Some essentials to improve the technology of carton printing
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With the continuous prosperity of the commodity economy, the packaging of products has become more and more stressful. Color corrugated boxes have become more and more popular among merchants. Color cartons (including color boxes) account for more and more market share, and quality control of carton products. Also attracted the attention of the business. Improving the quality of color corrugated boxes has become one of the important management contents of the carton factory production process control. Throughout the production process of colored corrugated boxes, the main links affecting the printing quality of carton products are: production process plan, plate making, base paper quality, ink blending, equipment adjustment, operation technology, staff quality, etc. Therefore, we must pay attention to the production In each link, careful control and control can be carried out to better improve the printing quality of color carton products and meet the requirements of customers.
1. To correctly choose the printing production process plan
In the process of ordering and process arrangement, the color carton products should first consider which production process is used, which can better guarantee the printing quality of the products. The author believes that the production process of prepress plate making and printing process should be determined according to the characteristics of the original. Among them, the factors that should be considered include: the printing process, the characteristics of the original paper, the ink performance, the production process, and the type of equipment. The production process shows that the correct setting of the printing process scheme of the color carton is the key link that determines the production efficiency and the printing quality of the product, and also the source of the product quality control. Choosing the right printing process is also effective in preventing the occurrence of printing defects and reducing the reliability of printing raw and auxiliary materials. Therefore, for a color carton with a finer layout, it is conceivable to use a pre-printing process for printing. Among them, the lithographic pre-printing process is simple and fast, and can print a simple layout and print a fine screen version, which is low in cost and suitable for printing production of less than 100,000 sheets. While the flexographic printing process is relatively easy to make, the resin plate material is relatively expensive, and the dot reproduction and overprinting precision are not as good as the lithographic printing process, so it is suitable for printing general color carton, and must be produced in a relatively large batch of products to offset The cost of making a plate is high. The gravure pre-printing process is more complicated in plate making, and the plate making cost is also the highest production process. However, the printing plate has higher printing durability, and is ideal for printing thick and fine color carton paper, suitable for fixed layout. Pre-printing of long-line color carton papers with a particularly large number of productions. For products with a small production volume, simple layout and low quality requirements, a flexographic printing slotting machine can be considered to complete the direct printing of corrugated cardboard at one time. Choosing a color carton printing process plan, both from the factory situation, but also to consider the product's performance and quality requirements; not only to reduce production costs, reduce production costs, but also to consider how to better shorten the production cycle, It is an important principle to meet the urgent needs of customers.
2. Control of plate making process technology
The control of the printing process technology of the color carton is of great significance to ensure the printing production efficiency and the quality of the product. In the printing process, from the color of the ink to the clarity of the printing of the product; from the printing durability to the overprinting accuracy of the printing, it involves the technical control of the printing plate. For example, in the case of flexographic printing, when the layout has a small text version, a textured version, and a solid or large-area line version, in order to ensure the production effect of the field, line and text version, and the screen version, the printing quality and printing are improved. The printing durability of the plate can be divided into two sections in the same color layout, which is divided into two sections, which are exposed and washed separately, so that the quality of the printing plate and the printing durability can be better. Improvement. This plate making can also take advantage of the flexographic multi-color printing unit, and use two color groups to print large-area solid, line and text versions, and anilox plates, so that the solid version and the line version remain thick and bright. The ink layer is printed, and the text version and the textured surface can obtain a suitable amount of ink coating, which can effectively avoid the occurrence of paste defects. In addition, in the printing operation, it should be checked whether the printing platform is flat or not, whether there is air leakage in the vacuum pumping; the exposure time should be determined according to the layout structure and the characteristics of the plate, and if necessary, the sample printing test can be carried out; The resin version of the dot should pay attention to the control of the washing and developing time to prevent the occurrence of defects such as line deformation and dot loss caused by excessive plate washing.
3. Control of color carton printing process technology
3.1 pay attention to the control of temperature and humidity in the printing environment. Color cartons are generally overprinted with more than 4 colors, and the lateral direction of the paper is most likely to be deformed due to changes in the temperature and humidity of the environment, resulting in inaccurate overprinting. Controlling the temperature and humidity of the printing workshop has become an important part of improving the overprinting accuracy of color carton products. Therefore, the temperature and humidity of the production site must be relatively stable and balanced, whether it is a flexographic process, a lithographic or gravure production workshop. There should be no obvious disparity in the printing process, so as to avoid the disadvantages of inaccurate overprinting. The printing process practice shows that the temperature of the printing production workshop is generally controlled at about 22 °C, and the humidity should be kept at about 60%. The paper and paperboard are not prone to deformation, which is more effective for ensuring accurate overprinting of the product.
3.2 loading technology control. The use of an offset press to pre-print the carton paper, the control of the plate-making technology is very important. Since the PS plate is thin, the total thickness of the photosensitive layer and the plate base is about 0.3 mm, and the plate base of the aluminum plate has a brittle characteristic. Care should be taken during the plate loading process, and the plate should be careful to avoid the layout. It is scratched by the parts on the machine; when the plate is pulled, it is necessary to pay attention to the moderate force, to prevent the force from being too strong and the plate to be stretched and deformed, resulting in inaccurate product overprinting and printing durability. The flexographic plate should pay attention to the position of the sticking plate as soon as possible, avoiding the repeated disassembly of the plate to deform the plate and affect the fastness of the plate. When the temperature is extremely high, high-quality double-sided tape should be considered to prevent the printing plate from malfunctioning during the printing process. High-quality double-sided tape should be strong in viscosity, good in flatness, uniform in thickness and good in temperature resistance. It can ensure the stability of viscosity in high and low temperature working environment. The plate and plate cylinder do not leave residual glue when dismantling.
3.3 offset printing ink balance control. The control of ink balance is a technical link that is crucial to the offset printing process. When printing facial tissue, the control of ink balance is often not in place, and the quality of the ink is indispensable. Therefore, in the printing process, the fountain solution should be as small as possible. The supply amount is ideally printed under the condition of maintaining the balance of ink and water, and it is forbidden to use the balance method of "large ink and water" for printing. The key to ink balance control is to require ink to maintain good cleanliness and reasonable fluidity. Try to use no or less drier to prevent the skin from appearing in the early drying of the ink; the printing workshop should pay attention to dust and powder protection. Try to avoid mixing old and new inks; the pH value of dampening solution should be properly controlled, the water quality should be kept pure; the rubber roller and water roller must maintain good precision and proper hardness; the printing speed should be kept moderate and constant, these are ink Balanced technical essentials and effective guarantee conditions.
3.4 Offset printing color sequence arrangement control. The printing of color carton is generally completed by one-color printing machine at one time. When printing, the ink is overprinted and overprinted in a moment of “wet and wet”. The time of lamination between the colors is quite short, so the printing color sequence It should be reasonably determined according to many factors such as layout structure, ink characteristics and paper properties. Generally speaking, the arrangement of the printing color sequence should be mastered according to the actual situation, such as the printing area and the small amount of ink, the printing of the layout and the large amount of ink; the ink with poor transparency is printed first, and the ink with good transparency is printed. The ink with high viscosity is printed first, and the ink with small viscosity is printed afterwards; the ink with slow dryness is printed first, and the ink with fast drying speed is printed. Considering the light fastness of the ink, the light resistance of yellow and magenta is poor, and it should be considered to arrange the first print, and the light resistance of the green and black can be printed in turn. When there are differences in the surface strength, gloss, ink absorption, moisture content, and pH of the material, it is necessary to prevent the powder from falling, pulling, sticking, misregistration, and poor drying, which causes obstacles to normal printing. The order arrangement should be considered from the paper characteristics. For paper with good gloss and tightness, the dark color should be printed first, followed by the light color. On the other hand, if the texture of the paper is rough and loose, it should be printed with a light color and then printed with a dark color.
3.5 product overprinting accuracy control. When the roller bites teeth, there is foreign matter or tooth surface wear; the bite force is insufficient or the amount of teeth is not suitable; the positioning device is worn and loose, so that the work is not normal; the paper guide wheel pressure is inconsistent or the conveyor belt is tight; the thickness of the lining is not suitable or the looseness occurs. If the printing pressure is too heavy or the cardboard is improperly transferred; the cardboard is not flat or the wave deformation occurs at the edge of the paper; the amount of the fountain solution or the ink is too large, which will affect the overprint quality of the product. Therefore, in order to improve the overprinting accuracy of the product, Pay attention to the serious inspection and control from the above links, and find that the problem should be taken in time to deal with the problem.
3.6 reasonable control of printing pressure. It is of great significance to control the printing pressure to improve the printing durability of the printing plate, prevent printing quality problems such as paste, dirty and missing plates, and ensure the clarity of printing. Special lithographic and flexographic printing processes must be printed with lighter pressure as much as possible, and the flatness of the liner should be good. The local depression should be partially padded, and it should not be adjusted by the method of comprehensive blind pressure. When adjusting the pressure, it should be carried out in a light and heavy manner in the case of the normal coating amount of the ink, so as to avoid the ink being insufficient and the imprinting is unclear and the pressure is increased.
3.7 ink selection and control of the process technology. For color carton paper printing, it is necessary to use ink with good fineness and moderate dryness. Different types of ink should not be mixed and used to prevent abnormal damage of PS plate layer and avoid dirty, paste and off-plate. Such as the production of printing quality defects. For large-area spot color printing, it is advisable to use the "deep ink thin printing" process for printing, that is, to properly adjust the color of the ink to a little, so that the ink layer is thinned during printing, which can meet the requirements of printing hue and be effective. Prevent the occurrence of printing defects such as dirty, paste, and blotting.
3.8 good printing "three Qin" off. After the completion of the calibration work, although the printing pressure and the amount of ink applied have been adjusted normally, due to various variability factors in the printing process, such as changes in ambient temperature and humidity, ink thixotropic, and quality of the base paper. Unstable, unexpected equipment failures, etc., may affect the stability of printing quality. Therefore, a skilled printing operator with a certain production experience and strong sense of responsibility will perform sampling inspections during the printing process. Stir the ink in the ink fountain and observe the moisture of the plate. This is an important measure to improve the printing quality and production efficiency, and it is also a reliable guarantee to avoid printing quality failure. By making good printing "three diligence", we can better maintain the ink and wash balance of printing, and also find hidden dangers of printing quality in time, so as to take preventive and corrective measures in time, reduce the production of defective products, and improve the pass rate of printing.
3.9 printing process technology control to remove paper powder. Due to the increasingly fierce market competition, the thin profit of the carton industry has become increasingly prominent. It is an objective situation that it is difficult to use high-quality base paper for the packaging of general products. Some medium and low-grade base papers are often easy to appear in the printing process due to poor surface strength. Quality defects such as powder and lint are also easy to cause chain printing failures such as paste, dirty and off-plate, which seriously affect production efficiency and product printing quality. In order to reduce or avoid the occurrence of these problems, the excess printing color set of the multi-color printing machine can be used to overcome and compensate the quality of the original paper by first performing water and air imprinting on the base paper in the first two color groups of the machine. Poor defects, effectively reducing or eliminating the problem of print quality, such as powder, lint, and ink.
4. Correct maintenance and adjustment of the machine
Machine is an important factor in determining the level of productivity and product quality, and also the source of printing quality. Therefore, we should pay attention to strengthening the maintenance of the machine, the key parts of the machine, such as the pair of paper teeth, pull gauges, front gauges, teeth. The relevant parts of the row, roller shaft, etc. shall be properly maintained in accordance with the specifications of the equipment to prevent the wear and tear of the damaged parts and looseness, resulting in the occurrence of inaccurate overprinting. Pay attention to the frequent inspection of the machine, find problems and hidden dangers and take timely measures to deal with them. By carefully maintaining the equipment, the accuracy of the machine is maintained in good condition. In addition, the correct adjustment of the machine is also an operating technology link that improves the printing quality of the product. The production process practice shows that the thickness of the lining of the drum must be strictly controlled according to the parameters of the equipment specification, and the liner, blanket and printing plate are tightly packed. The pressure of the roller to bite the teeth should not be too small; the amount of the mouth should be kept moderate and not too small. For the use of worn teeth and dental pads, it is necessary to replace the new accessories in time; the printing speed of the whole batch of products should be consistent, and the printing speed should not be too slow or too fast. In this way, the overprinting accuracy of the product can be better ensured.
In summary, optimizing the production process technology of color carton involves all aspects of the whole process of production. Therefore, as long as we strengthen the control of production technology, scientifically and rationally formulate flexible and standardized production process plans, focusing on prepress. Design to production process control; from raw material use to equipment operation; from production process to printing operation technology; from semi-finished product production to finished product inspection, step-by-step systematic control, not only can effectively reduce various printing ills Occurs, and the productivity and product quality can be improved simultaneously.