EP3170665B1 - Method for operating a printing press having an anilox roller - Google Patents

Description

The present invention relates to a method for operating a printing press according to the preamble of claim 1.

In the DE 10 2006 004 568 A1 describes an anilox inking unit in which, in the direction of rotation of the anilox roller, a leveling roller is placed on the anilox roller after a chamber doctor blade and before an inking roller. The leveling roller picks up some of the ink from the anilox roller cells and places it back on the anilox roller bars. As a result, the webs that were previously squeegeed ink-free by a working squeegee of the chamber squeegee are again covered with printing ink, so that an even ink film is created over the entire lateral surface of the anilox roller. Disturbances in ink transfer caused by ink-free areas on the webs, which would otherwise occur, are avoided by the even ink film. In their entirety, the cells form a recessed surface portion of the anilox surface of the anilox roller and the webs lying between the cells form in their entirety a raised surface portion of the screen surface. In the publication mentioned, no statement is made as to the size of the raised surface area.

In the paragraph "Zell opening" of the article "Anilox roller" on the website https://de.wikipedia.org./wiki/Anilox roller in the version of October 15, 2015, it says that a minimum web width is optimal for smooth inking. The article thus teaches that the aim should be to minimize the raised surface area so that the printed image is not unsteady.

A problem not dealt with by the prior art mentioned - the Offenlegungsschrift and the Internet article - is the very narrow adjustment range of the color density in anilox inking units. Some print jobs require a comparatively high color density. In such cases, ink transfer is enhanced by raising the temperature of the anilox roller, which is connected to a temperature control device. the However, the temperature of the anilox roller can only be increased up to an upper limit, because if the upper limit is exceeded there would be a risk of the detergents used in the anilox inking unit igniting spontaneously. Therefore, the only option left is to replace the anilox roller used in the printing press with another one that has a larger scoop volume. However, this anilox roller change is associated with machine downtimes.

In WO2009082225A2 a method is described in which an anilox roller is used, the webs of which occupy less than 10%, in one embodiment less than 5% or 3% and preferably less than 2% of the entire roller surface.

In EP1911586A2 describes a short inking unit which has an anilox roller and an inking roller, with which a roller with a relatively soft surface is in contact, with which a roller with a relatively hard surface is in contact.

In US4862799A a metering roller is shown with a grid structure, the bottom area of which is 20% in one embodiment and 44% in another embodiment.

The present invention is based on the object of specifying a method for operating a printing press in which machine downtimes caused by changing anilox rollers are required less frequently.

This object is achieved by a method having the features of claim 1.

The invention is based on the finding that the density adjustment range of an anilox inking unit can be expanded through the interaction of the rider roller with a sufficiently large raised surface area. If the raised surface area is sufficiently large, the rider roller not only equalizes the ink transfer, but also increases the ink transfer and thus expands the density control range. Investigations have shown that under practical conditions the raised area proportion is at least 10% of the grid area should be. This means, for example, that the ratio of the opening width to the land width of the grid area should not exceed 9:1. The opening width/land width ratio is also referred to as the so-called cell/land ratio, particularly in the case of cell screening.

For example, the anilox roller can be engraved with a line of 90 lines per centimeter and the engraving can be what is known as a hatch, in which instead of the cells there are one or more grooves running in a helical shape around the anilox roller. With the ruling mentioned, the grid spacing or the so-called cell width is 0.11 mm. Due to unavoidable manufacturing tolerances, the groove width (opening width) is between 80 µm and 90 µm and the land width is between 20 µm and 30 µm. That is, if at a certain location the groove width is 80 µm, then the associated land width is 30 µm, and if at another location the groove width is 90 µm, then at the associated location the land width is 20 µm.

Advantageous further developments of the method according to the invention are specified in the dependent claims.

In a development, the raised area is 15% to 35% of the grid area. In a further development, an anilox roller is used as the anilox roller, in which the anilox surface has a ruling of at most 135 lines per centimeter. In a further development, an anilox roller is used as the anilox roller, the anilox surface of which is a hazel surface, in which the raised surface area is formed by a web or several webs and the recessed surface area is formed by a groove or several grooves and each web and each groove is helically shaped runs.

In a further development, the rider roller is kept in rolling contact exclusively with the anilox roller in the first printing operating mode.

In a further development, the rider roller is held in rolling contact with the anilox roller by a spring in the first printing operating mode.

In a further development, in the first printing operating mode the rotation of the rider roller is driven exclusively by the anilox roller, with the anilox roller driving the rider roller via peripheral surface friction.

In a further development, no traversing roller or rider roller is used as the rider roller, but rather an axially stationary roller.

Figur 1

eine Druckmaschine in einem ersten Druckbetriebsmodus mit Abrollkontakt zwischen Reiterwalze und Rasterwalze,

Figur 2

die Druckmaschine aus Figur 1 in einem zweiten Druckbetriebsmodus ohne Abrollkontakt zwischen Reiterwalze und Rasterwalze,

Figur 3

ein Schema der Wirkungsweise der Reiterwalze bei der Entnahme von Farbe aus Haschur-Rillen der Rasterwalze,

Figur 4

ein Schema der Rasterwalze mit auf Haschur-Stegen abliegender Farbe nach der in Figur 3 dargestellten Phase,

Figur 5

ein Diagramm mit Dichtestellbereichen des Anilox-Farbwerks im ersten und zweiten Druckbetriebsmodus und

Figur 6

einen Programmablaufplan zur Steuerung des Anilox-Farbwerks.

Advantageous developments of the invention also result from the following description of an exemplary embodiment and the associated drawing, in which shows:

figure 1

a printing press in a first printing operating mode with rolling contact between rider roller and anilox roller,

figure 2

the printing press off figure 1 in a second printing mode without rolling contact between rider roller and anilox roller,

figure 3

a diagram of the mode of action of the rider roller when removing ink from the Hashur grooves of the anilox roller,

figure 4

a scheme of the anilox roller with color lying on haschur bars according to the in figure 3 shown phase,

figure 5

a diagram with density adjustment ranges of the anilox inking unit in the first and second printing operating mode and

figure 6

a program flow chart for controlling the anilox inking unit.

In the Figures 1 and 2 a printing press 1 is shown with an anilox inking unit, which comprises an anilox roller 2 and an inking roller 3 lying against it. The inking roller 3 rolls on a printing forme cylinder 4, which is moistened by a dampening unit 5 and rests against a rubber blanket cylinder, which is not shown in the drawing. The printing machine 1 is an anilox offset sheet-fed printing machine. On the anilox roller 2 is a feed device 6 for supplying the fluid - here specifically the color - to the anilox roller 2 at. The feed device 6 comprises a bowl-shaped container 7 with a doctor blade 8 and a pivoting rear wall 9. By pivoting the pivoting rear wall 9, the level of the ink in the container 7 is selectively raised above a cutting edge of the doctor blade 8, which is required for the printing operation, and below the cutting edge is lowered in order to be able to turn off the feed device 6 from the anilox roller 2 after the printing operation, without the ink overflowing from the container 7. The inking roller 3 forms a removal device which removes the color from the anilox roller 2 .

The invention can be used not only in an anilox offset printing unit, but also in a flexographic printing unit. Such a flexographic printing unit can be part of an offset printing machine, for example as a varnishing unit, which has a number of offset printing units in addition to the flexographic printing unit. In the flexographic printing unit, instead of the inking roller 3, a printing forme cylinder is arranged, with which the anilox roller 2 is in rolling contact during printing, and this printing forme cylinder forms the pick-up device. The inking roller 3 and the rubber blanket cylinder mentioned in connection with offset printing are omitted in the flexographic printing unit.

The anilox roller 2 and the inking roller 3 are rotated in a manner coordinated with one another, as required in EP 1 291 176 B1 described procedure is inherent. By applying the technical measures EP 1 291 176 B1 Within the scope of the present invention, it is prevented that a particularly rough line pattern of the anilox roller 2 has a negative effect on the printed image and shows up there in the form of uneven coloring. Due to the offset superimposition of the accumulations of color on the Inking roller 3 doubles the fineness of the screening, so to speak, and closed areas are achieved in the printed image, which would otherwise only be possible with an anilox roller 2 with finer lines. For example, an anilox roller 2 with a ruling of less than 135 lines per centimeter can be used without any problems, for example an anilox roller 2 with a ruling of 110 lines per centimeter.

In printing operation, the anilox roller 2 rotates in the direction of rotation 10. A rider roller 11 is arranged in this direction of rotation after the feed device 6 and before the inking roller 3. After the inking roller 3 and before the feed device 6, a roller group 12 is arranged. The rider roller 11 has a peripheral surface made of a soft and ink-friendly rubber material and is mounted at both ends in a roller lock 13 which is arranged on a bearing lever 14 which can be pivoted by an actuator 15, for example by a pneumatic cylinder. A control device 24 controls the actuator 15 according to a program running in the control device 24 .

Each roller lock 13 includes a spring 16 for pressing the rider roller 11 against the anilox roller 2. This spring system is advantageous in terms of its readjustment effect, which compensates for changes in the diameter of the rider roller 11 caused by aging or by changing the rollers. The roller covering of the rider roller 11, which is made of rubber or a rubber-like plastic, can shrink or swell over time, as a result of which the roller diameter can change. Due to wear, the rider roll 11 can be replaced by a replacement roll whose diameter differs slightly from that of the original rider roll 11 due to tolerances. The roll cover of the replacement roll can be slightly softer or harder than the roll cover of the original rider roll 11; such differences in the compressibility of the rolls are also compensated for by the spring system. During the printing operation, the rider roller 11 is in rolling contact exclusively with the anilox roller 2, that is to say no other roller or cylinder is in contact with the rider roller 11.

figure 1 shows a first printing mode of operation, in which on each side of the machine (drive side, operator side) the bearing lever 14 with the roller lock 13 and the the rider roller 11 rotatably mounted therein is pivoted towards the anilox roller 2 and the respective spring 16 presses the rider roller 11 against the anilox roller 2 . The actuator 15 is extended accordingly.

In figure 3 The rolling of the rider roller 11 on the anilox roller 2 is shown in a greatly simplified representation, the components involved not being shown in their true size ratio to one another for better understanding. The anilox roller 2 has an anilox surface 17 which extends in a circular ring over the entire circumference of the anilox roller 2, which cannot be seen in the section shown. The screen surface 17 does not have to extend over the entire axial length of the screen roller 2 . The grid surface 17 consists of a groove 18 and a web 19, which delimits the groove 18 and form the side walls. The groove 18 and the web 19 run parallel to one another in helical form or helically around the axis of rotation of the anilox roller 2, which axis of rotation is perpendicular to the plane of the image figure 3 is oriented. The direction of extension of the groove 18 and the ridge 19 is oblique relative to the plane of the image figure 3 . The grid structure formed by the groove 18 and the web 19 resembles a thread, with figure 3 three courses of this "thread" are shown. Such a grid structure is also referred to as a hash. The ridge 19 forms a raised surface portion 20 of the grid surface 17 and the groove 18 a recessed surface portion 21 and both surface portions 20, 21 together result in the entire grid surface 17.

If two webs 19 and two grooves 18 ran parallel to one another, which would also be possible, the grid structure would have the form of a multiple thread and the raised surface portion 20 would be formed by the two webs 19 together and the recessed surface portion 21 by the two grooves 18 together .

The raised surface portion 20 is at least 10% of the entire grid surface 17, so that the recessed surface portion 21 is at most 90% of the grid surface 17. For example, the raised surface area 20 - the so-called contact area - can be more than 15% and less than 35% of the entire grid area 17, with a ridge width S of the ridge corresponding to 15% to 35% of a cell width Z, which is the sum of the ridge width S and a Groove width R of the groove 18 is.

figure 3 shows that the rider roller 11, when rolling over the groove 18, removes color from this and, after a few revolutions, has a closed color film 22 on its peripheral surface. The rider roller 11 not only removes ink from the groove 18, but also deposits the extracted ink again on the roof surface of the web 19 due to the splitting back, so that the entire screen surface 17 including its raised surface area 20 is colored after the rider roller 11 has been rolled over it is like this in figure 4 is shown. The amount of ink 23 deposited on the web 19 has the effect that the anilox surface 17 of the anilox roller 2 is in principle completely covered with ink and correspondingly more ink is transferred to the inking roller 3 . The anilox roller 2 can thus transfer more ink to the inking roller 3 per unit area of the anilox surface 17 than would be possible without the rider roller 11 .

In the first printing operating mode, the rider roller 11 is driven in rotation exclusively by the anilox roller 2, i.e. there is no auxiliary drive provided specially for the rider roller 11 and there is no other roller apart from the anilox roller 2 that rests on the rider roller 11 and this drives via peripheral surface friction. The rubber covering of the rider roller 11 presses into the grid structure of the anilox roller 2 somewhat due to the roller pressure in the nip of the two rollers 2, 11, which increases the friction and the rider roller 11 runs with the anilox roller 2 with virtually no slippage. The rider roller 11 does not carry out any axial reciprocating movement, because such an oscillating movement would impair the desired build-up of color on the roof surface of the web 19.

In figure 5 a diagram is shown whose ordinate represents the color density of the color black in the printed image. The bar on the left in the diagram represents the density adjustment range that is achieved in the first printing operating mode using the rider roller 11 and ranges from 1.82 to 2.41. The color density can be adjusted within this range solely by increasing or reducing the temperature control of the anilox roller 2 . An existing temperature control for the anilox roller 2 with a temperature control circuit, in which the anilox roller 2 is involved, is for reasons of graphical simplification in the Figures 1 and 2 not shown.

In figure 2 a second printing operating mode is shown, in which the rider roller 11 is switched off from the anilox roller 2 and is passive. The actuator 15 linked to the bearing lever 14 is retracted to such an extent that the spring 16 is no longer able to press the rider roller 11 against the anilox roller 2 and the two rollers 2, 11 are out of contact with one another. The second print mode of operation is intended for a print job that requires a lower color density than the print job for which the first print mode of operation is intended.

The right bar in the chart according to figure 5 represents the density adjustment range in the second printing mode of operation, this density adjustment range being from 1.48 to 2.06. The density adjustment range in the second print operating mode (right bar) extends down to lower color density values than the density adjustment range in the first print operating mode (left bar). Within the density setting range for the second printing operating mode, the ink transfer from the anilox roller 2 to the inking roller 3 can be adjusted solely by changing the anilox roller temperature control. Increasing the anilox roller temperature reduces the ink viscosity and correspondingly more ink is transferred from the anilox roller 2 to the pick-up device (ink applicator roller 3). By lowering the anilox roller temperature, the viscosity of the fluid (ink) is increased and accordingly less fluid is transferred to the pick-up device.

By switching off the rider roller 11 in the second printing mode, print jobs can be printed in this mode that require such a low ink density that the first printing mode is no longer suitable, for the following reason: In the first printing mode, the temperature of the anilox roller 2 would have to be lowered so much in order to achieve the low color density that condensation problems would occur on the anilox roller 2, through which the print quality would be impaired. It is therefore advantageous that the anilox roller temperature can be kept above the critical lower limit by switching off the rider roller 11 . The amount of fluid transferred determines the color density that can be measured in the printed image on the substrate.

An advantage of the method according to the invention is that the density control range represented by the right-hand bar is expanded by switching on the rider roller 11 by the density control range represented by the left-hand value bar, which means that changing the anilox roller 2 to change the effective scoop volume of the anilox roller 2 is less necessary and the machine downtimes associated with changing anilox rollers can be minimized.

In figure 6 1 shows the flow chart of the operating method of the printing machine 1, with the steps of the program running in the control device 24 corresponding to this flow chart.

In a first method step 101, the color density or coloring is measured.

In a second method step 102, a decision is made as to whether the coloring is too slight or not. If the coloring is too low, a decision is made in a third step 103 as to whether or not the upper setting limit of the anilox roller temperature has already been reached. If the upper adjustment limit has already been reached, a decision is made in a fourth step 104 as to whether the rider roller 11 is already in contact with the anilox roller 2 or not. If the rider roller 11 is already placed on the anilox roller 2, i.e. is operated in the first printing operating mode, the anilox roller is exchanged in a fifth step (for a replacement anilox roller with a higher scoop volume) and/or the printing ink used is exchanged, for example with an ink with higher pigmentation. If it is determined in the fourth step 104 that the rider roller 11 is not yet in contact with the anilox roller 2, then in a sixth step 106 the rider roller 11 is placed against the anilox roller 2 and the anilox roller temperature is reduced. Then, in a seventh step 107, continuous printing begins.

If it is determined in the second step 102 that the coloration is not too low, then in an eighth step 108 it is decided whether the coloration is too high or not. If the inking is not too great, then continuous printing begins in the seventh step 107 . However, if the measurement in the eighth step 108 shows that the coloring is too high, then checked or decided in a ninth step whether the current anilox roller temperature already corresponds to the lower control limit for the anilox roller temperature or not. If the lower setting limit has already been reached, then in a tenth step 110 it is checked whether the rider roller 11 is already in contact with the anilox roller 2 or not. If this check establishes that the rider roller 11 is in contact with the anilox roller 2, then in an eleventh step 111 the rider roller 11 is switched off from the anilox roller 2, that is, from the first printing operating mode ( figure 1 ) to the second printing operation mode ( figure 2 ) is changed and the anilox roller temperature is increased on the temperature control device. Then the continuous printing 107 is started.

If the check carried out in the ninth step 109 shows that the lower control limit of the anilox roller temperature has not yet been reached, then in a twelfth step 112 the anilox roller temperature is adjusted by lowering the anilox roller temperature. Then the continuous printing 107 is started.

If the check carried out in the third step 103 shows that the upper setting limit of the anilox roller temperature has not yet been reached, then in the twelfth step 112 the temperature of the anilox roller is adjusted by increasing the anilox roller temperature. After that, production run 107 will also begin. If it is determined in the tenth step 110 that the rider roller 11 is not in contact with the anilox roller 2, i.e. that the anilox inking unit is operated in the second printing operating mode, then in a thirteenth step 113 the anilox roller is replaced (for a replacement anilox roller with a lower scoop volume) and/or the color adjusted, for example replaced by another color with a different pigmentation. Then the continuous printing 107 is started.

Reference List

1

printing press

2

anilox roller

3

inking roller

4

plate cylinder

5

dampening system

6

feeding device

7

container

8th

doctor blade

9

swiveling rear panel

10

direction of rotation

11

rider roller

12

roller group

13

roller lock

14

bearing lever

15

actuator

16

feather

17

grid area

18

groove

19

web

20

Raised surface area

21

Deeper surface area

22

color film

23

amount of paint

24

control device

25 to 100

-

101 to 113

process step

R

groove width

S

bridge width

Z

cell width

Claims (8)

1. Method of operating a printing press (1) comprising an anilox roller (2), a supply device (6) for supplying a fluid to the anilox roller (2), a takeoff device for taking the fluid off the anilox roller (2), and a rider roller (11), wherein the anilox roller (2) has a screen surface (17) consisting of a raised surface portion (20) and a recessed surface portion (21), the takeoff device (3) is a roller (3) or a cylinder, and the rider roller (11) is arranged downstream of the supply device (6) and upstream of the takeoff device in the direction of rotation (10) of the anilox roller (2),
   characterized
   in that the anilox roller (2) is an anilox roller (2) with a raised surface portion (20) amounting to a minimum of 10% of the screen surface (17) and in that in a printing operation in a first printing operation mode, the rider roller (11) is kept in rolling contact with the screen roller (2) and in a printing operation in a second printing operation mode, the rider roller (11) is kept out of rolling contact with the screen roller (2).
2. Method according to claim 1,
   characterized
   in that the raised surface portion (20) amounts to 15%-35% of the screen surface (17).
3. Method according to claim 1 or 2,
   characterized
   in that the anilox roller (2) is an anilox roller (2) with a screen surface (17) ruling of 135 lines per centimeter at the maximum.
4. Method according to any one of claims 1 to 3,
   characterized
   in that the anilox roller (2) is an anilox roller (2) with a tri-helical screen surface (17) in which the raised surface portion (20) is formed by one or more webs (19) and the lowered surface portion (21) is formed by one or more grooves (18), each web (19) and each groove (18) extending helically.
5. Method according to any one of claims 1 to 4,
   characterized
   in that in the first printing operation mode, the rider roller (11) is kept in rolling contact exclusively with the anilox roller (2).
6. The method recited in any one of claims 1 to 5,
   characterized
   in that in the first printing operation mode, the rider roller (11) is kept in rolling contact with the anilox roller (2) by a spring (16).
7. Method according to any one of claims 1 to 6,
   characterized
   in that in the first printing operation mode, the rotation of the rider roller (11) is driven exclusively by the anilox roller (2), the anilox roller (2) driving the rider roller (11) by circumferential surface friction.
8. Method according to any one of claims 1 to 7,
   characterized
   in that the rider roller (11) is not a distributor roller but an axially stationary roller (11).

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