EP3043995B1 - Method for the control of the rotational speed for a drive device of a printing roll - Google Patents

Description

The present invention relates to a method for the control of the rotational speed for a drive device of a pressure roller with an elastic pressure jacket of a flexographic printing machine and a flexographic printing machine with a control unit for carrying out such a method.

In the US 5,542,353 A a method and apparatus for controlling the rotational speed of a pressure roller with an elastic pressure jacket of a flexographic printing machine is described. It is generally known that in flexographic printing presses a pressure roller with an elastic pressure jacket is used. Often, this pressure jacket is also referred to as Drucksleeve or cliché and pushed onto the pressure roller. An essential feature of the printing functionality of this pressure jacket is the elastic training. During printing, this leads to deformation of the elastic pressure jacket during printing. Becomes changed the supply of the pressure roller relative to other rollers, the pressure situation on the elastic pressure jacket changed. When the pressure situation changes, the squeezing situation also changes accordingly.

It has been found that set different speeds for the platen depending on the squish situation. In particular, the pressure situation changes due to the change in the squeezing situation of the elastic pressure jacket, the speed of the respective pressure roller. In particular, increasing the pressure with an increase in crushing will be accompanied by an increase in the speed of the pressure roller. Increased speed, however, causes this increase in speed to be slowed down. This is done z. B. by a corresponding braking effect of the drive device. This continuous deceleration of the pressure roller leads to increased wear of the drive device. If the braking is dispensed with, undesirable slippage between the pressure roller and z. B. the printing medium or another roller come. This slip leads to friction between these two components, which can lead to increased wear of these components. Basically z. B. in the DE 10 2010 015 628 A1 already mentioned this problem. The solution in this document provides that the current pressure situation should be determined in the form of the impression depth of the pressure jacket. Based on this indentation depth, a check should be made to correct this effect. However, a decisive disadvantage is that this determination of the indentation depth is associated with a high constructive effort. In particular, complex sensor systems are necessary to determine this parameter.

It is therefore an object of the present invention to at least partially overcome the disadvantages described above. In particular, it is an object of the present invention to provide in a cost effective and simple manner the control of the rotational speed for the drive device of the pressure roller.

The above object is achieved by a method having the features of claim 1 and a flexographic printing machine with the features of claim 11. Further features and details of the invention will become apparent from the dependent claims, the description and the drawings. There are features and details that are related to the According to the invention are described, of course, also in connection with the flexographic printing machine according to the invention and in each case vice versa, so that with respect to the disclosure of the individual invention aspects always reciprocal reference is or may be.

• Bestimmen einer ersten Rotationsgeschwindigkeit der Druckwalze im Freilauf ohne aktive Antriebsvorrichtung bei einem ersten Beistellwert,
• Bestimmen einer zweiten Rotationsgeschwindigkeit der Druckwalze im Freilauf ohne aktive Antriebsvorrichtung bei einem zweiten Beistellwert,
• Erzeugen einer Kontrollkurve der Rotationsgeschwindigkeit bezogen auf den Beistellwert auf Basis der Bestimmungsschritte,
• Verwenden der Kontrollkurve für die Kontrolle der Rotationsgeschwindigkeit der Druckwalze mit aktiver Antriebsvorrichtung.

An inventive method is used to control the rotational speed for a drive device of a pressure roller with an elastic pressure jacket of a flexographic printing machine. Such a method according to the invention comprises the following steps:

• Determining a first rotational speed of the pressure roller in the freewheel without active drive device at a first Beistellwert,
• Determining a second rotational speed of the pressure roller in the freewheel without active drive device at a second Beistellwert,
• Generating a control curve of the rotational speed relative to the additional value on the basis of the determination steps,
• Use the control curve to control the rotational speed of the pressure roller with active drive.

In a method according to the invention, therefore, a sensory determination of the indentation depth can be dispensed with in a direct manner. Rather, as a so-called "simulated freewheel", the resulting changing speed is determined on the basis of the described crushing effect of the elastic pressure jacket. Thus, indirectly, the contusion and directly the impact of contusion can be determined. This simulated freewheel thus serves to determine the effect and thus the relative velocity to be established for the printing medium or rolls to be contacted. Subsequently, on the basis of this simulated freewheel, an adaptation in the form of a use of the determined or generated control curve can be carried out.

For the purposes of the present invention, "addition values" are to be understood as distances which are formed between the pressure roller and an adjacent roller. This may be the Beistellwert between pressure roller and anilox roller and / or the Beistellwert between pressure roller and counter-pressure roller. In particular, reference is made to the addition value in order to change the pressure force on the printing medium. Is the changed? Beistellwert, changes accordingly, the pressure situation for the elastic pressure jacket. Accordingly, in a method according to the invention not only to a single value, but to at least two Beistellwerten the associated rotational speed is determined. In this simulated freewheel thus at least two points can be specified for the control curve, which can serve by the determination as a basis for the generation of the control curve. The control curve can be generated by any mathematical or metrological methods. In addition to a purely linear connection of the two specific measuring points for the first and second addition values, complicated algorithms can also generate curved and non-linear curve profiles for the control curve.

In the context of the present invention, the method can be used both for a pressure roller with a pushed-on elastic pressure jacket and for a pressure roller with an elastic pressure jacket molded onto it. Of course, the effect according to the invention can also be achieved if the pressure roller is substantially completely formed from an elastic material as a pressure jacket.

According to the invention, a distinction must be made between an active and a passive drive device. An active drive device is understood to be the switched-on drive device in which torque is actively output from the drive device for generating the rotational speed to the pressure roller. Under a non-active drive device or a passive drive device of the simulated freewheel is to be understood. Is it in the drive device z. As an electric motor, this means that by the pressure roller and the corresponding drive from the printing medium or a contacting roller and a rotor of the drive device continues to rotate. Accordingly, the drive device is also in the passive state continues to rotate, so that the rotational speed, which sets here in the simulated freewheel, can be detected by the same sensor, as is the case with the control of the drive device. Thus, no additional sensor devices are necessary for a method according to the invention in order to carry out the determination according to the invention of the first and the second rotational speed. Compared to known methods is thus a decisive advantage, the design cost reduction and the avoidance of additionally attaching sensors.

The use of the control curve can be used both as a setpoint curve for a control, and as a setpoint curve for a control. In both cases, the control curve may provide the underlying values for the subsequent control. Of course, the control curve can also be used to adjust the rotational speed of a counter-pressure roller, an anilox roller or other rollers of the flexographic printing press.

If a change in the additional values is carried out during printing in the current process, in order, for. B. to achieve a change in the printed image, can be used on the generated control curve. A change in the addition values will lead to a change in the squeeze situation of the pressure jacket. However, this change in squeeze situation is taken into account in the use of the control curve in the control of the rotation speed of the pressure roller. Accordingly, the varying squeezing effect is at least partially offset by the change in control based on the pressure roller control curve.

By means of a method according to the invention, therefore, a compensation of the described crushing effect takes place at least in part. This leads to the fact that slippage between the contacting components or the contacting rollers can be reduced or prevented. In addition, it is possible to protect the drive device from unnecessarily high wear. Compared to known methods can be provided in this way in a cost effective and faster and easier way a compensatory control option for the compensation of the crushing effect described. In particular, such a method is used in register-free printing. The determination of the relative velocities or the rotational speeds to the Beistellwerte takes place z. In units of meters per second or revolution per minute. The determination of the individual values or the generation of the control curve is specific to the pressure roller used and / or the elastic pressure jacket used. If another elastic pressure jacket is mounted on a pressure roller, a method according to the invention should advantageously be carried out again in order to produce the specific control curve for this application situation and this elastic pressure jacket as well.

A method according to the invention can be further developed in such a way that the control curve is generated at least in sections as a linear course between the values determined relative to the addition values. It is a particularly simple and inexpensive and fast generation of the control curve. The two specific values in a diagram are simply connected linearly with a straight line. A particularly simple mathematical algorithm allows in this way a particularly cost-effective design of a corresponding control unit. Also, such a control curve as the basis for a subsequent control in the form of a control and / or a control a particularly simple control basis.

Another advantage can be achieved if, in a development of the method according to the invention, this is used for a register-free printing. Under a register-free pressure is a pressure to understand, which in particular has only a single color. Thus, no register retention, so no clean overlap of individual color sections to note. The register freedom means that a change in the printing speed can also be accepted by the control according to the invention of the rotational speed of the printing roller. In the case of registering, it is advantageous if registering is taken into account in the control of the rotational speed. This can be z. B. by an intervention on the rotational speed of different inking units or the vote in the control of the rotational speed of the pressure rollers of different inking done.

It is a further advantage if, in a development of the method according to the invention, at least one further rotational speed of the pressure roller in free-running without an active drive device is determined at a further additional value. In other words, at least at a third point in time with a third addition value, a third rotation speed or even a plurality of rotation speeds is determined at a plurality of addition values. For the generation of the control curve, this means a higher accuracy. Thus, a broader database for the generation of the control curve can be used. The course between the individual data points as a result of this determination can likewise be linear again, so that different inclined planes with different slopes result in part in the result Control curve are. Also, the curve may be generated from a plurality of discrete values in the form of stepwise training. In all these cases, the increase of the data points, ie the further number of further rotation speeds for other addition values, produces a higher accuracy in the generation of the control curve.

It is also advantageous if, in a further development of the method according to the invention, the determination steps are carried out continuously or substantially continuously with a continuous or substantially continuous change of the addition value. In other words, a substantially continuous curve is recorded and generated as a control curve. The pressure roller is fed to the corresponding contacting counter-roller or the pressure medium and thus changed the Beistellwert. At the same time continuously or substantially continuously the self-adjusting rotational speed is determined in the simulated freewheel. The written curve is the generated control curve. This can be, so to speak, a first calibration process, in which the pressure roller is moved over the entire adjustment range of the additional value. This produces a substantially continuous curve that, while generated based on a more elaborate calibration process, has a significantly improved accuracy accordingly. Such increased accuracy entails a corresponding more accurate fit when used for the control function.

It is also advantageous if the control curve for controlling the rotational speed of an anilox roller is used in a development of the method according to the invention. This additional use situation for the control curve brings about a further improvement with regard to the compensation of the described crushing effect. Thus, the anilox roller preferably rotates at the same or essentially the same rotational speed as the pressure roller. Of course, a control of other rotational speeds, such. B. rotational speed of the platen roller, based on the control curve conceivable. Thus, one and the same generated control curve, which is specific to the elastic pressure jacket, can be used to control several different rotational speeds of different components.

A further advantage can be achieved if, in a further development of the method according to the invention, a constructive undersize of the diameter of the pressure roller is taken into account in the control of the rotational speed of the pressure roller. Thus, the operator of a printing press can already consider the crushing effect when ordering the printing roller. By a constructive undersize, so a reduction in the diameter of the pressure roller, a change in the rotational speed of the pressure roller, ie in particular an acceleration of the pressure roller by the pressure effect, compensated. Thus, in the method of this constructive undersize, which is based on the order of the customer or the operator of the printing press, already taken into account.

It is also advantageous if, in a development of the method according to the invention, the generated control curve is stored with respect to the elastic pressure jacket used and / or with respect to the pressure roller. The storage takes place z. B. in a database relative to the elastic pressure jacket. Thus, a library can be generated which provides specific control curves generated for different elastic printing jackets. The calibration described, ie the implementation of a method according to the invention, then only has to be carried out with a completely new elastic pressure jacket. If an already used elastic pressure jacket is mounted, then the stored generated control curve can be recalled from the database. This speeds up the use when printing the flexographic printing press when changing between different elastic printing jackets.

In the method according to the preceding paragraph, it is also advantageous if the generated control curve is compared with a stored control curve. In particular, the comparison with control curves from a database. Thus, a standard deviation of differently generated control curves can be made to a specific elastic pressure jacket. The standard deviation serves to improve the subsequent use for controlling the rotation speed of the pressure roller. Also, monitoring of the change in the specific control curve generated may give an indication of a change or wear of the elastic pressure jacket. Thus, an early warning functionality can be provided by this comparison with a stored generated control curve.

A method according to the invention can be further developed such that the control curve is used in comparison to the rotational speed of at least one further roller, in particular an anilox roller and / or a counterpressure roller. As already explained, reference is made in particular to the relative speed between the pressure roller and the at least one further roller. When using the control curve for a plurality of rotating components in particular slippage between these rotating components can be effectively avoided.

Likewise provided by the present invention is a flexographic printing machine, comprising a pressure roller with an elastic pressure jacket and a control unit for controlling the rotational speed of the pressure roller. A flexographic printing machine according to the invention is characterized in that the control unit is designed for carrying out a method according to the invention. Accordingly, a flexographic printing machine according to the invention brings the same advantages as have been explained in detail with reference to a method according to the invention.

Fig. 1

eine erste Ausführungsform einer erfindungsgemäßen Flexodruckmaschine,

Fig. 2

die Ausführungsform der Fig. 1 mit dem elastischen Druckmantel in gequetschter Situation,

Fig. 3

eine erste Ausführungsform einer erzeugten Kontrollkurve,

Fig. 4

eine weitere Ausführungsform einer erzeugten Kontrollkurve,

Fig. 5

eine weitere Ausführungsform einer erzeugten Kontrollkurve und

Fig. 6

eine weitere Ausführungsform einer erzeugten Kontrollkurve.

Further advantages, features and details of the invention will become apparent from the following description in which, with reference to the drawings, embodiments of the invention are described in detail. The features mentioned in the claims and in the description may each be essential to the invention individually or in any desired combination. They show schematically:

Fig. 1

A first embodiment of a flexographic printing machine according to the invention,

Fig. 2

the embodiment of the Fig. 1 with the elastic pressure jacket in a crushed situation,

Fig. 3

a first embodiment of a generated control curve,

Fig. 4

a further embodiment of a generated control curve,

Fig. 5

a further embodiment of a generated control curve and

Fig. 6

a further embodiment of a generated control curve.

In Fig. 1 schematically an embodiment of a flexographic printing machine 100 according to the invention is shown. This flexographic printing machine 100 has a counterpressure roller 50, an anilox roller 40 and a pressure roller 10. On the pressure roller 10, an elastic pressure jacket 12 is arranged, which z. B. may be formed as a pressure sleeve. In addition, a drive device 20, for. B. in the form of an electric motor, which serves to drive the pressure roller 10. Also shown schematically is a control unit 60, which is coupled to control the rotational speed of the pressure roller 10 via a data link to the drive device 20. Also in Fig. 1 to recognize the course of the pressure medium 200th

In Fig. 1 schematically the flexographic printing machine 100 is shown with an inking unit of an anilox roller 40 and a pressure roller 10. In this embodiment, it is a register-free printing with a single color. Of course, other inking units are providable, with an anilox roller 40 and a pressure roller 10 can be provided for each inking unit.

In Fig. 2 the squish situation is shown. In this case, a squeezing situation for the pressure jacket 12 forms between the pressure roller 10 and the counterpressure roller 50. When promoting the printing medium 200 between these two rollers 10 and 50, the provision is made in Fig. 2 from top to bottom. The pressure roller 10 is thus fed to the platen roller 50 and reduces the intermediate pressure gap. When changing the Beistellwerts done after hitting the elastic pressure jacket 12 on the print medium 200 below a pinch of the elastic pressure jacket 12, as shown schematically in FIG Fig. 2 is shown. This pinching leads to a variation of the rotational speed of the pressure roller 10. This variation leads to an increased wear of the drive device 20 or to slip on the print medium 200, so that also here wear on the print medium 200 and the elastic pressure jacket 12 is observed. In order to avoid this crushing effect and the problems thus described, a method according to the invention is carried out, as will be explained below.

Thus, at a first instant, that is to say at a first addition value B1 in the simulated freewheel, that is to say without an active drive device 20, the first rotational speed V1 of the pressure roller 10 is determined. Subsequently, a second rotational speed V2 of the pressure roller 10 is determined at a second addition value B2. These two specific values are entered in a corresponding diagram, which plots the rotational speed above the addition value. Examples of such a diagram and the control curves 30 generated therefrom can be found in FIGS Fig. 3 to 6 ,

In Fig. 3 a particularly simple and inexpensive design of the generated control curve 30 is shown. Thus, the at least required specific parameters for a first additional value B1 and a second additional value B2 are shown here. The associated rotational speeds V1 and V2 form dots in this diagram, which in this embodiment have been connected along a straight line. Here, therefore, a linear relationship between rotational speed and Beistellwert was used for the generation of the control curve 30. The corresponding generation of the control curve could accordingly be achieved with a simple and inexpensive generation algorithm. On the basis of this control curve 30, an adaptation or control of the rotational speed of the pressure roller 10 via an actively acting drive device 20 now takes place.

In Fig. 4 a further variant of the control curve 30 is shown. In this variant, in addition to the first additional value B1 and the second additional value B2 to two additional Beistellwerte Bx each associated additional rotational speed Vx were determined. The progressions between the individual parameter values in the diagram according to Fig. 4 are also back on a linear basis. Thus, different inclined planes are formed between the individual data values, as is the control curve 30 in accordance with FIG Fig. 4 shows. In comparison to Fig. 3 Although the effort for the determination of the values is greater, but a higher accuracy in the generation of the control curve 30 is achieved. Alternatively or in combination, an embodiment according to the Fig. 5 to get voted. For example, a step function can be specified for additional values or data values in the diagram of the rotational speed via the additional value.

If the addition value is substantially continuously adjusted or varied and continuously or substantially continuously monitors the rotational speed that occurs, a completely free control curve 30 can be generated in this way by recording this correlation. This is in Fig. 6 shown. Although the calibration effort is highest here, an ideal or optimized accuracy in the generation of the control curve 30 is achieved.

The above explanation of the embodiments describes the present invention solely by way of example. Of course, individual features of the embodiments, if technically feasible, can be combined freely with one another, without departing from the scope of the present invention.

LIST OF REFERENCE NUMBERS

10

platen

12

elastic pressure jacket

20

driving device

30

control curve

40

anilox roller

50

Backing roll

60

control unit

100

flexographic printing

200

print media

B1

first additional value

B2

second additional value

Bx

additional additional value

D

Diameter of the pressure roller

V1

first rotation speed

V2

second rotation speed

Vx

further rotation speed

Claims (11)

1. A method for the control of the rotational speed for a drive device (20) of a printing roller (10) with a resilient printing sleeve (12) of a flexographic printing press (100), characterized in that the method has the following steps:

   - determining a first rotational speed (V1) of the printing roller (10) when running freely without an active drive device (20) at a first value provided (B1),

   - determining a second rotational speed (V2) of the printing roller (10) when running freely without an active drive device (20) at a second value provided (B2),

   - generating a control curve (30) of the rotational speed in relation to the value provided on the basis of the determination steps,

   - using the control curve (30) for the control of the rotational speed of the printing roller (10) with an active drive device (20).
2. A method according to Claim 1,
   characterized in
   that the control curve (30) is generated at least in sections as a linear course between the values determined for the values provided.
3. A method according to any one of the preceding claims
   characterized in
   that this is used for a register-free printing.
4. A method according to any one of the preceding claims,
   characterized in
   that at least one further rotational speed (Vx) of the printing roller (10) when running freely without an active drive device (20) is determined at a further value provided (Bx).
5. A method according to any one of the preceding claims,
   characterized in
   that the determination steps are carried out continuously or substantially continuously in the case of continuous or substantially continuous change of the value provided.
6. A method according to any one of the preceding claims,
   characterized in
   that the control curve (30) is also used for the control of the rotational speed of an anilox roller (40).
7. A method according to any one of the preceding claims,
   characterized in
   that in controlling the rotational speed of the printing roller (10) a constructive undersize of the diameter (D) of the printing roller (10) is taken into account.
8. A method according to any one of the preceding claims,
   characterized in
   that the control curve (30) generated with respect to the resilient printing sleeve (12) used and/or with respect to the printing roller (10) is stored.
9. A method according to Claim 8,
   characterized in
   that the control curve (30) generated is compared with a stored control curve.
10. A method according to any one of the preceding claims,
    characterized in
    that the control curve (30) is used in comparison to the rotational speed at least of one further roller, in particular, of an anilox roller (40) and/or an impression roller (50).
11. A flexographic printing press (100), having a printing roller (10) with a resilient printing sleeve (12) and a control unit (60) for the control of the rotational speed of the printing roller (10),
    characterized in
    that the control unit (60) is designed for carrying out a method with the features of any one of Claims 1 to 10.

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