mesh in the middle of the screen and is printed on the substrate (the squeegee has manual and Automatic two). The stencil on the screen seals a portion of the mesh aperture so that the pigment does not pass through the screen, and only the image portion can pass through, so that only the image portion is imprinted on the substrate. In other words, screen printing actually uses ink to permeate through the printing plate, which is why it is called silk screen printing rather than silk screen printing or silk printing because not only silk is used as a screen material, nylon, Polyester fibers, cotton, cotton, stainless steel, copper, brass, and bronze can all be used as mesh materials. In the field of screen printing, equipment, materials, processes, and technologies are all necessary prerequisites for a worker. This article will start with the most basic screen knowledge, so that readers have a comprehensive understanding of screen printing. Mesh Frames Frames are an integral part of the screen plate and are often made of wood to support the screen. The screen frame is a component of screen printing, with a wooden frame and an iron frame, and a combination of two materials. Although many screen versions have been made by screen-printing factories, screen-printing operators should know how to make their own frame and what type of frame is best suited to their job requirements. The type and shape of the frame are determined by the job to be printed. When making the frame, the single best material is used as much as possible, which helps to ensure and improve the quality of the printing. The most common frame is the flat screen frame, which is mainly used for printing flat substrates. Most screen printers use dried white pine or eucalyptus to make the frame. These materials have no knots and other irregularities. When buying a wooden bar, it is best to choose materials that can meet the requirements of the four sides of the frame. When making a frame with a size of 36 inches x 36 inches (81 cm x 81 cm), the mesh frame border should be 2 inches thick and 2 inches wide (5 cm x 5 cm). For larger screens, the size of the frame bars is proportionally thickened and widened. If the frame is too thin, the screen will bend and deform after being used, stored, and stretched. White pine is the most commonly used frame material, but sometimes the printer also uses mahogany, spruce, parsley and boxwood to make the frame. There are many ways to combine net frames. As long as they are carefully produced, each method can meet the requirements of screen printing. The four corners of the frame should be fastened with nails and glue or screws and glue. After the glue is over, the excess glue should be wiped off immediately with a damp cloth. The nails must be used, and the nails must be positioned in order to avoid scratching the stencil fabric. No matter which combination method is used for the frame, the four corners of the frame should be reinforced with corner plates or angle iron to ensure its durability. All the frame corners must be ground to a slightly rounded shape with sandpaper. All the frame edges must be sanded to ensure that there are no rough spots that could damage the screen. If necessary, shellac or linseed oil can be applied to the frame before stretching to increase the finish of the frame. There are four common methods for stretching the net. They are pin studs, pressure slots, automatic stretchers and commercial patented stretch netting technology. A 0.5 inch (1.2 cm) flat, flat carpet pin is used to stretch the net when the net is stretched with a pin. The warp direction of the screen cloth should be consistent with the long side of the frame, because most of the screen cloths have better pulling force in this direction and can withstand the drag and draw of the squeegee back and forth. In addition, the pattern must be aligned with the direction of dragging the squeegee to reduce the distortion of the image during printing. When the screen cloth is nailed to the net frame, the nails must first be started at the center of one side of the net frame. Each nail is about 0.75 to 1 inch and the nail is 3/8 inch (0.95 cm) from the edge of the frame. Tighten the screen cloth and nail a row of nails on one side of the frame. The first row of nails is on the outside, and it must be tightened so that the tack nails are in close contact with the wooden frame. After nailing it, nail the opposite side of the nail and notice that it must be tightened when nailing. Also, nail the other two sides of the frame. Finally, nail a nail in the position where the inner side of the frame is staggered with the outer nail to ensure that the screen cloth tightly stretches on the frame. After the screen cloth is nailed to the frame, it should be carefully cleaned with cold or warm water or soapy water. It not only removes any glue that may be present, but also helps to tension the screen. When the screen cloth dries, check if the tensioned screen is smooth. If there isn't enough tension in one place, you can use a screwdriver to carefully remove the nail from there, re-tighten the wire mesh, and then re-nail the nail. The screen cloth must be very tight, otherwise it is difficult to attach a screen printing film or a coating emulsion. Some screen printers gently grind the fibers of nylon, polyester, and other silk fabrics with fine pumice or clay to facilitate firm bonding before applying the screen cloth. But be careful not to weaken the elasticity of the screen. In addition, there are many other screen cleaning and degreasing methods in actual production. Some screen printers apply shellac at the bottom of the frame, that is, nails, to prevent ink from leaking between the screen and the frame. The gutter frame has a slot on the bottom edge of the frame that can be cut using a circular saw, or it can be dug using a special dedicated trenching tool or wood chisel. The depth of the groove should be slightly deeper than the thickness of the splint. If the splint is made of harder wood such as maple or birch, its service life is longer and it can be reused. About 3/8 inch (0.93 cm) is a good size for splints. Its shape can be a square wood strip or a round tip rod, which is suitable for being pressed into the groove. When the net is stretched, the screen is forced into the groove by the clamp. The edges of the grooves and splints should be smoothed with emery cloth to avoid scratching the screen during extrusion. Fix with about 3/4 inch (1.9 cm) of No. 4 or No. 5 flat-head wire nails. The screw holes in the clamp plate should be countersunk holes to ensure that the screw head can be tightly coupled with the clamp plate when nailing. The hole clearance is about two to four inches. When stretching the net, first press the wire into the groove and add the screw, but not too tight. Fix the splint on the opposite side of the frame to the same degree, and tighten the screen as much as possible during the fixing. However, it does not matter if it is loose at one end of the splint. Finally, it can be adjusted again. In the same way, fix the other two sides. After all the splints are fixed, tighten the screws step by step, one at a time, to achieve consistent tension at all points of the screen. Using automatic mechanical stretching is a very quick and easy method. The stapler is the same as the staple and is located approximately in the same position. If the stapler pulls in the direction parallel to the screen cloth, it will tear the screen cloth. In the actual operation, a piece of paperboard can be used to pad the screen cloth, and the stapler can hold the screen cloth and the paperboard together without pulling the screen cloth directly. This not only avoids pulling the screen, but also easily removes the stapler by pulling out the paper. The following provides a simple commercial stretching method, whether beginners or advanced screen printers can quickly get started. This method is suitable for screens of various sizes, but the frame needs to have the same grooves as the pressure grooved net frame. When the net is stretched, the screen cloth is placed on the groove, and a wire having a diameter of about 1/8 to 3/16 inch (0.31 to 0.47 centimeters) together with the screen is pressed into the groove with a tool. The rope can be reused for multiple tensions. At any time, when the screen cloth must be re-tightened, the groove can be deepened and then pressed back into the groove with the same rope. A netting system is included in the actual screen making process. The system features a separate aluminum frame with four sides that are automatically taut. The frame can stretch the screen to the desired degree of tension. And after printing, the screen can be removed, rolled up and re-installed. Regardless of the kind of stretch method used, there are various types of mesh frames that have been made available for use. However, for special product printing such as circuit printing or chemical mechanical or special screen printing machines, it is best to use patented stretch netting equipment, which helps to ensure the quality of printed products.