DE202006020066U1 - Device for optimum adjustment of the provision in a multiple printing units having rotary flexographic printing machine - Google Patents

Abstract

Device for optimal adjustment of the provision in a multiple printing units (9) having rotary flexographic printing machine by adjusting the relative positions between an anilox roller (1) and a forme cylinder (2) and the forme cylinder (2) and one of a counter-pressure cylinder (3) guided to be printed Material web (4) with the following components:
- With a control unit (16) having a computing unit (15),
- With an adjusting unit (13) for adjusting the relative position between the anilox roller (1) and forme cylinder (2) and forme cylinder (2) and impression cylinder (3), which is in signal communication with the control unit (16) for the exchange of position and status information and
- With a color-selective sensor (14), which communicates with the arithmetic unit (15) and the control unit (16) for the exchange of measurement data and control information for data acquisition in signal communication.

Description

The The invention relates to a device for optimum adjustment of Provision in a multi-printing rotary flexographic printing machine according to claim 1.

The order-based adjustment of the roll group in a flexographic printing machine, the at least the relative positioning of the plate cylinder to Ink applicator roll (also called anilox roll / anilox roll), whose The task is to color the cliché with printing ink and the positioning of the plate cylinder to the printing cylinder, the leads the substrate, involves considerable consumption of material and time. Usually This happens today so that from the known geometric Dimensions and positions of the inking roller, of the forme cylinder, the material and the printing cylinder relative positioning all cylinders involved calculated each other and then adjusted becomes. Is thereby the target of the calculation a certain pressure between the two pairings, this results in one Setting in which as a result of just this pressing also color in both Pairings is transported and thus creates a pressure. Such Motorized presetting systems are today in all modern To find machines.

there However, it is inevitable that concrete production tolerances the elements involved, various elasticity properties in particular the structure of the printing form, material thickness variations in the substrate, ink transfer properties etc. have an effect on the print result achieved.

It Therefore, there is still the task of each print job, the Adjust the machine so that a quality-appropriate pressure is created and in particular the printing form is not subjected to unnecessary wear which reduces the life of the mold and its replacement one represents a significant cost factor.

Becomes So for a print job according to the geometric data a first Setting done so this requires an extra Correction for optimal conditions to be able to produce.

These Most of the correction is still done by hand today Printer, for example, the pressure initially reduced so far until the the pressure no longer takes place and then again delivered so far - the pressure is increased - until a pressure just be reached again. The result of his actions he observed each visually directly on the printing line. This procedure is for both cylinder pairings and each printing unit on running machine performed in succession. Optionally, the printer also uses a video link observation device to do this, which takes a picture of the print result and on a screen reproduces.

In the EP 1 249 346 a method and a device is described, which transmit the procedure shown here directly into an automatic process and thus saves the individual Verstellhandlungen by being performed by engines.

This Although described method is an improvement, has but still a number of disadvantages. It is analogous to the Procedure of the printer by means of a known camera-based Inspection system in an interactive manner a sequence of adjustments the pressure in the cylinder pairings made and in their effect observed on the printed image respectively. This is always included checked at least two consecutive pictures, whether the Print shows fewer or more elements than the previous one Image. Each dependent the result is then decided whether the pressure increases or is reduced. Does not change more, the goal is achieved and on a completeness of the print closed. From the completeness of the print will not be in one described in more detail Sealed to the appropriate pressure in the respective pairings. adversely First of all, this procedure is separate and sequential for each color be performed needs and therefore a significant amount of material despite the automation the processes secondly, in the parked or non-printing Print the ink on the anilox roll or the form cylinder can dry and leads to an additional washing effort. thirdly can not be considered with this method, like a Playback of tonal values in the picture is really done, so this usually left to the printer in subsequent subsequent steps must stay. Not to be neglected is the high capital expenditure involved in using a full - surface inspection system for Picture capture and evaluation represents.

Of the Invention is therefore based on the object, a device for optimal setting of the provision in a multiple printing units to provide a rotary flexographic printing machine which makes it possible to with relatively simple technical means and little effort one Reduction of waste and a requirement of the printing process to achieve a better adjusted rule or tax result.

The solution of this task is performed by the Features of claim 1.

The under claims have advantageous developments of the device according to the invention Content.

From the DE 44 13 735 A1 While a method of controlling or regulating the dot size in a rotary press is known, this machine is not a rotary flexographic press. Furthermore, no color-selective sensor is used in the device described in said document, but an image pickup device which scans the print image to determine the grid dot size.

following an example of the device according to the invention for explanation the procedure of the invention closer to the drawing explained.

Become next to the printed image that makes up the actual printed product Additionally Placed brands, so can these are arranged so that marks printed by a printing unit a spatially separated from the brands printed from another printing unit Find space (for example, side by side or in a row or summarized in a block) and thus in a print marks from all printing units are included at the same time. This eliminates that otherwise required for differentiation of the pressure in not needed right now Printing units and the paint does not dry up.

For color-accurate image reproduction, it is of considerable importance that the reproduction of tone values in the individual colors takes place correctly, especially in autotypical four-color printing. In particular, this is also determined to a considerable extent by the pressing, so that it is advantageous, instead of the simple yes / no criterion of completeness of a print, to use the criterion of a correct tonal value reproduced by the printing characteristic (10, Figure 1 - Tonwert im Pressure FD _G depending on the nominal value FD _N on the mold). If, for each color, a plurality of stamps, each with a different tonal value known in its shape on the mold, are printed, it can be concluded by measuring the dot increments on the printed stamps on the properties of the tonal reproduction in the print.

These Approach also bypasses the dilemma for evaluating a completeness create or record a master that represents them. In a printing company, a predetermined dot gain for the Printing process known and goal for a quality-appropriate Print. According to the invention therefore, the target tone characteristic and the target solid density as a criterion for the Selection of a suitable pressure used.

For this purpose, for example, in four process steps, starting from the calculated original setting of the pressure, this between anilox roller 1 and form cylinder 2 and / or form cylinder 2 and impression cylinder 3 varies and the pressure characteristic is determined in each case. It is then selected that pressure in which the pressure characteristic of the target characteristic comes closest. For this it is not necessary to reduce the pressure to such an extent that the pressure in the printing unit is suspended. Rather, it is sufficient to have achieved a minimum pressure at which the characteristic comes close to the nominal tonal characteristic. Thus, for example, the printing of 3 marks with a coverage of 30%, 50% and 75% provides sufficiently good information on the characteristic curve that allows the selection of the correct pressing. In the case of a plurality of tonal characteristic curves, the adjustment of the rollers is preferably carried out on the basis of the characteristic curves that correspond to the desired tonal characteristic curve 17 comes closest. In a case in which two characteristics are approximately equal or close to the desired Tonwertkennlie 17 are arranged remotely, a setting is made according to a mean value. This further has the advantage that one does not have to add an empirical amount of pressure, starting from the exposure of the pressure (or a no longer occurring increase in elements), but can actually select a value that has already been realized.

In addition to The described measurements on halftone tag fields will still be a solid field printed. This solid field then allows one in the Densitometry usually used relation between pigment concentration per area and optical density a statement about the layer thickness printed by the coloring unit on the Substrate has been applied and in particular whether the for the printed product provided optical density is present during printing. Such specifications are, for example, by in-house standards or even universally valid Standards known or predetermined as predetermined target values. At the same time can from a sufficient homogeneity of the paint job on a solid surface closed on the right pressure between the cylinder pairings become. For example, if the pressure is too high, so-called pinched edges, if the pressure is too low, the pressure is "flaky".

The determination of the correct pressing is now carried out in such a way that, starting from the computationally determined pressing, there are two to three further pressing settings For example, X + 50 microns, X - 50 microns and X - 100 microns, in which the pressure characteristic is measured in each case on a printed copy or on several copies for the purpose of averaging. Already in the production of a printing form, a certain printing characteristic, namely the typical of the machine with which a product is to be printed, has been taken into account as known. Now, this expected characteristic curve is compared with the recorded characteristic curves and the pressure between the impression cylinder and the pressure cylinder, which comes closest to this characteristic, is set. Thereafter, the pressure between cliché and anilox roller is varied in the same way and the pressure is used, in which the characteristic corresponds to the specifications and further the full tone brand with its properties comes closest to the specifications.

to Measurement of color density on the solid tone or halftone fields Methods and devices used, such as in known inline density measuring devices find use in offset printing. Such measuring heads exist, for example from a remission probe, between the optical axis of the illumination and that of a measuring device has a geometry 0 ° / 45 °, 45 ° / 0 °, equipped with a plurality of optical filters, which are chosen so that for all measured colors as high as possible Influencing caused by the colors used or customary Standards and a device for synchronization of the Moment of measurement with the printed product has. Likewise for example, the optical principle is reversed to that effect, that the lighting in selected Spectral ranges and the detection then without color filter happens or a combination of both.

An example of a possible procedure according to the invention is described below:
A first pressure within a pair of cylinders is set, for example, the computationally determined pressure +50 microns.

The The measured color density values described above are now used by the Full-tone and half-tone measuring fields registered and from this the pressure characteristic constructed. Thereafter, the pressure in a cylinder pairing a fixed value decreased and again for the new pressing generates a pressure characteristic. In the next steps this will be Repeated procedure so that a set of pressure characteristics is created, wherein a characteristic belongs to a respective pressing adjustment. In addition will that characteristic inserted, in the production of the printing form as a characteristic for the printing press was assumed. There is now a change in the second press pairing carried out, which is traversed according to a same pattern. At the same time always measured the full-tone field, for which also a target Volltondichte may be assumed to be known.

It At the end, the mating setting is chosen, which is both the required Setpoint density parameters as well as the required pressure curve on next comes.

None the above procedures requires a complete shutdown of the pressure or the absence of self-printing elements.

He follows the measurement using a densitometric measuring head, so it provides both values for the color density as well as values for an optical area coverage, which is preferably calculated according to the known Morey-Davis equation becomes. A measuring head can thereby several consecutive mark fields also capture with a pass under the sensor, so that the number the needed for the measurement Specimens further reduced.

Instead of the gradual change the pressing is a further advantageous embodiment of Invention in that the adjustment of the pressure between the Cylinder pairings each continuously between two defined Limits, and from the knowledge of the time course and the path length between the press contact and the position of the sensor becomes one Measurement each associated with the correct pressure.

Alternatively, can also record the color density values and optical surface coverages be made by a camera, in the case of a lighting geometry is taken care of, which is similar to the described 0/45 or 45/0 arrangements. On this way you can equally several measurement fields are captured within a format and it it is not necessary to have a separate measuring device in the machine to install. Although normal RGB cameras are not for measuring a Color-matched suitable filters, this may be such as from Künzli, Noser, Loger and Murad (EMPA, St. Gallen 1993), in appropriate make be exploited for a quick way of working.

to Adaptation to the conditions in a machine or printing plate it can be useful over the Width of the pressure to arrange the corresponding measuring fields several times. It can handle it slight deviations from the parallelism or evenness of the participants Cylinders / shapes registered and compensated by mediation.

The only figure of the drawing shows a schematically greatly simplified representation of a device according to the invention for optimum adjustment of the provision in a plurality of printing units 9 having rotary flexographic printing machine, wherein representative of all printing works only one printing unit 9 is shown schematically greatly simplified.

The printing unit 9 has an anilox roller 1 with a diameter D ₁ . Furthermore, the printing unit has 9 a form cylinder 2 with a diameter D ₂ , with the anilox roller 1 cooperates and with respect to this over a displacement V _{1 is} adjustable to the pressure between the anilox roller 1 and the form cylinder 2 to be able to adjust.

Furthermore, the printing unit has 9 an impression cylinder 3 with a diameter D ₃ , which is used to guide a web to be printed 4 with the form cylinder 2 interacts. The relative position between the forme cylinder 2 and the impression cylinder 3 can be adjusted along a displacement V ₂ .

The device according to the invention also has a control unit 16 on that with a computing unit 15 is provided. Furthermore, an actuating unit 13 for adjusting the relative position between the anilox roller 1 and the form cylinder 2 as well as the form cylinder 2 and the impression cylinder 3 intended. The actuator 13 stands with the control unit 16 for exchanging position and status information in signal connection.

The device further comprises a color selective sensor 14 on that with the arithmetic unit 15 and the control unit 16 is in signal communication for the exchange of measured data and control information for measured value acquisition.

As the figure further clarifies, is by the printing unit 9 in the example, a series of print marks 5 . 6 . 7 and 8th on the material web 4 printed. This represents the brand 8th a full-tone mark.

The color selective sensor 14 who always seen in web direction L behind the printing units 9 is arranged, which are to be set with the procedure according to the invention, detects the print marks 5 to 8th for a plurality of adjustment steps between the anilox roller 1 and the form cylinder 2 in accordance with the predetermined adjustment path V ₁ or the forme cylinder 2 and the impression cylinder 2 according to the adjustment V ₂ . The measurement result is sent to the arithmetic unit 15 passed.

In this, actual tone values FD _G are obtained from the reflectance values resulting from the color-selective detection for each of the print marks 5 to 8th calculated. Further, a pressure characteristic curve 10 is generated from the calculated actual tone values FD _G , which are the calculated actual tone values FD _G over known nominal tone values FD _{N of} the print marks 5 to 8th applies (diagram A).

Furthermore, pressure characteristic curves will be 11 created, wherein each set during the recording of a characteristic relative position change between the anilox roller 1 and the form cylinder 2 or the form cylinder 2 and the impression cylinder 3 represents the share parameter.

In the diagram is also given for the printing process and taken into account in the printing plate production target Tonwerkkennlinie 17 entered and this is in the arithmetic unit 15 with the determined pressure characteristic family 11 compared (diagram B).

In a further method step, the detected solid density D _{G of} the full-tone mark 8th evaluated as a function of the relative positions of the cylinder, resulting in more characteristics DG _1/2 DG _2/3 , as can be seen from the figure (Diagram C).

The measured or calculated solid density D _{G of} the full mark 8th are compared with a nominal solid density D _N , which is predetermined for the printing process and is taken into account in the printing plate production.

Finally, according to the invention, the adjustment of the relative position between the anilox roller 1 and the form cylinder 2 and the form cylinder 2 and the impression cylinder 3 determined and by the actuator 13 set at which the Tonwerk characteristic of the desired Tonwertkennlinie 17 and the solid density of the target solid density D _N is closest.

Although this does not appear in detail from the schematically greatly simplified illustration of the figures, it is possible according to the invention that the color-selective sensor 14 on a traverse above the material web 4 is arranged movably controlled to the respective measuring position movable.

Furthermore, it is possible that a color-selective sensor 14 on the left and right side of the web 4 is arranged.

As possible training variants for the color-selective sensor 14 For example, a per se known color density measuring device or a video camera are conceivable.

Further, as another embodiment shape of the color-selective sensor 14 a sensor line arranged in the web running direction can be used, which consists of elements arranged one behind the other with different spectral sensitivity.

When Alternative can be a color-selective sensor one in the web running direction arranged sensor line can be used in the case of successive Measurements one filter each with different spectral characteristics is connected upstream.

definitions

Shade:

Measure (in%) for the Proportion of property within an area having only the two properties "0" and "1" (In the present case, the properties are in the Rule about properties of a visual nature).

Nenntonwert:

When Nominal Tone is the tone that represents a surface as Property is assigned by definition.

Dot gain:

As the dot gain caused by a process step, the difference of the tone value after the process is referred to the tone value before the process. In the present case, this is the difference between the tone value after printing and the nominal tone value 12 designated.

full tone:

brand with 100% area coverage (reference marks).

Color selective detection:

Reflectance measurement, in which is determined how much light from a mark in a given spectral range is remitted.

Target tone:

Of the Tonal value of a surface as a result of a machining process should have.

Tonwertkennlinie:

A Curve in which on one axis of an x, y coordinate system the nominal tone values and on the other axis those assigned tonal values of the same area are applied. For example, a typical procedure for printing is in that the nominal tone values on the one and actual tone values after Passing through a machining process applied on the other axis become.

Target Tonwertkennlinie:

A Tonwertkennlinie, in which on the one axis nominal tone and on the other axis, the target tone values are plotted.

Target solid density:

One given full-tone density, which must be achieved.

1

anilox roller

2

form cylinder

3

Impression cylinder

4

Web / print web

5-8

print marks

9

printing unit

10

Pressure characteristic curve

11

Pressure characteristic curves

12

Tone curve without dot gain

17

Target Tonwerkennlinie

V ₁

adjustment between 1 and 2

V ₂

adjustment between 2 and 3

FD _G

Actual tone

FD _N

Nominal tone

D _N

Target solid density

D _G

measured or calculated solid density

Claims (7)

Device for optimally adjusting the provision in a plurality of printing units ( 9 ) having a rotatory flexographic printing machine by adjusting the relative positions between an anilox roller ( 1 ) and a form cylinder ( 2 ) and the forme cylinder ( 2 ) and one of an impression cylinder ( 3 ) guided to be printed web ( 4 ) with the following components: - with a control unit ( 16 ), which is a computing unit ( 15 ), - with an actuating unit ( 13 ) for adjusting the relative position between anilox roller ( 1 ) and form cylinder ( 2 ) and form cylinder ( 2 ) and impression cylinder ( 3 ) connected to the control unit ( 16 ) is in signal communication for the exchange of position and status information and - with a color-selective sensor ( 14 ), which is connected to the arithmetic unit ( 15 ) and the control unit ( 16 ) is in signal communication for the exchange of measured data and control information for measured value acquisition. Apparatus according to claim 1, wherein the color selective sensor ( 14 ) on a traverse motor is moved to the measuring position controlled. Apparatus according to claim 1 or 2, wherein each color-selective sensor ( 14 ) is arranged on the left and the right side of the printing web. Device according to one of claims 1 to 3, wherein as a color-selective sensor ( 14 ) a known ink density measuring device is used. Device according to one of claims 1 to 3, wherein as color-selective sensor ( 14 ) a video camera is used. Device according to one of claims 1 to 3, wherein as a color-selective sensor ( 14 ) arranged in the web running direction sensor line is used, which consists of successively arranged elements with different spectral sensitivity. Device according to one of claims 1 to 3, wherein as a color-selective sensor ( 14 ) a sensor line arranged in the web running direction is used, which is preceded by a filter with different spectral characteristics in successive measurements.