EP4159442A1 - Measuring value correction of a reference mark on a material web - Google Patents

Abstract

The invention relates to a method for correcting a measured value of a reference mark (1) on a web of material. The invention further relates to a controller (6), a machine, a computer program and a computer program product that can carry out such a correction. In order to improve the determination of the position of a reference mark (1) on a web of material, it is proposed that on a machine in which the web of material is moved in a conveying direction (3) and the at least one first tool (4) acting in a non-positive manner, a tool (4) acting in the conveying direction has a second non-positively acting tool (5) located behind the first (4) and a sensor (7) located between the two tools (4, 5), a measurement error in the sensor (7), which is caused by an adjustment of the second tool (5 ) results in at least approximately determining at least the parameter values of the second tool (5) and correcting the measured value by the measurement error.

Description

The invention relates to a method for correcting a measured value of a reference mark on a web of material. The invention further relates to a controller, a machine, a computer program and a computer program product that can carry out such a correction.

Such a method can be used wherever webs of material are processed in several steps. In order to process a stretched web of material by unwinding it in several production stages (e.g. in a web-fed printing machine), the individual processing steps (e.g. the color printing unit) must fit exactly one on top of the other (e.g. color register). Path markings (e.g. print marks) applied at regular intervals are used for angular positioning of the processing tool. The processing requires continuous, fast and accurate measurement of the markings as well as continuous, fast and accurate alignment of the tool to the marking (e.g. register control). Force-locking tools (e.g. a gravure printing unit) can only be adjusted in the engaged state (print engagement) under the influence of a tensile force on the web. The adjustment could be either axial (adjustment of the phase position of the shaft) or longitudinal (shift of the shaft in the conveying direction, e.g. register roller). In any case, the adjustment of a non-positive tool leads to a tensile and elongation disturbance of the web.

The register control of a multi-color gravure printing system is considered below. In successive printing units, for example, printing cylinder n+1 applies the partial print image of the corresponding color separation n+1. The elastic thread model describes the conveying process of the printing substrate in terms of web elongation and conveying speed. The register control is corrected by adjusting the angle of the printing cylinder n+1 the exact superimposition of the color separations n to n+2. As a result of a register adjustment, as an inevitable side effect, the expansion of immediately adjacent register values n and n+2 is initially influenced. As the web runs, the changes in elongation are propagated to downstream sections n+2 of the web run. The strains gradually balance out and a new state of equilibrium is reached in which the strains of all sections n, n+1 etc. remain the same.

A distinction is made between two measurement principles: First, the comparison of two print marks (web-web measurement). The rollers print marks in addition to the printed image. These are recognized by sensors and measured against each other. This allows the cylinder to be optimally positioned. Second, the comparison of a print mark with the roller rotation angle (web-cylinder measurement). If a printing cylinder has no mark or a mark that is difficult to see, the angle of rotation of the roller must be synchronized with a reference mark on the paper. The adjustment influences and falsifies the web-cylinder measurement value. This falsification affects the measured value both in the previous and in the following path section.

The previous register decoupling strategy (see, for example, the "DRD" solution in the applicant's "SIMOTION Print Standard") relates to the avoidance of register errors as a result of a register adjustment. This strategy is also sufficiently accurate for orbit-to-orbit measurements. However, when using the web-cylinder measurement method, the previous decoupling strategy is not sufficient, since the register adjustment inevitably falsifies the measurement result and simulates an excessively large register deviation. Since the incorrect measurement acts against the conveying direction, it has a disruptive effect on the control stability of the entire machine.

In the case of gravure printing units or non-positive tools, a change in the printed image is caused by changes in the expansion of the material. Both subsequent and previous printing works affected. While there is already a solution to the problem for the subsequent printing units (e.g. "Dynamic Register Control"), the process of changing the manipulated variable on the preceding printing unit is to be described here, which leads to a problem particularly with web-cylinder measurements. Printing unit n+1 changes the angle of rotation and changes the state of stretching of the material section n...n+1 and thus also the positions of the reference marks on the material. Since printing unit n can only compare the cylinder position with the reference mark using the indirect measuring method, measuring errors occur which produce an error in the printed image as a result of correction.

The erroneous measurement is based solely on the "Web-Cylinder-Measurement" measuring method and is independent of the measuring principle of the sensor. The relative register shift is superimposed by an absolute web shift.

The object of the invention is to improve the determination of the position of a reference mark on a web of material.

This object is achieved by a method for correcting a measured value of a reference mark on a web of material that is moved in a conveying direction by a machine with at least one first tool that acts in a non-positive manner and a second tool that acts in a non-positive manner in the conveying direction behind the first one, with the measured value between is recorded between the two tools, with an adjustment of the second tool resulting in the measured value having a measurement error, with the measurement error being determined at least approximately via parameter values of the second tool, and with the measured value being corrected by the measurement error.

The object is further achieved by a controller, a machine, a computer program and a computer program product with the features specified in claims 4-7.

The measurement error is additively superimposed on the actual register value and must therefore be subtracted from the measured value for correction. For the at least approximate calculation of the measurement error, the time constant T is determined, which is the quotient of the path length between the two tools and the conveying speed, which is determined from the parameter values of the second tool. Generally: $${\mathrm{T}}_{\mathrm{n}+1}={\mathrm{L}}_{\mathrm{B}\left(\mathrm{n},\mathrm{n}+1\right)}/{\mathrm{v}}_{\left(\mathrm{n},\mathrm{n}+1\right)}.$$

The following incorrect measurement x _σ(n) occurs at sensor n (between tool n and tool n+1), which also includes the path length L _s(n) between tool n and sensor n: $${\mathrm{x}}_{\mathrm{\sigma }\left(\mathrm{n}\right)}={\mathrm{x}}_{\mathrm{right}}{\mathrm{pT}}_{\mathrm{n}+1}{\mathrm{L}}_{\mathrm{S}\left(\mathrm{n}\right)}/\left(1+{\mathrm{pT}}_{\mathrm{n}+1}\right){\mathrm{L}}_{\mathrm{B}\left(\mathrm{n},\mathrm{n}+1\right)}$$

The erroneous measurement is a dynamic effect that disappears in the stationary state. The amount of the incorrect measurement depends on the adjustment speed (dv _n / dt) and is briefly at most 10% of the measured value in typical applications: $${\mathrm{X}}_{\mathrm{right}}{\mathrm{L}}_{\mathrm{S}\left(\mathrm{n}\right)}/{\mathrm{L}}_{\mathrm{B}\left(\mathrm{n},\mathrm{n}+1\right)}.$$

The incorrect measurement is additively superimposed on the actual register value x. This leads to an erroneous measured value x _m : $${\mathrm{X}}_{\mathrm{m}}=\mathrm{x}+{\mathrm{x}}_{\mathrm{\sigma }}.$$

The erroneous measurement continuously calculated from the existing parameter values corresponds at least to a good approximation to the actual erroneous measurement. In order to correct the measurement error by compensation, the calculated erroneous measurement must be subtracted from the measured value.

The solution according to the invention thus enables a more precise measurement and thus also faster or better regulation. No additional sensors, control devices or actuators are required, since they are only on the existing ones Sensor as well as parameter values of the tools that are present in a controller are accessed. The proposed solution thus determines the position of the reference mark (passer) more precisely and increases the control quality overall.

In an advantageous form of the embodiment, at least the second tool has at least one cylinder or one roller and the radius and the rotational speed are used as parameter values. With this typical design of the tool, as found in printing presses (e.g. rotary presses), the conveying speed is simply calculated as follows: $${\mathrm{V}}_{\mathrm{n}}=2{\mathrm{\pi R}}_{\mathrm{n}}{\mathrm{n}}_{\mathrm{n}}.$$

In a further advantageous embodiment, at least one further measured value is recorded behind the second tool in the conveying direction, with an adjustment of the second tool causing the further measured value to have a further measurement error, with the further measurement error being determined at least approximately at least via parameter values of the second tool and wherein the further measured value is corrected by the further measurement error. Even if conventional solutions are known for influencing the material web in the subsequent web sections by adjusting a tool, the solution according to the invention for the "forward correction" can be used analogously as shown alternatively or additionally.

• eine schematische Darstellung einer Ausführungsform der erfindungsgemäßen Lösung.

The invention is described and explained in more detail below using the exemplary embodiment shown in the figure. The figure shows:

• a schematic representation of an embodiment of the solution according to the invention.

The figure shows a section of a machine according to the invention, in which the non-positively acting tools 4, 5 have two cylinders, as is the case, for example, with the printing units of a printing press. A web 2 is moved in the conveying direction 3 by the machine; the second tool 5 is therefore located behind the first tool 4 in the conveying direction 3 . A reference mark 1 is attached to the material web 2 and is detected by a sensor 7 . (In reality, reference marks are usually attached at regular intervals, but for the sake of simplicity only one is shown here.) Signals from the sensor 7 and parameter values from the exemplary printing units 4, 5 run into a controller 6 shown schematically, which is why it is emphasized here because a real controller is often not designed centrally, but as a complex system - e.g. as a decoupling network - and/or parts of the controller are decentralized - e.g. close to the drive or integrated into the drives - which can be advantageous for fast data processing, among other things .

If the second non-positively acting tool 5 is now adjusted, this has an effect on the material web 2 in front of and behind the tool 5, which leads to a measuring error when measuring the reference mark 1 by the sensor 7 as well as to a measuring error when measuring a - not here illustrated - another sensor in the conveying direction behind the second tool 5. While there are known solutions for subsequent path sections (e.g. the "Dynamic Register Control"), this is not the case for the preceding path section (i.e. between the two tools 4, 5 shown). . Nevertheless, the method according to the invention shown can also be used in an analogous manner as an alternative or in addition to error correction and thus for better adaptation of a pressure cylinder following the second tool 5 .

From parameter values of the second pressure cylinder 5 such as radius, speed and adjustment speed as well as other values such as in particular the path length between the two cylinders 4, 5 and the path length between the first cylinder 4 and the sensor 7, the measuring error can be determined (at least in good approximation) and the measured value can thus be corrected by this. This makes it possible for a register adjustment in a web-to-cylinder measurement to produce the same qualitative result as in a web-to-web measurement in which the printing cylinders print marks on the material web 2 that are compared with one another.

In summary, the invention relates to a method for correcting a measured value of a reference mark on a web of material. The invention further relates to a controller, a machine, a computer program and a computer program product that can carry out such a correction. In order to improve the determination of the position of a reference mark on a web of material, it is proposed, in a machine in which the web of material is moved in a conveying direction and which has at least a first tool that acts under a force fit, a second tool that acts under a force fit behind the first tool in the conveying direction, and has a sensor located between the two tools, to determine a measurement error in the sensor, which results from an adjustment of the second tool, at least approximately, at least via parameter values of the second tool, and to correct the measured value by the measurement error.

Claims (7)

Method for correcting a measured value of a reference mark (1) on a web of material (2) which is fed in a conveying direction (3) by a machine with at least one first tool (4) which acts in a non-positive manner and a second tool (4) which acts in a non-positive manner in the conveying direction (3) behind the first effective tool (5) is moved, with the measured value being recorded between the two tools (4, 5), with an adjustment of the second tool (5) leading to the measured value having a measurement error, with the measurement error at least exceeding parameter values of the second Tool (5) is at least approximately determined and the measured value is corrected by the measurement error. Method according to Claim 1, in which at least the second tool (5) has at least one cylinder or one roller and the radius and the rotational speed are used as parameter values. Method according to claim 1 or 2, wherein at least one further measured value is recorded in the conveying direction (3) behind the second tool (5), with an adjustment of the second tool (5) leading to the further measured value having a further measuring error, the further measurement errors are at least approximately determined at least via parameter values of the second tool (5) and the further measured value is corrected by the further measurement error. Controller (6) for a machine in which a web (2) is moved in a conveying direction (3), with at least one first tool (4) which acts in a non-positive manner, a second tool (4) which acts in a non-positive manner in the conveying direction (3) behind the first 5) and at least one sensor (7) located between the two tools (4, 5) for measuring a reference mark (1) on the material web (2), the controller (6) having means for carrying out a method according to one of the preceding claims . Machine, in which a material web (2) is moved in a conveying direction (3), with at least one first tool (4) which acts in a non-positive manner, a second tool (5) which acts in a non-positive manner in the conveying direction (3) behind the first one, at least one between the two tools (4, 5) lying sensor (7) for measuring a reference mark (1) on the web (2) and a controller (6) according to claim 4. Computer program for carrying out a method according to one of Claims 1 to 3 when running in a controller (6) according to Claim 4. Computer program product with at least one computer program according to Claim 6.

Images