Printing method to metal container and apparatus for performing printing on metal container

Abstract

To provide a method for performing printing on a metal container which is usable also in a metal container that has been molded in consideration of an actual basic condition.SOLUTION: A printing method to a metal container 11 includes the following steps: heating a metal container configured as, especially, a metal bottle that has been filled to a pretreatment temperature of 50-250°C; cooling the metal container to a temperature of lower than 100°C; locally activating a printing region so as to increase surface energy of a printing region 32 formed on the outside surface of the metal container and / or locally heating the printing region to a printing temperature of 30-70°C; and performing printing on the printing region using the printing method.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method of printing on a metal container and an apparatus for printing on a metal container. [Background technology]

[0002] Such printing methods and devices configured to carry them out are used, for example, in the field of mass production of beverage and aerosol cans. Depending on the application, contact or non-contact printing methods are used here. In many cases, printing of the outer surface of a metal container is carried out while the metal container still exists as a blank metal container with a cylindrical outer surface, and only in a deformation process to be carried out after printing is it plastically deformed into the desired geometric shape. Summary of the Invention [Problem to be solved by the invention]

[0003] SUMMARY OF THE INVENTION The object of the present invention is to provide a method and an apparatus for printing on metal containers that can be used in consideration of practical basic conditions and that can also be used on metal containers that have already been formed. [Means for solving the problem]

[0004] This problem is solved by a printing method comprising the following steps: heating a metal container, in particular configured as a filled metal bottle, to a pretreatment temperature in the range of 50°C to 250°C; cooling the metal container to a temperature below 100°C; locally activating the printed area formed on the outer surface of the metal container to increase the surface energy of the printed area and / or locally heating the printed area to a printing temperature in the range of 30°C to 70°C; and printing on the printed area using a printing method.

[0005] This printing method can also be used to print on metal containers whose outer surface, due to a previous treatment process, has a low surface energy and thus a low tendency for printing ink to adhere to them. This is because the implementation of the method according to the present invention results in an increase in the surface energy of the outer surface of the respective metal container. In this case, it is essential that the metal container is first heated to a pretreatment temperature in the range of 50°C to 250°C in order to create a favorable base condition for the outer surface of the metal container.

[0006] Preferably, a pretreatment temperature is selected in the range of 60°C to 130°C, which is expected to provide an advantageous compromise between efficient treatment of the surface to be printed and the smallest possible heat load on the coating already applied to the metal container, i.e., typically the inner paint and base paint.

[0007] After cooling the metal container to a temperature below 100° C., preferably just before the printing step is carried out, local activation of the printing area and / or local warming of the printing area is carried out.

[0008] Activation of the printed areas by suitable activation methods has the specific aim of increasing the surface energy of the printed areas, and therefore locally effective activation methods are used for this purpose.

[0009] Localized heating of the printing area is particularly useful for improving the ink flow of printing inks applied to the outer surface of the metal container, while changes in the surface energy of the metal container are not so important. Preferably, heating of the printing area is carried out immediately before the printing process, during which the temperature range favorable for printing is settled in the range of 40°C to 60°C.

[0010] Advantageous developments of the invention are the subject of the dependent claims.

[0011] Advantageously, the step of warming the metal container to the pretreatment temperature changes the positional distribution of a lubricant layer, in particular a wax or mineral oil layer, applied or distributed on the outer surface of the metal container, which was brought about to carry out at least partial plastic deformation of the metal container. It is generally envisaged that a metal container that is at least nearly completely, in particular completely, finished in terms of its final structure and geometry, and therefore no longer requires at least significant further plastic deformation, is provided with a lubricant layer, in particular within the scope of a previously carried out deformation process. This lubricant layer is necessary to carry out the respective plastic deformation process and cannot be removed from the outer surface of the metal container in an economical and technically advantageous manner, in particular during mass production of metal containers.

[0012] Therefore, the purpose of heating the metal container to the pretreatment temperature is to change the local distribution of the lubricant, especially in the printing area. For example, the goal is to make the layer thickness of the lubricant layer uniform, so that there are no essential layer thickness differences in the lubricant layer, especially in the printing area. Such layer thickness differences result in locally different adhesion of the printing ink and / or different color effects of the printing ink, which therefore affects the quality of the printing process.

[0013] Alternatively, it may be envisaged that within the scope of the change in the positional distribution of the lubricant, local concentrations of lubricant, preferably microscopically small lubricant droplets, are obtained, whereby the surface areas between the extremely 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 by selecting the correct processing temperature so that only slight, in particular no, disturbances perceptible to the naked eye occur in the printed image provided in the printing area.

[0014] If necessary, heating can result in at least partial evaporation of the lubricant, thus achieving a change in the positional distribution of the lubricant.

[0015] For example, when a metal container is configured as a beverage can blank, a large lubricant layer thickness is assumed in the area that will later be used for crimping the lid, or in the tapered neck area when the metal container is configured as a beverage bottle, because plastic deformation that should be assisted by the lubricant occurs there. In contrast, a smaller lubricant layer thickness is assumed in the container area adjacent to this area, which typically also includes the printing area, where the lubricant layer in the container area is not produced by active lubricant application but rather by entrainment of lubricant from the deformation area of ​​the metal container, and therefore significant non-uniformity in the lubricant layer thickness can occur.

[0016] Another method involves providing a metal container with a base coating before the plastic deformation process. The base coating is a coating applied to the metal container to protect it from environmental influences and to provide it with favorable surface properties during the plastic deformation process, particularly with respect to the deformation tools used during the deformation process, particularly the frictional properties of the metal container. In many applications, the base coating is applied as the last coating before finishing the metal container and therefore also the coating that largely determines the properties of the outer surface of the metal container. Typically, the base coating has high abrasion resistance, high scratch resistance, and high chemical resistance, and can also be used as a decorative element. It is also possible to provide a tubular top coating on the metal container with the base coating, which is applied to the metal container and then shrunk, which, unlike printing on the metal container, can result in undesirable secondary effects, such as poor reusability.

[0017] It is preferred to use a non-contact inkjet printing method to print the print area. This printing method, also known as digital printing, allows printing of individual print images, unlike printing plates that have a fixed, predetermined print image for each metal container. Therefore, inkjet printing is particularly important for highly customized small batches, but it is necessary to maintain narrowly defined conditions for the surface quality of the print area based on the printing ink used and the technical basic conditions for metering the printing ink. Since maintaining these conditions is difficult, especially in filled metal containers, due to the lubricant layer that is usually present, pre-treatment by a method and activation and / or warming immediately before printing are considered essential requirements for high-quality printing.

[0018] In another embodiment of the method, it is provided that after the printing process has been carried out, the printing area is provided with a coating, which serves in particular to mechanically protect the printed image applied to the printing area. Furthermore, the coating applied to at least the printing area also ensures protection of the printed image against environmental influences, for example against moisture.

[0019] Advantageously, the coating is applied to the metal container using a non-contact digital printing method, especially exclusively in the printing area. This coating is also called spot coating, and is preferably carried out using the same digital printing machine that also applies the printed image to the printing area. However, since the thickness of the coating is limited when using digital printing methods, this coating method is preferably considered for metal containers that are not exposed to relatively large mechanical and / or chemical influences until they are used.

[0020] In an alternative method procedure, a coating is applied to the outer surface of the metal container using a spraying method. The application of this coating to the metal container is preferably performed separately from the digital printing machine that applies the print image to the print area. The use of a separate spraying device to perform the spraying method is advantageous for metal containers that are stored and transported under harsh operating conditions until use, because the relatively large layer thickness can ensure more robust protection of the outer surface of the metal container.

[0021] Preferably, the metal container is heated to the pretreatment temperature over a holding period of at least 60 seconds, preferably at least 120 seconds, and in particular at least 240 seconds. In this context, the holding period is understood to mean the period during which the metal container actually reaches the desired target temperature, which is in the range of 50°C to 250°C. The holding period depends on the size and geometry of the metal container and the type and amount of lubricant used, such as wax or mineral oil. Furthermore, it must be taken into account whether the pretreatment is carried out continuously, for example, in a continuous oven, or in a batch process, i.e., for a predetermined number of metal containers that are always to be heated simultaneously.

[0022] Preferably, the step of cooling the metal container after the step of heating to the pretreatment temperature in the pretreatment chamber is carried out by transporting the metal container from the pretreatment chamber to a printing machine that prints in the printing zone using a transport device. In this case, the metal container must travel a predetermined transport section after leaving the pretreatment chamber, and then the metal container can be provided to the printing machine arranged downstream of the pretreatment chamber along a transport path, and this transport section is assumed to be configured to achieve the desired cooling of the metal container. In this case, the release of heat absorbed by the metal container is assumed, and if necessary, an additional cooling device, for example a blower, may be provided to cool the metal container.

[0023] In one development of the method, local activation of the printed area is assumed to be carried out using an activation method from the group consisting of corona treatment, plasma treatment, gas flame, and infrared radiation. In corona treatment, charge transfer between the electrode and a metal container used as a counter electrode is carried out by ionizing a non-conductive gas, for example, ambient air, in an alternating electric field. In plasma treatment, charge transfer between the electrode and a metal container used as a counter electrode is carried out in an alternating electric field of a conductive gas. When a gas flame is used to locally activate the printed area, the activation result can be influenced by the appropriate selection of the fuel gas and / or oxygen ratio. Infrared radiation can alternatively be achieved by using an infrared gas burner or an electrically operated infrared source.

[0024] In another embodiment of the method, it is envisaged that the warming of the printing area is carried out together with the activation, in particular as a result of the activation. For example, when a gas flame is used to locally activate the printing area, in addition to the oxidizing effect of the open flame, a warming of the printing area due to the combustion process of the fuel gas inevitably occurs.

[0025] Preferably, the metal container is placed on a holding mandrel with its opening or gripped and fixed at its bottom region in order to print the print area. Placing the metal container on a holding mandrel is advantageous when the cross-section of the container opening is the same size as or slightly smaller than the cross-section of the subsequent container, as is the case, for example, with beverage cans. Gripping and fixing the metal container at its bottom region is advantageous when the metal container has a typical bottle shape with a narrow bottle neck, allowing for a large contact area between the gripper and the metal container, thus enabling stable and accurate fixation of the bottle-shaped metal container, as required for carrying out the printing process. In contrast, gripping a metal container, which may be, for example, a beverage bottle, at its neck region, which has a cross-section significantly smaller than its bottom area, makes fixing the bottle-shaped metal container more prone to errors. Grippling and fixing the bottle-shaped metal container can be ensured by a force connection between the metal container and the gripper and / or by applying a vacuum to the bottom region of the metal container by the gripper.

[0026] According to a second aspect, the object of the present invention is achieved by an apparatus for printing on metal containers, comprising a transport device for transporting the metal containers along a transport path, a pre-treatment chamber arranged along the transport path and configured to heat the metal containers to a pre-treatment temperature in the range of 50°C to 250°C, and a printing machine arranged in the transport path downstream of the pre-treatment chamber, the printing machine comprising an activation device for a printing zone of the metal container and a printing device, in particular configured as a digital printing machine, for printing in the printing zone.

[0027] The conveying device may have various conveying means, such as a conveying chain with holding rods, an infeed wheel with a vacuum shell, a conveying belt, guide rails, a revolver head with a holding mandrel, etc. The conveying device is used to transport the metal containers from an infeed station for the metal containers, which is arranged upstream of the pre-treatment chamber, to an outfeed station, which is arranged downstream of the printing press. The conveying device may also be configured to handle pallets on which a large number of metal containers are stored. Furthermore, in this case, it may be assumed that the conveying device is configured to separate the metal containers stored on the pallets for subsequent linear transport.

[0028] The pretreatment chamber can be configured, for example, as a closed oven for batchwise pretreatment of metal containers. In this case, it can be assumed that the transport device first feeds the metal containers supplied on pallets into the pretreatment chamber and, after pretreatment, removes them again from the pretreatment chamber, thereby subsequently singulating the metal containers and further transporting them in a straight line towards the printing press. Alternatively, the pretreatment chamber can be configured as a continuous oven through which the transport device passes, so that the metal containers can travel through the oven section in a continuous row.

[0029] In one development of the device, it is provided that the activation device is configured to carry out an activation method from the group of corona treatment, plasma treatment, gas flame, infrared radiation.

[0030] In another embodiment of the present invention, the pre-treatment chamber is configured as a continuous furnace, and / or the printing press has a workpiece turntable supported on a machine frame for free rotational movement, and the workpiece turntable is provided with a plurality of holding mandrels, each configured to cover a metal container, or the workpiece turntable is provided with a plurality of gripping means, each configured to grip the bottom region of a metal container, and the activation device and the printing device are arranged along an arc-shaped transport section defined by the holding mandrels or gripping means.

[0031] When a continuous oven is used for the pre-treatment of metal containers, it is advantageous if the metal containers are transported at a distance from each other when they pass through the oven and then on their way to the printing press, so that the uniformity of the pre-treatment, which must be carried out on the lubricant layer applied to the outer surface, is not again affected by indefinite mechanical contact between adjacent metal containers.

[0032] The printing press, in particular configured as a digital printing press, has a workpiece turntable rotatably supported on a machine frame, the workpiece turntable being connected to a drive that is configured to provide the workpiece turntable with a rotary stepping movement. On the outer circumferential surface or in the outer circumferential region of the workpiece turntable, holding mandrels or gripping means are arranged with a regular angular distribution. The holding mandrels or gripping means are configured to cover the metal container or grip the bottom region of the metal container, respectively.

[0033] Preferably, the holding mandrel or gripping means is aligned with the workpiece turntable so that the central axis of the metal container held on the workpiece turntable is oriented radially or parallel to the rotation axis of the workpiece turntable. Due to the rotational stepping movement of the workpiece turntable, the holding mandrel or gripping means and the metal container held by the holding mandrel or gripping means are transported along an arc-shaped transport section. The printing press has a plurality of work stations, at least one of which is configured as a printing device, in particular a digital printing device, and is arranged so that the holding mandrel or gripping means and the metal container held by the holding mandrel or gripping means can process the outer surface of each metal container by the work station. It is preferably envisaged that the gripping means is configured to transmit a gripping force to the metal container by force connection and / or vacuum.

[0034] An advantageous embodiment of the present invention is shown. [Brief explanation of the drawings]

[0035] [Figure 1] 1 shows a highly simplified diagram of a converting apparatus configured to print on metal containers, the converting apparatus having a transport apparatus, a pre-processing chamber, and a printing press; DETAILED DESCRIPTION OF THE INVENTION

[0036] The processing device 1 shown in FIG. 1 is provided for printing on a metal container 11. The processing device 1 is realized, by way of example only, as a metal bottle having a cylindrical container portion 30 and a bottle neck 31 tapered from the container portion 30. The processing device 1 is used to print on a print area 32, which is, by way of example only, rectangular, provided on the container portion 30, assuming that the metal container 11 is at least substantially filled in terms of its structure and geometry. In practice, this means that the metal container 11 is subjected to further plastic deformation, again during the printing process and also after printing. Furthermore, in many cases, deformation processes to be performed directly on the metal container 11 have already been performed before it is fed to the processing device 1. It may be assumed that, after printing on the metal container 11, the metal container 11 is transported to a filling device and filled, for example, with a soft drink, a stopper, such as a crown cap, is attached to the open end region of the bottle neck 31. This may further cause a slight plastic deformation of the metal container 11, but this does not result in a significant change in the configuration of the metal container 11.

[0037] Furthermore, in the following description of the processing device 1 and the printing method for the metal container 11 that can be performed by the processing device 1, it is assumed that the metal container 11 is already provided with a base coating before the plastic deformation process is performed, which on the one hand contributes to the stabilization of the metal container 11 and on the other hand ensures favorable sliding friction properties with respect to the deformation tool (by which the plastic deformation of the metal container 11 is performed).It is also assumed that the metal container 11 is coated with a lubricant (not shown), in particular in the region of the bottle neck 31, which is likewise used to reduce sliding friction between the bottle neck 31 of the metal container 11 to be deformed and the deformation tool (not shown).

[0038] The processing device 1 comprises a conveying device 2 by means of which the metal containers 11 can be transported from an input position 35 to an output position 36, the conveying device 2 comprising various transport means such as, by way of example only, a first conveying belt 5, an input wheel 6, an output wheel 9 and a second conveying belt 10.

[0039] The first conveyor belt 5 has, by way of example only, an orbiting chain belt 40, an upper belt section 41 of which is guided partially through the pre-treatment chamber 3, which is, by way of example only, configured as a continuous oven, while a lower belt section 42 of the chain belt 40 is guided below the pre-treatment chamber 3. For example, it is assumed that the metal containers 11 are placed at intervals on the upper belt section 41 of the first conveyor belt 5 at the loading position 35, either manually by a user (not shown) or automatically by an industrial robot or other feeding device. In this case, it is assumed that the metal containers 11 are placed on the upper belt section 41 of the first conveyor belt 5 with a planar or annular contact surface (not shown) determined by the geometric shape (not shown) of the bottom region 33 of each metal container 11.

[0040] For example, it is assumed that the metal containers 11 are placed on the first conveyor belt 5 at intervals in a single row and are transported by the transport movement of the first conveyor belt 5 along the linear first transport path portion 45 to the first transfer position 37. The first distance 60 between the end of the pretreatment chamber 3 and the first transfer position 37 is adapted to the treatment temperature in the treatment chamber 3, the geometric shape of the metal containers 11, and the transport speed of the first conveyor belt 5, so that when the metal containers 11 are cooled at the first transfer position 37 and then fed to the printing press 4, only a small amount of heat is input into the printing press 4, so as not to impair its function.

[0041] By way of example only, it is assumed that an unloading process of the metal container 11 is carried out at the first transfer position 37 by means of the feed wheel 6. The feed wheel 6 performs a rotational movement proceeding counterclockwise in accordance with the representation in FIG. 1 and grips the metal container 11 by the bottle neck 31. The bottom area 33 of the metal container 11 is thus free and can be fixed to the workpiece turntable 7 by the respective gripping means 8, in particular by means of frictional force and / or vacuum, during the clockwise rotational movement of the workpiece turntable 7 arranged next to the feed wheel 6. Subsequently, the metal container 11, which has been fixed to the workpiece turntable 7 by the gripping means 8, is guided through a series of work stations 15 to 21, which will be described in more detail below, during the rotational stepwise movement of the workpiece turntable 7, which is set in the clockwise direction in accordance with the representation in FIG. 1. In this case, the work stations 15 to 21 are adapted to the rotary step movement of the workpiece turntable 7 and the arrangement of the gripping means 8 on the workpiece turntable 7 in such a way that the metal container 11j is positioned exactly opposite each of the work stations 15 to 21 during the pauses in the movement of the workpiece turntable 7.

[0042] For example, it is assumed that the first work station 15 is configured as an optical inspection device, which can check whether the metal container 11 is held in the gripping means 8 in a correctly aligned state. Furthermore, the optical inspection device of the first work station 15 can also determine the rotational position of the metal container 11 about its longitudinal axis (not shown), so that the activation and printing process on the metal container 11 can be performed in the correct position relative to the printing zone 32. In this case, it is assumed that each gripping means 8 is supported on the workpiece turntable 7 so as to be rotatable about the illustrated radial rotation axis 12, which is oriented coaxially with the axis of rotational symmetry 34, also referred to as the central axis, of the respective metal container 11. It can therefore be assumed that, for optical inspection by the first work station 15, the metal container 11 is rotated about its own axis of rotational symmetry, thereby making it possible to ascertain the rotational orientation of the metal container 11.

[0043] During the course of the rotational step movement of the workpiece turntable 7, each metal container 11 moves from a first work station 15 to a second work station 16, so that the metal container 11 is positioned opposite the second work station 16 during the subsequent movement of the workpiece turntable 7. The second work station 16, also referred to as an activation station, has an activation device (not shown) that performs an activation method from the group consisting of corona discharge, plasma discharge, gas flame, and infrared radiation.

[0044] Preferably, it is envisaged that the printing area 32 is aligned as precisely as possible opposite the activation device (not shown) in order to obtain the best possible activation result of the printing area 32 with the least possible energy input into the metal container 11. Depending on the choice of activation method and the configuration of the respective activation device, it may be envisaged that the metal container 11 is held in a fixed rotational position or rotated by at least a predetermined angle value during the activation process.

[0045] During the next three rotational steps, the metal container 11 is positioned opposite a third work station 17, a fourth work station 18, and a fifth work station 19. Each of these work stations has one or more digital print heads (not shown), which together form a digital printing device 25. At each of these work stations 17 to 19, ink is applied to a print zone 32 of the metal container 11. For example, it is assumed that each of work stations 17 to 19 ejects exactly one type of ink, such as cyan, yellow, or magenta, into the print zone 32, thereby achieving a multicolored print image of the metal container 11. Depending on the configuration of the digital printing device 25, the digital printing device 25 may have fewer or additional work stations equipped with print heads.

[0046] After printing has been carried out in the print zone 32 in the work stations 17 to 19, it is assumed, purely by way of example, that the print zone 32 is provided with a coating, which on the one hand ensures mechanical protection of the produced print image and, on the other hand, ensures protection of the print image against aggressive media, for example liquids. For example, the sixth work station 20 is designed to apply the coating contactlessly in an inkjet printing process and therefore likewise has one or more print heads (not shown).

[0047] In the course of a further rotational step movement of the workpiece turntable 7, the metal container 11 reaches a seventh work station 21. The seventh work station 21 is provided, by way of example only, for the additional curing of printing ink applied in a previous printing step, in which case the work stations 17 to 19 of the digital printing device 25 may optionally be equipped with radiation sources (not shown) for curing the printing ink applied at each of the work stations 17 to 19.

[0048] As the workpiece turntable 7 makes further rotational steps, each metal container 11 reaches the discharge position 36, where the discharge wheel 9 can grip each metal container 11 by the bottle neck 31, thereby removing the metal container 11 from the gripping means 8 and placing it on the second conveyor belt 10.

[0049] Based on the use of the infeed wheel 6, the workpiece turntable 7 and the discharge wheel 9, a second circular conveying path section 46, a third circular conveying path section 47 and a fourth circular conveying path section 48 are generated, to which a linear fifth conveying path section 49 is connected, which is established by the second conveyor belt 10. Of course, other components of the conveying device 2 may be used instead of the aforementioned components, thereby allowing other conveying paths 44 for the metal containers 11 to be established.

[0050] The execution of the printing method on the metal container 11 can be explained in relation to the processing device 1 as follows.

[0051] In a first step, a metal container 11, preferably configured to be fully filled, is placed from a box or pallet onto the upper belt section 41 of the first conveyor belt 5 at the loading position 35 either manually or by an automatic handling device, in particular an industrial robot, not shown, so that the metal container 11 is aligned in a straight line with other metal containers 11 already placed on the upper belt section 41.

[0052] By the conveying movement of the first conveyor belt 5 along the first conveying path section 45, the metal container 11 is conveyed through the pre-treatment chamber 3, where it is heated to a predetermined pre-treatment temperature in the range of 100° C. to 250° C. The temperature profile in the pre-treatment chamber 3, the conveying speed of the first conveyor belt 5 and the length of the pre-treatment chamber 3 are adjusted in accordance with the characteristics of the metal container 11 so that the metal container 11 is exposed to the pre-treatment temperature for a predetermined period, also referred to as the holding period, thereby achieving the desired uniformity of the lubricant layer.

[0053] After leaving the pretreatment chamber 3, the container 11 is at least largely passively cooled, with the container 11 reaching a temperature at the first transfer position 37 that prevents excessive heat input to the subsequent printing press 4. After the container 11 is removed from the upper belt section 10 of the first conveyor belt 5 and fed to the gripping means 8 of the workpiece turntable 7, the container 11 passes through the work stations 15 to 21 during the rotational stepping movement of the workpiece turntable 7. This involves first controlling the alignment of the container 11 with respect to the gripping means 8, followed by activation of the print area 32 of the container 11, which can then be printed and subsequently coated using a digital printing method. Finally, the container 11 passes through the seventh and final work station 21, where the final curing of the previously applied ink layer takes place. In a subsequent step, at a second transfer position 38, the metal container 11 is transferred to the discharge wheel 9, which subsequently places the metal container 11 on the second conveyor belt 10. The second conveyor belt 10 moves the metal container 11 to a discharge position 36 (not shown), at which the now finished metal container can be removed from the second conveyor belt 10, for example, manually or automatically, and the metal container 11 can be loaded into a transport box (not shown) or onto a pallet (not shown).

Claims

1. In a method of printing on a metal container (11), the following steps: heating the metal container (11) to a pretreatment temperature in the range of 50°C to 250°C; and cooling the metal container (11) to a temperature below 100°C; and locally activating the printing area (32) to increase the surface energy of the surface of the printing area (32) formed on the outer surface of the metal container (11), and / or locally heating the printing area (32) to a printing temperature in the range of 30°C to 70°C; and performing printing on the printing area (32) using a printing method; A printing method comprising the above steps.

2. The printing method according to claim 1, characterized in that, by the step of heating the metal container (11) to the pretreatment temperature, the positional distribution of the lubricant layer applied to the outer surface of the metal container (11) is changed in order to perform at least partial plastic deformation of the metal container (11).

3. The printing method according to claim 2, characterized in that a base paint is provided on the metal container (11) before performing the plastic deformation step.

4. The printing method according to claim 1, characterized in that printing is performed on the printing area (32) using a non-contact inkjet printing method.

5. The printing method according to claim 1, characterized in that a coating is provided on the printing area (32) after performing the printing method.

6. The printing method according to claim 5, characterized in that a coating is applied to the metal container (11) in the printing area (32) using a non-contact digital printing method.

7. The printing method according to claim 5, characterized in that a coating is applied to the outer surface of the metal container (11) using a spraying method.

8. The printing method according to claim 1, characterized in that the metal container (11) is heated to the pretreatment temperature for a holding period of at least 60 seconds.

9. The printing method according to claim 1, characterized in that the step of cooling the metal container (11) after the step of heating to the pretreatment temperature performed in the pretreatment chamber (3) is performed by transporting the metal container (11) from the pretreatment chamber (3) to a printing machine (4) for performing printing on the printing area (32) using a transport device (2).

10. The printing method according to claim 1, characterized in that the local activation of the printing area (32) is performed using an activation method from the group of corona treatment, plasma treatment, gas flame, and infrared radiation.

11. The printing method according to claim 10, characterized in that the heating of the printing area (32) is performed together with the activation.

12. The printing method according to claim 1, characterized in that the metal container (11) is gripped and fixed in the bottom region (33) for printing on the printing region (32).

13. In an apparatus (1) for printing on a metal container (11) for carrying out the method according to any one of claims 1 to 12, a conveying device (2) for conveying the metal container (11) along a conveying path (45, 46, 47, 48, 49); a pretreatment chamber (3) arranged along the conveying path (45, 46, 47, 48, 49), the pretreatment chamber (3) being configured to heat the metal container (11) to a pretreatment temperature in the range of 50°C to 250°C; a printing machine (4) arranged in the conveying path (45, 46, 47, 48, 49) downstream of the pretreatment chamber (3), the printing machine (4) having an activation device (16) for the printing region (32) of the metal container (11) and a printing device (25) for printing on the printing region (32); The apparatus comprising the above.

14. The apparatus according to claim 13, characterized in that the activation device (16) is configured to perform an activation method from the group of corona treatment, plasma treatment, gas flame, and infrared radiation.

15. The pretreatment chamber (3) is configured as a continuous furnace, and / or The printing machine (4) has a workpiece turntable (7) rotatably supported on a machine frame, and a plurality of holding mandrels configured to cover the metal container (11) respectively are arranged on the workpiece turntable (7), or a plurality of gripping means (8) configured to grip the bottom region (33) of the metal container (11) respectively are arranged on the workpiece turntable (7), and the activation device (16) and the printing device (16) are arranged along an arc-shaped conveying section (47) set by the holding mandrel or the gripping means (8). The apparatus according to claim 13.

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