A PRINTING SYSTEM FOR PACKAGING MATERIAL

A printing system for providing a printed image (30) to a web (1) of packaging material (3) is provided. The printing system comprises a detecting unit (130) configured to detect a feature (10) on the packaging material (3), a control unit (120) configured to determine a first position of the detected feature (10), and a printing unit (110) having a plurality of printing nozzles (112). The control unit (120) is further configured to: determine a second position of an image (30) to be printed, the second position being determined based on the first position, determine at least one printing nozzle (112) based on the second position, and to activate the at least one printing nozzle (112) in order to print an image (30) onto the packaging material (3) at the second position.

TECHNICAL FIELD

The invention relates to a printing system for packaging material. In particular the present invention relates to an adjustable printing system for printing images on a web of packaging material.

BACKGROUND ART

In the packaging industry, especially for producing individual consumer packages for content such as liquid food, the packages are manufactured by forming and sealing a planar packaging material. The packaging material, which typically comprises a core layer of bulk material being covered on both sides by one or more polymer layers, is produced as a continuous web.

The filling machine receives one end of the web of the laminated packaging material and a plurality of stations provide the required processing of the packaging material in a continuous manner. Such stations may e.g. include feeding, sterilization, tube forming, filling, sealing and cutting, and final forming in order to provide a flow of individual ready-to-use packages.

The web of packaging material is running at extremely high speed; machine speeds allowing for up to 40.000 packages per hour are commercially available. Also during lamination and production of the packaging material high speed are utilized, whereby the speed of the web is in the order of 400 m/min and above.

Manufacturing of the web, as well as transportation of the web through the filling machine, requires high, continuous precision position control. For example, manufacturing of the packaging material may include the step of providing folding crease lines, pre-cut holes, external devices such as caps or similar, and printed patterns such as register marks and décor. Especially the printing may be performed in separate steps, and the appearance of the final package will be dependent on the alignment of the different features. Uncontrolled variations in the continuous positioning of the packaging material during production in the converting factory or in the filling machine may induce various types of errors.

Hence it is not only desirable to provide high precision alignment between the pre-cut hole and the crease lines, but also to provide high precision alignment of a printed pattern or mark relative the crease lines, the pre-cut hole, as well as relative previous printed patterns. For the high-speed application mentioned above it is thus very difficult to achieve correct, continuous positioning of the printed pattern, especially if there is a sudden misalignment of the web of packaging material during operation.

SUMMARY

It is an object of the invention to at least partly overcome one or more of the above-identified limitations of the prior art. In particular, it is an object to improve the continuous positioning of printed images on a web of packaging material. Thus, while the substrate web is forwarded in a high speed manufacturing process, images or marks are printed onto the web surface, and the positioning of the printed images are continuously and dynamically adapted to any changes in the position of the substrate web during forwarding in the high speed process.

To solve these objects a printing system for providing a printed image to a web of packaging material is provided. The printing system comprises a detecting unit configured to continuously detect a feature on the packaging material, a control unit configured to continuously determine a first position of the detected feature, and a printing unit having a plurality of printing nozzles. The control unit is further configured to determine a second position of an image to be printed, the second position being determined based on the first position, determine at least one printing nozzle based on the second position, and to activate the at least one printing nozzle in order to print an image onto the packaging material at the second position.

The feature may be selected from the group comprising a lateral side edge of the web, a crease pattern, a pre-cut feature, an external device such as a cap, and a pre-printed pattern.

The printing detecting unit may be an optical detecting unit, such as an optical line scanner.

The printing unit may be a binary array printer.

The resolution of the printing unit may be 600 dpi (dot per inch) or above, such as 1200 dpi or above.

The printing unit may extend over at least a part of the total width of the web of packaging material, such as across the entire width, or only partly across the width, of the web of packaging material. The first position of the detected feature may be determined relative the position of the detecting unit, and/or relative the position of the printing unit.

According to a second aspect a method for providing a printed image to a web of packaging material is provided. The method comprises providing a detecting unit configured to detect a feature on the packaging material, providing a control unit configured to determine a first position of the detected feature, providing a printing unit having a plurality of printing nozzles, determining a second position of an image to be printed, the second position being determined based on the first position, determining at least one printing nozzle based on the second position, and activating the at least one printing nozzle in order to print an image onto the packaging material at the second position.

The printing system and the method may be applied either in the process of manufacturing of the packaging material or in the packaging process, i.e. the process of forming, filling and sealing of a packaging container, such as a carton-based packaging container, which is produced from a web or sheet of laminated packaging material and filled with liquid or semi-liquid food.

Still other objectives, features, aspects and advantages of the invention will appear from the following detailed description as well as from the drawings.

DETAILED DESCRIPTION

InFIG. 1parts of a web1of a packaging material3is shown. The packaging material3is provided with several features for facilitating forming of individual packages. Such features may e.g. include crease lines5, pre-laminated holes7, and one or more printed images30. As can be seen inFIG. 1during manufacturing of the packaging material3the web1is dimensioned to accommodate several segments12a-c,13a-c, whereby each segment12a-c,13a-cis dimensioned to produce a single package. The segments12a-fare arranged in sequence, both in lengthwise direction MD and cross-wise direction CD. Preferably the segments12a-c,13a-care staggered in the cross-wise direction CD for reducing vibrations during creasing.

The printed image30may be provided for various purposes, as explained above. It may e.g. form a reference mark for future handling of the packaging material, or it may include some kind of information which may be read and used for traceability or authentication. In other cases the printed image30is part of the décor, i.e. it's only purpose is to contribute to the aesthetic appearance of the package to be formed.

The packaging material3is preferably manufactured in a converting facility, where a core layer of a paper-based material is laminated with one or more polymer layers on both sides. Typically the packaging material3comprises a core material layer, an outer layer, and an inner layer.

The outer layer applied to one side of the core material layer is adapted to provide the outer surface of the package to be produced, which outer surface and outer layer faces the surroundings of the package. The inner layer is applied to the other side of the core material layer and is adapted to provide the inner surface of the package to be produced which is in contact with the product contained in the package.

The core material may be a sheet for providing rigidity to the packaging material3, and may preferably be made of material such as paper board or cardboard.

The outer layer may comprise at least one layer of polymer material, which is applied to the core material layer in a lamination process. Moreover, one of the layers making up the outer layer may be a decorative layer making up the outer appearance of the package to be formed. The process of laminating the outer layer to the core material layer is preferably performed after the image(s)30has been printed onto the packaging material3.

The inner portion of the laminated packaging material, on the inner, opposite side of the core layer, may comprise at least one layer of polymer material. The inner portion of the packaging material intended for the inside of the finished package, may e.g. comprise (starting from the core material layer): a lamination layer, a protective layer such as an Aluminum foil, functioning as a barrier against gases, such as oxygen gas, and a sealing layer. The lamination layer enables the core material to stick to any protective layer applied, while the sealing layer enables package sealing.

The polymer layers of the packaging material3may be of any suitable type of polymer material, preferably a thermoplastic material such as a polyolefin, such as polyethylene.

Alternatively, the image(s)30is printed onto the packaging material3after the process of manufacturing of the laminated packaging material. Then the printing system may according to a further embodiment form a part of a filling and packaging machine, and the method of printing may be performed on the outermost layer of the packaging material web or sheet, i.e. on the side of the laminated material facing the outside environment of a packaging container, made from the packaging material.

Before describing details of the printing system used for providing printed images to the packaging material3, a method20will be briefly described with reference toFIG. 2. When adding a printed image30to the packaging material3a number of subsequent steps are performed. Starting in step21, the packaging material3is fed through the converting station and an optical reader is continuously scanning the surface of the web1in order to detect a pre-applied feature of the packaging material3. Such feature may e.g. correspond to the lateral edge of the packaging material3, a pre-laminated hole7, a specific crease line5, etc.

When the feature is detected, a printing unit is activated in step22. The printing unit, comprising a plurality of printing nozzles arranged in an array extending in a direction being perpendicular to the feeding direction of the web1of packaging material3, receives upon activation data relating to the intended position of the printed image as well as data relating to the content of the intended image. The intended position of the printed image is based on the position of the detected feature.

Controlling the printing unit, i.e. setting operation parameters in order to activate one or more of the multiple printing nozzles at specific times, is performed in step23. In operation, i.e. when the printing unit is activated according to the set control scheme, the activated printing nozzles will discharge a printing substance, such as ink, onto the packaging material3. Activation of the printing unit is preferably made in a pulse-wise manner, whereby a specific number of printing nozzles are activated during each pulse. As the web1of packaging material3is fed through the printing system each pulse will provide one line of the printed image, whereby the printed image grows in the feeding direction. Once printed, the printed image is readable by optical means such as a camera, a scanner, or human eyes.

This step of operating the printing unit to form subsequently printed lines onto the web1of packaging material3thus forms a step24of providing the printed image10onto the packaging material3.

It should be noted that identification of variations in the placement or position of the reference feature can be based on multiple measurements, and not only to the position of a single feature. Multiple and different image-to-feature distances will add at least two major advantages. Firstly, using several features for determining the correct position of the printed image will provide better accuracy as any error from a single reading can be reduced from multiple readings. Secondly, by measuring the position of several different features it is possible to register position variations for potentially any type of feature present on the packaging material, and to allocate the measured positions to a unique reference ID. Such information could thereby later be used by retrieving this information and to adapt the filling machine behavior (or any other manufacturing process depending on dimension properties of the packaging material) accordingly.

An example of a printing system100is shown inFIG. 3. As already explained with reference toFIG. 2the printing system100is configured to operate in conjunction with a web1of packaging material3, which is fed forward in a lengthwise direction MD, indicated by the arrow inFIG. 3. Importantly, this configuration allows the printing system100to fit with existing converting stations which typically converts a core material layer (such as a paper board or carton board) to a packaging material3by lamination. Preferably, the printing system100is provided upstream a lamination station used to provide the outer layer onto the core material layer.

The purpose of the printing system100is to provide one or more printed images30onto the packaging material3. This is achieved by one or more printing units110, each printing unit110being connected to a control unit120.

Each printing unit110is arranged at a fixed position relative the surrounding equipment. This means that each printing unit110will have a fixed position, i.e. in the cross-wise direction, also relative the web1of packaging material3being fed through the printing system100.

As can be seen in the example ofFIG. 3the web1of packaging material3is dimensioned so that the entire width of the web1corresponds to the required width for forming two packages. Segments12a-eare longitudinally aligned, while segments13a-eare longitudinally aligned and arranged adjacent to segments12a-e. This configuration is applied for increasing the throughput during converting; before feeding the packaging material3to a filling machine, segments13a-eare normally separated from segments12a-eby a longitudinal cutting operation. As already explained, each segment12a-e,13a-eis designed to form one package.

As the web1of packaging material3travels forward, each printing unit110will be activated to provide the printed image30to the packaging material3. For controlling the operation of the printing units110, a control unit120is provided and connected to the printing units110.

The control unit120is further connected to at least one optical detecting unit130being arranged facing the web1of packaging material3to detect one or more reference features10. In the shown example the reference feature10is illustrated as a pre-printed mark, however as mentioned previously the reference feature10may correspond to the lateral edge of the web1of packaging material, a pre-laminated hole, a specific crease line, etc. Importantly, the reference feature10is required to be optically detectable by the detecting unit130.

The detecting unit130may e.g. be implemented as a camera or a line scanner. The detecting unit130is not only configured to detect the presence of a feature10, but also the position of the feature10. For example, the position of the feature10may be determined using a virtual coordinate system in which the positions of the detecting unit130and the printing unit110are well-defined.

The control unit120thus receives a signal corresponding to the detected feature (or several different features), or optionally the control unit120itself determines the presence and position of the detected feature(s)10by analyzing the signal received from the detecting unit130. The control unit120may further receive input relating to web speed. Based on the position of the reference feature10the control unit120is configured to control the operation of the printing unit110such that the printed image30has a correct position relative the reference feature10.

Details of the printing unit110are shown inFIG. 4. In this example the printing unit110has a plurality of printing nozzles112coupled to at least one ink supply117, each nozzle112being individually controllable by the control unit120. It should be noted that only some of the nozzles112are provided with reference numerals. Each nozzle112is facing the web1of packaging material3. The nozzles112are preferably arranged in a linear array, as shown inFIG. 4. The printing unit110preferably comprises several thousands of nozzles112, wherein the distance between adjacent nozzles112is extremely small. For example, the resolution of the printing unit110may be 600 dots per inch or even higher, such as 1200 dpi or higher. This means that the distance between two adjacent nozzles is 40 microns or less.

Each nozzle112has a unique ID, and the position of each nozzle112is retrievable in the same coordinate system as used for determining the position of the reference feature10. By determining the position of the reference feature10, and knowing the desired position of the printed image30, the control unit120is capable of activating the particular nozzles112being located relative the web1of packaging material3such that the actual printed image30will be provided at the desired position.

InFIGS. 5aand 5btwo different examples of printed images30are shown. InFIG. 5athe printed30forms a bar code50which can be read by a suitable scanner. InFIG. 5bthe printed image30is in the form of a 2D-code60, such as a QR code or similar. For both examples the printed image30is square shaped, i.e. the resolution in cross-wise direction is equal to the resolution in lengthwise direction (X*X pixels). This is however not required. The cross-wise resolution is determined by the number of nozzles112being activated, while the lengthwise resolution is determined by the number of consecutive activation lines as the web1of packaging material3passes the printing unit110. A printed image30can thus have other cross-wise extensions, whereby the limitation is set by the dimensions of the printing unit110.

InFIGS. 6aand 6ban example of a control scheme for a printing unit110is shown. In these figures the nozzles112are shown as diamonds, and an active nozzle112is marked as black, i.e. a nozzle112currently ejecting ink. It should be noted that also in these figures only a few of the nozzles112are provided with reference numerals.

When the printing unit110is activated, i.e. when it is determined to provide a line of the printed image as a web1of packaging material3passes the printing unit110, the control unit120controls the discharge of ink through the respective nozzles112. Importantly, the nozzles112are individually controllable. InFIG. 6afourteen nozzles are activated to discharge ink, while the remaining seven nozzles shown in the figure are inactive. Activation of a series of nozzles112represents one pulse. The pulse time may be extremely short, especially if the web1of packaging material3is running at high speeds. For example, in order to achieve a resolution of 600 dpi (dots per inch) also in the feeding direction on a web running at 400 m/min it would be required to set the pulse time to approximately 6 microseconds.

The next pulse will be emitted immediately after the first pulse, and the nozzles112are controlled accordingly. As can be seen inFIG. 6bfor this pulse another set of nozzles112is activated to discharge ink onto the packaging material3. By continuing emitting pulses the printed image30will grow in the lengthwise direction until the entire printed image30is provided onto the packaging material3.

So far the printing system100has been described to provide printed images30at fixed positions on the packaging material3. However, as will be understood from the following the printing system100can also be used to provide printed images at different positions, especially for ensuring the correct position of the printed image30relative other features10of the packaging material3.

InFIG. 7another example of a printing system100′ is shown. The printing system100′ comprises a printing unit110′ extending across the entire width of the packaging material3. As for the printing unit110described above a plurality of printing nozzles112are provided facing the moving packaging material3, each nozzle being individually controllable by the control unit120.

The packaging material3is provided with one or more reference features10. The reference features10are provided to assist in correct positioning of the printed images30. A detecting unit130is included in the printing system100′ and detects the presence and position of the reference feature10, especially the lateral or cross-wise position. The position of the detected reference feature10is transmitted to the control unit120which then associates the desired position of the image to be printed with the position of the reference feature10. By also knowing the speed of the web1the control unit120may thus activate the relevant nozzles112such that the position of the printed image30will be correct both in lateral direction and feeding direction.

It should be noted that for a downstream portion of the web1, one set of nozzles112ais used for printing images30on the left portion of the web1, while another set of nozzles112bis used for printing images30on the right portion of the web1. Within each set of nozzles112a-bspecific nozzles112are activated in a pulsed manner in order to form a growing image30as the web1moves forward.

As indicated inFIG. 7the web1is shifted to the right after a certain time due to some manufacturing error occurring. When this shifting occurs the detecting unit130will detect another lateral position of the reference feature10, whereby the control unit120will consequently determine new sets of outputs112c-dof the printing unit110′ so that the printed images30are located correctly relative the reference feature10.

InFIG. 8a schematic view of a method200is shown. The method200is performed to provide a printed image30to a web1of packaging material3, and comprises the following. In201, a detecting unit130configured to continuously detect a feature10on the packaging material3is provided. In202, a control unit120configured to continuously determine a first position of the detected feature10is provided, and in203a printing unit110having a plurality of printing nozzles112is provided.

In204a second position of an image30to be printed is determined, the second position being determined based on the first position. In205at least one printing nozzle112is determined based on the second position, and in206at least one printing nozzle112is activated in order to print an image30onto the packaging material3at the second position.

From the description above follows that, although various embodiments of the invention have been described and shown, the invention is not restricted thereto, but may also be embodied in other ways within the scope of the subject-matter defined in the following claims.