Overview of post press processing technology of th

Overview of carton post press processing technology

I. application and requirements of carton packaging

with the enhancement of people's awareness of environmental protection, the global carton/carton packaging industry has developed rapidly and the production capacity has increased significantly. Because the folding carton has the characteristics of low processing cost, convenient storage and transportation, suitable for various printing methods (lithography/offset printing, gravure printing, embossing/flexo printing, silk printing), easy molding processing (die cutting indentation, folding and bonding), suitable for automatic packaging (automatic completion of opening forming, packaging and sealing processes), convenient sales, display and recycling, and conducive to environmental protection, Especially after surface finishing (glazing, film coating, hot stamping, embossing), it is conducive to the publicity and promotion of goods, and improve the added value of products. It is widely used in the packaging of tobacco and alcohol, drugs, food, beverages, daily necessities, and handicrafts. In Europe, carton packaging for beverages and foods such as all kinds of fruit juice, milk, cooked food, fast food and snacks can be seen everywhere. In recent years, with the increasing demand for CD, VCD and DVD packaging in the software industry and music products industry, Swiss Pawi packaging company has launched a new carton packaging method of data PAC. This product has the characteristics of lighter weight and newer printing appearance. The surface of CD, VCD and DVD cartons can print all kinds of information required by customers without adding plastic cards or plastic packaging films. The packaging weight is reduced by 50%, and the mailing cost of products is also significantly reduced. According to the relevant data of China's tobacco Department, the proportion of hard packed cigarettes in China has reached 56%

with the rapid development of modern industry and the continuous improvement of people's living standards, people's demand for folding cartons will continue to increase, and higher requirements will be put forward for the quality of cartons. In order to avoid the waste products from the automatic folding and pasting machine and make the folding carton automatically complete the opening, forming, filling, sealing and other processes on the high-speed packaging machine, it is not only required that the structural size of the carton is designed reasonably, but also to ensure that the carton has sufficient die-cutting accuracy and folding and pasting accuracy. The increase of short version live parts, the improvement of processing quality and the reduction of production costs are also the market pressure and problems faced by carton packaging enterprises, which requires the application of new technologies in the carton packaging production process, as shown in Figure 1: technology, continuously improve the automation of equipment, reduce the adjustment time of equipment and the auxiliary preparation time of live parts. Only by constantly adapting to the new changes in the market and meeting the requirements of different users can the competitiveness of carton packaging enterprises be improved

second, carton surface finishing technology

due to the thin ink layer of offset printing, it is easy to cause insufficient ink saturation, and the overall gloss effect of printing is often poor. Use film covering or polishing technology to improve the surface gloss of printing, so as to improve the brightness of the ink layer of printing, and at the same time provide a layer of effective protection for carton packaging, so that its color can not fall off due to friction in post press processing and storage and transportation packaging. The plastic film used for coating is transparent, glossy and cheap. However, because the coated paper is difficult to recycle and regenerate, it is non degradable and easy to cause white pollution. Long term use will also endanger the health of workers. Therefore, the traditional instant coating adhesive materials will be replaced by high-quality environmental friendly new adhesives

1. Glazing

glazing can not only enhance the surface brightness, protect the printed text, but also do not affect the recycling of paper, so as to ensure that after the scientific research results come out, enterprises can save resources and protect the environment. Therefore, it is widely used in the surface finishing of carton packaging. Glazing paint mainly includes solvent glazing oil, water-based glazing oil, UV glazing oil, etc. Due to the poor effect of solvent varnish and its adverse effect on environmental protection, the scope of application is greatly limited

(1) glazing paint

① water based glazing oil takes water as the solvent, which is non-toxic and tasteless, and eliminates the harm to human body and the pollution to the environment. It has the characteristics of fast drying speed, good film transparency, stable performance, good glazing surface flatness, wide post press processing adaptability, good heat sealing performance, safe and reliable use, etc. It is increasingly valued by food, medicine, tobacco carton packaging and printing enterprises

② UV glazing relies on UV irradiation to cause chemical reaction inside the UV coating and complete the curing process. Due to the role of UV, UV glazing is instantly dry, and there is no solvent volatilization during curing, which will not cause environmental pollution. Prints with UV varnish have high surface gloss, heat resistance, wear resistance, water resistance and light resistance. However, due to the high price of UV glazing oil and high requirements for machine performance, it is currently only used for the glazing of high-end cartons

(2) glazing method

① single machine glazing: use a special glazing machine or calender to complete the carton glazing process

② online glazing: printing and glazing are completed at one time. It has the characteristics of fast speed and high efficiency, which reduces the trouble caused by the loss of printing products caused by the turnover of semi-finished products. The wetting device or inking device of the printing unit can be used for glazing, or the independent glazing unit on the printing machine can be used for online glazing. The glazing unit is used for glazing production, which has high efficiency and stable glazing quality. The glazing unit is monitored and controlled by the printer control center, such as horizontal and circumferential alignment adjustment of photosensitive resin plate, diagonal alignment adjustment, etc. The online polishing device can evenly polish the whole surface of the carton or local pictures and texts. Glazing can be done with blanket or flexo for fine local glazing; It can be used for both water-based and UV glazing. Online glazing device can be divided into roller glazing device and scraper glazing device

roller glazing: use a roller coating device to transfer the varnish to the surface of the carton. The glazing amount and pressure of the glazing unit are controlled by the printer control center. Like the glazing device of Heidelberg printing press, the glazing liquid supply mechanism can control the whole process of glazing liquid supply. The glazing liquid is pumped from the liquid storage barrel through a hose to the glazing liquid bucket by an electronic double diaphragm pump. The liquid level and the circulation of the polishing solution are monitored by the potentiometer to ensure that the polishing solution is evenly supplied. The ultrasonic monitor can monitor the polishing amount of the polishing solution at any time. The roller glazing device of gaobaoli Bida 105 offset press can be used as a two roller system for timely operation or a three roller system for reverse operation. When working in a two roll clockwise operation mode, the metering roll is disengaged, and the glazing coating amount is adjusted by the pressure between the glazing liquid bucket roll and the landing roll. The structure is simple. When working in the form of three roller reverse operation, the polishing roller and liquid bucket roller operate in the reverse direction to obtain a very bright polishing film layer: at the same time, when using high viscosity polishing liquid, it is not necessary to increase the pressure between the rollers to achieve the purpose of thin and uniform coating. This roller glazing device has the characteristics of short transmission route, few contact points, difficult drying of glazing liquid, uniform transmission of glazing liquid, simple and convenient operation, etc

scraper polishing: the closed scraper polishing system is adopted, which is composed of ceramic grain roller, closed scraper and flexible resin coating plate roller. Its main advantage is that by selecting different ceramic corrugated rollers, the coating can be completed accurately according to the required coating amount, saving glazing oil; It has the functions of quickly changing the wrinkle roll, glazing and coating plate device, and full surface coating and local glazing. It is usually composed of two scrapers and ceramic corrugated rollers for metering. The upper and lower scrapers and corrugated rollers form a closed box structure, and the polishing liquid is pumped through the pipeline. The scraper glazing device has the characteristics of uniform and constant glazing, high quality, good effect, good environmental protection, economy and easy to realize high-speed glazing. It can also adapt to the gold and silver glazing of the carton surface, and the glazing coating can achieve quite high wear resistance

2. Hot stamping

in the fierce market competition, in order to increase the added value of products and carry out packaging anti-counterfeiting more effectively, more and more packaging cartons adopt hot stamping technology. Hot stamping includes ordinary hot stamping, cold hot stamping, concave convex hot stamping and holographic hot stamping. Common hot stamping processes include flat hot stamping and round hot stamping. Because the round press hot stamping is a line contact, it has the characteristics of wide range of hot stamping substrates, suitable for large-area hot stamping, high hot stamping accuracy, and is widely used

(1) cold hot stamping: instead of using the heated metal plate, the metal foil is transferred by using the printing adhesive. Cold stamping process is a promising new process with low cost, energy saving and high production efficiency

(2) concave convex hot stamping (also known as three-dimensional hot stamping): Modern engraving technology is used to make female and male molds matching up and down. The hot stamping and concave convex pressing processes are completed at one time, which improves the production efficiency. The mold made by electric engraving can be curved surface transition, achieving the three-dimensional relief effect that is difficult to achieve by the mold made by general corrosion method. The emergence of concave convex hot stamping makes the hot stamping and embossing process complete at the same time, reducing the process and waste products caused by inaccurate overprinting

(3) holographic identification: use computer technology to change the amplitude and frequency of the grating, so that its effect is more bright and clear than the calculated pattern. If this holographic mark is used as the copy of the original, a large number of holograms will be lost, so as to achieve the purpose of anti-counterfeiting. According to the characteristics of hologram hot stamping logo, it can be divided into continuous holographic logo hot stamping and independent holographic logo hot stamping. Continuous holographic identification hot stamping is a new generation product of ordinary laser holographic hot stamping. Independent holographic logo hot stamping is to make the holographic logo on electrochemical aluminum into independent trademark patterns, and there are alignment marks next to each pattern

holographic identification can not only have very good anti-counterfeiting performance, but also include special numbers or words in the holographic identification according to customers' needs. Holographic logo hot stamping to the packaging carton, not only to the holographic logo hot stamping to the surface of the substrate, but also has a very high overprint accuracy, which is more and more widely used in high-end carton packaging

III. carton forming and processing technology

1. Die cutting plate making

(1) die cutting plate material

in addition to the multi-layer wood plywood plate commonly used in China at present, fiber plastic plate (durama) and sandwich steel plate (sandwic such as H) are also popular abroad. The fiber plastic board developed by Marbach company will not produce obvious size changes even when the temperature and relative humidity change greatly. It adopts the computer-controlled high-pressure water jet cutting process, which not only ensures the machining accuracy, but also avoids the environmental protection problems caused by the gas and smoke generated during laser cutting and slotting. The life of the die-cutting plate mainly depends on the quality of the die-cutting knife and the number of tool changes. Fiber plastic plate and sandwich steel plate not only have high accuracy, but also overcome the shortcomings of multi-layer wood plywood plate which is easily affected by humidity and temperature changes; And the number of knife changes is more than 3 times and 6 times that of multi-layer wood glued version respectively. The material of fiber plastic board is glass fiber reinforced plastic. The sandwich steel plate is made of steel plates up and down, with a synthetic plastic filler structure in the middle, and the bottom mold (backing) used with it is also made of steel plates. Its advantages are long service life and high precision. Multilayer wood plywood is prone to deformation and poor dimensional stability due to changes in ambient temperature and humidity. For example, the dimensional error of multi-layer wood plywood is ± 0.15 ~ 0.70 mm. Plastic is used as a new component material; For a single carton, the dimensional errors of fiber plastic plate and sandwich steel plate are ± 0.13MM and ± 0.i0iflm respectively, and for the whole discharge die-cutting plate, the dimensional errors are ± 0 respectively