EP3941747B1 - Method for determining a position of reciprocal contact between a printing roller and at least one counter-roller of a flexographic printing machine - Google Patents

Description

The invention relates to a method executed or at least executable in a flexographic printing machine for determining a position of mutual contact between a printing roller and at least one counter roller according to the preamble of claim 1.

through the EP 1 018 426 A1 a method is known for adjusting two cylinders of a printing press against one another, in which one of the two cylinders is allowed to rotate while the two cylinders are moved radially towards one another, and in which the torque acting on one of the two cylinders is monitored and in which, when the monitored torque causes a exceeds a predetermined threshold, the radial position of the two cylinders relative to each other reached at that moment is taken as the zero position for the engagement.

• Herbeiführung einer unterschiedlichen Umfangsgeschwindigkeit der zumindest zwei voneinander abgestellten Zylinder
• Anstellung der beiden Zylinder mit den Anstellmitteln
• Aufzeichnung oder Beibehaltung der Relativposition der beiden Zylinder zueinander, wenn zumindest ein Parameter der Drehbewegung der zumindest zwei Zylinder einen Grenzwert überschreitet.

through the WO 2010/142405 A2 a printing press with at least one inking unit is known, which inking unit comprises at least two cylinders which are set against one another during printing, the cylinders being rotatable with the aid of at least one drive, with sensors being provided in the printing press with which parameters of the rotary movement of the cylinders - such as the torque generated by the at least one drive or the rotational speed - are to be recorded, the printing machine having adjusting means with which the at least two cylinders can be adjusted in relation to one another in their radial direction, the printing machine being operatively connected to a control unit with which the adjusting means can be controlled and wherein the control unit is set in such a way that it causes the following method steps to set the contact position of the at least two cylinders:

• Bringing about a different peripheral speed of the at least two cylinders that are set off from one another
• Adjustment of the two cylinders with the adjustment means
• Recording or maintaining the relative position of the two cylinders to each other when at least one parameter of the rotational movement of the at least two cylinders exceeds a limit.

through the IT VR20 120 085 A1 discloses a method of identifying the tangential position between the face of a printing cylinder and another printing element in rotary printing presses.

through the DE 20 2011 052514 U1 a flexographic printing machine is known, which is equipped with several printing groups, which are arranged around a central counter-pressure roller on which the material to be printed is located, each of said printing groups integrating at least one printing roller and one inking roller, which are opposed during printing and with the aid of at least a rotary drive motor can be rotated, the printing machine being operatively connected to a control unit for detecting one or more parameters for the rotary movement of the rollers, such as the torque, the electrical current consumed by said rotary drive motor, or the rotational speed, and wherein the printing machine has force adjustment means applying a linear movement to the end points of said printing roller and inking roller, in their radial direction, and integrating positioning motors.

through the WO 2015/001126 A1 a method for mutual adjustment of two cylinders in a printing press is known, wherein the cylinders are each driven with at least one drive at different peripheral speeds, with at least the first cylinder by means of at least one adjustment device in the direction is moved onto the second cylinder, with the adjustment position being determined, with the values of at least one measured variable of at least one of the two cylinders being detected by a measuring or detection device, with the values of the measured variable being received by means of a control device and the adjustment device being controlled, with the Adjustment position is determined, with the first change in the value of the measured variable of the at least one cylinder compared to an initial value of this measured variable has resulted, whereby the value of the angle of rotation is recorded at which there is a deviation of the value of the measured variable from the initial value.

A flexographic printing machine has a central drum on which a printing material in the form of a sheet or a flexible foil is arranged in a printing process. One or more printing units are brought into contact with the central drum. Each printing unit has a printing roller and an inking roller, with the printing roller carrying at least one cliché on its lateral surface. The inking roller, which is usually designed as an anilox roller, is also called an anilox roller.

In a flexographic printing machine of the type described above, a first pair of electric motors moves the platen roller of each printing unit towards or away from the central drum, and a second pair of electric motors moves the inking roller of each printing unit towards or away from the respective printing roller. For this purpose, the respective axis of rotation of each printing roller or anilox roller is mounted on a guide orthogonal to the respective axis of rotation, with a motor being arranged at one end of each guide, which causes a linear movement of the respective printing roller or anilox roller. Each of these motors is then generally associated with a detection device for detecting the angular position of the respective motor shaft, i. H. assigned an encoder, wherein the respective angular position corresponds in each case to a linear position of the printing and/or inking roller.

In such a flexographic printing machine, there is the problem of determining the respective printing position of each printing roller relative to the central drum in order to ensure optimal printing. The optimal pressure is characterized by the fact that it is sufficient to produce a print image of good print quality on the substrate, but is not excessively large, since excessive pressure would damage the clichés used and/or cause deformation of the printing areas. what then to double borders and overapplied colors. Poorly adjusted pressure thus leads to poor ink transfer between the cliché and the printing material and/or between the inking roller and the cliché, each of which has a negative effect on the print quality.

A similar problem also occurs when determining the mutual position between the respective inking roller and the respective pressure roller.

To solve this problem, systems for adjusting the position of the printing rollers and inking rollers are known, which are based on a visual judgment by an operator, or there are automated systems such. B. in European patent no. EP 2 460 658 B1 described in the name of the same applicant.

Nevertheless, there is still a need to optimize, speed up and improve the automated process of determining the mutual contact position between the respective inking roller and the respective printing roller as well as the printing roller and the central drum in order to determine an optimal contact pressure between these rollers during the printing process .

It is therefore the object of the invention to provide an optimized method for determining a position of mutual contact between a pressure roller and at least one counter-roller.

The object is achieved according to the invention by a method having the features of claim 1. Furthermore, a flexographic printing machine according to claim 7 is provided, wherein this is designed to carry out the steps of the method according to the invention. The dependent claims relate to advantageous developments and/or refinements of the solution found.

The achievable with the invention consist in particular that a position of mutual contact between a pressure roller and at least one counter-roller is determined automatically, quickly and reproducibly, preferably also as a function of the shape or the relief of the cliché, the position of mutual contact being between a pressure roller or a cliché carried by it and a central drum and/or the position of the mutual There is contact between the printing roller or the cliché carried by it and an inking roller.

The solution found contributes to minimizing waste during the setting process of the printing units of the flexographic printing machine and/or the time required for this setting process.

An embodiment of the invention is shown in the drawings and is described in more detail below.

Fig. 1

eine schematische Draufsicht eines Ausschnitts aus einer Flexodruckmaschine;

Fig. 2

eine Seitenansicht des Ausschnitts von Fig. 1;

Fig. 3

ein Flussdiagramm bezüglich des Verfahrens zum Bestimmen einer Position des gegenseitigen Kontaktes zwischen einer Druckwalze und einer zentralen Trommel in einer Flexodruckmaschine;

Fig. 4

ein Flussdiagramm bezüglich des Verfahrens zum Bestimmen einer Position des gegenseitigen Kontaktes zwischen einer Druckwalze und einer Farbwalze in einer Flexodruckmaschine.

Show it:

1

a schematic plan view of a section of a flexographic printing machine;

2

a side view of the detail of 1 ;

3

Figure 12 shows a flow chart relating to the method for determining a position of mutual contact between a printing roller and a central drum in a flexographic printing machine;

4

Fig. 12 is a flowchart related to the method for determining a position of mutual contact between a printing roller and an inking roller in a flexographic printing machine.

A generic flexographic printing machine is designated as a whole by reference numeral 10 . Such a flexographic printing machine 10 has a pair of frame walls 20 arranged parallel to one another, between which a central drum 30 is rotatably mounted. In the printing process, a flexible foil F The printing material that is formed is guided at least around this central drum 30 or is carried by the central drum 30 rotating in the printing process. At least one printing roller 40 is or at least can be thrown onto this central drum 30 in order to apply a printed image to the printing material. The pressure roller 40 is between two backing rollers 30; 50 arranged, of which a counter-roller 30 as the central drum 30 and the other counter-roller 50 as an inking roller 50 are formed. A printing roller 40 cooperating with an inking roller 50 forms a printing unit in the flexographic printing machine 10. The inking roller 50 is z. B. designed as an anilox roller and is also referred to as an anilox roller.

1 shows an example of the aforementioned arrangement in a schematic plan view of a section of a flexographic printing machine 10. Furthermore, FIG 1 that both the pressure roller 40 and the relevant counter-roller 30; 50 each have a first electric motor 31; 41; 51 have and by means of the relevant first electric motor 31; 41; 51 can each be moved in rotation. Each of these first electric motors 31; 41; 51 each has a first encoder 32; 42; 52 on. The pressure roller 40 and the inking roller 50 each have a second electric motor 43 at each axial end; 53, wherein the pressure roller 40 and the inking roller 50 by means of the relevant second electric motor 43; 53 each in the direction D of a mutual approach between the pressure roller 40 and the counter-roller 30 in question; 50 can be moved translationally. Each of these second electric motors 43; 53 each has a second encoder 44; 54 on.

As the 2 example in a side view of the detail of 1 can be seen on the circumference of the central drum 30 more, z. B. be arranged eight printing units, each of these printing units preferably in the previously in connection with the 1 described manner is formed. The individual printing units can be operated independently of one another, ie each can be brought into an operative connection individually with the central drum 30 .

1. (a) rotatives Bewegen der mit der Druckwalze 40 in Kontakt zu stellenden Gegenwalze 30; 50 mittels des betreffenden ersten Elektromotors 31; 51, wobei die von dieser Gegenwalze 30; 50 beabstandet angeordnete Druckwalze 40 in einer vorbestimmten Winkelstellung nicht rotierend belassen wird;
2. (b) translatorisches Bewegen der nicht rotierenden Druckwalze 40 in Richtung D der mit der Druckwalze 40 in Kontakt zu stellenden Gegenwalze 30; 50 mittels des betreffenden zweiten Elektromotors 43; 53;
3. (c) Erfassen mindestens eines von Null verschiedenen Wertes eines Parameters mit Hilfe des ersten Encoders 42 des betreffenden ersten Elektromotors 41 der Druckwalze 40, wobei dieser Parameter eine durch den gegenseitigen Kontakt zwischen der mit der Druckwalze 40 in Kontakt gestellten Gegenwalze 30; 50 und der Druckwalze 40 bewirkte Schleppdrehung anzeigt;
4. (d) Bestimmen der Position des gegenseitigen Kontakts zwischen der Druckwalze 40 und der mit dieser Druckwalze 40 in Kontakt gestellten Gegenwalze 30; 50 auf der Grundlage des Wertes des erfassten Parameters;
5. (e) Verändern der bisherigen Winkelstellung der Druckwalze 40 um einen von Null verschiedenen Winkel;
6. (f) Wiederholen der Schritte (a) bis (d) und Bestimmen der entsprechenden Position des gegenseitigen Kontakts zwischen der Druckwalze 40 und der mit dieser Druckwalze 40 in Kontakt gestellten Gegenwalze 30; 50 für die im Schritt (e) geänderte Winkelstellung der Druckwalze 40;
7. (g) Berechnen einer durchschnittlichen Position des gegenseitigen Kontakts zwischen der Druckwalze 40 und der mit dieser Druckwalze 40 in Kontakt gestellten Gegenwalze 30; 50 in Abhängigkeit von jeder für eine bestimmte Winkelstellung der Druckwalze 40 bestimmte Position des gegenseitigen Kontakts zwischen der Druckwalze 40 und der mit dieser Druckwalze 40 in Kontakt gestellten Gegenwalze 30; 50, wobei die Position des gegenseitigen Kontakts zwischen der Druckwalze 40 und der mit dieser Druckwalze 40 in Kontakt gestellten Gegenwalze 30; 50 für jedes axiale Ende der Druckwalze 40 unabhängig voneinander bestimmt wird und die durchschnittliche Position des gegenseitigen Kontakts zwischen der Druckwalze 40 und der mit dieser Druckwalze 40 in Kontakt gestellten Gegenwalze 30; 50 für jedes axiale Ende der Druckwalze 40 unabhängig voneinander berechnet wird.

According to the invention, in this flexographic printing machine 10, a method for determining a position of mutual contact between a printing roller 40 and at least one backing roller 30; 50 or can at least be executed there, the method comprising the following steps:

1. (a) rotating the counter-roller 30 to be brought into contact with the pressure roller 40; 50 by means of the relevant first electric motor 31; 51, the counter-roller 30; 50 spaced pressure roller 40 is left non-rotating in a predetermined angular position;
2. (b) translating the non-rotating pressure roller 40 in direction D of the backing roller 30 to be brought into contact with the pressure roller 40; 50 by means of the relevant second electric motor 43; 53;
3. (c) detection of at least one non-zero value of a parameter by means of the first encoder 42 of the relevant first electric motor 41 of the pressure roller 40, this parameter being determined by the mutual contact between the counter-roller 30 placed in contact with the pressure roller 40; indicates drag rotation caused by 50 and pressure roller 40;
4. (d) determining the position of mutual contact between the pressure roller 40 and the counter-roller 30 brought into contact with this pressure roller 40; 50 based on the value of the sensed parameter;
5. (e) changing the previous angular position of the pressure roller 40 by a non-zero angle;
6. (f) repeating steps (a) to (d) and determining the corresponding position of mutual contact between the pressure roller 40 and the counter-roller 30 brought into contact with this pressure roller 40; 50 for the angular position of the pressure roller 40 changed in step (e);
7. (g) calculating an average position of mutual contact between the pressure roller 40 and the backing roller 30 contacted with this pressure roller 40; 50 as a function of each position of the pressure roller 40 determined for a specific angular position mutual contact between the pressure roller 40 and the backing roller 30 brought into contact with this pressure roller 40; 50, the position of mutual contact between the pressure roller 40 and the counter-roller 30; 50 is determined independently for each axial end of the pressure roller 40 and the average position of mutual contact between the pressure roller 40 and the counter-roller 30 placed in contact with this pressure roller 40; 50 is calculated for each axial end of the pressure roller 40 independently.

The respective specific angular positions of the printing roller 40 are preferably defined in each case as a function of a position in the relief of a cliché arranged on the outer surface of the printing roller 40 .

Calculating an average position of mutual contact between the pressure roller 40 and the counter roller 30 in question; 50 as a function of each position of mutual contact between the pressure roller 40 and the counter-roller 30 placed in contact with this pressure roller 40, determined for a specific angular position of the pressure roller 40; 50 has the advantage that by adjusting the position of mutual contact between the pressure roller 40 and the backing roller 30; 50 an excessive contact pressure from the cliché arranged on the printing roller 40 to the printing material and thus damage to the cliché used is avoided. Rather, the adjustment of an average position of mutual contact between the pressure roller 40 and the backing roller 30 brought into contact with this pressure roller 40; 50 leads to good print quality, since there is largely no unwanted deformation of the printing areas and the generation of double edges and/or an excessive application of ink to the printing material is avoided.

• (d1) Vergleichen des Wertes des erfassten Parameters mit einem zuvor festgelegten Wertebereich für diesen Parameter;
• (d2) Messen einer von der Druckwalze 40 oder der Z mit dieser Druckwalze 40 in Kontakt zu stellenden Farbwalze 50 durch ihre jeweilige translatorische Bewegung bis zur Position des gegenseitigen Kontakts zwischen der Druckwalze 40 und der mit dieser Druckwalze 40 in Kontakt gestellten Farbwalze 50 zurückgelegten Strecke mittels des zweiten Encoders 44; 54 des die betreffende translatorische Bewegung antreibenden zweiten Elektromotors 43; 53;
• (d3) Bestimmen der Position des gegenseitigen Kontakts zwischen der Druckwalze 40 und der mit dieser Druckwalze 40 in Kontakt gestellten Farbwalze 50 auf der Grundlage der gemäß Schritt (d2) gemessenen Strecke, wenn der Wert des erfassten Parameters im zuvor festgelegten Wertebereich für diesen Parameter liegt.

In a further development of the proposed method, the determination of the position of mutual contact between the printing roller 40 and the inking roller 50 that is in contact with this printing roller 40 in step (d) comprises the following steps:

• (d1) comparing the value of the detected parameter with a predetermined range of values for that parameter;
• (d2) Measuring an ink roller 50 to be brought into contact with this pressure roller 40 by the pressure roller 40 or the Z by their respective translational movement up to the position of mutual contact between the pressure roller 40 and the inking roller 50 placed in contact with this pressure roller 40 distance traveled by means of the second encoder 44; 54 of the second electric motor 43 driving the translatory movement in question; 53;
• (d3) determining the position of mutual contact between the pressure roller 40 and the inking roller 50 contacted with this pressure roller 40 on the basis of the distance measured according to step (d2) if the value of the detected parameter is in the predetermined range of values for this parameter .

An angular momentum is preferably selected as the parameter to be detected according to step (c), this angular momentum being transmitted by the respective counter-roller 30; 50 is given to the pressure roller 40.

If the pressure roller 40 and the inking roller 50 to be provided with the pressure roller 40—that is, both rollers 40; 50 - by their respective second electric motor 43; 53 are each moved translationally, the position of mutual contact between the pressure roller 40 and the inking roller 50 to be brought into contact with this pressure roller 40 is preferably determined independently of one another by means of the respective second encoder 44, 54 of each second electric motor 43, 53.

The calculated position of mutual contact between the pressure roller 40 and the counter-roller 30 to be brought into contact with this pressure roller 40; 50 is advantageously used in a printing process performed by the flexographic printing machine 10.

A preferably electronic control unit 100 is also provided and configured in such a way ( 1 ) that this control unit 100 determines the angular positions of the pressure roller 40 at the respective position of mutual contact between the pressure roller 40 and the counter-roller 30 to be brought into contact with this pressure roller 40; 50 defines and executes a printing process with these defined angular positions of the printing roller 40 . In this control unit 100 digital data are preferably stored in particular for certain angular positions of the pressure roller 40, these angular positions at the respective position of mutual contact between the pressure roller 40 and the counter-roller 30 to be brought into contact with this pressure roller 40; 50 correspond to significant positions in the relief of the plate arranged on the printing roller 40. This is because the relief of the cliché arranged on the printing roller 40 has projections or depressions corresponding to the print image to be produced at specific positions that are considered significant.

This also results in a flexographic printing machine 10, having at least one between two counter-rollers 30; 50 arranged pressure roller 40, wherein the one counter-roller 30 as a central drum 30 and the other counter-roller 50 as an inking roller 50 are formed, wherein both the pressure roller 40 and with this pressure roller 40 to be placed in contact

backing roll 30; 50 each have a first electric motor 31; 41; 51 have and by means of the relevant first electric motor 31; 41; 51 can each be moved in rotation, each of these first electric motors 31; 41; 51 each have a first encoder 32; 42; 52, the pressure roller 40 and the inking roller 50 having a second electric motor 43; 53 have and by means of the relevant second electric motor 43; 53 each in a direction D of mutual approach between the pressure roller 40 and the counter-roller 30 to be brought into contact with this pressure roller 40; 50 can be moved translationally, each of these second electric motors 43; 53 each have a second encoder 44; 54, this flexographic printing machine 10 being designed to carry out the steps of the method described above.

The method carried out in a flexographic printing machine 10 for determining a position of mutual contact between a printing roller 40 and a central drum 30 will now be described again using a flowchart according to FIG 3 explained. First, the pressure roller 40 is brought into its starting position with the aid of the second electric motor 43 .

At this point, the flexographic printing machine 10 is ready to transport the flexible film F driven at a minimum drive speed. The pressure roller 40 is driven in slow rotation by its first electric motor 41, so that the pressure roller 40 is arranged according to a (first) predetermined angular (absolute) position. When the pressure roller 40 is positioned in the first predetermined angular position, the pressure roller 40 is stopped, ie it is held still in this first angular position by the first electric motor 41, which remains in the "torque cut-off" mode, ie in the neutral position. The predetermined angular position of the pressure roller 40 can be chosen arbitrarily, z. B. by dividing the lateral surface of the printing roller 40 (ie the cliché arranged on it) into sectors (e.g. equivalent), the number of sectors (which are subject to a predetermined angle of rotation) being equal to the number of angular positions that are required for each Pressure roller 40 wants to scan.

Alternatively, the predetermined angular position of the pressure roller 40 can be selected in a weighted manner. In this case, each angular position and/or its first angular position is predefined on the basis of the conformity of the platen 40, in particular on the basis of a measured angular position of the relief of the cliché placed on the platen 40.

A print template is assigned to each cliché, i. H. a pdf file or a jpeg file in which the angular positions of the relief are precisely defined in a certain reference system, which defines the print image that is to be transferred to the flexible film F during printing.

Each predetermined angular position of the printing roller 40 can be selected from the angular positions in which the plate placed on the printing roller 40 has at least one relief or a group of reliefs.

In particular, each predetermined angular position is chosen to match the above-mentioned angular position (ie the selected reliefs) to the central drum 30 or a plane containing the D-direction, ie the axes of rotation of the central drum 30 and the pressure roller 40, aligns.

In any case, each predetermined angular position is stored in said memory unit.

After the pressure roller 40 has stopped in the first predetermined angular position, the central drum 30 is now set in rotation with its first electric motor 31 (block S1), e.g. B. with a predetermined (fixed) speed.

While the central drum 30 is rotating and the platen roller 40 is stationary, i. H. not rotated, in this method, the platen roller 40 is moved toward the center drum 30 in the D direction (block S2).

In practice, the method consists in driving one of the two second electric motors 43 individually in order to move the respective axial end of the pressure roller 40 towards the central drum 30. However, it can also be provided that the two second electric motors 43 are driven simultaneously in order to move both axial ends of the pressure roller 40 forward to the central drum 30 .

The method therefore envisages using the first encoder 42 to monitor the possible rotation caused by the contact between the rotating central drum 30 and the printing roller 40 (i.e. the cliché placed thereon) of the printing roller 40 (and thus the rotor of the first electric motor 41, in neutral position) is imposed.

According to the invention, the method provides for using the first encoder 42 of the first electric motor 41 of the pressure roller 40 to detect at least one non-zero value of a parameter indicative of a drag rotation when idling (in the "torque deactivated" mode) (S3 block), the Drag rotation through the achieved mutual contact between the rotating center drum 30 and the platen roller 40 is induced during the movement of the platen roller 40 toward the center drum 30 in the D direction.

In practice it has been observed that when the pressure roller 40 is stationary (i.e. not rotating), i.e. H. one of the reliefs present on the cliché, as it advances towards the central drum 30 in direction D, touches the central rotating drum 30 and is driven by it in rotation (in the opposite direction) - by friction.

The first encoder 42 of the first electric motor 41 of the printing roller 40 detects the angular momentum given by the central drum 30 to the printing roller 40, for example by detecting a value of the parameter consisting of a rotational speed of the printing roller 40 (i.e. a variation of the rotational speed of the platen 40 from a zero to a non-zero value) and/or an angular position of the platen 40 (i.e. a variation in the angular position of the platen with respect to the predetermined - previous - angular position in which the platen 40 was positioned ) was chosen.

In detail: If the first encoder 42 of the first electric motor 41 (on the left in "torque cut-off mode") detects a value of the rotational speed of the pressure roller 40 that is not zero and/or a value of the angular position of the pressure roller 40 that differs from the predetermined (first) angular position at which the platen roller 40 was positioned deviates, then the electronic control unit 100 is configured to determine that the platen roller 40 has received drive rotation induced by the mutual contact between the platen roller 40 and the central drum 30 .

The method consists in particular of using the value of the determined parameter a reference area thereof (block S4), e.g. B. with a minimum value (e.g. corresponding to a value close to zero angular velocity or the predetermined angular position in which the pressure roller 40 was positioned) and a maximum allowable value.

If the value of the parameter is within the reference range, then the detection can be considered acceptable.

Otherwise the detection is deemed unacceptable and the steps of the above procedure are repeated.

At this point, where the detection can be considered acceptable, the process continues by stopping (block S5), e.g. B. by immediately stopping the movement of the pressure roller 40 approaching the central drum 30 in direction D, i. H. the second, previously driven electric motor 41 is immediately stopped.

In practice, the pressure roller 40 is stopped in a (current) mutual (first) contact position with the central drum 30 itself in its advance towards the central drum 30 in the D-direction, i. H. where the reliefs of the cliché mounted on this printing roller 40 touch the central drum 30 with an optimal contact pressure defined by the contact pressure such that the rotational movement (through friction/resistance) between the central drum 30 and the Pressure roller 40 is transferred.

It has been found in experimental tests that this position of mutual contact, which determines the first rotation by pulling the print roller 40 through the rotation imposed by the central drum 30, determines the optimal pressure of mutual contact leading to an optimal and high quality print during normal operation of the flexographic printing machine 10.

When the pressure roller 40 is stopped on its way towards the central drum 30 in direction D in the said (current) position of mutual contact with the central drum 30 itself, the procedure consists in using the second encoder 44 of the second electric motor 43 of the pressure roller 40 the linear (absolute) position of the respective axial end of the pressure roller 40 in the D-direction and/or the linear path that the respective axial end of the pressure roller 40 in the D-direction travels from the starting position (and thus from the zero position) to the top said mutual contact position to measure (block S6).

This measurement is then identified or determined (block S7) as the first mutual contact position between the printing roller 40 and the central drum 30 of the flexographic printing machine 10 and stored as such in a memory of the control unit 100.

At this point, the above procedure is repeated a few or n times, noting that the platen roller 40 is to be rotated to a further n-1 (and different) predetermined angular positions.

In this case, the method makes it possible to obtain, for each pressure roller 40, a number n of mutual contact positions, determined as described above.

Here, too, the above method--as mentioned above--is carried out independently for each axial end of the pressure roller 40. In this case, the method makes it possible to obtain a number of 2n mutual contact positions, determined for each pressure roller 40 as described above.

At this point, the method is used to calculate (block S8) for each pressure roller 40 an average mutual contact position (with the central drum 30) in dependence on each (n or 2n) mutual contact position for each predetermined angular position of the pressure roller 40 has been determined and to store this average mutual contact position in the memory of the control unit 100.

• Reiner Mittelwert der n Proben, die an jedem axialen Ende der Druckwalze erkannt wurden.
• Mittelfilter der n Proben, die an jedem axialen Ende der Druckwalze erkannt wurden, durch Sortieren der Proben in aufsteigender Reihenfolge und Auswahl der Mitte der geordneten Serie.
• Mittelwert der n Proben, die an jedem axialen Ende der Druckwalze erkannt wurden, wobei das Minimum und das Maximum verworfen werden. Diese durchschnittliche gegenseitige Kontaktposition wird dann als erste Annäherung verwendet (S9-Block), um einen Druckvorgang mit Flexodruckmaschine 10 durchzuführen, wie zuvor aufgezeigt wurde.

According to the invention, the average mutual contact position is determined by at least the first of the following formulas:

• Pure mean of the n samples detected at each axial end of the print roll.
• Median filter the n samples detected at each axial end of the platen by sorting the samples in ascending order and selecting the center of the ordered series.
• Average of the n samples detected at each axial end of the print roll, discarding the minimum and maximum. This average mutual contact position is then used as a first approximation (S9 block) to perform a printing operation with flexographic printing machine 10 as previously indicated.

In addition, with special reference to 4 to determine the (correct and optimal) mutual contact position between the inking roller 50 and the printing roller 40 of each printing unit, proceed as follows.

First, the inking roller 50 is brought into its starting position with the second electric motor 53 (slightly detached from the respective pressure roller 40).

At this point, the flexographic printing press 10 is operated at a minimum drive speed (ie, a feed speed for the foil F). (predefined and stored in the memory of the control unit 100).

The pressure roller 40 is slowly rotationally driven by its first electric motor 41 so that it is arranged according to a (first) predetermined angular (absolute) position.

When the platen roller 40 is positioned at the first predetermined selected angular position, the platen roller 40 is stopped, i. H. it is in this first angular position by the first electric motor 41, which is in the "torque cut-off" mode, d. H. remains in the neutral position, held stationary.

As previously described, the predetermined angular position of the pressure roller 40 can be selected arbitrarily or weighted.

In particular, each predetermined angular position is such that the angular position (i.e., selected reliefs) is aligned with inker 50 or with a plane containing the D-direction (i.e., the axes of rotation of inker 50 and platen 40).

In any case, each predetermined angular position is stored in the memory of said control unit 100.

When the printing roller 40 is stationary in the first predetermined angular position, the inking roller 50 is now set in rotation with its first electric motor 51 (block P1), e.g. B. with a predetermined (fixed) rotational speed.

While the inking roller 50 is rotating and the platen roller 40 is left stationary, ie not rotating, the inking roller 50 is moved in the D-direction toward the corresponding platen roller 40 (block P2).

In practice, the method means that one of the two second electric motors 53 is driven in succession in order to move the respective axial end of the inking roller 50 towards the printing roller 40 forward.

However, it can also be provided that the two second electric motors 53 are driven simultaneously in order to move both axial ends of the inking roller 50 forward to the printing roller 40 at the same time.

The method thus consists in using the first encoder 42 to monitor any (uncontrolled) rotation caused by the contact between the rotating inking roller 50 and the printing roller 40 (i.e. the cliché placed thereon) of the printing roller 40 (and thus to the rotor of the first electric motor 41, in the neutral position) is imposed.

According to the invention, the method envisages acquiring at least one non-zero value of a drag rotation parameter using the first encoder 42 of the first electric motor 41 of the roller 40, which remains idle (in "torque disabled" mode) (block P3), the drag rotation being induced by the mutual contact achieved between the rotating inking roller 50 and the platen roller 40 during the movement of the inking roller 50 towards the platen roller 40 in the D-direction.

In practice it has been observed that the pressure roller 40 when stationary (i.e. not rotating), i. H. in the case of one of the reliefs on the cliché arranged on it, touches the rotating inking roller 50 during its forward movement towards the printing roller 40 in the D direction and is carried along by it in rotation (in the opposite direction) - through friction.

The first encoder 42 of the first electric motor 41 of the printing roller 40 detects the angular momentum exerted by the inking roller 50 on the printing roller 40, e.g. B. by the capture a value of the parameter ranging between a rotational speed of the platen 40 (ie a change in the rotational speed of the platen 40 from a zero to a non-zero value), an angular position of the platen 40 (ie a change in the angular position of the platen 40 from the predetermined - previous - angular position in which the pressure roller 40 was positioned) was selected.

In detail: If the first encoder 42 of the first electric motor 41 (on the left in the "torque deactivated" mode) has a non-zero speed value of the rotation of the pressure roller 40 and/or a different value of the angular position of the pressure roller 40 than the predetermined (earlier) angular position, in which the platen roller 40 was positioned, then the electronic control unit 100 is configured to determine that the platen roller 40 has received drive rotation induced by the mutual contact between the platen roller 40 and the inking roller 50.

The method includes in particular the comparison (block P4) of the value of the determined parameter with a reference range of the same, e.g. with a minimum value (e.g. corresponding to a value close to zero angular velocity or the predetermined angular position at which the platen 40 was positioned) and a maximum allowable value (e.g. the same as or different from those previously described).

If the value of the parameter is within the reference range, then the detection can be considered acceptable. Otherwise, the detection is deemed unacceptable and the steps of the method described above are repeated.

At this point, where the detection can be considered acceptable, the process continues by pausing (block P5), e.g. B. by immediately stopping the movement of the inking roller 50 approaching the platen roller 40 along the D-direction, ie the second previously driven electric motor 53 is stopped immediately.

In practice, on its way to the platen 40 in the D-direction, the inking roller 50 is stopped in a (current) mutual (first) contact position with the platen 40 itself, i. H. where the reliefs of the cliché mounted on this printing roller 40 touch the inking roller 50 with an optimal contact pressure defined by the contact pressure so that the rotary movement (through friction/resistance) is transmitted between the inking roller 50 and the printing roller 40.

In fact, it has been found experimentally that this mutual contact position, which determines the initial rotation of the platen roller 40 by the resistance of the inking roller 50, determines the optimal mutual contact pressure leading to an optimal, effective, precise and efficient transfer of the ink from the inking roller 50 to the reliefs of the printing roller 40 (which is reflected in a high and optimal print quality) during the normal operation of the flexographic printing machine 10.

When the inking roller 50 is stopped in said (actual) mutual contact position during its forward run to the printing roller 40 in direction D, the method consists in measuring the linear (absolute) position of the respective axial end of the inking roller 50 in the D direction or that of to measure the linear distance covered by the respective axial end of the inking roller 50 in the D direction from the starting position (and thus the zero position) to the above-mentioned mutual contact position (block P6).

This measurement is then identified or determined (block P7) as the first mutual contact position between the platen roller 40 and the inking roller 50 of the flexographic printing machine 10 and stored as such in the memory of the control unit 100.

At this point, the above process is repeated a number of times, care being taken to rotate the platen roller 40 according to each of the n-1 (and different) predetermined angular positions.

In this case, the method makes it possible to obtain, for each printing unit, a number n of mutual contact positions, determined as described above.

Here, too, the above method--as mentioned above--is carried out independently for each axial end of the inking roller 50. In this case, the method makes it possible to obtain, for each printing unit, a number of 2n mutual contact positions, determined as described above.

At this point, the method then calculates, for each printing unit, an average mutual contact position (between platen roller 40 and inking roller 50) in dependence on each (n or 2n) mutual contact position (block P8) determined for each predetermined angular position of the platen roller 40 and this store average mutual contact position in controller 100 memory.

• Reiner Durchschnitt der n Proben, die für jedes axiale Ende der Druckwalze 40 gemessen wurden.
• Medianfilter der n Proben, die an jedem axialen Ende der Druckwalze 40 erkannt wurden, wobei die Proben in aufsteigender Reihenfolge sortiert und das Zentrum der geordneten Serie ausgewählt wird.
• Mittelwert der n Proben, die für jedes axiale Ende der Druckwalze 40 gemessen wurden, wobei das Minimum und das Maximum verworfen werden.

According to the invention, the average mutual contact position is determined by at least the first of the following formulas:

• Pure average of the n samples measured for each axial end of the pressure roller 40.
• Median filter the n samples detected at each axial end of the platen 40, sorting the samples in ascending order and selecting the center of the ordered series.
• Average of the n samples measured for each axial end of the pressure roller 40 where the minimum and maximum are discarded.

This average mutual contact position is then used as a first approximation (block P9) to perform a printing operation with flexographic printing machine 10, as shown below.

The printing process consists in particular in setting the flexographic printing machine 10 in such a way that the printing roller 40 and the inking roller 50 of each printing unit of the flexographic printing machine 10 are positioned in their respective fixed (average) mutual contact positions, and then the first electric motors 31, 41 and 51 (with a predetermined rotation speed higher than the above driving speed) so that the flexible film F can run between the center drum 30 and the printing roller 40 (each printing unit) to carry out the printing thereof.

As is known, one or more unwinding devices can be arranged in front of the flexographic printing machine 10, on which the flexible film F to be printed is stored in special rolls and unwound one by one.

In addition, a dryer can be arranged behind the flexographic printing machine 10, through which a flow of heat, e.g. B. hot air, is introduced into the printed flexible film F to dry the print, and a winder in which the printed and dried flexible film F is wound around a cylinder to be wound up again.

The flexographic printing machine 10 can also be equipped with drive units that support the drive of the flexible foil F and with web guiding units that keep the web centered with respect to the D direction, as well as with optical systems (such as. B. Control cameras) for the automatic control of the pressure obtained on the flexible film F.

Reference List

10

flexographic printing machine

20

rack wall

30

counter roller; central drum

31

first electric motor

32

first encoder

40

pressure roller

41

first electric motor

42

first encoder

43

second electric motor

44

second encoder

50

counter roller; paint roller

51

first electric motor

52

first encoder

53

second electric motor

54

second encoder

100

control unit

D

direction of mutual rapprochement

f

foil

Claims (8)

1. Method for determining the position of mutual contact between a printing roller (40) and at least one counter roller (30; 50), wherein the printing roller (40) and the counter roller (30; 50) to be placed in contact with said printing roller (40) are both arranged in a flexographic printing press (10), wherein the printing roller (40) is arranged between two counter rollers (30; 50), of which one counter roller (30) is in the form of a central drum (30) and the other counter roller (50) is in the form of an inking roller (50), wherein the printing roller (40) and both of the counter rollers (30; 50) to be placed in contact with said printing roller (40) each have a first electric motor (31; 41; 51) and can be moved in rotation, each by means of its respective first electric motor (31; 41; 51), wherein each of these first electric motors (31; 41; 51) has a first encoder (32; 42; 52), wherein the printing roller (40) and the inking roller (50) each have a second electric motor (43; 53) at each axial end and can be moved translationally, each by means of its respective second electric motor (43; 53), in the direction (D) of a mutual approach between the printing roller (40) and the counter roller (30; 50) to be placed in contact with said printing roller (40), wherein each of these second electric motors (43; 53) has a second encoder (44; 54), and wherein the method comprises the following steps:

   (a) moving the counter roller (30; 50) that is to be placed in contact with the printing roller (40) in rotation by means of its respective first electric motor (31; 51) while the printing roller (40), which is arranged spaced from said counter roller (30; 50), is left in a predetermined angular position and not rotating;

   (b) moving the non-rotating printing roller (40) translationally in the direction (D) toward the counter roller (30; 50) that is to be placed in contact with the printing roller (40), by means of the corresponding second electric motor (43; 53) ;

   (c) detecting at least one non-zero value of a parameter by means of the first encoder (42) of the corresponding first electric motor (41) of the printing roller (40), wherein this parameter indicates a slip rotation induced by the mutual contact between the counter roller (30; 50) that has been placed in contact with the printing roller (40) and the printing roller (40) ;

   (d) determining the position of mutual contact between the printing roller (40) and the counter roller (30; 50) that has been placed in contact with the printing roller (40), based on the value of the detected parameter;

   characterized by the following steps:

   (e) changing the previous angular position of the printing roller (40) by a non-zero angle;

   (f) repeating steps (a) to (d) and determining the corresponding position of mutual contact between the printing roller (40) and the counter roller (30; 50) that has been placed in contact with said printing roller (40) for the angular position of the printing roller (40) that was changed in step (e) ;

   (g) calculating an average position of mutual contact between the printing roller (40) and the counter roller (30; 50) that has been placed in contact with said printing roller (40), on the basis of every position of mutual contact between the printing roller (40) and the counter roller (30; 50) that has been placed in contact with said printing roller (40), determined for a specific angular position of the printing roller (40), wherein the position of mutual contact between the printing roller (40) and the counter roller (30; 50) that has been placed in contact with said printing roller (40) is determined for each axial end of the printing roller (40) independently of the other end, and the average position of mutual contact between the printing roller (40) and the counter roller (30; 50) that has been placed in contact with said printing roller (40) is calculated for each axial end of the printing roller (40) independently of the other end.
2. Method according to claim 1, characterized in that each of the specified angular positions of the printing roller (40) is defined on the basis of a location in the relief of a cliche which is arranged on the lateral surface of the printing roller (40) .
3. Method according to claim 1 or 2, characterized in that the determination of the position of mutual contact between the printing roller (40) and the inking roller (50) to be placed in contact with said printing roller (40), which is carried out in step (d), comprises the following steps:

   (d1) comparing the value of the detected parameter with a previously defined range of values for that parameter;

   (d2) measuring the distance traveled by the printing roller (40) or by the inking roller (50) to be placed in contact with said printing roller (40) in its respective translational movement up to the position of mutual contact between the printing roller (40) and the inking roller (50) that has been placed in contact with said printing roller (40), by means of the second encoder (44; 54) of the second electric motor (43; 53) which drives the relevant translational movement;

   (d3) determining the position of mutual contact between the printing roller (40) and the inking roller (50) that has been placed in contact with said printing roller (40), based on the distance measured in step (d2), if the value of the detected parameter is within the previously defined value range for that parameter.
4. Method according to claim 1 or 2 or 3, characterized in that, as the parameter to be detected according to step (c), an angular momentum is detected, wherein this angular momentum is imparted to the printing roller (40) by the respective counter roller (30; 50).
5. Method according to claim 1 or 2 or 3 or 4, characterized in that the position of mutual contact between the printing roller (40) and the inking roller (50) to be placed in contact with said printing roller (40) is determined by means of the respective second encoder (44, 54) of each second electric motor (43, 53), each independently of the other, when the printing roller (40) and the inking roller (50) to be placed in contact with said printing roller (40) are moved translationally, each by its respective second electric motor (43; 53).
6. Method according to claim 1 or 2 or 3 or 4 or 5, characterized in that the calculated position of mutual contact between the printing roller (40) and the counter roller (30; 50) that has been placed in contact with said printing roller (40) is used in a printing process carried out by the flexographic printing press (10).
7. Flexographic printing press (10) comprising at least one printing roller (40) arranged between two counter rollers (30; 50), the one counter roller (30) being in the form of a central drum (30) and the other counter roller (50) being in the form of an inking roller (50), wherein the printing roller (40) and both of the counter rollers (30; 50) to be placed in contact with said printing roller (40) each have a first electric motor (31; 41; 51) and can be rotated, each by means of its respective first electric motor (31; 41; 51), wherein each of these first electric motors (31; 41; 51) has a first encoder (32; 42; 52), wherein the printing roller (40) and the inking roller (50) each have a second electric motor (43; 53) at each axial end and can be moved translationally, each by means of its respective second electric motor (43; 53), in the direction (D) of a mutual approach between the printing roller (40) and the counter roller (30; 50) to be placed in contact with said printing roller (40), wherein each of these second electric motors (43; 53) has a second encoder (44; 54), and wherein this flexographic printing press (10) is configured to carry out the steps of the method according to any one of claims 1 to 6.
8. Flexographic printing press (10) according to claim 7, characterized in that a control unit (100) is provided and is configured such that this control unit (100) defines the specific angular positions of the printing roller (40) at the respective positions of mutual contact between the printing roller (40) and the counter roller (30; 50) to be placed in contact with said printing roller (40) and carries out a printing process using these defined angular positions of the printing roller (40).

Images