Manufacturers Talk about the Functions and Applications of Offset Printing Machines (I)

This issue highlights the printing machine status function and application. The following are the highlights of the industry's top printing press manufacturers such as Heidelberg, Manroland, KBA, Komori, Mitsubishi Heavy Industries and other companies of senior engineers on their machines in the technical function and application of the introduction. (Note: The content of this issue is provided by Zhaosheng Graphic Arts Senior User Zhaoyang.)

Heidelberg: Mr. Shao Yuanlin

First, the mechanical structure of the offset press

The main prerequisite for the efficient production of sheetfed multicolor offset presses is the availability of a stable and reliable paper feeder. Therefore, all major offset press manufacturers have incorporated them into their own production systems.

At present, according to different printing materials and specifications, the sheet feeding method adopted by the sheet-fed offset press—step belt type vacuum suction belt type feeding under the standard feeding paper has its own advantages. The reason is that it has a stable structure. Accurate paper feed and guide lines form a right angle. In addition to the paper roll, brush and paper feeder, it can be widely applied to a variety of substrates, such as corrugated paper and micro-crimped paper. This is important for printing papers with poor specifications and performance.

Below the medium format, such as the four-open and eight-opening offset press on the use of suction belt conveyor, because the operation and adjustment is simple and easy.

In order to adapt to the status quo of short-run jobs, that is, frequently changing jobs and changing paper sizes, Heidelberg has introduced a preset paper feeder with higher reliability and speed. This system retains the structure and methods of traditional walking belts, but in many aspects has been optimized to make the system more tight and easy to automate the operation and control. One of its characteristics is that the paper forms an accurate method structure with the front gauge and side gauges. In order to ensure the reliability and speed of paper feeding, the second is that the pile of paper is upgraded stepless rather than stepped, so that the actual thickness of the paper can be increased to maintain a stable distance from the suction nozzle; Semi-closed systems have a positive effect on noise reduction, dust protection, and maintenance free.

In addition, Heidelberg adopts the adjustment of the tumbling-type tooth decay speed to automatically correct the paper in the range of 200° to 312° instead of the traditional fixed angle correction.

The roller layout and arrangement of the printing section is one of the hot topics discussed in the industry right now. In fact, in the face of diverse and specialized market demands, whether it is "seventh" or five, there are irreplaceable features.

The feature of “seven” o'clock is that each group of papers is handed over after printing, and it is advantageous for arranging large drums such as double-diameter impression cylinders, which is very suitable for thick paper printing (mainly packaging printing) requiring large curvature. It is useful, but practice shows that this method is not perfect for publishing and commercial printing based on thin paper.

The "five" clock method is good for arranging better ink routes.

Heidelberg follows the natural requirements of market segmentation and uses the "seven" dot roller arrangement for SM102 and CD102. SM102 is a three-roller (A single-diameter, double-diameter, and B-single-path) transfer and inversion system, and the blanket cylinder, impression cylinder, and A single-pass transfer cylinder are almost in a “one” shape layout, which is very favorable for printing paper. The transfer (even if the full version of printing is also very good); CD102 is a double-diameter impression cylinder and a three-pass roller as the transfer system, its advantages are well known.

For the SM102, Heidelberg also did not use an air-guided paper guide system. Instead, it used a metal sleeve with an ultra-fine irregular chrome-plated bump (the so-called Micro Jaket device) mounted on a reverse-printing impression cylinder. In order to prevent the dry surface in the printing press, filthy dirt.

Heidelberg did not adopt the air-cushion transmission method on the device for preventing dirt and scratches printed after turning over. Instead, it used the method of applying a silicon metal anti-fouling film, a super blue cloth and a steel sleeve on the transfer paper roller. means.
In fact, one of the focuses of the battle between the number of rollers and the way of arrangement is the influence of the paper misalignment caused by the difference in the number of times of paper transfer to the print quality.

Heidelberg's view is that the number of paper transfers does not have a substantial impact on print quality. The key is to consider the accuracy of the transfer structure itself. Practice has proved the correctness of this view.

For walk-and-go rollers, the specific structural characteristics of the drum, transmission gears, bearings, etc. should be determined. Judging from the current level of offset press manufacturing technology, walking roller printing can ensure high-quality printing, low noise operation and the best durability of the machine.

Heidelberg's ink inking and dampening system is also very characteristic. First, it has 21 ink rollers. It adopts the front vertical type (the first two ink inking rollers inking, the latter two ink inking rollers are all ink), and the shortest ink path has only 8 ink rollers. , can achieve rapid response to ink flow.

The dampening system is a five-roll type structure and has an automatic speed compensation function, which has the advantage of maintaining the stability of the water supply while quickly realizing the ink balance and changing the printing speed.

When printing a small-format or large-area non-image area job, the need for fountain solution is less than that of a normal job, and therefore the water supply volume of the fountain roller is correspondingly reduced. Heidelberg's practice is to partition the fountain roller relative to the (32) ink zones and use an axially adjustable blower fan to evaporate the excess fountain solution.

The paper delivery section has an important influence on the speed of production of offset presses and the quality of printed products. Heidelberg has introduced a blowing air guide device that allows paper to be smoothly introduced into the paper cassette without scratches, while the dual dusting device not only makes the paper cassette stable and neat, but also saves up to 30% of the powder.

Second, automation and integration

The level of automation of the offset press is one of the key points of the competition among all the manufacturers. Its development goal is to free the operator from the daily complicated manual operations, thus concentrating their efforts on the printing quality and efficiency, and at the same time enabling the user to In the environment where short-run jobs have soared, there is a means of winning competition.

The further improvement of the automation level of offset printing presses is based on the continuous improvement and optimization of the machine's mechanical performance and electronic control level. It can realize the pre-adjustment of the printing material specifications, realize the automatic monitoring and control of printing quality, and fully digitalize the configuration. The electronic display system realizes integrated operation and management in order to achieve better quality, shorter preparation time, less maintenance time, and higher output.

Heidelberg has gained industry acclaim by adding functions such as image color control and automatic on-line register control in these aspects.

In order to avoid the change of printing color and ensure stable printing quality, Heidelberg first used spectral spectroscopy to scan images and simultaneously perform online color adjustment.

The online automatic registration and registration system not only performs quick fine-tuning and registration at the beginning of printing, but also continuously monitors and corrects during the entire printing process, which can greatly reduce the machine's accurate stop time and paper waste.

Integration is the development direction of the printing industry in the future, because printing is transforming from a simple link to a complete production process (including prepress and postpress), and digitization is undoubtedly the leading factor in this transition.

Digitization and integration will optimize and automate changes in information such as efficient production planning, automatic machine presetting, and capture of effective production data. As a result, job preparation time and production time are further shortened, and at the same time new highs are ensured in the quality of printed matter and remote services.

Manroland: Mr. Zhang Jianfa, Director of Product Sales

First, on the structure of the offset press
 

The paper feeding part is a part of the traditional manual sheet-fed offset printing machine, but in the case of high-speed multi-color printing, the modern offset printing press has higher requirements for the accuracy and smoothness of feeding and automation.

In order to make the paper transport smooth and accurate, the pendulum-type delivery mechanism and the front gauge are designed to be mainstream, and the manufacturers' side pull gauges and the feed speed change mechanism (to ensure that the high-speed running paper arrives at the front gauge has an instantaneous speed of zero) Differently, Roland offset presses are known for vacuum paper feeders, variable speed suction belts and pneumatic side pull gauges; they accurately control the left and right side of the paper stack and the front and rear of the paper feeder with position switches, which are double and printed with paper. Misplacement is particularly important.

In the preparation of prepress operations, by inputting the paper thickness and other data into the console, the precise and rapid pre-adjustment of the paper feeder, front gauge, side gauge, dust-powder device and printing pressure can be automatically and accurately performed, thereby reducing the exact stop time. , improve production efficiency.

At present, the paper size pre-adjustment function is the basic configuration of a modern sheet-fed multi-color offset press.

The printing section is the heart of the printing press. After years of practice and theoretical discussion, the printing section has three rollers that are arranged at “seven o'clock”. The structure of double-diameter impression roller and transfer roller is already the mainstream of multi-color offset printing presses. The double-diameter transfer cylinder of the impression cylinder is a "five o'clock" arrangement, such as the traditional four-boot series of several large manufacturers. The advantages of using double-diameter impression cylinders are well known: First, the number of paper transfers between multi-color units is reduced, and the paper transfer error is greatly reduced; second, the paper red finishes printing during the impression cylinder pick-up. , And then to the transfer roller, so as to avoid overprinting caused by the paper is still printing errors; Third, due to the large curvature of the roller, the surface is smooth, embossing can reduce the dot transfer deformation.

In addition, when the offset printing machine wears and wears for a certain number of years, this arrangement will not cause the phenomenon of printing on the paper regardless of the thickness of the paper when printing at the maximum paper width.

For the combination of multi-color machines, the “in-line” printing method with overturning in several major printing presses in Germany has the features of low center of gravity, good rigidity, and top-down characteristics of the ink path. This ensures the printing quality and stability. It is beneficial, but each has its own solution to problems such as blemishes, tears, front and back registering, and double gargles brought about by flipping. Japanese manufacturers have introduced double-sided printing with double-sided printing for single-sheet double-layer multi-color offset printing presses. Since the ink path of the color group is bottom-up, it will have an impact on the quality of printed products, and it is inconvenient to maintain. Small is its advantage.

The ink supply system is the key to ensure ink balance and prevent some common printing failures. At present, two or three plants, including Mann Rolland, have adopted a fast-response ink system. They are characterized by a small number of ink rollers (less than 16), diameters, and good heat dissipation. They are suitable for high-speed printing, but they are water-free. The ink roller is circulated and cooled only during offset printing and UV printing.

In addition, in the printing of prints with different contents, such as Damoji's packaged printing products and lined with small ink-colored single commercial products, it is very important to discharge the ink at various speeds at a uniform speed. Only in this way can the consistency of the supplied ink viscosity be guaranteed. For this reason, Roland offset press has a variety of programs 1:3:6:9:18 for the initial setting on the ink supply cycle to ensure the stability of the print quality.

Second, on the automation and auxiliary functions

In order to increase the degree of automation of sheet-fed multicolor offset presses, improve printing quality and reduce labor levels, various manufacturers have adopted similar pre-setting and management control systems, which are not described here. Only talk about "dynamic automatic register" and "print quality inspection control method".

The dynamic auto-registration and registration system has been applied to some manufacturers' sheetfed offset presses, but it is not as important as the web press to adjust the counterprinting devices by tension. Therefore, this system is on a sheet-fed offset press. The application effect is yet to be verified in practice.

Up to now, Roland still insists on checking and controlling the printing quality and its process based on the density of printed inks, but does not follow the industry's monitoring and control methods of switching to spectroscopy. The reason is that the current print products are two-dimensional graphics, with a number of mature monitoring and control bar, such as Luna print control signal to achieve the detection of print quality, and spectrophotometric detection is based on the spectral 3-dimensional detection, It is not very practical for today's print products.

The auxiliary functions such as light, drying and dusting are similar to each other. The polishing mechanism mainly includes two-roll coating and cavity blade coating. The former can quickly respond to changes in the coating amount of the coating solution. It is not economical; the latter, due to the use of ceramic anilox rollers, can very precisely control the coating thickness of the glazing solution on the entire sheet, and the glazing effect is simple and economical, making it suitable for various applications. There are IR, UV and hot air drying methods, which must be selected according to the actual application. As to whether the spraying is single-sided spraying or double spraying, the actual application area is not very large.

Gao Bao: Mr. Wang Lianjun, Head of Products, Beijing Representative Office

First, mechanical structure (performance) and automation

The importance of the paper feeder for a modern sheet-fed multicolor offset press at a speed of 15000 rpm is self-evident. First of all, it should be able to steadily and reliably separate and transfer printing materials of different materials, widths, and thicknesses (such as paper, cardboard, plastic cards, and plastic film bases of different weights) one by one; Paper stack front-end detection, phase and skew correction and edge gauge adjustment device, for this reason, manufacturers have commonly used high-performance paper feeders produced by themselves.

Up to now, several production plants have used vacuum suction belts for speed transfer, and pneumatic side pulling gauges for precise positioning, especially for commonly used paper media, but additional equipment is required for cardboard, composite materials, etc. Such as KBA's auxiliary press guide device is very suitable for the delivery of thick paper.

To prevent double-sheet, empty-sheet, skew, and other paper feed failures, many manufacturers have adopted optoelectronic and capacitive control technologies, while KBA has adopted ultrasonic technology as a control method on some models. This is a problem for some paper failures that are difficult to distinguish, such as Thick paper, special printing materials, and a thick ink print are very advantageous.

As a founding member of the double roller press and transfer roller transfer method, Planeta, one of KBA’s predecessor companies, used this low-curvature technology for sheetfed multi-color offset printing as early as 30 years ago. The company's machine-type multi-color machine, and now, this approach has been respected by many manufacturers to accept and evolve some other forms.

For modern sheet-fed multicolor offset presses, the transfer rollers, whether they are double or triple, have a large effect on the grippers, such as the double-diameter transfer roller of KAB. The two rows of fangs are treated with the "cat claw" function, which eliminates the need for the adjustment of the squeezing row for the transfer of thick paper during the printing process.

In addition, the installation of the blowing and suction device of the air-suspension type paper guide system, which cooperates with the transfer roller, is also a great mystery. This is particularly important in the printing of thick cardboard and ultra-thin paper.

Of course, the transfer roller has the function of rapid overprinting for modern offset printing. It can be used as a correction for the positional deviation adjustment of the printing plate, rather than a traditional one. The long-term damage of accuracy has played an active role in the rapid response of overprinting, the saving of paper, and the protection of machine precision.

At present, only two or three production plants have this function. Several leading manufacturers of offset press production technology have their own characteristics in the design of some printing and water supply devices, but most of them adopt the multi-ink roller dual ink channel ink layout, except that KBA adopts 5 on several main models. Root inking systems with different diameters depending on the printing roller. The features of the ink roller are as few as 15 rollers. The roller diameter is large. The first roller is connected to the water supply and wetting device to make the ink and the roller act as the pre-emulsification of the ink, which can shorten the ink ink balance time and change the printing ink color. Make a quick response, reduce paper waste and cleaning time.

KBA's water supply and wetting device is also characterized by straight-line water transfer, which is characterized by a continuous film-type water supply by means of a rubber-impregnated water roller and a chrome-plated water transfer roller. This simple and quick water supply can be used for low alcohol or alcohol-free fountain solutions without modification.

In addition, the constant temperature system of the inking device should also be the standard configuration of today's offset press, because it can further improve the stability of the long live printing process, and can also do waterless offset printing to meet the development needs of future offset printing technology.

Second, auxiliary functions and other

In addition to on-line glazing and drying functions, modern offset presses also have a variety of online functions that can increase production efficiency, shorten the printing cycle, save manpower expenses, and reduce intermediate storage locations. For example, a web cut sheet unit with longitudinal and lateral cutting blades can be used for printing and punching holes for 4+4 color mail advertisements and newspaper supplements, numbering mechanism, color printing apparatus, non-stop delivery, etc. .

15,000 rpm is an ideal rotational speed in modern offset press production operations. At present, all manufacturers are trying to find out how to use this press to better realize the overall benefits of the press, instead of simply increasing the speed of printing.

The full sheet machine is a giant in sheet-fed multi-color offset printing machines. At present, only a few manufacturing plants in the world are producing, and only 1200 mm×1620 mm specifications can be produced by the KBA. The market demand for full-length machines is a long-term existence, and this demand is growing both in the fields of commercial publishing and packaging and printing. The range of printed materials is also quite extensive, including paper, cardboard, and corrugated paper. High-precision prints.

Satisfying the ergonomic requirements, focusing on the protection of the environment, and modern and future offset presses should be the key considerations. Because the offset ink, alcohol, dusting, ultraviolet light, noise, etc. have a considerable impact on the operator's physical and mental health, and environmental protection. KBA took the lead in this step. At present, the 105 machines have won the honor of the world's first green machine and are named "ECOPRESS 2000".