In order to cope with the continuous shortening of the printing cycle, the continuous improvement of quality, the increase in demand for short-run work, the intensification of competition, and the decreasing profit margin, adding a connecting device to the sheet-fed offset printing press can not only improve efficiency, but also develop differentiation Printing, improve competitiveness. However, the configuration of the connection device must be selected realistically according to its own needs, and the one that meets the needs is appropriate, otherwise it will not only increase the investment in equipment purchase, but also make the structure of the equipment complicated and inconvenient to use, adding more.
News: In order to cope with the continuous shortening of the printing cycle, the continuous improvement of quality, the increase in the demand for short-form work, the intensification of competition, and the decreasing profit margin, adding a connection device to the sheet-fed offset press can not only improve efficiency, but also develop Differentiate printing to improve competitiveness. However, the configuration of the connection device must be selected realistically according to its own needs, and the one that meets the needs is appropriate, otherwise it will not only increase the investment in equipment purchase, but also make the structure of the equipment complicated and inconvenient to use, adding more.
1. Roll paper-single sheet feeder
Roll paper-single-sheet paper feeder is a paper feeder that cuts the roll paper online into a single sheet of paper and directly feeds it into the single-sheet offset press as required. Since the web-sheet feeder can reduce costs and improve efficiency, it has been increasingly valued by people since 2005.
Roll paper-The single-sheet paper feeder continuously cuts the online roll paper into a single sheet of paper. The cut single sheet of paper is fed directly into the front of the original single-sheet paper feeder at a certain step and position , So that the paper delivery mechanism feeds the paper into the impression cylinder, which can replace the original sheet feeder. The cutting length of the roll paper can be adjusted steplessly according to the needs of the printing paper. The characteristics and selection of the main connection device are generally up to ± (0.2 ~ 0.5) mm, and the width is the width of the roll paper.
The structure of different roll paper-sheet feeders is somewhat different, but the basic principle is the same. It is generally composed of a roll paper holder, a floating roller unit, a paper feed roller, a cutting unit, a nesting unit, a nesting printing logistics and delivery Paper roll and other components. The function of the floating roller unit is to reduce or eliminate the change of tension when the roll paper is unfolded, so that the paper belt enters the feed roller more smoothly for cutting, and its performance determines the accuracy of cutting the paper. The nesting unit and nesting printing logistics will cut the cut sheets according to the sheet step requirements of the sheet-fed offset press, and stack the cut sheets.
Using the roll paper-single-sheet paper feeder, you can cancel the original single-sheet paper feeder and directly connect the roll paper-single-sheet paper feed to the printing unit. The original sheet-fed paper feeder can also be immobile, install the roll-fed feeder behind the original sheet-fed paper feeder, and transfer the roll-fed feeder The table is lengthened and directly connected to the paper table of the original sheet feeder. The former covers a small area and is cheap, but it has poor flexibility. The latter covers a large area and is expensive. Both sheet and roll paper can be used, which is very flexible.
Advantage
First, it can store a large amount of paper, reduce the number of paper changes and downtime, and improve machine utilization; second, roll paper is cheaper than a single sheet of paper, which can reduce the cost of paper by 5% to 25%, if it is coated cardboard or film , The use of coiled material can also obtain higher economic benefits; third, the paper cutting length can be adjusted steplessly, easy to use, and will not cause waste of paper before the single sheet of paper is printed on the top and bare feet; fourth, It can make waste. It is printed with thin paper and thin plastic that cannot be used with a sheet-fed offset press. Fifth, it completely solves the problem of double or multi-sheet feeding. Sixth, the operator does not need to stack paper and reduces labor intensity.
Disadvantage
First, the roll paper cannot be selected in advance, so the quality requirements of the roll paper are relatively high. The roll requires no or few joints. The roll is standard (no defects such as ellipticity and taper), and the roll cannot have wrinkles. , The paper itself must not have quality defects (such as small holes, tears, tears, etc.). Second, the dry humidity of the roll paper can not be dried like a single sheet of paper. The dry humidity of the roll paper used directly should have certain requirements, and the dry humidity of the paper should pay attention to the quality of the paper during the storage of the roll. influences. Third, the flatness of the paper is best in large paper rolls, the worse the core, the thicker the paper, the greater the difference. Thicker paper, paper near the core of the paper may affect the use, and it may be necessary to add a flat paper device. Therefore, too thick paper or cardboard and corrugated cardboard should not be used.
2. Laminating, plastic sheet printing and corona treatment
Sheet-fed offset presses can now be coated online, for example Roland 700 can be used to coat printed materials before color printing begins.
The first unit of the printing press prints adhesive on the substrate, the rubber cylinder of the second unit is wrapped with a film, and the corresponding part of the printing material is pasted with a film when passing. This process is completed at normal temperature, completely avoiding the influence of temperature on the film and printing materials.
The sheet-fed offset press can also print plastic sheets, but the ink adhesion on the surface of the plastic sheets is poor. For this reason, online corona treatment can be provided. For example, KBA Rapida74, Rapida105 and other models can be equipped with a corona unit in front of the first printing unit to perform high-pressure discharge treatment on the surface of special materials (such as plastic sheets) to improve the adhesion of ink on the surface of the material, thereby improving printing Quality and speed. In order to solve the problem of inaccurate overprinting caused by temperature changes in the plastic printing process, KBA can also provide special anti-scratch paper guide components, plastic sheet static elimination devices and impression cylinder cooling devices.
In order to cope with the continuous shortening of the printing cycle, the continuous improvement of quality, the increase in demand for short-run work, the intensification of competition, and the decreasing profit margin, adding a connecting device to the sheet-fed offset printing press can not only improve efficiency, but also develop differentiation Printing, improve competitiveness. However, the configuration of the connection device must be selected realistically according to its own needs, and the one that meets the needs is appropriate, otherwise it will not only increase the investment in equipment purchase, but also make the structure of the equipment complicated and inconvenient to use, adding more.
3. Online cold stamping
Now many sheet-fed offset presses can provide online cold stamping devices. The first unit before foil placement prints a special adhesive on paper according to the pattern required for cold foil aluminum foil. Bonding (hot stamping) where the adhesive is printed, the remaining aluminum foil is taken away by the winding mechanism above the third unit. When no hot stamping is required, the first and second units can print normally as other units.
Advantage
(1) Printing and hot stamping can be completed at one time, which can realize accurate overprinting. Because the special adhesive can be used like ink to achieve very fine patterns and text hot stamping.
(2) Cold stamping does not require heating, will not cause paper deformation, and will not affect the printing on and after aluminum foil.
(3) It can be reprinted on the aluminum foil to make the aluminum foil form any graphics and special color effects, such as printing yellow and magenta on silver aluminum foil to get gold.
(4) Since re-printing can make the aluminum foil get different colors, therefore, the printing factory does not need to buy aluminum foil of various colors, just silver foil, which can reduce inventory and warehouse.
(5) Operators do not need to master hot stamping technology, as long as they can offset printing technology.
(6) When hot stamping is not performed, the original unit can perform normal printing.
(7) A cold stamping system can be installed on the old machine.
(8) Packaging and printing often require an online cold stamping device, which can be installed anywhere on the machine as required.
Disadvantage
(1) When printing on aluminum foil, the ink drying time is affected to a certain extent, if necessary, a drying device or a glazing and drying device should be added.
(2) The current hot stamping structure, the utilization rate of aluminum foil is low, especially the single reel type. Using multi-roller type can improve the utilization rate of aluminum foil and reduce the use cost. [next]
4. Wiring and drying
Nowadays, packaging can not only protect the goods, but more importantly, it can stimulate people's desire to buy, and even become one of the criteria for deciding to buy. Therefore, about 80% of folding cartons, 70% of labels, and many books and magazines use glazing technology to attract people's attention.
Standard offset printing units can also be used to coat or print metallic inks, such as printing water-based varnish with coated offset plates. However, due to the thin ink layer and the use of wetting fluid and additives, the polishing effect is not good. Therefore, the current glazing device mainly uses flexographic printing, and generally has one or two separate glazing units. When the glazing requirements are high, two glazing units are required. The first glazing unit is generally a water-based varnish, which acts to seal the ink and paper surface, reducing the penetration of varnish into the wet ink during the first glazing. Loss of light and paper. After drying, the second glazing can make the varnish distribution more uniform, forming a high-gloss glazing layer. The second glazing unit can use UV varnish, which has better effect than pure UV, and can also use water-based varnish to further improve the glazing effect, or use special effect pigments to show special effects.
The double glazing unit is generally arranged at the rear of the printing unit, and there should be a drying device behind each glazing unit. If you need to apply an opaque white or special effect primer on the surface of the substrate before printing, you should install a flexographic coating unit and drying device before the first printing unit. The choice of glazing unit should be determined according to the requirements of the printed matter.
(1) Selection of oil supply method: The varnishing unit mainly differs in the varnish supply method. The amount of glazing oil can be adjusted as needed. Generally, the gap or pressure between the two rollers is adjusted, and the rotation speed of the roller is changed. This kind of mechanism is widely used at present, but it is troublesome to adjust.
The newly developed closed varnish supply device is composed of anilox roller and cavity scraper. Two scrapers are installed in the chamber box, one of them applies the varnish evenly along the rotation direction of the anilox roller, and the other one scrapes off the excess varnish on the anilox roller against the rotation direction of the anilox roller. The size of the anilox roller mesh hole determines the amount of varnish, which is easy to control. If you need to change the amount of glazing oil, you need to replace the anilox roller. Therefore, the glazing device is often equipped with 2 to 3 anilox rollers with different mesh sizes. The standard varnish capacity of general anilox roller is 20cm3 / m2. The thickness of the varnish layer printed on the substrate is about 8μm, and the basis weight is 8g / m2. This cavity type varnish supply device can prevent dust, flying ink and varnish from drying and scaling. The installation position of the cavity polishing blade must be correct, otherwise it will not work properly. The general cavity type varnish supply device needs to be equipped with an automatic varnish pump in order to automatically varnish.
(2) Selection of glazing plate cylinder: when all glazing, the glazing plate is generally a blanket. When partially glazing, the glazing printing plate is generally a flexible plate, which mainly has two types of rubber plate and polyester plate.
Whether the glazing plate cylinder needs to be adjusted depends on the glazing requirements. Only all glazing is carried out, and the roller generally does not need to be adjusted. In order to achieve accurate overprinting during partial glazing, the glazing plate cylinder can be adjusted axially and circumferentially, and when the requirements are high, the diagonal adjustment of the cylinder is also required. Middle and high-end machines generally control the adjustment of the coating drum on the central console.
It must be dried immediately after glazing. Sheet-fed offset presses often use water-based varnishing and UV varnishing according to the needs of printed matter, and the requirements of printed matter can be changed at any time. There are roughly two corresponding drying methods. That is, use oily ink + water-based varnish, use IR (far infrared) and / or hot air drying; use UV ink + UV varnish, use UV dry curing. Of course, it is also possible to use both IR / UV. The specific selection should be based on the varnish and product use. There are three types of UV curing devices, namely, internal baking plate method, drying unit method, and long-line transmission method. The inner baking board method does not require a special unit, and is generally installed between the units. It is more convenient to change the installation position, but the drying capacity is the lowest among the three methods. The drying unit method requires a dedicated unit, but the drying capacity is the highest.
The long-line transmission method is to lengthen the paper collection distance. Install IR, UV and hot air drying devices after the last glazing unit, taking into account both IR / UV drying methods (glazing oil is different to replace the drying method or the drying lamp. Internal drying It is difficult to use both IR / UV drying methods for the board method and the drying unit method. In order to reduce the thermal deformation of the paper, a low-heat UV device or a cooling device (generally behind the UV lamp that lengthens the paper) can be used.
In order to adapt to the variability of sheet-fed offset press varnishing, generally a sheet-fed offset press is behind the last printing unit or varnishing unit, and is equipped with infrared, UV, hot air drying devices at the same time to form an elongated paper collection device. Printed materials need to open different drying devices. For example, when water-based glazing, infrared and hot air drying devices, the two have a good drying effect. UV glazing turns on the UV drying device.
Generally, the extended paper collecting device is also equipped with a cooling device (circulating cold air), which on the one hand cools the printed paper and on the other hand is conducive to ink drying. In order to ensure the proper drying of the ink between the various colors of the printing unit, it is necessary to install a UV or infrared drying device between the printing units, and both can be replaced.
In order to cope with the continuous shortening of the printing cycle, the continuous improvement of quality, the increase in demand for short-run work, the intensification of competition, and the decreasing profit margin, adding a connecting device to the sheet-fed offset printing press can not only improve efficiency, but also develop differentiation Printing, improve competitiveness. However, the configuration of the connection device must be selected realistically according to its own needs, and the one that meets the needs is appropriate, otherwise it will not only increase the investment in equipment purchase, but also make the structure of the equipment complicated and inconvenient to use, adding more.
V. UV offset printing
UV printing was first applied to screen printing and then to flexo printing. In the past 10 years, UV offset printing has developed greatly. UV offset printing can be roughly divided into two types: color printing and surface finishing. Color printing is basically the same as conventional printing. Surface finishing, such as UV glazing, can replace the laminating film, which can be used for both overall and partial glazing. Using UV ice or UV matte ink printing can form a "three-dimensional" image and colorful texture effects on the surface of the substrate. UV offset printing and composite ink printing, which have quietly emerged in recent years, have many advantages, and of course have their own problems.
Disadvantage
(1) Special supporting device: printing equipment
UV offset printing must be equipped with special rubber rollers, printing plates and blankets, and special cleaning agents are needed for cleaning; the ink roller needs to add a water cooling system; due to the poor overprinting of UV inks, it is generally necessary to add special UV inks between the units Curing and drying device.
(2) High printing cost: first, the price of UV equipment is high, and the cost of depreciation is high; second, the UV ink is expensive, generally 4 to 5 times that of ordinary ink; third, the management and operation cost is high, and the UV offset printing technology content is relatively high High, must have a perfect process plan and strict management, increase management costs. Due to the lack of workers skilled in UV printing technology, workers in UV printing operations have high wages.
(3) The process is more complicated and difficult: First, the UV ink has a narrow balance of water and ink balance, which is easy to cause serious ink emulsification, dirty version, and increased manipulation difficulty. , The printed matter is easy to stick and dirty, the curing temperature is too high, and it may deform the paper and affect the overprint; third, UV inks have high color sequence requirements, and improper arrangement of color saturation will be affected; fourth, UV inks dry quickly and stop during printing If the time is too long or the machine speed is too slow, the ink may skin or even dry, affecting the printing quality. [next]
6. Sheet-fed offset printing machine
With the development of double-sided offset presses, double-sided glazing mentioned the agenda. The difficulty of double-sided glazing is that the first side must be fully dried after printing. In addition to UV printing and drying can be carried out immediately (UV printing costs are relatively high, and some printed products can not be UV printed) water-based glazing is mainly due to insufficient drying time. Komori recently launched two processing units after the first glazing unit. The processing unit is not equipped with plate cylinders and rubber cylinders, only the impression cylinder and paper transfer cylinder, so that the paper has sufficient drying time before turning over .
Advantage
First, there is sufficient drying time to ensure drying after glazing; second, it is conducive to the removal of heat generated by drying; third, the drying ability is improved. In order to adapt to changes in water and UV glazing, IR and UV drying are added at the same time. Device to adapt to different printing and glazing requirements for drying, improve the scope of use of the machine; Fourth, the printing quality and production efficiency are improved, and the scrap rate is very low.
Disadvantage
Due to the addition of two processing units, the product price is higher and the floor space is increased.
Seven, line numbering, embossing, punching
It can be completed by a marking and embossing unit after the printing unit, or a simple marking and embossing device can be installed on the printing unit. It is composed of ink supply unit and code box shaft. The orientation of the numbers on the axis of the number box is different, and vertical or horizontal numbers can be printed on the printed sheet. Remove the number box and install a embossed block in its place to emboss the printed matter. Fig. 5 is a punching device arranged on a sheet-fed offset printing machine. To punch, cut, indent, and emboss in the longitudinal direction (printing and paper-feeding direction), install the corresponding tools (such as a punching knife) on a bracket, and install the bracket in the position to be processed (laterally adjustable). Perforation, cutting, creasing and embossing in the horizontal direction (perpendicular to the paper feeding direction), the relevant processing tools are installed on the support shaft. Whether it is vertical or horizontal drilling, cutting, creasing and embossing, it is The relevant tools and the impression cylinder are squeezed, so the surface of the impression cylinder should be protected.
8. Die-cutting and indentation
In recent years, die-cutting and creasing devices have also been installed on sheet-fed offset printing machines. Initially, the die cutting and indentation were carried out in the glazing unit, that is, the die cutting plate was installed on the glazing plate cylinder, the position of the glazing plate cylinder was adjusted to the correct die cutting, and the die cutting or indentation was closed. Some also install the die-cut plate on the rubber cylinder and squeeze it with the impression cylinder. It is now possible to equip a separate die-cutting unit.
Separate die-cutting and creasing units can be equipped with waste removal devices. Equipped with a suction and blowing system on the die-cutting drum. The die-cut waste is sucked firmly on the die-cutting drum. When the die-cutting drum is turned to the exhaust exhaust position, the suction of the die-cutting drum is immediately changed to blowing, and the die-cut waste is blown away. Suctioned by exhaust exhaust system.
Whether it is die cutting, indentation, embossing, or punching, it is necessary to protect the surface of the impression cylinder. Generally, a lining or sheath is used.
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