Apparatus and method for controlling direct printing machines

Abstract

The invention relates to a method for printing objects, in particular containers, wherein the containers are transported along a specified transport path, and the outer surface of the containers is printed at least temporarily by means of at least one printing unit, wherein a controller controls the printing of the containers by means of the at least one printing unit on the basis of at least one printing parameter. According to the invention, at least one object to be printed is printed with at least one test marking in order to ascertain the printing parameter, and the object provided with the test marking is then inspected by means of at least one inspection device, wherein the printing parameter is derived from the result of the inspection.

Claims

1. A method for printing objects, in particular containers, including: applying prints to the containers, wherein the containers are transported along a specified transport path, and the outer surface of the containers is printed at least temporarily by at least one printing unit, wherein a controller controls the printing of the containers by the at least one printing unit on the basis of at least one printing parameter, wherein at least one object to be printed is printed with at least one test marking in order to ascertain the at least one printing parameter, and the at least one object provided with the at least one test marking is then inspected by at least one inspection device, wherein the at least one printing parameter is derived from the result of the inspection, wherein the prints are checked by a test program using a different inspection device, wherein a test is run before production and/or specific test cycles are used, and wherein an optimization loop takes place during an ongoing production without having to initiate a special procedure.

2. Method according to claim 1, wherein the printing of the at least one object with the at least one test marking takes place in the context of a test mode.

3. Method according to claim 2, wherein in a normal working operation a color camera is used and for the test mode an inspection device is used.

4. Method according to claim 1, wherein a further object is printed with an object test marking.

5. Method according to claim 1, wherein the at least one test marking is compared with at least one reference value.

6. Method according to claim 1, wherein the containers are printed by at least two printing units.

7. Method according to claim 1, wherein the at least one inspection device performs an evaluation of at least one colour property of the at least one test marking.

8. Method according to claim 1, wherein the at least one inspection device is suitable and intended for detecting at least one defect of the at least one test marking.

9. Method according to claim 1, wherein the at least one inspection device inspects the at least one test marking by means of an inspection element which is selected from a group of inspection elements which includes spectrophotometers, densitometers, in particular colour densitometers and spectral densitometers.

10. Apparatus for printing objects and in particular containers, including: a transport device which transports the objects along a predetermined transport path; at least one printing unit, which is suitable and intended for applying a print to an outer wall of the objects in the context of a working operation; and a control device for controlling a first printing unit of the at least one printing unit, characterized in that the first printing unit is suitable and intended for applying at least one test marking to an outer surface of the objects in the context of a test operation, and with a first inspection device for inspecting the objects printed with the at least one test marking, wherein the first inspection device is arranged downstream of the first printing unit in a transport direction of the objects and outputs at least one inspection result processed by the control device for controlling the first printing unit, wherein the print is checked by a test program using a different inspection device, wherein a test is run before production and/or specific test cycles are used, wherein after the test is run the first inspection device is moved or driven into a protection region, and wherein the protection region provides an overpressure that protects the first inspection device against a spray mist caused by a printing operation.

11. Apparatus according to claim 10, wherein the apparatus has at least one second inspection device which is suitable and intended for inspecting prints applied to the objects during a working operation.

12. Apparatus according to claim 10, wherein the apparatus comprises an inspection device which is used in the working operation that can meet different criteria than an inspection device used in the test operation.

13. Apparatus according to claim 10, wherein the apparatus has an illumination device which illuminates the containers during an inspection thereof by the first inspection device.

14. Apparatus according to claim 10, wherein the first inspection device is movable between a working position and a rest position.

15. Method according to claim 1, wherein the at least one test marking is a test wedge and/or the at least one test marking has a test wedge.

16. Method according to claim 1, wherein the at least one inspection device has a color camera or a related image recording device that is suitable for recording spatially resolved images.

17. Method according to claim 1, wherein color and position adjustments are carried out quickly and precisely with a defined criteria by an automated optimization loop.

Description

(1) Further advantages and embodiments are apparent from the appended drawings.

(2) In the drawings:

(3) FIG. 1 shows a schematic representation of an apparatus according to the invention; and

(4) FIG. 2 shows a flow diagram for a method according to the invention.

(5) FIG. 1 shows a schematic representation of an apparatus 1 according to the invention for printing containers 10. In this case the containers 10 are delivered by means of a delivery device 52 and are discharged by means of a discharge unit 54. Furthermore, the apparatus 1 has a carrier 24 which is rotatable with respect to an axis of rotation D and is a component of a transport device 2. Holding devices 22 which serve for holding the containers 10 to be equipped (of which only one is shown) are arranged on this carrier. Furthermore, printing units 4, 6, 7 are arranged on the carrier 24, but only three of these equipment units are shown. The reference numerals 14, 16 and 17 relate in each case to control devices for controlling the printing units 4, 6 and 7.

(6) The embodiment shown in FIG. 1 involves printing units which apply a direct print to the containers 10. In this case these printing units 4, 6, 7 can have a plurality of print heads, for example three print heads, which are arranged one above the other. Furthermore, the apparatus has rotation devices which enable each individual container 10 to be rotated with respect to its longitudinal direction (which here extends perpendicularly to the drawing plane).

(7) The reference P identifies the transport path, in this case circular, of the containers 10 to be equipped.

(8) An inspection device 8 which checks the containers is arranged downstream with respect to the holding elements and the equipment units. In this case this inspection device inspects these containers or the test markings thereon, in particular in the context of a test operation of the device. For this purpose the inspection device can have a storage device 32 in which reference images are stored, in particular reference images of test prints. Furthermore, the apparatus has a comparison device 34 which compares the recorded images of the test markings with the reference images. On the basis of this comparison printing parameter of the control device can be changed, in particular in order to achieve an improvement in the printing.

(9) FIG. 2 shows a flow diagram for a method according to the invention. In this case first of all a test program or test method is started. As mentioned above, this start can be triggered by the user, i.e. for example manually, but it would also be possible for the start to take place automatically according to defined specifications, for instance after a product changeover. The reference numeral 18 designates a storage device into which the inspection device can be introduced, in particular during a production operation of the apparatus 1.

(10) This storage device preferably has a housing which protects the inspection device at least against contaminations such as for instance colour splashes. In this case the apparatus can have a carrier (not shown), relative to which the inspection device 8 can be moved in order thus to be moved from a rest position (represented by a broken line in FIG. 1) into a working position (during a test operation). The reference numeral 12 designates a further inspection device which inspects the containers (in particular during a production operation). Moreover, the apparatus preferably has an assigning device (not shown), by which the printing unit which has produced the inspected print is assigned to the inspection result of the further inspection device. However, it would also be possible for this inspection device to be arranged directly on a movable carrier, for instance the discharge device 54.

(11) Two branches are shown in FIG. 2, wherein the right branch illustrates actions by the inspection device and the left branch illustrates actions by the printing unit. First of all, with regard to of the at least one printing unit there is a changeover to the printing with the test marking.

(12) Additionally it is possible that, as well as the test marking, metadata are also printed, as mentioned above, for instance a date or a time. In addition, at the beginning of the measuring program an inspection device is also activated, which also serves especially for detecting the test marking.

(13) In this case it is possible for this inspection device to be moved for example out of a housing into a working or measurement position. In this case, particularly preferably, a measurement sensor can be brought automatically into a suitable measurement position. Subsequently a test object, such as in particular a container, can be moved in and can be printed with the test marking. This container thus printed is subsequently inspected by the inspection device and in this case at least one measurement is carried out. Within the context of this inspection it is possible that one or more recordings of the test markings are carried out.

(14) In a further method step the recorded image or the measurements carried out are compared with reference images and in particular also reference colours.

(15) If this comparison results in a sufficient conformity between the measured values and the reference values, this is a sign that the printing is satisfactory and the production can be started. In this case it is also possible to determine limiting values within which a test print carried out is still regarded as satisfactory. Outside these limits the container thus obtained and/or the printing can be regarded as defective.

(16) In addition, documentation of the test can be carried out and for this purpose in particular the container provided with the test marking can also be discharged. If the result of the inspection is that the test marking is unsatisfactory, a calibration takes place, in particular a calibration of the control device and/or of the printing unit. In this case a container is moved in and printed with the test marking. Subsequently, here too, a measurement or an inspection of the test marking takes place and it is checked whether this meets the predetermined criteria. If required, these steps can be carried out a number of times. In this case in particular the method described here can proceed automatically and thus, in particular at the start of production, can carry out a controlled calibration of the printing unit.

(17) Sometimes the available measuring means cannot completely detect the test marking. Therefore the transport of the printed containers is preferably halted in the region of the inspection device or the container transport is stopped. In this position scanning of the container can then be carried out in a vertical direction. If for example a second scan is necessary, the machine can be moved further by the necessary amount and, if required, the rotated position of the container with respect to the measuring means can be corrected again and a further image or a further scan can be produced.

(18) After the measurement or the calibration is carried out, the inspection device can be moved back into a protection region, as mentioned above.

(19) The applicant reserves the right to claim all the features disclosed in the application documents as essential to the invention in so far as they are, individually or in combination, novel over the prior art. Furthermore it is pointed out that features which may be advantageous per se have also been described in the individual drawings. The person skilled in the art recognises immediately that a specific feature described in a drawing may also be advantageous without the incorporation of further features from this drawing. Furthermore the person skilled in the art recognises that advantages may also result from a combination of several features shown in individual drawings or in different drawings.