EP2746050B1 - Pad printing machine and method for operating a pad printing machine - Google Patents

Description

TECHNICAL AREA

The present invention relates to a method for operating a pad printing machine, which has at least one printing pad and a plate and is used for printing objects, as well as a pad printing machine for operation with such a method.

STATE OF THE ART

Pad printing machines are known in the prior art in numerous designs and are used for printing differently shaped objects. In this case, a print image is taken from a cliche by means of a printing pad and then transferred to an object to be printed. By forming the printing pad from an elastic material, it is also possible to print on uneven surfaces.

Usually, a large number of similar objects are printed by pad printing machines. In particular, the printing speed with which the individual objects can be printed represents an important parameter in order to be able to maximize the throughput. At high print speeds, however, the likelihood that poor spots in the print result will occur and thus compromise print quality will increase. Defective areas arise in the print result, in particular when the printing pad during the print image recording from the cliché and / or the subsequent print image transfer to an object to be printed, so is moved quickly that it comes to trapped air between the printing pad and cliché or the object to be printed. Such air pockets are a problem, especially when printing images on objects with uneven surfaces. In the often occurring case that by means of a rotationally symmetrical printing pad a likewise rotationally symmetric object is printed with an uneven surface, it can come at an increased printing speed to circular, for the viewer well recognizable printing artifacts. Such objects relate to, for example, plates or the dials of watches. The challenge, on the one hand, of maximizing the printing speed and, on the other, ensuring a satisfactory print quality.

In the WO 03/082575 a tampon printing machine is described in which the speed of the tampon movement is specified during the print image recording according to a specific motion profile. Vibrations of the tampon during the print image recording, which can lead to a deterioration in the quality of the print result, are avoided by slowing down the printing pad during print image recording. However, the speed of the print pad as it moves away from the cliche is faster in comparison to maximize print speed.

A method with an optimized motion profile of the printing pad for the print image recording is also in the DE 163 13 753 disclosed.

In the document EP 0 879 698 a tampon printing machine is disclosed in which a change in speed in the vertical movement is registered upon impact of the printing pad on the object to be printed by means of an optical sensor to subsequently limit the further downward movement of the printing pad to a certain distance.

The disadvantage of these disclosed in the prior art method, however, is particularly in the relatively cumbersome determination and adjustment of the motion profile or the speed function with which the printing pad is moved during the print image recording. When using different Print tampons, the speed function for the print image recording has to be re-optimized and adapted to the condition and shape of the respective printing tampon. An optimization of the speed function is also desirable in terms of print image transmission depending on the respective object to be printed. This is a tedious and time-consuming task for the operator.

PRESENTATION OF THE INVENTION

It is therefore an object of the present invention to provide a method for operating a pad printing machine, which allows the most efficient and easy for the operator quick and easy optimization of the printing speed. To solve this problem, a method is proposed, as indicated in claim 1. In addition, a tampon printing machine for carrying out this method is specified in claim 12. Advantageous embodiments of the invention are specified in the dependent claims.

1. a.) Erfassen der Position von zumindest einem Kontaktpunkt, in welchem der Drucktampon und das Klischee während einer ersten Druckbildaufnahme aufeinandertreffen, und/oder von zumindest einem Kontaktpunkt, in welchem der Drucktampon und das zu bedruckende Objekt während einer ersten Druckbildübertragung aufeinandertreffen;
2. b.) Ermitteln einer Geschwindigkeitsfunktion basierend auf dieser erfassten Position; sowie
3. c.) Bewegen des Drucktampons während einer zweiten Druckbildaufnahme relativ zum Klischee bzw. während einer zweiten Druckbildübertragung relativ zu dem zu bedruckenden Objekt mit einer Geschwindigkeit gemäss dieser Geschwindigkeitsfunktion.

The present invention thus provides a method for operating a pad printing machine, which has at least one printing pad and a cliché, wherein the method has at least the step that by means of the printing pad a print image is taken from the cliche (print image recording), and that a printed image is transferred from the printing pad to an object to be printed (print image transfer). The method also has at least the following additional steps:

1. a.) Detecting the position of at least one contact point, in which the printing pad and the cliché meet during a first print image recording, and / or at least one contact point, in which the printing pad and the object to be printed meet during a first print image transfer;
2. b.) determining a speed function based on this detected position; such as
3. c.) Moving the printing pad during a second print image recording relative to the cliche or during a second print image transfer relative to the object to be printed at a speed according to this speed function.

A contact point is determined in particular by the fact that at this point the printing pad with a print image transfer surface for receiving and for Transferring the print image is used, meets a surface of the plate or the object to be printed. By "meeting" at the point of contact, it is meant that the print image transfer surface of the print pad and the surface of the plate or object to be printed are just touching at the point of contact, but not in an area immediately adjacent to the contact point. During the print image recording or during the print image transfer is formed between the printing pad and cliché or between the printing pad and the object to be printed each have a contact surface in which touch the printing pad and the cliché or the object to be printed with their surfaces. The outer edge of this contact surface then forms such contact points. In step a.) The position of at least one of these contact points, but advantageously of a plurality of these contact points, is detected.

By detecting the position of at least one contact point during the print image recording or print image transmission by means of a detection device of the pad printing machine in step a.), A relationship between the tampon movement and the arrangement and design of the cliché or the object to be printed can be established. In particular, it is known at which point in time the printing pad with its printed image transfer surface strikes a specific point of the printing plate or of the object to be printed. This information can be utilized in step b.) In order to adapt the speed function for the movement of the printing pad with regard to a later print image recording or print image transmission. For example, it is possible to determine the point in time at which the printing pad encounters the surface of the cliché or the surface of the object to be printed, or in which the printing pad strikes its printing image transfer surface with a certain uneven spot of the object to be printed. The speed function may then be slowed down, in particular, with respect to the movement of the printing pad during contact with the surface of the cliché, the object to be printed or the uneven spot in comparison to the rest of the movement. Air pockets, which lead to deficient areas in the print result, can thereby be efficiently avoided.

The first print image and the second print image respectively the first Print image transfer and the second print image transfer can, but need not, follow each other directly. Thus, after the first print image recording or the first print image transmission, further print image recordings or print image transfers can take place before step c.) Is carried out and the print pad is moved at a speed in accordance with the newly determined speed function.

For detecting the position of the at least one contact point, a camera is advantageously used. The position detection then takes place based on image data. In this case, the camera preferably captures an image sequence which, in particular, records the entire process of a respective print image recording or print image transmission. As a result, for example, the time at which the printing pad is placed on a specific location of the plate or the object to be printed, can be determined very accurately. For this purpose, the camera advantageously has a CCD chip and is preferably suitable for taking pictures with a temporal resolution of less than 5 milliseconds, in particular less than 3 milliseconds. For the transmission of the data captured by the camera, a real-time bus system with cycle times of preferably at most 100 μs and a jitter of at most 1 μs is advantageously provided. Preferably, in step a.) Even the positions of more than one contact point are detected in order to obtain even more information regarding the tampon movement relative to the cliché or the object to be printed. For this purpose, several cameras are advantageously used, which capture the print image recording or print image transmission, in particular from different directions.

The printing pad is usually rotationally symmetrical. Usually, the printing pad is made of silicone rubber and thus formed elastically. The hardness of the printing pad is preferably in the range of 40 Shore 00 to 90 Shore 00 and particularly preferably in the range of 50 Shore 00 to 70 Shore 00.

Usually, the printing pad is moved during the print image recording or the print image transmission in each case along a main movement direction, which preferably extends along a longitudinal central axis of the printing pad. The capture of Position of the at least one contact point is then preferably from a direction which is substantially perpendicular to this main movement direction. The position of the contact point can be detected very accurately.

Preferably, in step b.) The speed function is determined by the fact that based on the detected position of the contact point, the change in size and / or shape of the contact surface between the printing pad and the plate during the print image recording or between the printing pad and the object to be printed during the print image transfer is calculated, and that based on this calculation, the speed function is determined. Since the change in the size and / or shape of the contact surface has a direct influence on the formation of air pockets, this procedure is particularly suitable for optimizing the speed function while ensuring sufficient print quality. To calculate the contact surface based on the position of the contact point, for example, the previously known, for example rotationally symmetrical shape of the printing pad and / or the object to be printed can be used.

• a0.) Überprüfen des Druckergebnisses an dem zu bedruckenden Objekt.

According to a development of the invention, the method has the following additional step:

• a0.) Check the print result on the object to be printed.

By executing step a0.), The print quality can be checked before and / or after determining a new speed function in step b.) And in particular in a subsequent step b.) Be taken into account in the determination of a new speed function. For this purpose, the speed function is determined in step b.) Upon detection of a defective printing result in step a0.), Preferably based on the position of defective locations in the printed result. The determination of the position of defective places in the print result can be carried out by the operator. However, this determination is advantageously carried out fully automatically, for example by means of an evaluation unit and an additional camera connected to it, which is arranged such that it can take an image of the printed object after the print image has been transmitted. In the evaluation unit can for comparison purposes the image of an ideal print result can be stored.

In a preferred embodiment, the speed function in step b.) Is determined in such a way that the movement of the printing pad in step c.) Is slowed down when contacting those areas of the cliché or object to be printed which correspond to the defective locations in the printed result Comparison to the movement of the printing pad during the first print image recording or print image transmission when contacting the same areas. The formation of trapped air can be avoided.

Advantageously, step a0.) And / or a.) And / or b.) And / or c.) Are carried out fully automatically. The necessary interventions by the operating staff are thereby reduced to a minimum.

In a further development of the invention, a plurality of printing operations are carried out in step a0.) In which the speed of movement of the printing pad relative to the plate during the print image recording and / or the speed of movement of the printing pad relative to the object to be printed during the print image transmission at least once from is increased to a printing operation to a subsequent printing operation, and wherein the printing result is checked at least once after this increase in the speed of the object to be printed. Advantageously, the speed of the movement of the printing pad during the print image recording and / or the print image transfer is thereby increased from printing process to printing process until a deficient printing result is determined. In other words, therefore, the speed of the printing tampon movement is increased until a defective printing result is determined. The speed function is then redetermined in step b.) In order to achieve a satisfactory printing result, preferably at substantially the same speed in step c.).

• d.) Durchführen von zwei oder mehr Durchgängen, welche jeweils alle Schritte a0.) bis c.) umfassen, wobei ab dem zweiten Durchgang das Ermitteln der Geschwindigkeitsfunktion in Schritt b.) zusätzlich jeweils auf der im vorhergehenden Durchgang ermittelten Geschwindigkeitsfunktion basiert.

Die Geschwindigkeitsfunktion kann dadurch von Durchgang zu Durchgang weiter optimiert werden.Preferably, the method has the following additional step:

• d.) performing two or more passes, each comprising all steps a0.) to c.), wherein from the second pass, the determination of the speed function in step b.) additionally in each case on the previous passage determined speed function based.

The speed function can thus be further optimized from one pass to the next.

There is also provided a tampon printing machine for operation by a method as set forth above, comprising at least one printing pad and at least one cliché, the printing pad being movable relative to the cliche and serving to receive a print image from the cliche and transfer it to an object to be printed. The pad printing machine has at least one detection device, which serves for detecting the position of at least one contact point, in which the printing pad and the cliché meet during a print image recording, and / or at least one contact point, in which the printing pad and the object to be printed during a Collide print image transfer.

The pad printing machine also has a determining unit which serves to determine a speed function for the movement of the printing pad during the print image recording relative to the cliche or during the print image transfer relative to the object to be printed based on a position determined by the detection device of a contact point. The pad printing machine also has a motion control unit, which serves to control the movement of the printing pad relative to the plate or to the object to be printed at a speed according to this speed function. The detection device is preferably a camera, which is advantageously arranged at the level of the cliché surface or at the level of a surface to be printed of the object to be printed.

In addition, the pad printing machine preferably has an electric motor, in particular a servomotor, for moving the printing pad. Other drive devices for moving the printing pad, in particular a pneumatic drive, are conceivable, but less preferred.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1

eine perspektivische Ansicht einer Tampondruckmaschine gemäss einer ersten Ausführungsform;

Fig. 2

eine perspektivische Teilansicht der in der Fig. 1 gezeigten Tampondruckmaschine zu Beginn der Druckbildaufnahme;

Fig. 3

eine perspektivische Teilansicht des Klischees der in der Fig. 1 gezeigten Tampondruckmaschine zu Beginn der Druckbildaufnahme, mit eingezeichneter Kontaktfläche;

Fig. 4

eine perspektivische Teilansicht der in der Fig. 1 gezeigten Tampondruckmaschine während der Druckbildaufnahme bei vollständig abgesenktem Drucktampon;

Fig. 5

eine perspektivische Teilansicht des Klischees der in der Fig. 1 gezeigten Tampondruckmaschine während der Druckbildaufnahme bei vollständig abgesenktem Drucktampon, mit eingezeichneter Kontaktfläche;

Fig. 6

eine Seitenansicht auf den Drucktampon und das Klischee der in der Fig. 1 gezeigten Tampondruckmaschine in Blickrichtung der Kamera, zu Beginn der Druckbildaufnahme;

Fig. 7

eine Seitenansicht auf den Drucktampon und das Klischee der in der Fig. 1 gezeigten Tampondruckmaschine in Blickrichtung der Kamera, bei vollständig abgesenktem Drucktampon;

Fig. 8

eine Seitenansicht einer Tampondruckmaschine gemäss einer zweiten Ausführungsform zu Beginn der Druckbildübertragung auf ein erstes zu bedruckendes Objekt;

Fig. 9

eine Seitenansicht der in der Fig. 8 gezeigten Tampondruckmaschine während der Druckbildübertragung auf ein erstes zu bedruckendes Objekt; sowie

Fig. 10

eine Seitenansicht der in der Fig. 8 gezeigten Tampondruckmaschine während der Druckbildübertragung auf ein zweites zu bedruckendes Objekt.

Preferred embodiments of the invention will be described below with reference to the drawings, which are given by way of illustration only and are not to be interpreted as limiting. In the drawings show:

Fig. 1

a perspective view of a pad printing machine according to a first embodiment;

Fig. 2

a partial perspective view in the Fig. 1 shown pad printing machine at the beginning of the print image recording;

Fig. 3

a partial perspective view of the cliche in the Fig. 1 shown pad printing machine at the beginning of the print image recording, with marked contact surface;

Fig. 4

a partial perspective view in the Fig. 1 shown pad printing machine during the print image recording with fully lowered pressure pad;

Fig. 5

a partial perspective view of the cliche in the Fig. 1 shown pad printing machine during the print image recording at fully lowered printing pad, with marked contact surface;

Fig. 6

a side view of the printing pad and the cliché in the Fig. 1 shown pad printing machine in the direction of the camera, at the beginning of the print image recording;

Fig. 7

a side view of the printing pad and the cliché in the Fig. 1 shown pad printing machine in the direction of the camera, with fully lowered pressure pad;

Fig. 8

a side view of a pad printing machine according to a second embodiment at the beginning of the print image transfer to a first object to be printed on;

Fig. 9

a side view of the in the Fig. 8 shown pad printing machine during the print image transfer to a first object to be printed; such as

Fig. 10

a side view of the in the Fig. 8 shown pad printing machine during the print image transfer to a second object to be printed.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the FIGS. 1 to 7 a tampon printing machine 1 is shown, which is suitable for operation with a method according to a first embodiment.

As it is in the FIG. 1 1, the pad printing machine 1 has a machine frame 10 with an upper arm 101 extending in the horizontal direction. At the end face of this arm 101, a display 102 is arranged, which serves to display operating conditions, machine parameters, etc. Below the display 102 a plurality of input elements 103 are provided on the arm 101, which serve for setting and operating the pad printing machine 1 by the user.

As it is in particular from the FIGS. 1 and 2 it can be seen, on the machine frame 10 below the arm 101, a plate carrier 11 is arranged with a cliché attached thereto 12, which has a surface extending in the horizontal direction. By means of adjusting elements 110, the position of the plate 12 on the plate carrier 11 is manually adjustable. In a region near the plate 12, a paint pot 13 is also arranged.

On the underside of the arm 101, a pad carrier 14 displaceable in the horizontal direction along the arm 101 is arranged, to which a printing pad 15 is attached. As it is in particular from the FIG. 2 it can be seen, the pad carrier 14 is in this case attached to the underside of a rail 101 displaceable along the arm, that the printing pad carrier 14 and thus the printing pad 15 in a direction perpendicular to the longitudinal direction of the arm 101 direction are manually displaced horizontally. There may be locking elements, such. As screws, may be provided which allow fixing of the tampon carrier 14 on the underside of this provided with a scale rail.

Here, the printing pad 15 has a rotationally symmetrical shape which is well known from the prior art, with an upper, slightly conical downwards tapered base part, which is followed at the bottom by a print image transfer part with a downwardly arched print image transfer surface 150. In this case, the print image transfer surface 150 is in particular designed in such a way that, when the printing pad 15 is lowered onto a flat, horizontal surface, in particular the surface of the printing plate 12, it first rests on it with a central region and then, on a further lowering onto the surface, forming an enlarging, circular contact surface 2 with the surface (see Figures 3 and 5 ). Due to the overall rotationally symmetrical shape of the printing pad 15, a longitudinal center axis 151 of the printing pad is defined. The printing pad 15 is usually made of silicone rubber and formed correspondingly elastic. The hardness of the printing pad 15 is preferably in the range of 40 Shore 00 to 90 Shore 00 and more preferably in the range of 50 Shore 00 to 70 Shore 00. Specifically, in the present case, printing pads with hardnesses of about 54 Shore 00 and about 64 Shore 00 used.

When lowering the printing pad 15 on the plate 12 for printing image recording or the subsequent lifting of the printing pad 15 of the printing pad 15 is moved along a main movement direction, which here is perpendicular to the surface of the plate 12 and extends along the vertical direction. The main movement direction also extends along the longitudinal center axis 151 of the printing pad 15.

In order to detect the position of the printing pad 15 relative to the printing plate 12, the pad printing machine 1 has a camera 19 which is directed from one direction to the contact area between the printing pad 15 and the printing plate 12, which is substantially perpendicular to the main movement direction or to the longitudinal center axis of the printing pad 15 stands. The camera 19 is arranged in particular at the level of the surface of the plate 12. The camera 19 may in particular be a camera with a CCD sensor, which allows the acquisition of images with a temporal resolution of advantageously less than 5 milliseconds, in particular less than 3 milliseconds.

As it is in the FIG. 1 can be seen, the pad printing machine 1 for moving the Pressure pads 15 in the vertical direction to a servo motor 16, which is arranged in the interior of the arm 101. By means of the servomotor 16, the movement of the printing pad 15 relative to the plate 12 is controlled very precisely. To control the servomotor 16, a motion control unit 18 is provided inside the machine frame 10 and a detection unit 17 connected to it. The detection unit 17 is also preferably connected to the camera 19 in order to evaluate the images recorded by the camera 19 in the To enable determination unit 17. For the transmission of the data recorded by the camera 19 to the determination unit 17, for example, the real-time bus system EtherCAT ™ can be used which has a cycle time of at most 100 μs and a jitter of at most 1 μs. In an alternative embodiment, the detection unit could also be arranged outside of the machine frame 10 and be designed, for example, in the form of an external computer.

To determine an optimal speed function for the movement of the printing pad 15 relative to the plate 12 during the print image recording, the printing pad 15 is moved in a first step according to a predetermined, based on experience speed function, in which a qualitatively satisfactory recording of the printed image from the cliche 12 to each Case is guaranteed. By means of the predetermined speed function, the printing pad 15 is braked continuously, for example, before reaching the lowermost point, and continuously accelerated after reversal of its direction of movement during lifting. The transition from the lowering to lifting movement can be done in particular harmonious. The recorded by the printing pad 15 print image is then transferred in accordance with the usual printing process of the pad printing machine 1 on an object to be printed and checked the printed result. This check of the print result can be performed by the operator. Advantageously, however, the check is carried out fully automatically, for example by means of an evaluation unit and an additional camera connected to it, which is arranged such that it can take a photo of the printed object after the print image transfer.

This process of print image recording according to a predetermined speed function, the print image transfer to an object to be printed and checking the printing result is repeated a plurality of times, wherein the speed of the printing pad 15 is incrementally increased during the print image recording at each pass. In this case, an image sequence is detected at each pass from the camera 19 during the print image recording and z. B. stored in a memory module of the determination unit 17. In this image sequence, in particular the respective position of a contact point 3 is detected, in which the print image transfer surface 150 of the printing pad 15 impinges on the surface of the printing plate 12. Contact points in which the print image transfer surface 150 of the printing pad 15 impinges on the surface of the printing plate 12 are arranged along the entire outer edge of the contact surface 2 (see FIG. 5 ). The camera 19 is arranged and adjusted such that it can detect at least the radial distance of one of these contact points 3 relative to the longitudinal central axis 151 of the printing pad 15 during the entire print image recording. A suitable image capture area 4 of the camera 19 used in this embodiment is shown in FIGS FIGS. 6 and 7 represented by a dashed line. The image-capturing area 4 is selected such that, on the one hand, the first contact point 3, in which the print-image transfer area 150 first impinges on the cliché 12 during lowering of the printing pad 15, is detected (see FIG FIG. 6 ). On the other hand, the image-capturing area 4 is selected such that even the outermost contact point 3, in which the print image transfer area 150 impinges on the cliché 12 at the maximum lowering of the printing pad 15, is detected (see FIG FIG. 7 ).

Of course, the image capture area 4 of the camera 19 could also be chosen such that not only the contact point 3 is detected, but at the same time also in the Figures 5 and 7 illustrated contact point 3 ', in which the print image transfer surface 150 on the relative to the contact point 3 diametrically opposite side of the contact surface 2 impinges on the plate 12.

The image sequence advantageously comprises temporally images taken at regular intervals, wherein the first image is taken immediately before the first touch of the printing pad 15 with the cliché 12 when lowering the printing pad 15 and the last image immediately after the last contact of the printing pad 15 with the cliché 12th is recorded during subsequent lifting of the printing pad 15.

As soon as a deficient position in the print result is determined during the checking of the printing result due to the increase in the speed of the printing pad 15 during the print image recording, a new speed function is determined by the determination unit 17. First, the radial position of the defective point in the printed image is determined. Subsequently, the image sequence recorded by the camera 19 during the preceding printing operation is evaluated with regard to the position of the contact point 3 between the printing pad 15 and the printing plate 12 during the print image recording. Due to the known rotationally symmetrical shape of the printing pad 15 can be concluded from the position of the contact point 3 relative to the longitudinal center axis 151 of the printing pad 15 on the shape and size of the contact surface 2 and in particular their change during the print image transfer. To determine the new speed function, the point in time at which the contact point 3 occupies the radial position relative to the longitudinal center axis 151, which corresponds to the radial position of the defective point in the printed image on the printed object, is determined on the basis of the recorded image sequence. Starting from this point in time, a corresponding vertical position of the printing pad 15 can be calculated. The speed function is then modified to slow down the printing pad 15 as it is lowered and / or raised in the range of that vertical position as compared to the previous printing operation. Air pockets between the printing pad 15 and plate 12, which have arisen due to the rapid movement of the printing pad 15 and have led to the defective location in the print result, can be avoided in the subsequent passage.

The printing pad 15 is thus moved in the subsequent printing process according to a newly determined speed function. It may be followed by further printing operations in which the speed of the printing pad 15 is further incrementally increased during the print image recording. If defects occur in the printed result, the speed function can again be determined again by the determination unit 17, as described above, and the method can be repeated as often as desired in order to further optimize the speed function and to maximize the printing speed.

The above-mentioned method steps for adjusting the speed function of the printing pad 15 during the print image recording and thus for maximizing the printing speed can each be carried out completely automatically, so that no interventions by the operating personnel are necessary. In order to enable such a fully automatic implementation of this method, the pad printing machine 1 advantageously has a second camera which is directed onto the object to be printed in order to record an image of the printed image printed on the object after the print image transfer. In this case, this second camera is preferably connected to the determination unit 17, in which the recorded images are compared with images of an ideal printing result stored in the determination unit 17.

In the FIGS. 8 to 10 a tampon printing machine 1 is shown according to a second embodiment. Equal or similar elements of the pad printing machine 1 of this embodiment will be denoted below with the same reference numerals as the corresponding elements in the FIGS. 1 to 7 shown first embodiment.

The in the FIGS. 8 to 10 Pad printing machine 1 shown has a camera 19 ', which is directed to an object to be printed 6 to detect the position of a contact point 3, in which impinges upon transfer of the print image of the printing pad 15 on the object to be printed. The image detection area 4 imaged by the camera 19 'is in the FIGS. 8 to 10 indicated by a dashed line on the relative to the camera 19 'opposite side of the printing pad 15. The camera 19 ', which is arranged at the height of the printable top side of the object to be printed 6, is aligned such that it detects the position of the contact point 3 from a horizontal direction, which is perpendicular to the longitudinal center axis 151 of the printing pad 15 and to the vertical Main movement direction 151 of the printing pad 15 is during the image transfer to the object to be printed 6.

The object 6 to be printed is on during a print image transfer Slide 5 is arranged and advantageously held in this. For manually adjusting the position of the object 6 to be printed relative to the printing pad 15 during the print image transfer, the slide 5 has adjusting elements 50.

The method for determining an optimal speed function for the movement of the printing pad 15 relative to the object to be printed 6 during the print image transfer is analogous to the above-performed method, by means of which an optimized speed function for the movement of the printing pad 15 during the print image recording at the in the FIGS. 1 to 5 embodiment shown is determined.

In the FIGS. 8 and 9 an object to be printed 6 is shown, which has a flat surface which is printed by means of the pad printing machine 1. In the FIG. 10 however, an object 6 'to be printed is shown, which has an uneven surface to be printed on. The method according to the invention is particularly advantageous in the case of objects of this kind having uneven surfaces to be printed, since in the case of these objects the danger of air inclusions between the print image transfer surface 150 and the object 6 'to be printed is increased. The change in the contact surface 2 during the print image transfer is here dependent in particular on the shape of the surface of the object 6 to be printed. By means of the method according to the invention, an optimized speed function can be determined automatically and without prior knowledge of the exact shape of the object 6 'to be printed, which in particular ensures uniformly fast movement of the contact point 3 and thus of the outer edge of the contact surface 2 relative to the surface of the object 6' to be printed. ensures throughout the print image transfer.

Of course, the invention described herein is not limited to the mentioned embodiments and a variety of modifications is possible. For example, in the FIGS. 1 to 7 embodiment shown also with in the FIGS. 8 to 10 shown embodiment, so that the pad printing machine according to two cameras and the speed function is optimized both during the print image recording and during the print image transmission. To capture the position of the contact point must In addition, not necessarily be provided a camera. Instead of a camera for contact point position detection, for example, a laser measuring device could be provided. Instead of just one camera, a plurality of cameras or detection devices could also be provided in order to detect the positions of different contact points from different directions during the print image recording and / or the print image transmission. This is particularly advantageous in the case of non-rotationally symmetric pressure pads and / or non-rotationally symmetric objects to be printed. A variety of other modifications is conceivable.

LIST OF REFERENCE NUMBERS

1 Pad Printing Machine 16 servomotor 10 machine frame 17 determining unit 101 poor 18 Motion control unit 102 display 19, 19 ' camera 103 input elements 11 plate holder 2 contact area 110 adjusting 3, 3 ' contact point 12 cliche 4 Image capture area 13 paint pot 14 Pressure pad carrier 5 slides 15 printing pad 50 adjusting 150 Print image transfer surface 6, 6 ' Object to be printed 151 Longitudinal central axis

Claims (14)

1. Method for the operation of a pad printing machine (1) which comprises at least a printing pad (15) and a printing plate (12), wherein the method comprises at least the step that a print image is taken up from the printing plate (12) by means of the printing pad (15) and that a print image is transferred from the printing pad (15) onto an object to be printed on (6, 6'), wherein the method comprises the following step:

   a.) Detecting the position of at least one contact point (3) in which the printing pad (15) and the printing plate (12) get into contact with each other during a first take-up of a print image, and/or of at least one contact point (3) in which the printing pad (15) and the object to be printed on (6, 6') get into contact with each other during a first transfer of a print image,

   characterized in that the method comprises at least the following further steps:

   b.) Determining a velocity function based on this detected position; as well as

   c.) Moving the printing pad (15) during a second take-up of a print image relatively to the printing plate (9) or during a second transfer of a print image relatively to the object to be printed on (6, 6') at a velocity in accordance to this velocity function.
2. Method according to claim 1, wherein a camera (19) is used for the detection of the position of the at least one contact point (3).
3. Method according to claim 1 or 2, wherein the printing pad (6) is moved along a main direction of motion in each case during the take-up of a print image or the transfer of a print image, and wherein the detection of the position of the at least one contact point (3) is carried out from a direction which is essentially perpendicular to this main direction of motion.
4. Method according to one of the preceding claims, wherein in step b.) the velocity function is determined such that the change of the size and/or form of the contact surface (2) between the printing pad (15) and the printing plate (12) during the take-up of the print image or between the printing pad (15) and the object to be printed on (6, 6') during the transfer of the print image is calculated based on the detected position of the contact point (3) and that the velocity function is determined based on this calculation.
5. Method according to one of the preceding claims, wherein, before determining a new velocity function in step b.), the method comprises the further step:

   a0.) Checking of the printing result on the object to be printed on (6, 6').
6. Method according to claim 5, wherein, if a flawed printing result is detected in step a0.), the velocity function is additionally determined in step b.) based on the position of flawed spots in the printing result.
7. Method according to claim 6, wherein the velocity function is determined such in step b.) that the motion of the printing pad (15) in step c.) when getting into contact with the areas of the printing plate (12) or of the object to be printed on (6, 6') that correspond to the flawed spots in the printing result is slowed down as compared to the motion of the printing pad (15) when getting into contact with the same areas during the first take-up or a print image or transfer of a print image.
8. Method according to one of claims 5 to 7, wherein each of the steps a0.), a.), b.) and c.) is carried out fully automatically.
9. Method according to one of claims 5 to 8, wherein a plurality of printing processes are carried out in step a0.), in which the velocity of the motion of the printing pad (15) relatively to the printing plate (12) during the take-up of a print image and/or the velocity of the motion of the printing pad (15) relatively to the object to be printed on (6, 6') during the transfer of a print image is increased at least once from a printing process to the subsequent printing process, and wherein the printing result is checked at least once on the object to be printed on (6, 6') after this increase of the velocity.
10. Method according to claim 9, wherein the velocity of the motion of the printing pad (15) during the take-up of a print image and/or the transfer of a print image is increased from printing process to printing process until a flawed printing result is detected.
11. Method according to claim 10, wherein the method comprises the additional step:

    d.) Carrying out two or more rounds each of which includes all of steps a0.) - c.), wherein from the second round on the determination of the velocity function in step b.) is additionally based on the velocity function as determined in the previous round.
12. Pad printing machine (1) for operation with a method as claimed in one of the preceding claims, comprising at least one printing pad (15) and at least one printing plate (12), wherein the printing pad (15) is movable relative to the printing plate (12) and serves to take up a print image from the printing plate (12) and to transfer the print image onto an object to be printed on (6, 6'),

    wherein the pad printing machine (1) comprises at least one detection device (19) which serves for the detection of the position of at least one contact point (3) in which the printing pad (15) and the printing plate (12) get into contact with each other during a take-up of a print image and/or serves for the detection of the position of at least one contact point (3) in which the printing pad (15) and the object to be printed on (6, 6') get into contact with each other during a transfer of a print image,

    characterized in that the pad printing machine (1) additionally comprises a determination unit (17) for the determination of a velocity function for the motion of the printing pad (15) during the take-up of a print image relatively to the printing plate (12) or during the transfer of a print image relatively to the object to be printed on (6, 6') based on the position of the contact point (3) as determined by the detection device (19) and comprises a motion control unit (18) which serves to control the motion of the printing pad (15) relative to the printing plate (12) or to the object to be printed on (6, 6') with a velocity in accordance to this velocity function.
13. Pad printing machine (1) according to claim 12, wherein the detection device is a camera (19).
14. Pad printing machine (1) according to one of claims 12 or 13, which comprises an electric motor, in particular a servo motor, for moving the printing pad (15).

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