Analyze the technical points of the whole process before printing from color screen printing

Today, screen printing begins to involve the color field. In addition to paper, color printing on special substrates such as plastic bottles and metals has become common. The main difference between the color printing and the general line text printing lies in the dot. This is not different from other printing techniques. The standard of evaluation is to see if the original can be restored. Color screen printing is not only a production process, but also a process of image transmission. Color screen printing contains many important factors, which are extremely important for the arrangement of work orders and for obtaining accurate colors.

Template analysis

Customers often provide samples for manufacturers to design solutions. He simply explains his intentions to you and most tasks are done by you. Understanding his intentions is very important, and many situations cause disputes because you do not really understand his real ideas. You also need to figure out the type of template material and determine the printing process. Sometimes customers know the type of material, but most of the time, they don't know it. You can identify it based on your own judgment. The type of material also determines the choice of printing parameters, such as the number of screens, the number of screens, prepress, and the hardness of the squeegee.

Select ink

Choosing ink is difficult and simple. You may be familiar with the suitability of ink for printing materials. Knowing which resin contains the ink is very suitable for this material, but as a printing manufacturer, you can't make ink yourself, which makes you powerless. However, the division of labor does not care much about how much you understand. You just have to choose according to the information provided by the existing ink manufacturer. The manufacturer has actually done this for you. But you have to verify the authenticity of the data. In most cases, the ink may be suitable for this material, but there are exceptions in some special circumstances, you may wish to prepare an ink for testing. Determining an ink means being half successful. This step is related to the whole process of the job. It can accurately set the ink and various technical indicators. The accumulation of experience of the company is critical, and it is also possible to avoid detours later. Now that the digital printing industry is not doing well in data development, we basically do this with experience. However, in order to achieve stable printing quality, data is a very important issue. Dataization also provides the basis for improving the quality of printing and identifying the advantages and disadvantages of printed materials. A simple analogy: Yesterday's weather was hot, and today's weather is also very hot. But on what day the weather is hotter, it can only be judged by experience. If the thermometer is used, this problem will be solved. The basis for good data is to use a large number of detection instruments, which requires a certain amount of investment. Dataization eliminates the blindness of human factors in the technological decision-making of enterprises and facilitates the adoption of new technologies and new processes. This investment is not optional.

The choice of ink must first of all have a simple understanding in theory, and the key is to test according to the existing ink type. The general company's ink mainly has the following brands. Gao's ink (COATES ink) is a famous ink brand produced by British Gao's Brothers. In the long-term production practice, it has established the authority status of solvent-based ink; France's Dolby UV ink is not unfamiliar to you as an environmentally friendly product. Although Dolby is a small company, UV ink is the leader. From the initial screen printing inks and pad printing inks to UV credit card inks and offset printing inks, Dolby has a good performance; apollo ink with its bright colors Covers all printing materials for screen printing. At present, it is widely praised for ink type and adaptability; if you want to print on metal products and glass products, please select Apollo ink first; German ink quality is always The best in the world, the leading level of printing technology has created excellent system quality, which of course includes ink resins and pigments. Today, German ink still maintains the world record of fineness and adhesion; in the special printing field You can't help but pay attention to Marabu ink from Malay Bao; "Extreme" is a product developed by Heng Fai Industrial Co., Ltd. for the development of mid-range market. Special inks, we respect quality, but more emphasis on results. The printing effect of the ink on plastic is comparable to that of European ink.

Consider the curing process

The vast majority of inks used in plastic substrates are naturally dry, depending on the type of ink used. After the solvent contained in the solvent-based ink is volatilized, the ink is dried on the substrate. However, some printing methods require the drying device to dry the ink so that the ink can be dried. In particular, printing involves metals, ceramics, and glass, and a drying device is generally required. How to configure the drying device is very important. For printing with UV inks, curing equipment and equipment must be considered. UV inks do not contain solvents and only cure under UV light. Both the drying device and the UV-curing device must be capable of drying or curing the ink at a faster speed, which on the one hand saves energy and on the other hand increases the production efficiency. We also need to consider the influence of the degree of curing on the quality of the ink layer. The degree of curing is too low. The ink ink layer will exhibit poor adhesion and the gloss will be very poor. If the curing is excessive, the ink ink layer will be brittle and it is easy to Cracked and deformed.

Printing color sequence

Color prints reproduce the rich color and gradation information of the original by four-color overlays. Theoretically, the ink must be completely transparent to ensure the true reduction of color, but the ink is composed of resin binder and pigment, the resin cannot be completely transparent, and the pigment itself also has a certain hiding power, which ultimately affects the color. Printing color sequences are based on the physical and optical properties of the ink and are as important as the printing press and the printing setup.

The printing color sequence is related to the transparency of the ink. The transparency of the ink is not high hiding power, should be printed. The yellow ink was the first to have the least transparency. It was necessary to print the yellow ink first. Now that the situation has changed, the yellow ink has little to do with printing. In theory, apart from the hue of four-color inks, the other indicators should be as close as possible, but the fact is another case. The saturation of cyan has a great influence on the printing coloration. The saturation of cyan is high and the print tends to be a cool tone. Therefore, when the saturation of cyan is high, cyan can be placed in a slightly earlier sequence. The role of black is to increase the brightness of prints and increase the contrast. If the graphic requirements for contrast are high, the black is printed last. The density of black is also influential on the printed matter. Excessive density will cover some layers, so the darker black ink can be printed on the first color sequence, and the darker black ink on the final print.

Determine the number of screens

The number of lines is the number of dots copied within a unit distance. Common line/cm. The higher the number of lines, the richer the level of reproduction. However, excessive screen lines increase the difficulty of screen printing. To determine the number of screens, we must first consider the visual environment, which is what kind of distance to observe the image. The visual distance should be the most basic criterion for determining the number of lines. The visual distance is near, and the number of screen lines can be higher, which can improve the clarity; the visual distance is far, and the number of screen lines is appropriately lower, which can reduce the printing difficulty. Sometimes customers do not understand the characteristics of screen printing, blindly require unnecessary screen lines, you should talk to him to change his mind. In fact, it is not necessary for the customer to request excessively high screens. The number of lines is too high and is often limited by the copying accuracy of the printing press and the copying range of the plate making system. You cannot be identified within the visual distance, resulting in a large number of results. The information is redundant. The range of screen printing copying is usually less than 80 meshes. The screens printed in the high-light areas with higher screen number will lose dots, and the fine levels cannot be reproduced. It is necessary to reduce the number of screens. In addition, the high number of screens will make it difficult to select screens. According to the usual selection method, the number of screen meshes should be 4 times the screen number of the printing film. Excessively high number of screen lines will cause the ink layer to be too thin, and the contrast of the graphic and text will be reduced. This will also affect the expressiveness of the image.

With the increase in the number of lines, the dot size continues to decrease until the dots cannot be printed. Screen printing does not duplicate 3% to 98% of outlets like offset printing. Strictly speaking, it can only copy 15% to 85% of outlets. Less than 15% of outlets must be lost, and outlets higher than 85% will expand. Into the ground. For a very fine-grained manuscript, scanning into the computer requires gradation correction and gradation compression to be restored. With the compressed image, highlights and dark points are easily restored at a given number of lines. Of course, over-compression of the tonal range can result in some slight loss of the image.

Determine the film output resolution

There are two kinds of processes for making films: photographic processes and photosetting processes. The edges of the film dots made by photography have a good order. However, the film obtained by the photo-composing machine does not have very good resolution and sharpness, and setting a suitable dot resolution can help improve the smoothness of the dot.

If the output resolution (dpi) is set too low, the film will appear jagged; if the resolution is too high (the number of lines does not change), the level of the printing film will be more abundant, but the number of gray levels will increase exponentially. The copying ability of screen printing is limited, which even results in screen printing being impossible. Practice has proved that screen printing is difficult to copy over 100 lines of printed matter. Of course, the development of technology is driving the progress of screen printing. This conclusion is not absolute either. The perfect combination of plate making process and printing process may affect the reproduction ability of screen printing.

Select the screen

The screen should have a consistent number of lines and balanced tension in the latitude and longitude direction, otherwise it will cause moire and overprinting. Wire mesh parameters should include screen diameter, screen mesh number and tension curve, and screen thickness. Most screen makers provide corresponding product descriptions and related parameters when providing screens. The basis for selection is the fineness of the original.

(1) Rough graphic printing Select a screen with a low screen mesh, fine graphic and hierarchical printing to select a high-mesh screen.

(2) The number of screen meshes should be matched with the number of screening lines of the printing film. Generally, four times of screen printing lines are used as screen mesh number.

(3) For UV inks, the screen mesh number should not be less than 165 mesh, considering the curing effect.

(4) Fine graphic printing and gradation printing preferentially select dyeing screens, and the resolution of dyed screens is much higher than that of white screens.

(5) Selecting the Mesh Calculator helps you to get data support and can determine the relationship between the number of static screen meshes and the number of dynamic screen meshes.

Set the press stroke

First, place the substrate, and then use the hand to hold the scraper to move on the surface of the substrate. When the position is proper, the stop can be fixed. For curved screen printers, the stroke of screen movement should be adjusted to exceed the perimeter of the plastic bottle.

Proper travel can save time, increase printing speed, and reduce the intermittent disjunction of ink, and can print clean outlets. As the length of the stroke decreases, the time for the ink to remain on the screen is reduced, so the viscosity of the ink is more stable.

Select squeegee length

The length of the scraper is generally longer than the image length of 5 ~ 10 mm, the choice of the squeegee involves two aspects of hardness and shape. The harder squeegee enables very fine graphic and gradation printing; the softer squeegee is suitable for printing substrates with very rough surfaces and the printing ink layer is also thick. Curved printing often uses a sharp scraper. Plane printing often uses a scraper with a rectangular cross section.

Select frame