1. Printing methods are mainly (lithography/offset printing, gravure printing, relief/flexo printing, screen printing), easy-to-form processing (die-cutting indentation, folding and bonding), suitable for automatic packaging (automatic completion of opening-forming and sealing processes), easy to sell, display and recycle, and conducive to environmental protection, especially through tables. After finishing (polishing, film coating, hot stamping and embossing), it is conducive to the publicity and promotion of commodities and the increase of added value of products. It is widely used in the packaging of tobacco, alcohol, medicine, food, beverage, daily department stores and handicraft products.
2. Paper Packaging Surface Finishing Technology
Because the ink layer of offset prints is thin and easy to cause insufficient ink saturation, the overall gloss effect of the prints is often poor. Coating or polishing process is used to improve the surface gloss of the prints, thus improving the brightness of the ink layer of the prints. At the same time, it provides an effective protection for Paper Packaging packaging, so that its color can be processed after printing. And in the storage and transportation packaging, it will not fall off due to friction. The plastic film used for coating is transparent, glossy and cheap. However, it is difficult to recycle and regenerate the coated paper, which is non-degradable and easy to cause white pollution. Long-term use will also endanger the health of workers. Therefore, the traditional coating adhesives will be replaced by high-quality environmentally friendly new adhesives.
The polishing not only enhances the surface brightness and protects printed pictures and texts, but also does not affect the recycling and reuse of paper. It can save resources and protect the environment. Therefore, it is widely used in surface finishing of Paper Packaging packaging. The polishing coatings mainly include solvent polishing oil, water-borne polishing oil, UV polishing oil and so on. Solvent polishing oil has poor effect and is not conducive to environmental protection, so its application scope is greatly limited.
Water-based polishing oil is non-toxic and tasteless with water as solvent, eliminating harm to human body and environmental pollution. It has the characteristics of fast drying speed, good transparency of film layer, stable performance, good smoothness of polishing surface, wide post-press processing adaptability, good heat sealing performance and safe and reliable use. It has been paid more and more attention by the packaging and printing enterprises of food, medicine and tobacco Paper Packagings.
(2)UV polishing relies on the irradiation of ultraviolet light, which causes the chemical reaction inside the uV coating and completes the curing process. Because of the effect of ultraviolet radiation, UV shining dries instantaneously, and solvents do not volatilize during curing, which will not cause environmental pollution. Prints with UV polishing have high surface gloss, heat resistance, wear resistance, water resistance and light resistance. However, due to the high price of UV polishing oil and the high requirement for machine performance, it is only used for the polishing of high-grade Paper Packagings.
Single machine polishing: Paper Packaging polishing process is completed by using special polishing machine or calender.
On-line polishing: printing and polishing 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 due to the turnover of semi-finished products. The wetting device or ink feeding device of the printing machine can be used for polishing, and the independent polishing unit on the printing machine can also be used for online polishing. The polishing unit is monitored and controlled by the printing press control center, such as transverse and circumferential alignment adjustment of photosensitive resin plate, diagonal alignment adjustment, etc. The on-line polishing device can uniformly polish the whole surface or part of the Paper Packaging. The polishing can be carried out either by rubber cloth or by flexible plate for fine local polishing, water-based polishing or UV polishing. Online polishing device can be divided into roller polishing device and scraper polishing device.
Roller polishing: Roller coating device is used to transfer polish oil to the surface of Paper Packagings. The polishing quantity and pressure of the polishing unit are controlled by the control center of the printing press. For example, the polishing liquid supply mechanism of the polishing device of Heidelberg Printing Machine can control the whole process of polishing liquid supply. The polishing liquid is pumped from the storage tank through a hose to the polishing liquid bucket by an electronic double diaphragm pump. The height of liquid surface and the circulation of polishing liquid are monitored by potentiometer to ensure the uniform supply of polishing liquid. The ultrasonic monitor can monitor the polishing liquid at any time. The roll polishing device of Gaobaoli Bida 105 offset press has two roll polishing systems which can run in time and three roll polishing systems which can run in reverse. The metering roll is detached when the two rollers work in a clockwise manner. The amount of polishing coating is adjusted by the pressure between the polishing liquid bucket roll and the polishing liquid roll. The structure is simple. When working in the form of three-roll reverse operation, the polishing drum and bucket rollers can be reversed to obtain a good brightness of the polishing film. 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. The roller polishing device has the advantages of short transmission route, few contact points, hard to dry, uniform transmission of polishing liquid, simple and convenient operation, etc.
Scraper polishing: A closed ink scraper polishing system consisting of a ceramic mesh roller, a closed ink scraper and a flexible resin coated plate roller is adopted. Its main advantage is to select different ceramic mesh rollers to finish coating accurately according to the required amount of coating and save polishing oil. It has the functions of rapid replacement of mesh rollers, polishing plate device, whole surface coating and partial polishing. Usually, it consists of two scrapers and ceramic mesh rollers, the upper and lower scrapers and the mesh rollers form a closed box structure, and the polishing liquid is pumped through the pipeline. The scraper polishing device has the characteristics of uniform and constant polishing, high quality, good effect, good environmental protection, economy and easy to achieve high-speed polishing. It can also adapt to the gold and silver polishing on the surface of Paper Packagings, and the polishing coating can achieve fairly high wear resistance.
In the fierce market competition, in order to increase the added value of products and more effectively carry out anti-counterfeiting packaging, more and more packaging Paper Packagings adopt hot stamping technology. There are common hot stamping, cold hot stamping, concave-convex hot stamping and holographic hot stamping. The common hot stamping processes are flat stamping and round stamping. Because of the line contact of flat stamping, it has a wide range of hot stamping substrates, suitable for large area hot stamping, high precision, and is widely used.
Cold stamping: instead of using a heated metal plate, the metal foil is transferred by printing binder. Cold stamping process is a new process with a bright future because of its low cost, energy saving and high production efficiency.
Concave and convex hot stamping (also known as three-dimensional hot stamping): the use of modern sculpture technology to produce up and down with the cathode and cathode die, hot stamping and concave and convex pressing process completed at one time, improve production efficiency. The mold made by electric carving can transit curved surface to achieve the three-dimensional relief effect which is difficult to achieve by common corrosion method. The emergence of concave and convex stamping makes the process of concave and convex stamping complete at the same time, and reduces the process and waste products caused by improper overprinting.
Holographic marking: Computer technology is used to change the amplitude and frequency of grating, so that its effect is brighter and clearer than the calculated pattern. If the holographic mark is used as a copy of the original, a large number of holographic losses will be generated, thus achieving the purpose of anti-counterfeiting. According to the characteristics of hologram stamping mark, it can be divided into continuous hologram stamping and independent hologram stamping. Continuous holographic marking stamping is a replacement product of laser holographic stamping. Independent holographic label stamping is to make the holographic label on aluminium electrolyte into individual trademark patterns, and there are corresponding labels beside each pattern.
Holographic identification can not only have a very good anti-counterfeiting performance, but also according to the needs of customers to achieve a special number or text in the holographic identification. Holographic label stamping on packaging Paper Packagings not only needs to stamp holographic label on the surface of the substrate, but also has a high overprint accuracy. It is more and more widely used in high-end Paper Packaging packaging.
3. Forming and Processing Technology of Paper Packaging
Die-cutting plate making
In addition to MULTIPLEX, which is commonly used in China, the computer-controlled high-pressure water jet cutting technology not only ensures the processing accuracy, but also avoids the environmental problems caused by gas and smoke during laser cutting slotting. The life of die-cutting plate mainly depends on the quality of die-cutting tool 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-ply wood plywood which is vulnerable to humidity and temperature changes, and the number of tool changes is three times and more than six times as many as multi-ply wood plywood. Fiber reinforced plastic is the material of fiberglass reinforced plastic. The sandwich steel plate is made of steel plate on top and bottom, and the composite plastic filler is used in the middle. The bottom die (backing) matched with the sandwich steel plate is also made of steel plate. Its advantages are long life and high accuracy. Multilayer wood plywood is vulnerable to environmental temperature and humidity changes, resulting in deformation and poor dimensional stability. For multi-layer wood plywood, the dimension error is (+0.15-0.70 mm); for single Paper Packaging, the dimension error of fibre plastic plate and sandwich steel plate is (+0.13 mm) and (+0.i0 iflm), respectively, for the whole layout die, the dimension error is (+0.30 mm) and (+0.20 mm). In foreign countries, besides high pressure water jet grooving for fibre plastic plate, multi-layer wood plywood plate and sandwich steel plate are usually made by laser cutting method.
Paper Packaging structure and die cutting layout
The popular Paper Packaging structure CAD software in the international market should not only have the basic functions of common interactive graphics software (high quality, fast completion of graphics generation, editing, modification, dimensioning, etc.), but also meet the special requirements of Paper Packaging design, conveniently call Paper Packaging graphics library and select satisfactory Paper Packaging structure. After inputting the box size (length, width, height) and cardboard thickness, it can display or print the structure drawing of the box immediately, automatically arrange the material, and output the cutting layout drawing of the box die, the printing outline drawing and the processing drawing of the backing (bottom die). When the user designs or calls the required Paper Packaging structure drawing, as long as the size and clearance of the layout board are input, different layout schemes can be arranged and compared, and the optimized layout drawing and related parameters (such as the number of layout, the utilization ratio of cardboard, etc.) can be displayed. Reasonable layout not only saves cardboard material, but also reduces unnecessary repeated die cutting, shortens processing time and prolongs die cutting tool life.
Besides choosing standard box type and changing Paper Packaging shape, it can also arbitrarily design special box type, rotary Paper Packaging stereogram and display the opening and closing process of Paper Packaging. For different cutting edges, indentation lines, slotting and breaking lines, the corresponding line types should be selected to control Paper Packaging sample, die cutting plate, bottom die (backing) plate and die cutting knife. The production of the tool improves the processing accuracy of die cutting plate and backing plate and the manufacturing accuracy of Paper Packaging.
Laser Cutting System for Die Cutting Plate
The laser cutting system of die-cutting plate is composed of laser cutting head, computer aided design (cAD) software, computer numerical control device (CNC), worktable and so on. Laser processing head is composed of focusing lens, gas nozzle, height sensor, etc. Driven by servo motor, height sensor controls the spatial position of focus. The graphics are cut by the relative motion of the worktable and the laser beam. When cutting, the procedure of retaining bridge, bridging and cutting edge frame should be compiled according to the technological requirement, and the optimum path of laser cutting for die cutting plate should be determined. Computer numerical control device (CNC) adopts programmable logic control technology controlled by microprocessor. After the CNC software generated by CAD is fed into CNC, laser cutting of plywood can be controlled, including fault detection, servo drive and positioning, auxiliary gas pressure control and so on. The expert system can automatically select the best process parameters (power, speed, pressure, etc.) according to the type, performance, thickness and processing requirements of sheet metal. The application of laser cutting die plate not only has the advantages of high speed, high precision and good repeatability, but also has the advantages of cutting multi-plate and duplicating die plate.
Die Cutting Tool Forming System
In order to ensure the manufacturing accuracy of die-cutting plate, the length of cutting tool and indentation tool and the size of bridge gap are calculated automatically by CAD software, and transmitted to the computer-controlled tool forming machine for slotting, cutting angle, bending and cutting. Because of the use of hydraulic cutter, liquid crystal display, hydraulic transmission and vernier positioning, the accuracy of tool forming is effectively guaranteed.
Base Die (Backing) CAM System
The width of indentation groove, cutting depth and precision should meet the requirement, and the engraving speed and depth should be adjustable. The application of CAM technology can not only shorten the manufacturing cycle, but also improve the manufacturing accuracy of Paper Packagings.
In order to verify the rationality of Paper Packaging structure design, a certain number of Paper Packaging samples were trial-produced using multi-functional Paper Packaging sample CAM equipment before the formal mass production. After consulting users and consumers, the Paper Packaging samples were modified or redesigned to avoid mass production.
The unreasonable design and manufacture of the back Paper Packaging structure can also check whether the design meets the user's requirements. Multifunctional Paper Packaging sample CAM system is equipped with combined cutter and press cutter. When the control part receives the execution instructions, the executing part automatically chooses indentation and cutting tools according to its cardboard type, and draws, indentates and cuts automatically according to the structure data and program of computer aided design, and realizes automatic tool change.
Die Cutting Technology
Flat die cutting
The flat die cutting of sheet paper relies on the mechanical positioning of front gauge and side gauge, while the flat die cutting of online sheet paper relies on the positioning of printing marks and does not have the paper toothbars. In order to realize the change of intermittent movement from continuous transmission of paper to die-cutting position in rotary printing unit, an adjustable eccentric mechanism is usually set up in the paper feeding device. The flat die cutting machine manufactured by Dai's Printing Machinery Co., Ltd. has the advantages of high precision, low failure rate, pneumatic clutch, overload protection and so on.
Circular Die Cutting
(1) Die-cutting mode
The upper roll of press-cut die-cutting roll is knife roll and the lower roll is smooth roll. Main features: low manufacturing cost, easy installation of knife rollers, easy adjustment of knife rollers, but the knife edge is not as flat as the shear type, and the service life of die cutting tools is shorter. There are two types of die-cutting rollers: integral type and full plug type. At present, the domestic gravure printing production line mostly adopts the full plug die-cutting roll. The die-cutting roll of various cigarette boxes, wine boxes, food packaging boxes and non-adhesive trademarks is basically the integral die-cutting roll.
The upper and lower rolls of the shearing die-cutting roll are both cutter rolls. It realizes die-cutting by using the principle of scissors. Main features: Because the shear die-cutting roll avoids the direct contact between metal and metal, prolongs the service life of the die-cutting roll (about 3-5 times of the press-cutting die-cutting roll). The die-cutting roll can be adjusted, the cut is flat and the die-cutting quality is high, but the manufacturing cost is high. The roll structure of the shear die-cutting roll is mostly integral. Only when some patterns need to be replaced, concave and convex parts, wear-prone parts, cutting edges for internal cutting and special patterns are processed, the combined plug die-cutting roll is selected. The shearing die-cutting roll is mainly suitable for the production of cigarette boxes, beverage boxes, pharmaceutical boxes, fast food boxes and other products.
(2) On-line circular die cutting production line
The main feature of on-line circular die cutting production line is that the printed web cardboard is processed into final products by hot stamping, die cutting and scrap cleaning. It avoids a series of quality problems, such as surface dirty, inaccurate positioning of ordinary and holographic stamping, high reject rate and so on, caused by multi-channel post-printing processes such as conventional stamping, holographic stamping, stamping, die cutting and manual scrap removal, and reduces equipment investment and space occupation, and saves the cost of equipment. A large number of operators have shortened the production cycle. Due to the continuous improvement of the properties of hot stamping materials and the development and application of high-quality new materials, the current maximum speed of rotary die cutting and hot stamping linkage production equipment for web paper has reached 180 m/min.
Because of the linear contact between the round stamping and die cutting, the line pressure during die cutting is much lower than that of the flat surface, so the power of the equipment is smaller and the smoothness is obviously better than that of the flat flat die cutting. Because of the continuous rolling die cutting, the production efficiency is high, the maximum die cutting of the round stamping die cutting machine in the overseas roll paper printing production line is achieved. The speed can reach 300-350 m/min. Because of the intermittent motion of flat die cutting, the die cutting speed is greatly affected. The circular die-cutting machine is equipped with high precision alignment device and die-cutting phase adjusting device, which can obtain fairly high die-cutting accuracy.
IV. Window Sticking and Paste Box
In order to increase the visual effect of commodities in sales, publicize and beautify commodities, a curvilinear visual window can be embedded in rich and colorful printing patterns, and plastic sheets can be pasted into the die-cut box window by automatic window-pasting machine. The film coating process can also be used to realize the bonding between the cartridge and the film. The window sticking process has become an effective means to realize and improve the value of commodities.
In order to meet the needs of modern industrial production, folding Paper Packagings such as food Paper Packagings, pharmaceutical Paper Packagings, toothpaste boxes and so on, which are used everyday, must meet the basic requirements of the increasingly popular high-speed automatic packaging production line for packaging Paper Packagings, such as uniform size, complete squareness, easy opening, even gluing, no dirt and damage, production week. The period is getting shorter and shorter. Therefore, packaging and printing companies should try to choose high-speed, multi-functional folding paster.
Fifth, code jetting.