EP2014470B1 - Method for automatic regulation of the register between imprints in a multi-colour rotary printing press - Google Patents

Description

The invention relates to a method for automatically controlling the register between impressions (printed images) in a multicolor rotary printing press according to claim 1.

In rotary printing presses, the colors in the respective printing units must be printed one above the other in register. If this does not succeed, an unsightly and therefore unsaleable pressure arises, ie a material loss occurs. In continuous printing operation, the register deviations can be measured, for example, by means of a register controller and automatically regulated to the predetermined desired position. For this purpose, at least one marking of each printing unit is printed, whose respective position is measured to the mark printed by another printing unit. From a deviation from a desired position, a correction signal is generated, which is then carried out by suitable devices (such as register rollers). As a rule, a register controller operates in such a way that the markings for measuring the register positions are printed in a relatively small acquisition window in the circumferential direction. Therefore, the print images of the printing units to be measured must be prepositioned to a few mm during the setup of a print job, so that the printed on a web markers in the detection window next to each other or come to rest. In order to achieve this, a web path length (web path) between the printing units must be brought to a certain size, for example an integer multiple of the print format (cylinder circumference). This can be achieved, for example, by adjusting the web path length between 2 printing units by rolling in the web path, which are adjusted, for example, by register spindles, or by adjusting the relative angular positions of the cylinder carrying the printing plate happen. The resulting roll positions or angular positions in turn depend, for example, on the web guide, the printing format and the stretching of the printing material.

Usually, when working without additional aids, the procedure is such that the entire printing system is brought into the register for new jobs by manually giving control commands to rollers in the web path or to the positioning means of the forme cylinder. The result is checked by means of a web monitoring system. For an automatic control, the achieved actual positions are then taken over as set positions and stored and subsequently kept constant there, for example in a control process. This process is very lengthy and depends on the skill of the operator, which inevitably but always has a large consumption of substrate result. A quite conceivable solution is that due to unique presumed positions for each print size (cylinder circumference), a default of the forme cylinder or Bahnwegwalzen using register spindles (hereinafter also spoken by spindle positions) is made. The determination of the target positions generates a great deal of effort when commissioning the machine. Changes in the printing unit assignment, web guide, or in the material properties (elongation) lead after the pre-positioning to a still significant register deviation, which can even lead to the register marks still lie outside the measuring window and thus miss the desired result almost entirely ,

In most cases, the parameters that would be required for a prior computational determination of this size, previously not known with sufficient accuracy, so that it is practically always required, while the material is running to perform this pre-positioning by means of a search process. In any case, a significant amount of material is needed to deliver non-salable products and waste, resulting in significant economic losses.

There is therefore still a need to find a method that minimizes material costs and thus saves both material and unused machine time.

The EP 0 070 565 describes a method in which the brand printed by him in each printing unit is driven in each case under the sensor immediately following the printing unit. Investigations carried out within the scope of the invention have shown that this method is very time-consuming and, despite some improvements, still consumes a considerable amount of material and is not very precise due to mechanical engagement. It also depends on the skill of the printer, the brands of the individual printing units suitably place.

A clear improvement offers the EP 1 132 203 B1 with the approach to make such a pre-positioning automatically. The basic idea is that by skillfully switching on and off of pressure in an iterative process, an automatic determination of any actual positions of marks and their correction can take place. Thus, printing is first started in the last unit and the position of the mark printed there is detected by the sensor behind this printing unit and the position signal of a fixed rotary encoder in which the mark has been detected is finally registered for this position Position around a measurement window formed. This operation is initially in the machine from the beginning back to the second Performed printing unit, so that now for each printing unit a measuring window is formed uniquely around the printed by the respective previous printing brand. Thereafter, the procedure is reversed so that only in the first printing unit is printed and the mark is placed in the middle of the measuring window of the sensor behind the second printing unit by adjusting the path to the incoming web. Thereafter, the subsequent printing unit is turned on and proceeded equally, etc.

A disadvantage of this method is that a double pass each with a pressure in each printing unit is required.

Furthermore, the described method can only be used if only the register mark per printing unit lies in the scanning path of the web scanner. If other objects or marks are also printed within the scanning track, which is often the case, one code mark per printing unit must be additionally printed at a known distance from the mark for recognition. The disadvantage of this is that the ID tag occupies an extra space, which increases the measurement window and thus reduces the usable area for the subject.

In addition, in gravure printing, the existing forms can only be changed with a considerable financial outlay, as would be required, for example, by the subsequent insertion of the code marks.

It is therefore an object of the present invention to provide a method according to claim, which overcomes the disadvantages of the prior art and thus makes it possible to achieve a further saving in material without making costly machine-side changes required.

The solution of this object is achieved by the features of claim 1. The subclaims have advantageous developments of the method according to the invention content.

Fig. 1

eine schematisch stark vereinfachte Darstellung einer Rotationsdruckmaschine bzw. Regelungsvorrichtung mit einer Zylinderverstellung, und

Fig. 2

eine der Fig. 1 entsprechende Darstellung einer weiteren Rotationsdruckmaschine bzw. Regelungsvorrichtung mit Registerspindel.

Further details, advantages and features of the present invention will become apparent from the following description of exemplary embodiments with reference to the drawing. It shows:

Fig. 1

a schematically simplified view of a rotary printing machine or control device with a cylinder adjustment, and

Fig. 2

one of the Fig. 1 corresponding representation of another rotary printing press or control device with register spindle.

In Fig. 1 a rotary printing machine RD is shown, which has in the web running direction L of a web 10 successively arranged printing units D1, D2, D3 and D _N. This means that, depending on the number of colors to be printed, corresponding numbers of printing units are present, with the printing unit D _N symbolizing the last printing unit in the web running direction L in each case. Each of the printing units has an associated printing cylinder 1, 2, 3 or N1 and an associated impression 4, 5, 6 N2.

Per printing unit D1 to D _N , a control and regulating unit 7, 8, 9 and N3 is provided for the impression roller position and the pressure.

Furthermore, each printing unit D1 to D _{N is associated with} a drive controller 11, 12, 13 or N4 for the printing cylinders 1, 2, 3 or N1.

Encoder 14, 15, 16 and N5 for the angular position of the respective printing cylinder 1, 2, 3 and N1 are assigned to each printing unit D1 to D _N.

In the web running direction L in each case behind the printing units D1, D2, D3 and D _N , a measuring system or a scanner 17, 18, 19 or N6 is also provided, which serves to detect the position of one or more register marks, the pressure units D1 , D2, D3 and D _N are printed on the web 10 together with the impression or the printed image.

Further, a control unit 30 is provided for the impression rollers 4 to N2, which is signal-connected to the respective control and regulation units 7, 8, 9 and N3.

The control unit 30 is further coupled to a sequence control unit 33, which in turn is signal-connected or coupled to a control unit 31 for angle-synchronous positioning of the pressure cylinders 1, 2, 3 or N1. This control unit 31 is in turn connected to the drive controllers 11, 12, 13 and N4. The measuring systems 17 to N6 are, as is apparent Fig. 1 results, further connected to a computing unit 32 for calculating the angular position of the printing cylinder 1, 2, 3 and N1 in relation to the printed image. As Fig. 1 Furthermore, the computing unit 32 is coupled to the sequencer 33.

In the embodiment according to Fig. 2 are all elements according to those of the embodiment Fig. 1 correspond with the same reference numerals. The Fig. 2 however, represents a rotary printing press RD _R , with register spindles 36, 37 and N8 is provided. In contrast to the rotary printing machine according to Fig. 1 is the register in the web direction L not on the relative angular position of the printing cylinder 1 to N1, but via the web path between the printing units D1 to D _N by means of each one of the associated register spindles 36, 37 and 38 set, each in the web running direction L behind the printing units D1 to D3 are arranged.

In the Fig. 2 illustrated embodiment of the invention further comprises drive units 34, 35 and N7, which serve to position the associated register spindles 36, 37 and N8. These drive units 34, 35 and N7 are connected to a control unit 38 for the register spindles, which is coupled to the sequencer 33, as shown in detail in the illustration of Fig. 2 results.

In the two embodiments according to the Fig. 1 and 2 prints or print images in the successively arranged printing units are printed D1 to D _N are each individually and successively to the material web 10, the web of material passes through 10 for this purpose, the printing units D1 to D _N in a fixed sequence one after the other. The cylinders 1, 2, 3 and N1 carry in the Fig. 1 and 2 not shown in detail and the impression rollers 4, 5, 6 and N2 are intended to produce a transfer pressure for producing the impression on the material web 10, wherein the pressure of the impression rollers (cylinder) 4, 5, 6 or N2 and can be turned off. The arithmetic unit 32 and the control unit 33 drive the printing units D1 to D _N to regulate the entire printing operation.

• a) Der Presseur N2 der letzten Druckeinheit D_N geht in Druck an. Zusammen mit dem Druckbild wird in der letzten Druckeinheit D_N eine Registermarke auf die Materialbahn 10 gedruckt.
• b) Falls der Abtastkopf des Bahntasters N6 quer zur Bahnlaufrichtung L nicht in der Spur der Registermarke steht, stellt der Bediener den Abtastkopf des Bahntasters N6 in die richtige Position oder der Abtastkopf des Bahntasters N6 wird automatisch über eine Linearverstellung vorpositioniert. Diese Seitenausrichtung ist ein optionaler Schritt, der natürlich nur dann vorgenommen werden muss, falls der Abtastkopf des Bahntasters N6 tatsächlich quer in Bahnlaufrichtung nicht korrekt eingestellt ist. Erfindungsgemäß kann hierbei vorausgesetzt werden, dass die Abweichung der Markenposition in Seitenrichtung (falls überhaupt vorhanden) kleiner ist als die Markenbreite, was bedeutet, dass die Ausrichtung aller Abtastköpfe entsprechend denjenigen des letzten Abtastkopfes des letzten Bahntasters N6 ausreichend ist.
• c) Der hinter dem Druckzylinder N1 angeordnete Bahntaster N6 sucht die Position der Registermarke in Bahnlaufrichtung L und meldet die Erkennung der Registermarke an die Recheneinheit 32.
• d) Die Position der Registermarke in Relation zum Druckzylinder N1 der letzten Druckeinheit D_N wird mittels des Drehgebers N5 ermittelt und in der Recheneinheit 32 gespeichert. Ferner wird um die Registermarke ein Messfenster in einer vorgegebenen Breite gebildet.
• e) Das in Bahnlaufrichtung L vor dem Druckwerk D_N angeordnete Druckwerk D3 geht nunmehr in Druck an und druckt ebenfalls ein Druckbild und eine zugehörige Registermarke auf die Materialbahn 10.
• f) Der Bahntaster N6 erfasst die Position der jetzt zusätzlich gedruckten Registermarke des vor dem Druckwerk D_N liegenden Druckwerks D3.
  Die Position der Registermarke des Druckzylinders 3 der Druckeinheit D3 in Relation zum Druckzylinder N1 der Druckeinheit D_N wird in der Recheneinheit 32 berechnet und gespeichert.
• h) In der Recheneinheit 32 wird ferner eine Differenz zwischen den gespeicherten Registermarkenpositionen berechnet und mit dem per Definition vorher bereits bekannten Sollmarkenabstand verrechnet. Das Ergebnis wird als Korrekturwert an die Steuereinheit 33 weitergeleitet. Dabei wird der Abstand zwischen einem virtuellen Nullpunkt und der zuerst gedruckten Registermarke mit dem Abstand zwischen dem Nullpunkt und der nachgedruckten Registermarke verrechnet. Ferner wird der definitionsgemäße Sollabstand zwischen den Registermarken addiert bzw. subtrahiert. Die Steuereinheit 33 berechnet nunmehr das Stellkommando für den Antriebsregler 13, der die Winkellage des Druckzylinders 3 der Druckeinheit D3 entsprechend korrigiert (Fig. 1) bzw. für die Antriebseinheit N7, die den Bahnweg über die Registerspindel N8 entsprechend verstellt (Fig. 2). Zur schnellen und dehnungswirkungsarmen Verstellung bei größeren Winkelkorrekturen wird der Presseur 6 der Druckeinheit D3 für die Dauer der Verstellung abgehoben und danach wieder angestellt.
• j) Nach dem Durchlauf der Materialbahn 10 vom Druckzylinder 3 zum Bahntaster N6 wird die automatische Registerregelung für den Druckzylinder N1 aktiviert und die nunmehr gemessene Registerabweichung am Druckzylinder N1 bzw. der Registerspindel N8 korrigiert. Dies stellt das Aktivieren einer automatischen Registerregeleinheit der Druckeinheit dar, die der jeweils zuletzt angestellten Druckeinheit in Bahnlaufrichtung L nachgelagert ist, im zuvor beschriebenen Falle, also der Druckeinheit D_N, die der Druckeinheit D3 in Bahnlaufrichtung L nachgelagert ist.

An inventive method sequence or a sequence of a pre-positioning is described by way of example below:

• a) The impression roller N2 of the last printing unit D _N is pressurized. Together with the printed image, a register mark is printed on the material web 10 in the last printing unit D _N.
• b) If the scanning head of the N6 webbing scanner is not in the track of the registration mark, then the operator sets the scanning head of the N6 web scanner to the correct position or the scanning head of the N6 web scanner is automatically pre-positioned via a linear adjustment. This page orientation is an optional step, which, of course, only has to be done if the scanning head of the N6 web scanner is actually incorrectly set transversely in the web running direction. According to the invention, it can be assumed here that the deviation of the mark position in the lateral direction (if present at all) is smaller than the mark width, which means that the alignment of all scanning heads corresponding to that of the last scanning head of the last web scanner N6 is sufficient.
• c) The arranged behind the printing cylinder N1 web scanner N6 searches the position of the register mark in the web running direction L and reports the detection of the register mark to the computing unit 32nd
• d) The position of the register mark in relation to the printing cylinder N1 of the last printing unit D _N is determined by means of the rotary encoder N5 and stored in the arithmetic unit 32. Furthermore, a measurement window in a predetermined width is formed around the register mark.
• e) arranged in the web running direction L in front of the printing unit D _N printing unit D3 is now in print and also prints a printed image and an associated register mark on the web 10th
• f) The path sensor N6 detects the position of the now additionally printed register mark of the lying before the printing unit D _N printing unit D3.
  The position of the register mark of the printing cylinder 3 of the printing unit D3 in relation to the printing cylinder N1 of the printing unit D _N is calculated and stored in the arithmetic unit 32.
• h) In the arithmetic unit 32, a difference between the stored register mark positions is further calculated and offset against the reference mark distance already known by definition. The result is forwarded to the control unit 33 as a correction value. In this case, the distance between a virtual zero point and the first printed register mark is offset with the distance between the zero point and the reprinted register mark. Furthermore, the nominal distance defined by definition is added or subtracted between the register marks. The control unit 33 now calculates the setting command for the drive controller 13, which corrects the angular position of the printing cylinder 3 of the printing unit D3 accordingly ( Fig. 1 ) or for the drive unit N7, which adjusts the web path accordingly via the register spindle N8 ( Fig. 2 ). For quick and low-expansion adjustment with larger angular corrections of the impression roller 6 of the printing unit D3 is lifted for the duration of the adjustment and then turned back on.
• j) After the passage of the material web 10 from the printing cylinder 3 to the path sensor N6, the automatic register control for the printing cylinder N1 is activated and the now measured register deviation corrected on the printing cylinder N1 and the register spindle N8. This represents the activation of an automatic register control unit of the printing unit, which is located downstream of the last employed printing unit in the web running direction L, in the previously described case, ie the printing unit D _N , which is downstream of the printing unit D3 in the web running direction L.

The procedure described above is repeated for the respective preceding printing unit D2 or D1 until all printing units D1 to D _N involved in the printing have been set.

Preferably, after these steps have elapsed, a sequential control - each printing unit D1 to D _N following its preceding in the "mark-and-mark" mode - can be switched over to a control according to a stand color. However, this operation is generally not required to achieve registering. As a rule color by level here a method is referred to, in which the register error for each printing unit D1 to D _N with respect to a predetermined printing unit that prints the so-called. Stand color, measured and adjusted accordingly. Conveniently, this is the first printing unit D1.

With this procedure, the machine is now already regulated, without the pressure is turned off again. Upon reaching the first printing unit D1 with this above procedure, the entire rotary printing machine is in a normal and typical state of register control in continuous printing. This makes it possible to further save material when pre-positioning, since at least one idle deleted.

If, in addition to the markers for the register controller, other printed elements are located in the track scanned by the measuring head, a clear recognition of a mark will also be necessary here. From the choice of a suitable brand form, this can be handled well by conventional means, in particular, this applies to the commonly used triangular register marks when the register measuring head is provided with a rectangular mask, the long side of the rectangle is perpendicular to the web running direction. Here it is sufficient to adapt to the typical signal curve of the flanks and an intermediate one expected to serve, for example, plateau-like course of the measurement signal as a criterion to ensure sufficient detection in almost all cases.

Another advantageous embodiment of a sensor is the construction as a spectral multi-range probe (for example, RGB), which can be used in addition to the color code. This is very helpful insofar as it can be assumed that when known colors are used, spectral identifiers are also present, which can then be used in the second level to confirm the detected objects. Such an identifier may consist, for example, of data from a color database or a color parameter information transmitted from the prepress.

The coding and decoding described above is much easier if, as a register measuring head, it is advantageous to use a camera which determines the brand form in a simple manner according to conventional digital image processing methods of recognition. If a color camera is used, by means of the at least three color channels present there, the selective color information obtained there can additionally or also be used alone in the manner described above.

With the procedure according to the invention, the abovementioned disadvantages of the known procedures are overcome or further reduced in this way.

In addition to the written disclosure of the invention is hereby explicitly on their graphic representation in the Fig. 1 and 2 directed.

Claims (9)

1. A method for automatically regulating the registers between imprints being applied individually and successively onto a web (10) by at least two printing units (D1 to D_N) arranged successively in the direction of travel (L) of the web in a rotary printing press, the printing units being passed successively by the web (10) for this purpose, the method comprising the following steps:

   [1] setting the contact pressure in the printing unit (D_N) being the last in the direction of travel (L) of the web;

   [2] detecting and storing a speed sensor position detected by a speed sensor (14 to N5), in which position a register mark being printed together with the imprint is detected by a scanning unit (17 to N6) arranged behind the printing unit put into operation last in direction of travel (L) of the web;

   [3] setting the contact pressure of the printing unit arranged in front of the printing unit being put into operation last in the direction of travel (L) of the web;

   [4] detecting the register mark applied by the printing unit put into operation during the previous method step [3] by a scanning unit behind the printing unit following said printing unit in the direction of travel (L) of the web and storing the associated speed sensor position in which said register mark was detected;

   [5] calculating a correction value for the position of the imprints by comparing the two speed sensor positions such that the correction amount is effective in that, after performing the correction, the two register marks will be located in a finite, predetermined closely adjacent distance;

   [6] stopping the contact pressure of the printing unit put into operation last and performing the calculated correction by a control unit (33) and again setting the contact pressure of said printing unit;

   [7] activating an automatic register regulation of the printing unit following the printing unit respectively put into operation last in the direction of travel (L) of the web; and

   [8] successively repeating the method steps [1] to [7] for all other printing units upstream in the direction of travel (L) of the web.
2. The method of claim 1, characterized in that a lateral positioning of the respective web scanner is performed behind the last printing unit (D_N) and that all other lateral positioning of the web scanners of the upstream printing units are performed automatically.
3. The method of claim 1, characterized in that a lateral positioning of the web scanners is calculated and performed based on data pre-known from a prepress.
4. The method of claim 1, in which the executions of the corrections are performed by a drive control (11 to N4) or by changing the position of a web guiding roller (36, 37, N8) being inserted into the web path between the printing units (D1 to DN) such that it is capable of changing the web length between two printing units.
5. The method of claim 1, in which the executions of the calculated corrections are performed by a relative correction of the angular position of the printing unit passed earlier by the material web (10).
6. The method of claim 1, in which the method steps [1] to [8] are performed simultaneously.
7. The method of claim 1, in which a plurality of register marks per printing unit is imprinted and in which the register mark to be scanned is provided with a code information.
8. The method of claim 7, in which the register mark comprises at least one edge arranged perpendicular to the direction of travel (L) of the web and at least one further edge arranged in a predetermined angle and distance to the direction of travel (L) of the web and that these characteristics are used for differentiation with respect to other marks for identification in that the slopes of the flanges of the edges are formed when passing below a scanning head being provided with a slot-shaped mask having a longitudinal extension perpendicular to the direction of travel (L) of the web for this purpose.
9. The method of claim 7, in which all marks printed by respectively one printing unit are provided with different colours, wherein a scanning in at least two spectral ranges is performed in the scanning heads and the fractions of each range detected therewith are used as a code for differentiating between a printed register mark and the respectively other printed colours, wherein the spectral fractions of each of the printed register marks are pre-known such that a superimposed printing of marks is recognized in that an expected combination of fractions is not sufficiently existent.

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