EP4137327A1 - Imprinting method for a metal container and device for imprinting a metal container - Google Patents

Abstract

The invention relates to a printing method for a metal container (11) with the steps: heating the metal container (11), in particular designed as a ready-to-fill metal bottle, to a pretreatment temperature which lies in an interval between 50 degrees Celsius and 250 degrees Celsius, cooling the metal container ( 11) to a temperature below 100 degrees Celsius, locally activating a printing zone (32) formed on an outer surface of the metal container (11) to increase a surface energy of the printing zone (32) and/or locally heating the printing zone (32) to a printing temperature that is in an interval between 30 degrees Celsius and 70 degrees Celsius, printing the printing zone (32) with a printing process.

Description

The invention relates to a printing method for a metal container and a device for printing a metal container.

Such printing methods and devices set up for carrying out the method are used, for example, in the field of mass production of beverage cans and aerosol cans. Depending on the application, contact-based or contactless printing methods are used for this purpose. In many cases, the outer surface of the metal container is printed at a time when the metal container is still in the form of a metal container blank, which has a circular-cylindrical outer surface and is only formed into the desired geometry by plastic deformation in a deformation process to be carried out after printing.

The object of the invention consists in specifying a method and a device for printing a metal container which, taking into account practical framework conditions, can also be used for metal containers that have already been formed.

This object is achieved for a printing process with the following steps: heating of, in particular as ready-to-fill metal bottle, metal container to a pretreatment temperature ranging between 50 degrees Celsius and 250 degrees Celsius, cooling the metal container to a temperature below 100 degrees Celsius, local activation of a printing zone formed on an outer surface of the metal container, for Increasing a surface energy of the printing zone and/or local heating of the printing zone to a printing temperature that is in an interval between 30 degrees Celsius and 70 degrees Celsius, printing the printing zone with a printing process.

This printing method can also be used to print metal containers whose outer surface has a low surface energy due to previous processing and thus a low tendency for printing inks to adhere, since the implementation of the method according to the invention causes an increase in the surface energy of the outer surface of the respective metal container. It is of considerable importance here that the metal container is first heated to a pretreatment temperature in an interval between 50 degrees Celsius and 250 degrees Celsius in order to bring about an advantageous basic conditioning for the outer surface of the metal container.

It is preferably provided to select the pretreatment temperature in an interval between 60 degrees Celsius and 130 degrees Celsius in order to achieve an advantageous compromise between efficient treatment of the surface to be printed and the lowest possible thermal load for the coatings already applied to the metal container, i.e. typically one Interior paint and a base coat to achieve.

After the metal container has cooled down to a temperature below 100 degrees Celsius, a local activation of a printing zone and/or a local heating of the printing zone takes place, preferably immediately before the printing process is carried out.

The activation of the printing zone by means of a suitable activation process is explicitly aimed at increasing the surface energy of the printing zone. Accordingly, a locally effective activation method is used for this purpose.

The local heating of the printing zone serves in particular to improve the flow of ink for the printing ink applied to the outer surface of the metal container, while the change in the surface energy of the metal container is less important. The printing zone is preferably heated immediately before the printing process is carried out, with an advantageous temperature interval for the printing being in a range from 40 degrees Celsius to 60 degrees Celsius.

Advantageous developments of the invention are the subject matter of the dependent claims.

It is expedient that with the step of heating the metal container to the pretreatment temperature, a change in a local distribution of a layer of lubricant applied or distributed on the outer surface of the metal container, in particular a layer of wax or a layer of mineral oil, is carried out to carry out at least regionally plastic deformation of the metal container was done. In principle, it can be assumed that metal containers with regard to their final Structure and geometry are at least almost completely, in particular completely, finished and thus at least no longer require any further significant plastic deformation, in particular in the area of the preceding deformation process are provided with a layer of lubricant. This layer of lubricant is required to carry out the respective plastic deformation process and cannot be removed from the outer surface of the metal container in an economically and technically sensible manner, particularly in the mass production of metal containers.

Accordingly, the aim of heating the metal container to the pretreatment temperature is to change the local distribution of the lubricant, particularly in the printing zone. For example, a homogenization of the layer thickness of the lubricant layer is sought, so that there are no significant layer thickness differences for the lubricant layer, particularly in the printing zone. Such differences in layer thickness result in locally different adhesion of the printing ink and/or in a different color effect of the printing ink and thus call the quality of the printing process into question.

Alternatively, it can be provided, within the scope of the change in the local distribution of the lubricant, to achieve a local concentration of the lubricant into, preferably microscopically small, lubricant droplets. In this case, it is assumed that surface areas between the very small and finely distributed lubricant droplets are at least largely, in particular completely, free of lubricant and the distribution and size of the lubricant droplets can be adjusted through the targeted selection of the pretreatment temperature in such a way that only minor, in particular no impairments perceptible to the naked eye occur in the printed image with which the printing area is provided.

If necessary, at least partial evaporation of the lubricant can be achieved by heating, so that a change in the local distribution of the lubricant can be achieved in this way.

For example, if the metal container is designed as a beverage can blank in the area that will later be used to crimp the lid, or if the metal container is designed as a beverage bottle in the tapered neck area, a large layer thickness of the lubricant can be assumed, since the plastic deformation was carried out there, which to be supported by the lubricant. In contrast, in the adjacent container area, which typically also includes the printing zone, a lower layer thickness of the lubricant layer can be assumed, whereby the lubricant layer in the container area is not caused by an active application of lubricant but rather by lubricant being carried over from the deformation zone of the metal container and thus causing a can have significant inhomogeneity in terms of the layer thickness of the lubricant layer.

In a further embodiment of the method, it is provided that the metal container is provided with a base coat before the plastic deformation process is carried out. The base coat is the coating that is applied to the metal container, on the one hand to protect it from environmental influences and on the other hand to provide advantageous surface properties for the metal container when carrying out the plastic deformation process, in particular with regard to the friction properties of the metal container with respect to the deformation tools used during the deformation process. In many applications, the base coat is also the coating that is applied as the last coating before the metal container is finished and thus significantly determines the properties of the outer surface of the metal container. The base coat usually has high abrasion resistance, high scratch resistance and high resistance to chemical substances and can also be used as a decorative element. Provision can also be made for the metal container provided with the base coat to be provided with a tubular covering which is pushed onto the metal container and then shrunk on, with undesirable side effects such as poorer reusability resulting here, in contrast to printing the metal container.

Provision is preferably made for the printing zone to be printed using a contactless inkjet printing method. This printing process is also referred to as a digital printing process and, in contrast to a printing plate with a fixed print image, enables each metal container to be printed with an individual print image. Accordingly, the inkjet printing process is of particular interest for small batch sizes with a high degree of customization, but requires compliance with narrowly defined conditions for the surface quality of the printing zone due to the printing ink used and the technical framework conditions for dosing the printing ink. These conditions are difficult to comply with, particularly in the case of metal containers that are ready to be filled, because of the layer of lubricant that is usually present, so that the pretreatment and activation according to the method immediately before printing and/or the heating immediately before printing is to be regarded as a basic requirement for high-quality printing.

In a further embodiment of the method, it is provided that the printing zone is provided with a coating after the printing method has been carried out. This coating serves in particular to mechanically protect the printed image applied in the printing zone. Furthermore, the coating, which is applied at least in the printing zone, also ensures protection of the printed image against environmental influences, for example against moisture.

It is advantageous if the coating is applied to the metal container, in particular exclusively, in the printing zone using a contactless digital printing process. Such a coating is also referred to as spot varnishing and can preferably be carried out on the same digital printing machine with which the print image is also applied to the printing zone. However, the layer thickness for the coating is limited when using the digital printing process, so that this type of coating is preferred for metal containers that are not exposed to any greater mechanical and/or chemical influences before they are used.

An alternative procedure provides for the coating to be applied to the outer surface of the metal container using a spraying process. This coating of the metal container is preferably applied away from the digital printing machine with which the printed image is applied to the printing zone. The use of a separate spray device to carry out the spraying process for metal containers is advantageous until use stored and transported under harsh operating conditions, since the thicker layer of the coating ensures more robust protection for the outer surface of the metal container.

Provision is preferably made for the metal container to be heated to the pretreatment temperature for a holding time of at least 60 seconds, preferably at least 120 seconds, in particular at least 240 seconds. In this case, the holding period is understood to mean that period of time within which the metal container reliably has the desired target temperature, which lies in the interval between 50 degrees Celsius and 250 degrees Celsius. The holding time depends on the size and geometry of the metal containers as well as the type and amount of lubricant used, such as wax or mineral oil. It must also be taken into account whether the pre-treatment is to be carried out in a continuous process, for example a continuous furnace, or in batches, i.e. always with a predefined number of metal containers that are to be heated at the same time.

It is preferably provided that the step of cooling the metal container after the step of heating it to the pre-treatment temperature, which is carried out in a pre-treatment chamber, is carried out by transporting it with a conveyor from the pre-treatment chamber to a printing press, in which the printing zone is printed . It is assumed here that the metal container, after leaving the pre-treatment chamber, has to cover a certain conveying distance before it can be made available to the printing machine arranged downstream along the conveying path after the pre-treatment chamber, and that this conveying distance is designed in such a way that the desired cooling of the metal container can be achieved. Radiation of the heat absorbed by the metal container is assumed here; if necessary, additional cooling devices, for example fans, can also be provided in order to bring about the cooling of the metal container.

In a development of the method, it is provided that the local activation of the printing zone is carried out using an activation method from the group: corona treatment, plasma treatment, gas flame, infrared radiation. In a corona treatment, a charge is transported between an electrode and the metal container serving as a counter-electrode in an alternating electric field by ionization of an electrically non-conductive gas, for example ambient air. In a plasma treatment, a charge is transported between an electrode and the metal container serving as a counter-electrode in an alternating electric field of an electrically conductive gas. When using a gas flame for local activation of the printing zone, the activation result can be influenced by a suitable selection of the fuel gas and/or the proportion of oxygen. Infrared radiation can be achieved using either an infrared gas burner or an electrically powered infrared source.

In a further embodiment of the method it is provided that the heating of the printing zone takes place together with the activation, in particular resulting from the activation. For example, when using a gas flame for local activation of the printing zone, in addition to the oxidation effect caused by the open flame, the printing zone is inherently heated due to the combustion process for the fuel gas.

It is advantageous if the metal container for printing in the printing zone is pushed onto a receiving mandrel with a container opening or is gripped and fixed at a bottom area. Sliding the metal container onto a receiving mandrel is advantageous if a cross section of a container opening is the same size or only slightly smaller than a cross section of the adjoining container, as is the case with beverage cans, for example. The gripping and fixing of the metal container at the bottom area is advantageous if the metal container has a typical bottle shape with a slender bottleneck and enables a large contact area between the gripping tongs and the metal container and thus stable and precise fixing of the bottle-shaped metal container, as required for implementation of the printing process is required. On the other hand, gripping the metal container, which can be a beverage bottle, for example, in the neck area, which has a significantly smaller cross section than the base area, would lead to error-prone fixing of the bottle-shaped metal container. The gripping and fixing of the bottle-shaped metal container can be ensured either by a non-positive connection between the metal container and gripping tongs and/or by applying a vacuum to the bottom area of the metal container with the gripping tongs.

The object of the invention is achieved according to a second aspect with a device for printing a metal container. In this case, the device comprises a conveying device for conveying metal containers along a conveying path, a pretreatment chamber arranged along the conveying path, which is designed for heating the metal container to a pretreatment temperature that lies in an interval between 50 degrees Celsius and 250 degrees Celsius, and with one Printing machine arranged downstream of the pre-treatment chamber on the conveying path, which has an activation device for a printing zone of the metal container and a printing unit, in particular designed as a digital printing unit, for printing the printing zone.

The conveying device can include different conveying means such as conveyor chains with receiving rods, loading stars with vacuum shells, conveyor belts, guide rails, turret heads with receiving mandrels. The conveying device serves to transport the metal containers from a loading station for the metal containers arranged upstream of the pretreatment chamber to an unloading station arranged downstream of the printing press. The conveying device can also be designed to handle pallets on which a large number of metal containers are accommodated. Furthermore, in this case it can be provided that the conveying device is designed for separating the metal containers received on a pallet for subsequent linear transport.

The pre-treatment chamber can be designed, for example, as a closable oven for the batch pre-treatment of metal containers. In this case, it can be provided that the conveyor device first feeds the metal containers delivered on pallets into the pre-treatment chamber and, after the pre-treatment has been carried out, removes them from the pre-treatment chamber again in order to subsequently separate and transport the metal containers in a linear fashion in the direction of the printing machine. Alternatively, the pre-treatment chamber can be designed as a continuous furnace through which the conveying device passes, so that the metal containers can run through the furnace section as a continuous row.

In a development of the device, it is provided that the activation device is designed to carry out an activation method from the group: corona treatment, plasma treatment, gas flame, infrared radiation.

In a further embodiment of the invention, it is provided that the pre-treatment chamber is designed as a continuous furnace and/or that the printing machine has a rotary workpiece table which is rotatably mounted on a machine frame and on which a plurality of holding mandrels are arranged, each of which is designed for pushing on a metal container, or on which a plurality of Gripping means are arranged, which are each designed to grip a bottom area of the metal container, and that the activation device and the printing unit are arranged along a circular-arc-shaped conveying path determined by the receiving mandrels or the gripping means.

When using a continuous furnace for the pretreatment of the metal containers, it is advantageous if the metal containers are already conveyed at a distance from adjacent metal containers when passing through the continuous furnace and also during the subsequent transport to the printing press, in order to achieve the homogenization effect of the pretreatment, which is necessary for the on the outer surface applied layer of lubricant is to be moved, not to be called into question again by undefined mechanical contacts between adjacent metal containers.

The printing machine, which is designed in particular as a digital printing machine, comprises a workpiece turntable which is rotatably mounted on a machine frame and is coupled to a drive device which is designed to provide a rotary incremental movement on the workpiece turntable. On an outer peripheral surface or in the area of an outer periphery of the workpiece rotary table, receiving mandrels or gripping means are arranged at regular angular intervals, which are each designed for pushing on the metal container or for gripping a bottom area of a metal container. Provision is preferably made for the mounting mandrels or the gripping means to be aligned on the workpiece rotary table in such a way that the central axes of the metal containers accommodated therein are either aligned in the radial direction or are aligned parallel to an axis of rotation of the workpiece rotary table. The arbors or the gripping means and the metal containers held on them are conveyed on a circular arc-shaped conveying path by the step-by-step rotary movement of the workpiece rotary table. The printing machine comprises a plurality of work stations, at least one of which is designed as a printing unit, in particular as a digital printing unit, and which is arranged in relation to the holding mandrels or the gripping means and the metal containers held thereon in such a way that the respective outer surface of the metal containers can be processed by the work stations . Provision is preferably made for the gripping means to be designed for a non-positive and/or vacuum-based gripping force transmission to the metal container.

Figur 1

eine streng schematische Darstellung einer Bearbeitungseinrichtung, die eine Fördereinrichtung, eine Vorbehandlungskammer sowie eine Druckmaschine umfasst und zur Bedruckung von Metallbehältern ausgebildet ist.

An advantageous embodiment of the invention is shown in the drawing. This shows:

figure 1

a strictly schematic representation of a processing device, which includes a conveyor, a pre-treatment chamber and a printing machine and is designed for printing metal containers.

One in the only figure 1 Processing device 1 shown is provided for printing metal containers 11, the are realized purely by way of example as metal bottles with a circular-cylindrical container section 30 and a bottle neck 31 tapered starting from the container section 30 . The processing device 1 is used to print a rectangular printing zone 32 provided on the container section 30, as an example, it being assumed that the metal container 11 is at least largely ready to be filled with regard to its structure and geometry. In practice, this means that the metal container 11 is again subjected to a further plastic deformation in the course of the printing and also after the printing. Rather, the forming processes that are to be carried out directly on the metal container 11 are already carried out before they are fed to the processing device 1 . If necessary, it can be provided that after the metal container 11 has been printed and the metal container 11 has been transported to a filling device and the filling has been carried out, for example with a soft drink, a closure such as a crown cap is applied to the open end region of the bottle neck 31, whereby a slight plastic deformation of the metal container 11 can occur, but this does not result in a substantial change in shape for the metal container 11.

Furthermore, for the following description of the processing device 1 and the printing process that can be carried out with it for metal containers 11, it is assumed that the metal containers 11 have already been provided with a base coat before the implementation of plastic deformation processes, which on the one hand contributes to a stabilization of the metal container 11 and on the other hand ensures favorable sliding friction properties for the deformation tools with which the plastic deformation of the metal container 11 is carried out. It is also assumed that the metal container 11, in particular in the area of the bottleneck 31, is provided with a lubricant application, not shown in detail, which also serves to reduce the sliding friction between the bottleneck 31 to be formed of the metal container 11 and the deformation tools, not shown.

The processing device 1 comprises a conveyor device 2, with which the metal containers 11 can be transported starting from a loading position 35 to an unloading position 36, the conveyor device 2 purely by way of example having different conveyor means such as a first conveyor belt 5, a loading star wheel 6, an unloading star wheel 9 and a second conveyor belt 10.

The first conveyor belt 5 comprises, purely by way of example, an endlessly revolving chain belt 40 , the upper run 41 of which is guided in sections through a pretreatment chamber 3 embodied purely as an example as a continuous furnace, while a lower run 42 of the chain belt 40 is guided below the pretreatment chamber 3 . By way of example, it is provided that the metal containers 11 are placed on the upper run 41 of the first conveyor belt 5 at a distance from the upper run 41 of the first conveyor belt 5 at the loading position 35 manually by an operator or automatically by an industrial robot or another feed device. It is provided here that the metal containers 11 are placed on the upper run 41 of the first conveyor belt 5 with a contact surface (not shown) that is planar or annular in shape and is determined by a geometry (not shown in detail) of a bottom region 33 of the respective metal container 11 .

By way of example, it is provided that the metal containers 11 are each spaced apart in a single row on the first conveyor belt 5 are placed and are conveyed by the conveying movement of the first conveyor belt 5 along a first conveying path section 45 configured in a straight line to a first transfer position 37 . A first distance 60 between the end of the pre-treatment chamber 3 and the first transfer position 37 is adapted to a pre-treatment temperature in the pre-treatment chamber 3 and to a geometry of the metal containers 11 and to a conveying speed of the first conveyor belt 5 in such a way that the metal containers 11 are at the first transfer position 37 have cooled down to such an extent that when the metal containers 11 are subsequently fed to the printing machine 4, only a small amount of heat is introduced into the printing machine 4, which does not impair the functioning of the printing machine 4.

Purely by way of example, it is provided that at the first transfer position 37 a removal process for the metal container 11 is carried out with the aid of the loading star 6, which is one as shown in FIG figure 1 counterclockwise rotating movement and the metal container 11 at the bottle neck 31 takes. Accordingly, the bottom area 33 of the metal container 11 is free and can be fixed to the workpiece rotary table 7 by the respective gripping means 8 in the course of an opposite rotational movement of the workpiece rotary table 7 arranged adjacent to the loading star 6, in particular using frictional forces and/or a vacuum. Subsequently, the metal containers 11 set on the workpiece rotary table 7 by means of the gripping means 8 are placed in the course of the process shown in FIG figure 1 clockwise stepping movement of the workpiece turntable 7 past a series of work stations 15 to 21 described in more detail below. In this case, work stations 15 to 21 are adapted to the stepping rotary movement of the workpiece turntable 7 and the arrangement of the gripping means 8 on the workpiece turntable 7 adjusted so that the metal containers 11 j are arranged exactly opposite each other to the work stations 15 to 21 during the movement pauses of the workpiece rotary table 7 .

By way of example, it is provided that the first work station 15 is designed as an optical inspection device, which can be used to check whether the metal container 11 is correctly aligned and is held in the gripping means 8 . Furthermore, the optical inspection device of the first workstation 15 can also be used to determine a rotational positioning of the metal container 11 about its longitudinal axis (not shown) in order to be able to carry out the activation and the printing process for the metal container 11 in the correct position relative to the printing zone 32. It is assumed here that each of the gripping means 8 is rotatably mounted on the workpiece rotary table 7 about an axis of rotation 12 shown, which is oriented in the radial direction and is coaxial with an axis of rotational symmetry 34, also referred to as the central axis, of the respective metal container 11. Accordingly, in order to carry out the optical inspection by means of the first work station 15, the metal container 11 can be rotated about its axis of rotational symmetry in order to be able to determine the rotational alignment of the metal container 11 in this way.

In the course of performing a rotary incremental movement through the workpiece rotary table 7, the respective metal container 11 is moved from the first work station 15 to the second work station 16, so that it is arranged opposite the second work station 16 in the subsequent movement profile of the workpiece rotary table 7. The second workstation 16 is also referred to as an activation station and includes an activation device, not shown in detail Implementation of an activation process from the group: corona discharge, plasma discharge, gas flame, infrared radiation.

Provision is preferably made for the imprinting zone 32 to be aligned as exactly as possible opposite the activation device, not shown in detail, in order to achieve the maximum possible activation result for the imprinting zone 32 with the lowest possible energy input into the metal container 11 . Depending on the selection of the activation method and the configuration of the respective activation device, provision can be made for the metal container 11 to be held in a constant rotary position while the activation is being carried out, or at least to be rotated by a certain angle.

In the course of the next three rotary step movements, the metal container 11 is arranged opposite the third work station 17, the fourth work station 18 and the fifth work station 19, each of which has one or more digital print heads (not shown) and which together form a digital print unit 25. At each of these workstations 17 to 19, an ink application takes place in the printing zone 32 of the metal container 11. For example, it is provided that exactly one color, for example cyan, yellow, magenta, is applied to the printing zone 32 at the workstations 17 to 19 in order to to realize a multicolored printed image for the metal container 11. Depending on the design of the digital printing unit 25, it can also have fewer or more work stations with print heads.

After the printing of the printing zone 32 at the work stations 17 to 19 is provided purely as an example to provide the printing zone 32 with a coating that on the one hand mechanical protection for the printed image produced and, on the other hand, protection against aggressive media, such as liquids, for the printed image. For example, the sixth work station 20 is designed for contactless application of the coating in an inkjet printing process and therefore also includes one or more print heads (not shown).

In the course of a further incremental rotary movement for the workpiece rotary table 7, the metal container 11 reaches the seventh work station 21, which is provided purely as an example for a subsequent and additional curing of the printing ink applied in the previous printing steps, with the work stations 17 to 19 of the digital printing unit 25 possibly also not having radiation sources shown can be equipped for curing the printing ink applied at the workstations 17 to 19 in each case.

With a further incremental rotary movement of the workpiece rotary table 7, the respective metal container 11 reaches an unloading position 36, at which an unloading star wheel 9 can grip the respective metal container 11 by the bottleneck 31 in order to remove it from the gripping means 8 and place it on the second conveyor belt 10.

The use of the loading star 6, the workpiece turntable 7 and the unloading star 9 results in a circular segment-shaped, second conveyor path section 46, a circular segment-shaped, third conveying path section 47 and a circular segment-shaped, fourth conveying path section 48, on which a straight fifth conveying path section determined by the second conveyor belt 10 49 connects. It goes without saying that other components can also be used instead of the components of the conveyor device 2 described above can be used to specify a different conveying path 44 for the metal container 11.

The implementation of the printing process for the metal container 11 can be described in connection with the processing device 1 as follows:
In a first step, a metal container 11, which is preferably designed to be ready to be filled, is placed from a box or from a pallet manually or with an automatic handling device (not shown), in particular an industrial robot, at loading position 35 onto upper run 41 of first conveyor belt 5, see above that it is aligned in a straight line with other metal containers 11 already set up on the upper strand 41 .

The conveying movement of the first conveyor belt 5 along the first conveying path section 45 transports the metal container 11 through the pre-treatment chamber 3 and is heated there to a predetermined pre-treatment temperature ranging between 100 degrees Celsius and 250 degrees Celsius. A temperature profile in the pre-treatment chamber 3, a conveying speed of the first conveyor belt 5 and a length of the pre-treatment chamber 3 are matched to the properties of the metal container 11 in such a way that the latter is exposed to the pre-treatment temperature for a specified period of time, which is also referred to as the holding period the desired homogenization of the lubricant layer is achieved.

After leaving the pre-treatment chamber 3, the metal container 11 is at least predominantly passively cooled, the metal container 11 having a temperature at the first transfer position 37 with which an excessive heat input on the subsequent printing machine 4 is avoided. After the metal container 11 has been removed from the upper run 41 of the first conveyor belt 5 and the metal container 11 has been fed to the gripping means 8 of the workpiece rotary table 7, the metal container 11 passes the work stations 15 to 21 in the course of the rotary incremental movements of the workpiece rotary table 7. The alignment is first checked here of the metal container 11 opposite the gripping means 8, the printing zone 32 of the metal container 11 is then activated, and then the printing and the subsequent coating of the printing zone 32 can be carried out using digital printing methods. Finally, the metal container 11 passes through the seventh and last work station 21, at which a final curing of the paint layers applied beforehand is carried out. In a subsequent step, the metal container 11 is transferred at the second transfer position 38 to the unloading star wheel 9 , which then places the metal container 11 onto the second conveyor belt 10 . The second conveyor belt 10 moves the metal container 11 to the unloading position 36, not shown in detail, at which, for example, the now finished metal container can be removed manually or automatically from the second conveyor belt 10 and the metal container 11 can be placed in a transport box, not shown, or on a pallet, not shown can be done.

Claims (15)

Printing method for a metal container (11) with the steps: heating the metal container (11), in particular designed as a ready-to-fill metal bottle, to a pretreatment temperature which lies in an interval between 50 degrees Celsius and 250 degrees Celsius, cooling the metal container (11) to a temperature below 100 degrees Celsius, local activation of a printing zone (32) formed on an outer surface of the metal container (11) to increase a surface energy of the printing zone (32) and/or local heating of the printing zone (32) to a printing temperature, which is in an interval between 30 degrees Celsius and 70 degrees Celsius, printing the printing zone (32) with a printing process. Printing method according to Claim 1, characterized in that the step of heating the metal container (11) to the pretreatment temperature involves changing a local distribution of a layer of lubricant applied to the outer surface of the metal container (11), in particular a layer of wax or a layer of mineral oil, which is used to carry out a plastic deformation of the metal container (11), at least in some areas, takes place. Printing method according to Claim 2, characterized in that the metal container (11) before the implementation of the plastic deformation process is provided with a base coat. Printing method according to Claim 1, 2 or 3, characterized in that the printing zone (32) is printed using a contactless inkjet printing method. Printing method according to one of the preceding claims, characterized in that the printing zone (32) is provided with a coating after the printing method has been carried out. Printing method according to Claim 5, characterized in that the coating is applied, in particular exclusively, to the metal container (11) in the printing zone (32) using a contactless digital printing method. Printing method according to Claim 5, characterized in that the coating is applied to the outer surface of the metal container (11) using a spraying method. Printing method according to one of the preceding claims, characterized in that the metal container (11) is heated to the pretreatment temperature for a holding time of at least 60, preferably at least 120, in particular at least 240 seconds. Printing method according to one of the preceding claims, characterized in that the step of cooling the metal container (11) after the step of heating to the pre-treatment temperature in a pre-treatment chamber (3) is carried out, is carried out by transport with a conveyor device (2) from the pretreatment chamber (3) to a printing machine (4), in which the printing of the printing zone (32) is carried out. Printing method according to one of the preceding claims, characterized in that the local activation of the printing zone (32) is carried out using an activation method from the group: corona treatment, plasma treatment, gas flame, infrared radiation. Printing method according to Claim 10, characterized in that the heating of the printing zone (32) takes place together with the activation, in particular resulting from the activation. Printing method according to one of the preceding claims, characterized in that the metal container (11) for printing in the printing zone (32) is gripped and fixed at a bottom area (33). Device (1) for printing a metal container (11), in particular for carrying out the method according to one of Claims 1 to 12, with a conveyor device (2) for conveying metal containers (11) along a conveyor path (45, 46, 47, 48, 49), with a pretreatment chamber (3) arranged along the conveying path (45, 46, 47, 48, 49) for heating the metal container (11) to a pretreatment temperature ranging between 50 degrees Celsius and 250 degrees Celsius is formed, and with a printing machine (4) which is arranged downstream of the pre-treatment chamber (3) on the conveying path (45, 46, 47, 48, 49) and which has an activation device (16) for a printing zone (32) of the metal container (11) as well as one, in particular as a digital print work trained, printing unit (25) for printing the printing zone (32). Device according to Claim 12, characterized in that the activation device (16) is designed to carry out an activation method from the group: corona treatment, plasma treatment, gas flame, infrared radiation. Apparatus according to Claim 12, characterized in that the pre-treatment chamber (3) is designed as a continuous furnace and/or that the printing machine (4) has a workpiece rotary table (7) which is rotatably mounted on a machine frame and on which a plurality of receiving mandrels are arranged, each of which can be pushed on of a metal container (11), or on which several gripping means (8) are arranged, which are each designed to grip a bottom area (33) of the metal container (11), and that the activation device (16) and the printing unit (16) along a circular arc-shaped conveying path (47) determined by the receiving mandrels or the gripping means (8).

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