EP3831603A1 - Printing machine with hybrid printing technology - Google Patents

Abstract

The invention relates to a printing machine with hybrid printing technology for printing a moving material web (204). In order to create a printing machine with hybrid printing technology that can be adapted and used flexibly in the course of the current trends in digitization, the printing machine according to the invention with hybrid printing technology for printing a moving material web (204) is a printing machine with a rotating central cylinder (201) on which Surface, the material web (204) is guided from a contact point (303) to a detachment point (304) for printing, with several digital printing inking units (202) for printing the material web (204) and in the area of an upper half of the central cylinder (201) In the area of a lower half of the central cylinder (201) several flexographic printing inking units (202) for printing the material web (204) are arranged, with an unwinding station (205) for unwinding the material web (204) to be printed from a roll and a winding station (206) ) for winding the printed material web (204) onto a roll, the unwinding station (205) and the A winding station (206) are arranged on a first side of the central cylinder (201), with feed guide rollers (301) for feeding the material web (204) unwound from the unwinding station (205) to the central cylinder (201) and with discharge guide rollers (306) for removing the printed material web (204) from the central cylinder (201) to the winding station (206), the feed guide rollers (301) and the discharge guide rollers (306) being arranged on a second side of the central cylinder (201), with a feed - Guide roller (302) for placing the material web (204) at the contact point (303) on the central cylinder (201) and a strip guide roller (305) for detaching the material web (204) from the central cylinder (201), the feed guide roller ( 302) and the strip guide roller (305) are designed in such a way that the contact point (309) and the detachment point (304) are arranged on the lower quadrant (Q3) of the central cylinder (201).

Description

The invention relates to a printing machine with hybrid printing technology for printing a moving material web.

In the context of the present invention, hybrid printing technology is understood to mean the combination of flexographic printing and digital printing.

In packaging printing, the flexographic printing process is a suitable and proven process for the economical production of long print jobs. In addition, a large number of technical developments have opened up new procedural possibilities in flexographic printing, such as the use of more colors and finer grids.

The term digital printing stands for various digital printing processes. What all these printing processes have in common is that there is no analogue printing form, but that printing is carried out directly from the digital database of prepress. Toners or inks are transferred directly or indirectly to the substrate. In contrast to flexographic printing, there are no costs for the production of the printing form. On the other hand, the running operating costs in digital printing are higher, since digital color systems are 10 to 20 times more expensive than flexographic printing color systems. The profitability in digital printing is therefore also dependent on the motif and its color assignment, because the more color is applied, the greater the influence on profitability.

In the course of digitization, a trend towards ever shorter product cycles can be observed in the packaging industry. This leads to the Packaging pressure for decreasing print runs for both first and repeat orders. In particular, when new products or product variants are brought onto the market, the required length of the print job can often hardly be determined precisely. Digital printing offers the option of changing the length of the print job at short notice and, in addition, in the case of a short print job, there are no high setup costs. The process therefore delivers the right amount at the right time. In addition, there are no costs for the storage of the packaging due to the need-based print run. The problem-free possibility of reprinting also reduces the risk of unnecessary supply rolls. The promotion of new products, the promotion of the most diverse variations in small and very small editions is possible in the shortest possible time. For short print jobs, digital printing offers greater flexibility and is a cost-effective alternative to flexographic printing.

Another trend in the packaging industry is variable data printing. In this area too, digital printing has an advantage over flexographic printing. Since there is no permanent print image memory with digital printing, each design can be implemented individually in one work step. This opens up the possibility of mass personalization in order to segment and address consumers in a targeted manner or to design the product promotion individually according to customer requirements with variable designs.

Out WO 2012/163829 A1 a digital printing machine with two central cylinders and a dryer unit located between the central cylinders is known. Several inkjet printing inking units for printing the material web are arranged on the first central cylinder. A device for the electrostatic discharge of particles adhering to the printing substrate web is located on the second central cylinder. The combined use of digital printing and flexographic printing is on the other hand WO 2012/163829 A1 not disclosed. In such a digital printing machine, there is therefore no possibility of combined use of flexographic printing or of retrofitting the printing unit. However, customer requirements for the above trends are changing. That is why digital printing machines have to be adaptable and flexible.

Out WO 2017/207590 A1 a printing machine with hybrid printing technology is known in which a flexographic printing roller is removed and the space released by the printing roller can be equipped with an inkjet printing unit. As a rule, the inkjet printing unit will have a smaller printing width than the removed printing roller. According to a preferred embodiment, a linear guide is therefore provided so that the inkjet printing unit can be displaced transversely to the material web. The disadvantage of such a printing machine with hybrid printing technology is that digital printing can only be combined with flexographic printing for very special applications.

• Geringe Flexibilität für kleine und verschiedenartige Aufträge: Wie kann die Flexibilität bei gleichbleibend geringen Kosten maximiert werden?
• Bedarf an verschiedenen Drucktechniken für verschiedene Aufträge: Üblicherweise wird ein Auftrag je nach der verfügbaren Produktionskapazität entweder für den Flexodruck oder für den Digitaldruck vorbereitet. Können alle Aufträge an einer einzigen Druckmaschine abgearbeitet werden?

In the known printing machines, the following problems arise overall:

• Low flexibility for small and diverse jobs: How can flexibility be maximized while maintaining low costs?
• Need for different printing techniques for different jobs: Usually, a job is prepared for either flexographic or digital printing, depending on the available production capacity. Can all orders be processed on a single printing press?

The object of the invention is therefore to create a printing machine with hybrid printing technology that can be used flexibly and adaptably in the course of the current trends in digitization.

This object is achieved by the features of claim 1. Further preferred embodiments emerge from the subclaims.

The printing machine according to the invention with hybrid printing technology for printing a running material web is a printing machine with a rotating central cylinder, on the surface of which the material web is guided from a contact point to a separation point for printing, with several digital printing inking units for printing in the area of an upper half of the central cylinder the material web and several in the area of a lower half of the central cylinder Flexographic printing inking units are arranged for printing the material web, with an unwinding station for unwinding the material web to be printed from a roll and a winding station for winding the printed material web onto a roll, the unwinding station and the winding station being arranged on a first side of the central cylinder, with Feed guide rollers for feeding the material web unwound from the unwinding station to the central cylinder and with discharge guide rollers for discharging the printed material web from the central cylinder to the winding station, the feed guide rollers and the discharge guide rollers being arranged on a second side of the central cylinder, with a feed Guide roller for placing the material web at the point of contact on the central cylinder and a strip guide roller for detaching the material web from the central cylinder, the feed guide roller and the strip guide roller being designed in such a way that the contact point and the detachment point at the lower quadrant n of the guide cylinder are arranged.

The printing machine according to the invention enables a hybrid printing technique with which the gap between conventional flexographic printing and digital printing can be closed. Since several digital printing inking units for printing the material web are arranged in the area of an upper half of the central cylinder and several flexographic printing inking units for printing the material web are arranged in the area of a lower half of the central cylinder, flexographic printing can be performed both before digital printing and after digital printing in one pass be applied. Since the contact point and the detachment point are also located on the lower quadrant of the guide cylinder, the material web can be conveyed to a drying station after flexographic printing without the printed side of the material web coming into contact with a guide roller until it reaches a drying station.

The printing machine according to the invention thus has a high degree of flexibility, since the material web can be printed using flexographic printing, digital printing or even a combination of both techniques. In view of the service life of the printing press according to the invention, the possibility of frequent changes in the workflow results in higher productivity. Ultimately, this technology also enables greater flexibility in production planning.

Despite the small installation space in the area of the central cylinder, the invention enables the inkjet inking units to be arranged in the area of the upper half of the central cylinder. This enables error-free operation of the inkjet printing inking units without the influence of the gravitational vector having a negative impact on the print image. In contrast, it was found that the quality of the inkjet printing declines when the inkjet printing inking units have to be operated in the area of the lower half of the central cylinder. The arrangement of the inkjet printing inking units in the area of the upper half of the central cylinder is therefore particularly advantageous.

According to a preferred embodiment it is provided that the material web consists of a plastic film or a plastic film replacement or an aluminum web or a paper web. Plastic film is predominantly used in the packaging printing of flexible packaging, so that the printing machine according to the invention can be used with preference in this field. Instead of a plastic film, however, a plastic film substitute such as polylactide (PLA) can also be used. Polylactide (PLA) is a non-naturally occurring polyester that is produced from sugar through a multi-stage synthesis. Sugar is fermented to lactic acid and this is polymerized to PLA. PLA is biodegradable according to EN 13432, but certain environmental conditions are necessary for this, which are usually only found in industrial composting plants. It is also possible to print an aluminum web or a paper web with the printing machine according to the invention.

According to a further preferred embodiment it is provided that 4 flexographic printing inking units are arranged in the area of the lower half of the central cylinder and 8 digital printing inking units are arranged in the area of the upper half of the central cylinder. Such a combination results in a high degree of flexibility with good economic efficiency at the same time. However, all other conceivable combinations are also possible. For reasons of cost, less than 8 digital printing inking units can be arranged in the upper half of the central cylinder or less than 4 flexographic printing inking units can be arranged in the lower half of the central cylinder. In the same way you can increase flexibility in the upper half of the Central cylinder arranged more than 8 digital printing inking units or arranged in the lower half of the central cylinder more than 4 flexographic printing inking units.

According to a further preferred embodiment it is provided that 2 flexographic printing inking units are arranged behind the contact point and 2 flexographic printing inking units are arranged in front of the detachment point. The 2 flexographic printing inking units behind the contact point can preferably be provided for applying a primer and / or a partial primer and / or a full-surface colored primer. The 2 flexographic printing inking units in front of the separation point can preferably be provided for finishing (e.g. application of varnish, etc.) of the printed material web.

According to a further preferred embodiment it is provided that a drying station for drying the printed material web is arranged on said first side of the central cylinder in front of the winding station. Since the contact point and the detachment point are also located on the lower quadrant of the guide cylinder, the material web can be conveyed to a drying station after flexographic printing without the printed side of the material web coming into contact with a guide roller until it reaches a drying station.

According to a further preferred embodiment, a digital printing switch-off device is provided so that the printing machine can be operated as a pure flexographic printing machine. In a corresponding manner, alternatively or in combination with this, a flexographic printing switch-off device can also be provided so that the printing machine can be operated as a pure digital printing machine.

The digital printing inking units can be designed on the basis of a suitable digital printing process, depending on the application. Two essential and fundamentally different processes are used in digital packaging printing: electrophotography, with the dry toner process or the liquid toner process, and inkjet printing, which in turn is divided into drop-on-demand and continuous inkjet.

In the electrophotographic process, the image is first created on a negatively charged image drum covered with photoreceptors. Using exposure The charge is removed via a print head using an LED or laser beam and a latent, electrostatic charge image is generated. In the developer station, the toner adheres to the neutralized parts of the image drum. The print image is transferred to the substrate either directly or via a rubber cylinder, fixed there and recreated for each printing process. The imaging drum requires an exactly even exposure over the entire width, which means that conventional electrophotographic processes are limited to a maximum printing width of less than 800 mm.

The dry toner process is one of the oldest and most frequently used digital printing processes. It fixes the toner to the substrate at a high temperature. This results in the process-related disadvantage of the shrinkage of temperature-sensitive substrates, for which, however, appropriate solutions have been found. In the packaging sector, the dry toner process comes close to the print quality of the liquid toner process, but due to the powdery toner it is somewhat slower than liquid toner and therefore does not offer the possibility of using spot colors in packaging applications. In view of the fact that the toner is fixed by heat, the dry toner process does not require a primer compared to the other processes and, according to the manufacturer, is suitable for both indirect and direct contact with dry food in various combinations of substrates and toners. With the dry toner process, the color sequence can be freely selected for the various applications in frontal, reverse and interlayer printing.

The liquid toner process in packaging printing offers a level of quality that is comparable to that of analog processes. In this process, too, an image drum is exposed and a latent printing form is created, which is then colored with an electrically charged liquid toner. This is heated during transfer and gels on the blanket cylinder. The transfer by means of a blanket cylinder and the particle size of the liquid toner allow parallels to conventional offset printing. When it comes into contact with the substrate, the liquid toner cools down very quickly and solidifies on it.

In the one-shot process with web printing systems, all color separations are first collected on the blanket cylinder and then transferred together to the printing material. Multi-separation is only used in sheet-fed printing, with the sheet running through the printing unit repeatedly until all colors have been transferred. In principle, the liquid toner process allows a very high transmission speed, but this is reduced accordingly by the collection and joint transmission of the colors. The printing speed of the liquid toner process is therefore somewhat slower than that of inkjet systems with a comparable resolution.

With the liquid toner process, the four basic colors CMYK can be supplemented with orange, green and violet in order to print in the extended color space or to create an improved simulation of the Pantone colors. Five colors are often used for this, depending on where the desired color is in the color space. In addition, the seven colors of the extended color space plus reflex blue, rhodamine red, light yellow and transparent spot colors can be mixed according to special colors analogous to the offset process and used as full tone colors in one of the inking units. Liquid toners are known which are suitable for indirect contact with dry foods. The electrically charged particles dissolved in liquid have a size of 1-2 microns and, due to their small size, can accurately represent fine details. They form a smaller thickness of the toner layer compared to dry toners.

The inkjet process does not require an image carrier, as the ink is transferred directly to the substrate from the fine nozzles of a print head. The individual inkjet print heads differ from one another in their structure. The contactless transfer of ink (non-impact printing) reduces the impact on the printing material. The print heads are arranged so that large print widths can also be covered.

With the drop-on-demand process, the ink droplets are generated according to the print image and ejected onto the substrate. In the piezo drop-on-demand process, the piezo-ceramic element on the inkjet spray head is controlled with the digital data. By contraction or expansion of this element in the An acoustic wave forms in the pump chamber, which leads to the formation of droplets at the outlet opening of the spray head. The shape and mass of the drop formation as well as its speed depend on the electrical pulse shape and frequency as well as the ink parameters surface tension and viscosity. Between 10,000 and 100,000 ink drops with a nominal volume of 1 to 100 picoliters can be generated per second. The quality of the ink has a decisive influence on the print quality.

In the thermal drop-on-demand process, also known as bubble jet, there is a small heating element above the nozzle opening of the storage container, which generates a vapor bubble when it receives a current pulse for an image signal. The bubble ejects a precisely defined amount of ink from the nozzle opening. When the bubble clears, an appropriate amount of ink is drawn from the cartridge and the process starts again. Heating and cooling take place in the microsecond range. In comparison to other inkjet processes, thermal inkjet heads are inexpensive, which is why their number can be correspondingly large in order to cover the corresponding printing widths, printing speeds and resolutions. They can also be exchanged quite easily, but are subject to wear and tear.

With continuous inkjet there is constant pressure in the nozzle and the size of the droplets that constantly emerge is controlled by the image signal. At printing points, the droplets are larger and reach the substrate, while they are smaller at pressure-free points and are directed by an air stream into a drip catcher, from where they run through the circuit again. Up to 440,000 ink drops can be generated per second, which enables a high resolution and thus a correspondingly high print quality.

Inkjet processes work in packaging printing with aqueous pigment or UV inks. Up to seven colors, four basic colors plus light magenta, light cyan and light black or orange, green, violet or blue and / or special colors are used. Spot colors mixed from a basic color system do not occur because changing the color heads in the machine would be too time-consuming. Low-migration, water-based inks are available for food packaging are available, which are approved according to their purpose. UV inks are rated very critically by the food industry with regard to migration and because of their smell.

According to a further preferred embodiment it is provided that the digital printing inking units consist of inkjet printing inking units. Inserts are preferably provided for the inkjet printing inking units in such a way that the positions of the inkjet printing inking units are interchangeable. For this purpose, a star-shaped ink supply can be provided in such a way that, depending on the inkjet printing inking unit located in the insert, the insert is automatically supplied with the corresponding printing ink.

Fig. 1

zeigt eine schematische Darstellung der Ortsverhältnisse am Zentralzylinder der erfindungsgemäßen Druckmaschine,

Fig. 2

zeigt eine perspektivische Darstellung der erfindungsgemäßen Druckmaschine, und

Fig. 3

zeigt eine Seitenansicht der erfindungsgemäßen Druckmaschine.

Further details and advantages of the invention are described with reference to the accompanying drawings:

Fig. 1

shows a schematic representation of the local conditions on the central cylinder of the printing press according to the invention,

Fig. 2

shows a perspective view of the printing press according to the invention, and

Fig. 3

shows a side view of the printing machine according to the invention.

Fig. 1 shows a schematic representation of the spatial relationships on the central cylinder of the printing press according to the invention. To describe the spatial relationships, it is assumed, without loss of generality, that the central cylinder 101 rotates clockwise 102 within the framework of the fixed coordinate system with a horizontal X-axis and a vertical Y-axis, the origin of the coordinate system being at the pivot point of the central cylinder 101 . Furthermore, the force of gravity vector 103 is aligned parallel to the Y axis in the negative Y direction.

In this constellation, the upper half 104 of the central cylinder 101 designates the space above the X axis, while the lower half 105 of the central cylinder 101 defines the space below the X axis.

In a corresponding manner, the left side 106 of the central cylinder 101 designates the space to the left of the Y axis, while the right side 107 of the central cylinder 101 defines the space to the right of the Y axis.

Finally, the central cylinder 101 is divided into the 4 quadrants Q1, Q2, Q3 and Q4, with the quadrant Q1 in the range 45 ° to 135 °, the quadrant Q2 in the range 135 ° to 225 °, the quadrant Q3 in the range 225 ° to 315 ° and the quadrant Q4 is in the range 315 ° to 45 °. From the preceding designations it also follows that the quadrant Q1 is the upper quadrant, the quadrant Q3 is the lower quadrant, the quadrant Q2 is the left quadrant and the quadrant Q4 is the right quadrant.

Fig. 2 shows a perspective view of the printing press according to the invention. According to the basic structure, the printing machine according to the invention consists of a central cylinder 201, with 8 inkjet printing inking units 202 (which are designated together with a reference number for the sake of simplicity) in the area of the upper half of the central cylinder and 4 flexographic printing in the area of the lower half of the central cylinder Inking units 203 (which are designated together with a reference number for the sake of simplicity) are arranged. The arrangement of the inkjet inking units 202 in the area of the upper half of the central cylinder 201 enables error-free operation of the inkjet printing inking units without the influence of the gravitational vector having a negative impact on the print image. In contrast to this, it was found that the quality of the inkjet printing declines when the inkjet printing inking units have to be operated in the area of the lower half of the central cylinder 201. The arrangement of the inkjet printing inking units in the area of the upper half of the central cylinder 201 is therefore particularly advantageous.

The material web 204 is guided from the unwinding station 205 to the central cylinder 201 for printing. The finished printed material web is wound up again in the winding station 206.

A housing 207 is located on the left side of the central cylinder 201. In the housing 207 there are feed guide rollers for feeding the material web 204 unwound from the unwinding station 205 to the central cylinder 201 and discharge guide rollers for discharging the printed material web from the central cylinder 201 to the winding station 206.

On the right side of the central cylinder 201 there is a drying station 208, which is arranged in front of the winding station 206 for drying the printed material web.

Fig. 3 shows a side view of the printing machine according to the invention. According to Fig. 2 Components already described are marked with the same reference numerals, so that in this respect the description in accordance with Fig. 2 is referred. In addition, the path of the web of material 204 is described in detail below:

From the unwinding station 205, the material web 204 arrives at the feed guide rollers 301 (which are designated together with a reference number for the sake of simplicity), which are located on the left side of the central cylinder in the housing 207. The feed guide rollers 301 guide the material web on to the feed guide roller 302, from where the material web passes via the feed guide roller 302 to the contact point 303 on the surface of the central cylinder 201.

On the surface of the central cylinder 201, the material web is guided past the individual inking units 202 and 203 in perfect register. At the separation point 304, the material web is then separated from the surface of the central cylinder 201 by the strip guide roller 305 in a defined manner. Both the contact point 303 and the detachment point 304 are located in the area of the lower quadrant Q3 of the central cylinder 201. In this way, the material web can be removed to the drying station 208 after flexographic printing without the printed side Material web still comes into contact with a guide roller until it reaches a drying station.

From the separation point 304, the material web arrives at the discharge guide rollers 306 (which for the sake of simplicity are designated together with a reference number), which are also located on the left side of the central cylinder in the housing 207. The discharge guide rollers 306 guide the material web on to the drying station 208, where the printed side of the material web is dried in the winding station 206 before being wound up.

Claims (12)

Printing machine with hybrid printing technology for printing a moving material web,
with a rotating central cylinder, on the surface of which the material web is guided from a contact point to a detachment point for printing, with several digital printing inking units for printing the material web in the area of an upper half of the central cylinder and several flexographic printing inking units in the area of a lower half of the central cylinder are arranged for printing the material web,
with an unwinding station for unwinding the material web to be printed from a roll and a winding station for winding the printed material web onto a roll, the unwinding station and the winding station being arranged on a first side of the central cylinder,
with feed guide rollers for feeding the material web unwound from the unwinding station to the central cylinder and with discharge guide rollers for discharging the printed material web from the central cylinder to the winding station, the feed guide rollers and the discharge guide rollers being arranged on a second side of the central cylinder,
with a feed guide roller for placing the material web at the contact point on the central cylinder and a strip guide roller for detaching the material web from the central cylinder, the feed guide roller and the strip guide roller are designed in such a way that the contact point and the detachment point at the lower quadrant of the Guide cylinder are arranged. Printing machine according to claim 1, wherein the material web consists of a plastic film or a plastic film substitute or an aluminum web or a paper web. Printing machine according to one of Claims 1 to 2, 4 flexographic printing inking units being arranged in the area of the lower half of the central cylinder and 8 digital printing inking units being arranged in the area of the upper half of the central cylinder. Printing machine according to one of Claims 1 to 3, 2 flexographic printing inking units are arranged behind the contact point and 2 flexographic printing inking units are arranged in front of the detachment point. Printing machine according to Claim 4, the 2 flexographic printing inking units behind the contact point for applying a primer and / or a partial primer and / or a full-surface colored primer. Printing machine according to one of Claims 4 to 5, the 2 flexographic printing inking units being provided in front of the separation point for finishing the printed material web. Printing machine according to one of Claims 1 to 6, a drying station for drying the printed material web being arranged on said first side of the central cylinder in front of the winding station. Printing machine according to one of Claims 1 to 7, with a digital printing switch-off device, so that the printing machine can be operated as a pure flexographic printing machine. Printing machine according to one of Claims 1 to 8, with a flexographic printing switch-off device, so that the printing machine can be operated as a pure digital printing machine. Printing machine according to one of Claims 1 to 9, the digital printing inking units consisting of inkjet printing inking units. Printing machine according to Claim 10, inserts are provided for the inkjet printing inking units in such a way that the positions of the inkjet printing inking units are interchangeable with one another. Printing machine according to Claim 11, with a star-shaped ink supply such that, depending on the inkjet printing inking unit located in the insert, the insert is automatically supplied with the corresponding printing ink.

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