Marking system and method for creating an image for a band of packaging material

Abstract

A laser erosion marking system (100, 100') for providing an image (10) to a strip (1) of packaging material (3), comprising at least one marking device (110, 110') having at least one laser (117) comprising a plurality of individually controlled light outputs (112) arranged in the transverse direction (CD) of the strip (1) of packaging material (3), each light output (112) having a power output of at least 60 W and being configured to emit light in order to provide laser erosion, a controller (120) that is connected to the marking device (110, 110') and configured to control the light outputs (112) according to the speed of the packaging material belt (1) (3), so that the emitted light always impacts the packaging material belt (1) (3) at the same angle, where the plurality of light outlets (112) are arranged in a linear array; where the linear array extends in a direction that is perpendicular to the direction of displacement of the strip (1) of packaging material (3), and The controller (120) is configured to activate the marking device (110, 110') in a pulsed manner, so that the transverse resolution is determined by the number of laser outputs (112), while the longitudinal resolution is determined by the number of consecutive laser pulses as, during use, the strip (1) of packaging material (3) passes through the marking device (110, 110').

Description

Marking system and method for creating an image for a band of packaging material Technical field The invention relates to a laser erosion marking system and a method of creating an image on a strip of packaging material, see claims 1 and 13. Background In the packaging sector, particularly for the production of individual consumer packages for contents such as liquid food, the packages are manufactured by forming and sealing a flat packaging material. The packaging material, which typically comprises a central layer of filler material covered on both sides by one or more polymer layers, is produced as a continuous web. The filling machine receives one end of the laminated packaging material from the web, and a plurality of stations continuously process the necessary packaging material. These stations may include, for example, feeding, sterilization, tube forming, filling, sealing and cutting, and final forming to provide a flow of ready-to-use individual packages. The packaging material belt moves at a very high speed; machines with speeds of up to 40,000 packages per hour are commercially available. Furthermore, a high speed is used during the lamination and production of the packaging material, whereby the belt speed is on the order of, for example, 400 m / min and higher. The manufacturing of the packaging material web, as well as its transport through the filling machine, requires highly precise positional control. For example, the manufacturing of the packaging material may include the step of providing crease lines for folding, pre-cut holes, and printed patterns, such as registration marks and / or decorative elements. In particular, the printing step may be performed in separate stages, and the appearance of the final package will depend on the alignment of the various features. Uncontrolled variations in the placement of the packaging material during production at the converting plant or on the filling machine can lead to various types of errors. Therefore, it is desirable not only to provide a high precision alignment between the pre-laminated hole and the fold lines, but also to provide a high precision alignment of the printed pattern with respect to the fold lines, the pre-cut hole, external devices such as caps and the like, as well as the respective previously printed patterns. In addition, it is desirable to add unique information to the packaging material band. This information may relate to, for example, the manufacturing date, the converting plant, etc., for traceability and / or authentication purposes. The information can be provided, for example, in a coded format, or characters or images can be used. A unique code can also be used to track errors and / or deviations in conversion, and such markers can further facilitate defect elimination. Therefore, marking packaging material can be done for various purposes, such as providing unique information or creating placement reference marks. By reading the reference mark, it may be possible to adjust the position of the packaging material strip, particularly laterally or transversely, or to read the encoded information. Subsequent printing, using continuous printing techniques such as offset printing, can then be correctly positioned in relation to the reference mark and, consequently, also in relation to other features added to the packaging material. WO2016166379 discloses a system for creating markings on packaging. In this system, an image to be printed is divided into two or more parts, and a laser is configured to erode at least one of the image parts to form a corresponding marking on the packaging. Optionally, different lasers are provided for eroding the respective parts of the image. Each laser emits light through an optical system that has two mirrors that can be moved to deflect the laser beam in the x and y directions. As the container passes through the laser, the movable mirrors thus help to create a two-dimensional eroded mark corresponding to a portion of the image. The system described above suffers from two major drawbacks. First, since the mobility of the mirrors is limited, several lasers and associated mirrors are provided to extend the lateral or transverse dimensions of the eroded mark. Secondly, for a high-speed application, control of the mirrors will be virtually impossible, since the time required to physically move the mirrors will result in curved erosion; during the time required to move the mirrors, the container will have moved in the feed direction, which is why the mark will be tilted in relation to the transverse direction of the container. US patent 2009 / 323753 A1 describes a laser erosion marking system, with at least one marking device having at least one laser comprising a plurality of individually controlled light outputs arranged in a linear array and configured to emit light for the purpose of laser erosion of a product, and a controller connected to the marking device and configured to control the light outputs based on the speed of the product, so that the emitted light always impacts the product at the same angle. Compendium It is an object of the invention to solve, at least partially, one or more of the limitations identified above in the prior art. In particular, it is an object to provide a system and method capable of creating unique laser-eroded marks with high precision on a web of packaging material moving at a very high speed, such as 400 m / min or higher. To solve these problems, claim 1 defines a laser erosion marking system for creating an image on a strip of packaging material according to the present invention. In one embodiment, the power of the light emitted from each light outlet is in the range of 60-1000 W, such as 60-500 W. The marking system may further comprise at least one coating device configured to provide a coated area on the packaging material strip. The coating device(s) can be placed before the marking device(s). The number of light outputs can be greater than ten, such as greater than fifteen, preferably greater than twenty. Each light output can be connected to an optical fiber having a distal end that facilitates the output of a laser beam. The dimension of the laser beam produced, when it impacts the strip of packaging material, can be 1 mm2 or less. For each pulse, the plurality of light outputs can be controlled individually. The controller can be configured to control each light output in a binary fashion, to either emit light or not. The controller can also be configured to control the marking device to remove or erode selected portions of a coating substance applied to a coating area on the packaging material strip. The controller can be configured to control the marking device to erode the entire coating substance on the selected parts. The controller can be configured to control the marking device in order to erode only a portion of the coating substance layer on those selected parts. The belt moves at a constant speed, that is, it moves continuously forward in the longitudinal direction of the belt. Claim 13 defines a laser erosion method of an image on a strip of packaging material according to the present invention. Nevertheless, other objectives, features, aspects and advantages of the invention will become evident from the following detailed description, as well as from the drawings. Brief description of the drawings The embodiments of the invention will now be described by way of example with reference to the attached schematic drawings, in which Figure 1 is a top view of a packaging material that forms part of a band. Figure 2 schematically shows a method according to one embodiment. Figure 3 is a schematic view of a laser erosion marking system according to one embodiment. Figure 4 is a schematic view of a marking device for use with the laser erosion marking system shown in Figure 3. Figure 5a is a cross-sectional view of a packaging material after laser erosion marking. Figure 5b shows a first example of a mark created by the laser erosion marking system shown in Figure 3. Figure 5c shows a second example of a mark created by the laser erosion marking system shown in Figure 3. Figures 6a-b are schematic views of parts of a marking device. Figure 7 is a schematic view of a laser erosion marking system according to another embodiment. Detailed description Figure 1 shows the parts of a web 1 of a packaging material 3. The packaging material 3 is provided with various features to facilitate the forming of individual packages. These features may include, for example, crease lines 5, pre-laminated holes 7, and one or more laser-etched marks 10. As can be seen in Figure 1, during the manufacture of the packaging material 3, the web 1 is dimensioned to accommodate various segments 12a-c, 13a-c, whereby each segment 12a-c, 13a-c is dimensioned to produce a single package. The segments are arranged sequentially in the longitudinal, machine direction MD, and transverse directions CD.Preferably, segments 12a-c, 13a-c are staggered in the transverse direction CD, as further shown in Figure 3, to reduce vibrations during folding and allow smoother operation of the rotary folding tool across the width of the packaging material web. As explained above, mark 10 can be created for various purposes. It can, for example, serve as a reference mark for future handling of the packaging material, or it can include certain types of information that can be read and used for traceability or authentication. Preferably, packaging material 3 is manufactured in a converting facility, where a core layer of a paper-based material is laminated with one or more polymeric layers on both sides. Typically, packaging material 3 comprises a core material layer, an outer layer, and an inner layer. The outer layer, applied to one side of the core material layer, is designed to form the outer surface of the packaging to be produced, with both the outer surface and the outer layer facing the packaging environment. The inner layer is applied to the other side of the core material layer and is designed to form the inner surface of the packaging to be produced, which is in contact with the product inside. The core material may be a sheet to provide rigidity to the packaging material 3 and, preferably, may be made of a material such as cardboard or corrugated board. The outer layer may comprise at least one layer of polymeric material, which is applied to the core material layer in a lamination process. Furthermore, one of the layers constituting the outer layer may be a decorative layer that provides the external appearance of the container to be formed. Preferably, the lamination process of the outer layer to the core material layer is carried out after the mark(s) 10 have been added to the packaging material 3, such as on the production line for the laminated packaging material. Alternatively, the laser etching of the marks onto a coated material layer may take place after the lamination and manufacturing of the packaging material, e.g., on a filling machine. The inner portion of the laminated packaging material, on the inner side opposite the core layer, may comprise at least one layer of polymeric material. The inner portion of the packaging material intended for the interior of the finished package may comprise, e.g. (starting from the core material layer): a lamination layer, a protective layer, such as an aluminum foil that acts as a barrier against gases, such as oxygen, and a sealing layer. The lamination layer enables the core material to adhere to any applied protective layer, while the sealing layer enables the heat sealing of the package. The polymeric layers of the packaging material 3 can be made of any suitable type of polymeric material, preferably a thermoplastic material such as a polyolefin, such as polyethylene. Before describing the details of the marking system used to create the laser-etched marks on the packaging material 3, a method 20 will be briefly described with reference to Figure 2. Several subsequent steps are performed when a laser-etched mark 10 is added to the packaging material 3. Starting with step 21, the packaging material 3 is coated so that a coated area is available at the location of the desired mark. The coating can be obtained, for example, by printing. The specific dimensions of the coated area are less important, provided that the mark to be formed can be fitted within the outer limits of the coated area. When the area is coated, a marking device is activated in step 22. This marking device, a laser with multiple individually controllable outputs (as described below), receives data upon activation regarding the intended position of the mark and the intended pattern. Preferably, the position of the mark will correspond to one or more fold patterns and the remaining printed design of the packaging material. In step 23, the marking device is controlled; that is, its operating parameters are set to activate one or more of the multiple outputs at specific times.During operation, when the marking device emits light according to the established control scheme, the emitted light erodes the coating substance of the coated area, exposing the underlying core material layer. The contrast between the coated area (i.e., the unexposed portions) and the core material layer (i.e., the eroded portions) creates a pattern that can be read by optical means such as a camera, scanner, or the human eye. This step of operating the marking device to emit light, and thereby erode selective parts of the coated area, thus constitutes a step 24 in creating mark 10 on packaging material 3. The method described above is suitable for high-speed applications, while also maintaining good accuracy and high resolution of the eroded mark. The marking device may have, for example, at least ten individually controlled outlets arranged transversely across the packaging material web, each outlet being stationary relative to the moving packaging material. Therefore, the belt moves at a constant speed, that is, it travels continuously forward in the longitudinal direction of the belt while the laser erosion marking system is operating. The belt's travel speed can be 300 m / min and higher, such as 400 m / min and higher, or 600 m / min and higher. The higher the belt speed, the higher the power output required from the laser light sources. In order to perform high-speed laser erosion, as is routinely required in modern production facilities, a high-power light output is necessary. As will be further explained below, it has been shown that each light output should be configured to emit light with a power of at least 60 W, such as within the range of 60–1000 W, or from 60 to 500 W, depending on the specifications of the packaging material, manufacturing conditions, etc. Figure 3 shows an example of a laser erosion marking system 100. The laser erosion marking system 100 is configured to operate in conjunction with a web 1 of packaging material 3, which is fed forward in a longitudinal direction MD, indicated by the arrow in Figure 3. Importantly, this configuration allows the laser erosion marking system 100 to fit into existing converting stations, which typically convert a core material layer (such as cardboard or packaging board) into packaging material 3 by lamination. Preferably, the laser erosion marking system 100 is positioned upstream of a lamination station used to provide the outer layer to the core material layer. The purpose of the laser erosion marking system 100 is to provide one or more laser-eroded marks 10 on the packaging material 3. This is achieved by means of one or more marking devices 110, each marking device 110 being connected to a controller 120. Each marking device 110 is positioned in a fixed location relative to the surrounding equipment. This means that each marking device 110 will have a fixed position, i.e., in the transverse direction, also relative to the packaging material belt 3 that is fed through the marking system 100. Therefore, laser erosion marking provides an efficient method for marking a substrate compared to conventional printing techniques, such as inkjet printing, particularly for codes and similar elements, such as QR codes or barcodes. As shown in Figure 3, the packaging material strip 3 is sized so that the entire width of strip 1 corresponds to the width required to form two packages. Segments 12a-e are aligned longitudinally, while segments 13a-e are aligned longitudinally and positioned adjacent to segments 12a-e. This configuration is used to increase throughput during converting. Before feeding the packaging material 3 to a filling machine, segments 13a-e are typically separated from segments 12a-e by a longitudinal cutting operation. As previously explained, each segment 12a-e and 13a-e is designed to form one package. As the packaging material 3 band 1 moves forward, each marking device 110 is activated to erode an optical pattern onto a coated area 14, which is provided on the packaging material 3. If each package is intended to have a mark 10, a coated area 14 is provided for each segment 12a-e, 13a-e. In Figure 3, the coated areas 14 are created by means of the coating devices 130. Each coating device 130 is configured to apply a coating substance onto the packaging material 3, preferably directly onto the core material layer before it is eroded and subsequently laminated with an outer layer. The coating devices 130 can be configured, for example, as printing rollers or similar. Since the coated area 14 should be homogeneous and fully covered, simple equipment can be used.It should also be understood that the 130 coating devices could be implemented as a single device spanning across band 1. Preferably, the coating devices 130 are controlled by the controller 120. The controller can receive, for example, an input related to the belt speed, thereby enabling the coating devices 130 to be controlled accordingly, so that the coated areas 14 are located in their respective desired positions. The coating substance used for the coating of areas 14 can be any suitable substance that can be eroded when it absorbs laser energy. Various inks or toners have been shown to meet this requirement. In particular, the selected coating substance should have a comparatively high absorption rate of infrared light with a wavelength below 1 gm. Optionally, the coating substance can be provided with magnetizable particles so that the mark can be detected magnetically. Such a coating substance can comprise, for example, magnetite. Figure 4 shows details of the marking device 110. In this example, the marking device 110 has twenty-one outputs 112, each output 112 being coupled to a laser 117. Generally, it is preferred that the number of outputs be 16 or more, such as 21 or more, to have the desired information capacity for marking and information transfer in the packaging business. Therefore, each output can be individually controlled by the controller 120, which is connected to one or more laser control devices 118. Each output 112 is further coupled to an optical fiber 114 that extends away from the device housing 115 and into the packaging material band 1 3. A laser beam is emitted from the distal end 116 of each fiber, whereby it impacts a delimited portion of the coated area 14 to laser-etch the coated area 14.A suitable multi-output marking device for this configuration may include, for example, an array of laser diodes emitting light in the wavelength range of approximately 850–980 nm. Depending on the specific coating material chosen, each laser diode has a light output of at least 60 W; preferably, each laser diode may have a light output in the range of 60–1000 W, in order to erode the coating material to a thickness of, for example, 5 gm. It should be understood that the selection of the coating material, as well as its thickness, will affect the absorption and, consequently, the erosion properties. Ideally, the laser diodes should be selected to operate at a wavelength that is completely, or at least mostly, absorbed by the coating material. Additionally, absorption of the emitted light by the underlying core material layer should be avoided. Therefore, each output 112 could be associated with a particular laser 117, or a single laser 117 could be coupled to a plurality of outputs 112, with each output 112 being individually controlled. Preferably, the distal ends 116 are arranged in a linear array, as shown in Figure 4, extending perpendicular to the feeding direction of the packaging material, i.e., in the transverse direction of the packaging material. When activated, each laser output 112 will emit light in a fixed direction, meaning that no dynamic deflection of the laser beam is provided. Therefore, the emitted light will always strike band 1 of packaging material 3 at the same angle. Furthermore, each distal end 116 is sized so that each output 114 erodes only a delimited area, or module, of the coated area 14. For example, the width of the laser beam emitted from each distal end 116 is less than 1 mm, on the order of 0.5 mm. Therefore, the transverse resolution of the marking device 110 is, in this case, 0.5 mm. The module height is not fixed but varies with the speed of the packaging material band 1 3, as well as with the exposure time of the marking device 110. Assuming the laser beam has a constant width of 0.4 mm, an exposure time may be preferred such that the packaging material band 1 travels 0.1 mm during the exposure. If band 1 travels at a speed of 400 m / min, the exposure time will then be on the order of 0.15 ms. For the suggested module size of 0.5*0.With a 5 mm thickness and a web speed of 400 m / min, the laser 117 of the marking device 110 can therefore emit a pulse using a pulse time of approximately 0.15 ms. However, in practice, even shorter pulse times may be preferable to provide more uniformly etched areas. Therefore, a pulse time of, for example, 20 gs can be selected; in the example mentioned above, a subsequent pulse occurs 0.15 ms after the previous pulse. In the example shown, the marking device 110 has a side width of 10.5 mm, the total width being defined by the twenty-one outlets. Figure 5a shows the packaging material 3 after erosion. As can be seen, the coating substance 30 is applied directly onto the core material layer 32, forming a coated area 14. Preferably, the coated area 14 is dark in color, primarily to achieve IR absorption of the laser beam, but also to provide high contrast against the much brighter color of the core material layer 32. The mark 10 is formed by eroding one or more recesses 34 in the coating substance 30, as explained above. The recesses 34 do not necessarily extend the full distance to the core material layer 32; sufficient contrast can also be achieved if some of the coating substance 30 remains. As is evident, the level of contrast of the mark will depend on the power of the laser light. As described above, a high power light output (i.e., > 60 W) is necessary to achieve vigorous erosion of the coating substance 30, especially for high-speed packaging material manufacturing applications. By comparison, prior art laser marking systems that operate by activating an ink that can change color, rather than eroding the substances of a coating 30, will not be suitable, or even compatible, with the design and configuration of the laser erosion marking system described herein. Figures 5b and 5c show two different examples of marks 10. In Figure 5b, the mark 10 forms a barcode 50 that can be read by a suitable scanner. In Figure 5c, the mark 10 is in the form of a 2D code 60, such as a QR code or similar. For both examples, the mark 10 is square, meaning the resolution in the transverse direction is equal to the resolution in the longitudinal direction (21 x 21 pixels). However, this is not required. According to the present invention, the transverse resolution is determined by the number of laser outputs 112, while the longitudinal resolution is determined by the number of consecutive laser pulses as the band 1 of packaging material 3 passes through the marking device 110.Therefore, a mark 10 may have other longitudinal extensions, so that it provides rectangular-shaped marks, according to which the dimensions of the covered area 14 establish the limit. Figures 6a and 6b show an example of a control scheme for a marking device 110. In these figures, the laser outputs 112 are shown as circles, and an active circle is marked in black. It should be noted that reference numbers are provided for only a few of the outputs 112. When the marking device 110 is activated—that is, when a coated area 14 of a strip 1 of packaging material 3 passes through the marking device 110—the marking device 110 controls the emission of light through the respective outputs 112. Importantly, the outputs 112 can be controlled individually. In Figure 6a, fourteen outputs are activated to emit light, while the remaining seven outputs are inactive. The pulse time is, for example, 0.15 ms, as in the example mentioned above. The next pulse will be emitted immediately after the first pulse, and outputs 112 are controlled accordingly. As can be seen in Figure 6b, another set of outputs 112 is activated to emit light for this pulse. As pulse emission continues, the mark array will grow in the longitudinal direction until the entire mark 10 is created on the packaging material 3. Although the example described above refers to a laser erosion marking system that uses several consecutive laser pulses, in some embodiments, the laser erosion marking system can be configured to erode entire lines without interruption by keeping the laser in an active or light-emitting mode as the web of packaging material passes through the marking system. Up to this point, the laser erosion marking system 100 has been described for creating marks 10 in fixed positions on the packaging material. However, as will be understood from what follows, the marking system 100 can also be used to provide marks 10 in different positions, particularly to ensure the correct position of the mark 10 in relation to other features of the packaging material 3. Figure 7 shows another example of a laser erosion marking system 100. The laser erosion marking system 100 comprises a marking device 110 that extends across the entire width of the packaging material 3. With respect to the marking device 110 described above, a plurality of light outputs are provided, directed towards the moving packaging material 3, and the lateral alignment of each output can be individually controlled by the controller 120. The band 1 of packaging material 3 is provided with a plurality of coated areas 14; in the example shown, the coated areas 14 are distributed so that each final package is provided with a coated area 14.The power levels of the 110 marking device are similar to those of the 110 marking device described above, i.e., each light output is set to emit a light in the range of 60-1000 W, such as 60-500 W. The packaging material 3 is also provided with one or more reference marks 140. The reference marks 140 are provided to help correctly position the eroded marks 10. A sensor is included in the marking system 100 and detects the position of the reference mark 140, specifically its lateral or transverse position. The detected position of the reference mark 140 is transmitted to the controller, which then associates the position of the reference mark 140 with the position of the already applied coated areas 14. As illustrated in Figure 7, the dimensions of the coated areas 14 can be extended compared to the final dimensions of the mark 10. Therefore, the controller 120 can subsequently determine a set of outputs 112 of the marking device 110 that should be activated in order to erode a desired portion of the coated area 14, thus positioning the mark 10 in its intended location. It should be noted that for a later section of band 1, a set of outputs 112a is used to provide 10-marks on the left side of band 1, while another set of outputs 112b is used to provide 10-marks on the right side of band 1. Within each set of outputs 112a-b, specific outputs are pulsed to form an increasing 10-mark as band 1 moves forward. Each output 112a-b is configured to emit a light with a power output in the range of 60-500 W. As shown in Figure 7, the belt shifts to the right after a certain time. This can be caused by various reasons, such as accidental misalignment of the feeding equipment or similar issues. If this shift occurs, sensor 150 will detect a different lateral position of the reference mark 140, and controller 120 will accordingly determine new sets of outputs 112c-d of the marking device 110 so that the marks 10 are correctly positioned relative to the reference mark 140. From the above description it follows that, although various embodiments of the invention have been described and shown, the invention is not restricted to these, but can also be put into practice in other ways within the scope of the content defined in the following claims.

Claims

1. A laser erosion marking system (100, 100) for providing an image (10) to a web (1) of packaging material (3), comprising at least one marking device (110, 110) having at least one laser (117) comprising a plurality of individually controlled light outputs (112) arranged in the transverse direction (CD) of the web (1) of packaging material (3), each light output (112) having a power output of at least 60 W and being configured to emit light in order to provide laser erosion, a controller (120) being connected to the marking device (110, 110) and configured to control the light outputs (112) as a function of the speed of the web (1) of packaging material (3), such that the emitted light always impacts the web (1) of packaging material (3) at the same angle,wherein the plurality of light outputs (112) are arranged in a linear array; wherein the linear array extends in a direction perpendicular to the direction of travel of the packaging material strip (1) (3), and the controller (120) is configured to activate the marking device (110, 110) in a pulsed manner, such that the transverse resolution is determined by the number of laser outputs (112), while the longitudinal resolution is determined by the number of consecutive laser pulses as, during operation, the packaging material strip (1) (3) passes through the marking device (110, 110).

2. The marking system according to claim 1, wherein each light output (112) has a power output in the range of 60-1000 W, such as 60-500 W.

3. The marking system according to claim 1 or 2,further comprising at least one coating device (130) configured to provide a coated area (14) on the strip (1) of packaging material (3).

4. The marking system according to claim 3, wherein the coating device(s) (130) are arranged upstream of the marking device(s) (110, 110).

5. The marking system according to any one of the preceding claims, wherein the number of light outputs (112) is greater than fifteen, preferably greater than twenty.

6. The marking system according to any one of the preceding claims, wherein each light output (112) is connected to an optical fiber (114) having a distal end (116) from which a laser beam is permitted to emerge.

7. The marking system according to any one of the preceding claims, wherein the dimension of the laser beam produced, when it impacts the strip (1) of packaging material (3),is 1 mm² or less.

8. The marking system according to any one of the preceding claims, wherein for each pulse, the plurality of light outputs (112) are individually controlled.

9. The marking system according to any one of the preceding claims, wherein the controller (120) is configured to control each light output (112) in a binary manner to emit light or not.

10. The marking system according to any one of the preceding claims, wherein the controller (120) is configured to control the marking device (110, 110) to erode selected portions of a coating substance disposed in a coated area (14) on said strip (1) of packaging material (3).

11. The marking device according to claim 10, wherein the controller (120) is configured to control the marking device (110,110) in order to erode the entire coating layer on said selected parts.

12. The marking device according to claim 10, wherein the controller (120) is configured to control the marking device (110, 110) in order to erode only a portion of the coating layer on said selected parts.

13. A method for providing an image (10) to a strip (1) of packaging material (3), comprising providing at least one marking device (110, 110) having at least one laser (117) and a plurality of individually controlled light outputs (112) connected to said laser(s) (117), wherein each light output (112) is configured to emit light having a power output of at least 60 W in order to provide laser erosion, wherein the plurality of light outputs (112) are arranged in a linear array,providing a controller (120) that is connected to the marking device (110, 110) and configured to control the light outputs (112) based on the speed of the web (1) of packaging material (3), and controlling at least one of the light outputs (112) to emit light in order to erode selected portions of a coating substance disposed in a coated area (14) on said web (1) of packaging material (3), such that the emitted light always impacts the web (1) of packaging material (3) at the same angle, extending the linear array in a direction that is perpendicular to the direction of travel of the web (1) of packaging material (3), and controlling the marking device (110, 110) by the controller (120) in a pulsed manner, such that the transverse resolution is determined by the number of laser outputs (112),while the longitudinal resolution is determined by the number of consecutive laser pulses as, during use, the strip (1) of packaging material (3) passes through the marking device (110, 110).

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