EP2061659B1 - Device for producing embossed structures in a surface of a cylinder - Google Patents

Abstract

A device for producing embossed structures in a surface (5a) of a cylinder (5) comprises an electromechanical engraving unit with a stylus (4), which is movably mounted on a base of the engraving unit for working the surface (5a), a drive (23) for moving the stylus (4) in relation to the base, in a direction perpendicular to the surface (5a) of the cylinder, and a mechanism for setting and maintaining a basic distance between the base of the engraving unit and the surface (5a) of the cylinder (5). The electrochemical engraving makes it possible to produce embossed structures on cylinder surfaces (5a) quickly and at low cost. Used for example as basic elements for the embossing cylinders are copper-coated engraving cylinders (5), which, once the embossed structures have been introduced, are provided with a chromium film to increase the hardness and resistance.

Description

Technical area

1. a) einem an einer Basis der Graviereinheit beweglich gelagerten Stichel zum Bearbeiten der Oberfläche;
2. b) einem Antrieb zum Bewegen des Stichels relativ zur Basis, in einer Richtung senkrecht zur Oberfläche des Zylinders;
3. c) einem Mechanismus zum Einstellen und Halten eines Grundabstands zwischen der Basis der Graviereinheit und der Oberfläche des Zylinders.
4. d) einer Steuerung zum Steuern des Antriebs zum Bewegen des Stichels in Abhängigkeit von Eingangsdaten.

The invention relates to a device for producing embossed structures in a surface of a cylinder, comprising an electromechanical engraving unit with

1. a) a spatula movably mounted on a base of the engraving unit for working the surface;
2. b) a drive for moving the stylus relative to the base, in a direction perpendicular to the surface of the cylinder;
3. c) a mechanism for setting and maintaining a pitch between the base of the engraving unit and the surface of the cylinder.
4. d) a controller for controlling the drive to move the stylus in response to input data.

Furthermore, the invention relates to a method for producing embossed structures.

State of the art

Embossing methods are known per se and have a wide range of applications. Embossing is especially produced in flat materials such as metal foils or coated metal foils. For embossing in flat material, for example, embossing dies or embossing rolls with embossed structures such as elevations and / or depressions are pressed against the material, whereupon corresponding depressions or elevations form in the material as an image of the embossed structures.

The embossing of sheet material is advantageously carried out continuously, while the material between two embossing rollers (or an embossing roller and a counter-roller without embossed structure) is passed therethrough. Such a continuous process allows high production rates and thus embossing of industrial quantities, such as those incurred in the production of packaging material.

Conventionally, the embossing rollers are produced for example by Molettieren. However, this process is time consuming and expensive. Other known methods, such as specific mechanical, chemical or laser engraving methods, or the introduction of the embossed structure by embossing in a thermoplastic intermediate mold and subsequent production of a casting, share these disadvantages, allow only a poor reproducibility or require a lot of expertise and mechanical skills. Often, therefore, refrained from generating an impression only for aesthetic reasons. In cases where an embossing is needed for other reasons, eg. For example, in order to prevent adhesion of superimposed film layers, unspecific standard patterns are used due to the high costs and non-specific patterns, picture elements or logos.

With imprints to be provided material, eg. For example, for packaging for consumer goods, is often already provided with a print. In these cases, it is often desired that the embossing to be produced is introduced into the material to match the imprint, for. B. contours of a lettering or a picture element by the embossing to reproduce and thus further emphasize. However, the embossing in the register with the imprint is difficult with the known embossing methods.

From the DE 101 49 828 A1 (Hell Gravure Systems GmbH) is a method for correcting positional deviations of an engraving element in an electronic engraving machine known. During the engraving, the engraving stylus, which is controlled by an engraving signal, cuts gravure-line cups into a printing cylinder. With the aid of a measuring device, a position-free correction of the position of the engraving element can take place, so that the position of the engraving element is regulated and kept constant with respect to the surface of the printing cylinder during the engraving. For controlling the engraving element, an engraving control signal is generated from engraving data, which are read out in a memory, and a superposed periodic screen signal.

Presentation of the invention

The object of the invention is to provide a the technical field mentioned above associated device and a corresponding method, which allow a simple, fast and cost-effective production of embossing cylinders.

The solution of the problem is defined by the features of claim 1. According to the invention, the control is designed such that embossed structures can be produced in a plurality of successive engraving processes, wherein material is removed from the surface at the same position of the surface of the cylinder in the successive engraving processes.

It has surprisingly been found that many aspects of an electromechanical engraving unit for imaging gravure printing cylinders and associated devices (engraving system, image processing station, etc.) are also useful and advantageous in connection with the production of embossing cylinders. Embossing cylinders are used for the production of imprints on flat materials, wherein during the embossing process no Color is applied, so to speak, a dummy pressure is executed. An important difference between a gravure die and a die is the depth and geometry of the recesses (cups) created in the surface of the cylinder.

Electromechanical engraving machines for the transmission of image information to a gravure cylinder have long been known. Achieving the required depth for embossing cylinder can be accomplished with conventional engraving machines and the tools used with it but not readily, because on the one hand normal engraving systems by design can hardly reach the engraving depth required for embossing cylinder and the tools used for the required Material removal are suitable. At engraving depths required for embossing cylinders, it is also particularly important to avoid cracking or to limit their consequences to the current engraving process. Another point to keep in mind is the significant chip development that goes hand in hand with the deep structures. Finally, the material to be embossed during the embossing process is claimed mechanically unequally greater than in a printing operation. This circumstance must also be taken into account in the production of the embossing cylinder.

The engraving unit used in the context of the invention has thus been improved in particular with regard to the engraving depth required for the introduction of embossing structures and the material removal associated therewith. The electromechanical engraving enables rapid and cost-effective production of embossed structures on cylinder surfaces. For example, copper-coated engraving cylinders are used as green bodies for the embossing cylinders, which are provided with a chromium layer after the introduction of the embossed structures to increase the hardness and resistance. But in principle, other materials such as zinc or plastics can be processed.

The device according to the invention advantageously comprises a controller for controlling the drive for moving the stylus as a function of input data.

1. a) Empfangen der Eingangsdaten;
2. b) Erzeugen eines Antriebssignals in Abhängigkeit von den Eingangsdaten;
3. c) Antreiben eines Stichels einer elektromechanischen Graviereinheit mit dem Antriebssignal zum Bearbeiten der Oberfläche des Zylinders.

In a method according to the invention for producing embossed structures in a surface of a cylinder, the following steps are carried out accordingly

1. a) receiving the input data;
2. b) generating a drive signal in response to the input data;
3. c) driving a stylus of an electromechanical engraving unit with the drive signal for machining the surface of the cylinder.

The drive signal is generated in such a way that it is suitable for generating embossing structures in the surface of the cylinder by means of the stylus.

The controller may comprise computing means for processing the input data, such that, as input data, usual image data for engraving printing cylinders, In particular, halftone data, received and can be transformed such that based on the transformed data, the drive signal can be generated, which is suitable for generating the embossed structures. The user can thus also use the existing methods, devices and computer programs for generating engraving data for the preparation of the embossing process. On the basis of the same data, it is also possible to first print on a flat material and then emboss it, the embossing being applied in register with the pressure on the material. In the simplest case, places that are printed with intense tones, at the same time receive a raised or recessed embossing. Halftone data can also be used, resulting in infinitely variable embossing depths.

In order to produce deep structures, at least one of the embossed structures is advantageously produced in several successive engraving processes, wherein material is removed from the surface at the same position of the surface of the cylinder in the successive engraving processes by the stylus. The control is thus advantageously designed such that such a method is feasible. The amount of material to be removed per engraving process at a given depth of the structure to be introduced can thus be reduced by a multiple. This has a much longer life of the stylus and a significantly reduced risk of Stichelbruchs result. It can also be achieved with this measure engraving depths that can not be achieved in a single-step engraving.

Especially with a multi-level engraving, however, the problem arises that common sliding feet, which support the base of the engraving unit on the surface of the cylinder and thus ensure a defined distance between base and surface, in the second and all subsequent engraving stages are no longer applicable: On the one hand, the sliding feet can not be readily supported on an already partially and possibly large-area machined surface and could also injure this surface, and on the other hand results due to the relief generated during the previous processing steps no defined Distance between the (original) cylinder surface and the base of the engraving unit.

The mechanism for setting the basic distance is therefore preferably free of support with respect to the surface of the cylinder, d. H. during the engraving process, it does not support itself on the cylinder surface. The mechanism maintains the engraving system at a precisely defined distance from the cylinder surface and is such that throughout the range of cylinder circumferences used, this well-defined distance of the cutting tool can be achieved and maintained. For a good processing result, the accuracy and repeatability of the distance should be better than 10 microns.

Because no Gleitfuss is used and therefore the already machined cylinder surface does not have to serve as a mechanical reference, in contrast to known devices with Gleitfuss the engraving process can be continued seamlessly after an unexpected breaking of the cutting tool by replacing the tool, the engraving in the axial direction to a Set back before breaking the tool and restart the engraving.

The support-free mechanism can be designed in various ways. The mechanism may, for. B. include an adjustable stop, which limits a spring-driven feed movement of the base of the engraving unit in the direction of the surface of the cylinder. Such a stop can be structurally simple form and store adjustable. In addition, existing solutions for conventional sliding feet can essentially be taken over and only have to be supplemented by the adjustable stop. The spring-driven delivery of the engraving unit is retained.

The non-support mechanism may additionally or alternatively include means for measuring a distance between the base of the engraving unit and the surface of the cylinder and a drive for adjusting the base distance between the base of the engraving unit and the surface of the cylinder depending on the measured distance. The measurement is carried out in particular contactless, for example by a optical sensor, a capacitive sensor or by a laser interferometer. The setting takes place, for example, by means of a fast servomotor, which acts on an adjusting device of the stop or directly on the base. The adjustable bearing or the stop are in both cases designed so that the retroactive forces occurring during the engraving process can be taken over by the base. Instead of the continuous adjustment of the base, it is also conceivable that depending on the measured distance, the engraving signal is reshaped, ie that the signal amplitude corresponding to the measured distance is amplified or attenuated - in this case, the basic distance is thus already changed at the level engraving signal. The latter possibility can be particularly simple and inexpensive to implement without additional mechanical parts, but it - depending on the tolerances in the cylinder diameter - a reduction in the maximum engraving depth of the engraving system result.

When adjusting the basic distance, an already completed material removal at the currently processed position can be taken into account by taking into account the input data during readjustment. The measured distance is thus corrected by the already performed removal. This measure is indicated in a multi-level engraving and also allows further engraving after an interruption, z. B. after a break of the stylus.

Alternatively or additionally, before or during a first of the engraving operations, a profile of the surface of the cylinder can be measured out and stored. This is then taken into account when adjusting the basic distance. The profile reflects both the geometry of the unprocessed cylinder surface and inaccuracies in cylinder centering. Its consideration in determining the basic distance to be set ensures that engraving of the concrete cylinder surface is always followed and that the given engraving depths are precisely maintained over the entire cylinder surface. A puncture or other interruptions do not affect the precise engraving, because it can always fall back on the original profile of the cylinder. Finally, measuring the Cylinder profile and the machining of difficult workpieces, z. B. cylinders with increasing or changing diameter in the axial direction.

Instead of a dynamic adjustment of the basic distance, the latter can also be kept constant during an entire engraving process, whereby the basic distance between the base of the engraving unit and the surface of the cylinder is reduced by a predetermined value, in particular as a function of the input data, between successive engraving operations. The predetermined value can always be the same or different changes can be made between different engraving operations. In addition, the values can be selected independently of the embossing structures to be generated or else depending on the input data. The latter opens up the possibility of choosing the values such that, for example, the removal of material in the individual engraving processes remains approximately constant or that only chips are produced during processing which can be removed without difficulty.

So that the basic distance can be kept constant during an engraving process without real-time correction, high demands are placed on the concentricity and on a minimal taper of the cylinder. Deviations should not exceed a few microns.

In order to achieve this, it is possible to provide receptacles for the cylinder, which are designed to be adjustable, so that concentricity errors of the cylinder can be minimized by means of a corresponding adjustment before engraving.

Alternatively or in addition to the mechanical adjustment of the concentricity, a smoothing engraving can also be carried out in the surface of the cylinder before the embossing structures are produced. For this purpose, at least a substantial part of the surface of the cylinder is processed by the stylus before generating the embossed structures, wherein the distance between the stylus and an axis of rotation of the cylinder predetermined by the engraving device is kept constant. The feed rate is chosen in view of a long life of the stylus. The engraving depth is adjusted so that the stylus during one complete revolution of the cylinder and over its entire length stays in contact with it. As a result, concentricity errors are smoothed and any conicity is reduced to a minimum, and it is ensured that during the subsequent introduction of the embossing structures, the cutting depth is exactly constant to a few micrometers.

In addition, the untreated cylinder may have a low quality surface in relation to its roughness and deviations from a perfect cylinder, and therefore all operations prior to introduction of the embossing structures must be much less precise and thus more cost effective and faster.

In addition to the support-free mechanism for setting the basic distance, the device may additionally comprise a conventional sliding foot. The device is in this case designed such that it can be switched over between an embossing cylinder and a pressure cylinder mode. This means that when creating embossed structures, the support-free mechanism for setting the basic spacing is used, while the gliding foot is used when producing intaglio cups. The slide foot can be retracted, folded away or removed for embossing cylinder mode. The device has characteristics of edge steepness that meets the requirements of engraving in the imaging of gravure cylinders. In addition, the engraving system can be operated in the frequency engraving mode necessary for the imaging of gravure cylinders.

The fact that the same machine can be used to produce both embossing and gravure cylinders has several advantages. First, it can be better utilized, especially in smaller operations, saving space and much of the cost of an additional machine , On the other hand, there are synergies and advantages when a material is both printed and - in the register with the printing - to be embossed: The precision of the registration is particularly high, and the input data can - possibly with some modifications - used for the production of both cylinders become.

A multi-level engraving is also possible with a supporting mechanism for setting the base distance. For this purpose, a circular engraving is performed, in which the same track is processed during at least two complete (consecutive) cylinder revolutions. The working depth of the burin is thereby increased from a first approach to a second approach in the same track (and for any further rounds). The axial position of the engraving system is maintained. As soon as the desired engraving depth is reached along the corresponding circular line, the engraving system is moved to the next track, whereupon it can be processed in the same way.

The base distance between the base of the engraving unit and the surface of the cylinder can be adjusted by means of a sliding foot supported on a still unprocessed area of the surface. The basic distance is therefore maintained from the first handling to the second handling (and also in other possible passages). The increase of the working depth of the stylus takes place by a modification of the drive signal. The drive signal is superimposed, for example, with a correspondingly rising signal, or amplified with a stepwise increasing gain factor. By using a sliding foot deviations from the concentricity is taken into account, and the device can be structurally simple.

Flexible materials are stretched during embossing. The embossed structures should be such that the embossing process proceeds as gently as possible in order to prevent the material from breaking or becoming too thin at certain points. It is therefore advantageous if, when generating the drive signal as a function of the input data, the input data representing an image are modified with regard to smoother transitions between regions of the image of different brightness values. This can be done in particular by a soft-focus transformation. In this process, sudden transitions in the brightness value are distributed over a larger image area, which also results in smoother transitions in the embossed structure and finally in the embossing.

If imprints are to be produced with a high relief, it is advantageous if the embossing takes place between two embossing cylinders, which are used as die and male interact. In order to obtain drive signals for the corresponding engraving processes, the input data for one of the cylinders can be inverted. At the same time, it may be advantageous if the image represented by the input data is compressed and / or stretched in order to form the structures on the matrix and the male mold correspondingly in such a way that no squeezing of the material to be embossed takes place. The upsetting or stretching can be carried out by algorithms known per se and available in many devices for the production of a printing original, which are usually used for widening or narrowing fonts.

Advantageously, embossed structures may be produced which comprise one or more substantially continuous engraved characters composed of a plurality of adjacent tracks on the surface of the cylinder. When engraving conventional gravure forms of the stylus is excited by a sinusoidal frequency. This sine frequency is superimposed on a modulated video signal. Conventional intaglio printing forms therefore have a large number of distanced cells, each of which absorbs ink and releases it to the paper during the printing process. Because the color dissolves and because the eye usually does not perceive the individual halftone dots, the printed image appears visually coherent.

However, when embossing, the situation is completely different: on the one hand, with a three-dimensional embossing, different depths can not be achieved, such as different magnitudes of a two-dimensional pressure, by differently sized depressions in the mold. On the other hand, the texture of a "gridded" embossing is clearly different than that of a continuous embossing. It is therefore of great advantage if large continuous areas can be marked.

A method for engraving large continuous areas of gravure cylinders, for example, from EP 0 805 957 B1 (MDC Max Dätwyler AG) known. In this case, a pulse width or pulse width modulated drive signal is generated. The usual sinusoidal signal is omitted. Surprisingly, this method is particularly well suited for the production of embossing cylinders. By an additional modulation of the amplitude, intermediate values can also be engraved in a simple manner. These Intermediate values correspond to areas of the embossed structure which have a smaller depth (or height) than the maximum depth (or maximum height).

The chip produced during the production of embossed structures can become very long, in particular if the engraved structures are non-planar and comprise oblong tracks in the direction of rotation of the machined cylinder. When removing the chip, therefore, problems may arise, for example, when the chip catches in a suction device or wraps around parts of the machine or the embossing cylinder. Advantageously, therefore, structures are created in the surface of the cylinder for breaking a chip created during machining of the surface of the cylinder.

The structures for breaking the chip are, in particular, small-scale structures with a depth that is less than a depth of the surrounding embossed structure. It has been shown that predetermined breaking points in the span can already be created by small depth differences. It is therefore basically sufficient to retract the engraving tool in the area of large areas at regular or irregular intervals, so that the diameter of the chip is slightly reduced at the corresponding point.

In order to generate the specific structures, the computing means are preferably designed and controlled in such a way that data for generating structures for breaking a chip resulting during engraving are automatically recorded in the transformed data. For this purpose, for example, the controller, which receives and processes the data necessary for the introduction of the embossed structures, examines these data for large areas to be engraved and, if the areas exceed a predetermined size, at suitable intervals modify the data such that the engraving tool briefly withdrawn so far that the desired reduction in the diameter of the chip or its complete demolition is achieved.

Advantageously, the device according to the invention comprises a device for extracting chips, wherein a suction opening of this device in the region of the stylus the base of the engraving unit is arranged. The opening is designed so that at this point the exhaust air undergoes maximum acceleration, so that in particular long, thick chips can be sucked in the region of origin, without them getting caught and clog the suction.

To produce embossed structures, the stylus advantageously has a tool angle of 90-140 °, preferably 90-120 °. The tool angle denotes the angle at which the cutting flanks of the tool are in relation to each other. The feed rate is chosen to optimize the machining speed while maintaining unwanted bumps and indentations on the engraved surface at a level that does not interfere with the subsequent stamping operation. With tool angles of 90 to 140 °, feed distances of up to 50 times have proven to be advantageous. With a tool angle of 120 ° and a feed distance of 50μm, unwanted structures of 14.5 μm depth are created. With the relatively small angle of maximum 140 °, preferably 120 °, the depth of such structures can thus be kept within limits. It has also been shown that tool angles in the specified range at the same time allow the production of robust stylus.

In order to produce embossed structures of great depth, which at the same time have vertical walls as possible, the stylus advantageously has a lower tapering portion and an upper portion adjoining the lower portion above, wherein delimiting edges of the upper portion enclose an angle that is smaller as the tool angle, which is enclosed by the edges in the tapered part. The angle is in particular at least 45 °, preferably at least 60 °, smaller than the tool angle. Thus, from a certain depth, the minimum cross-sectional area of the recesses to be created increases only very slightly as the depth of the engraved structure is increased.

From the following detailed description and the totality of the claims, further advantageous embodiments and feature combinations of the invention result.

Brief description of the drawings

Fig. 1A, 1B

Zwei Schrägansichten eines Ausführungsbeispiels einer erfindungs- gemässen Graviereinheit zum Erzeugen von Präge- und Tiefdruckstrukturen;

Fig. 1C

eine Draufsicht auf das Ausführungsbeispiel;

Fig. 2

eine schematische Darstellung der Steuerung der erfindungsgemässen Graviereinheit;

Fig. 3A, 3B

eine Querschhittdarstellung eines für die erfindungsgemässe Graviereinheit geeigneten Stichels und einer damit erzeugten Vertiefung als Teil einer Prägestruktur;

Fig. 4A-D

eine schematische Darstellung der Verarbeitung eines Bildsignals zu einem Antriebssignal zum Erzeugen von Prägestrukturen in einer Matrize und einer Patrize;

Fig. 4E

einen Querschnitt durch die mittels dem Antriebssignal hergestellte Matrize bzw. Patrize; und

Fig. 5A-E

eine schematische Darstellung eines erfindungsgemässen mehrstufigen Verfahrens zur Erzeugung einer Prägestruktur.

The drawings used to explain the embodiment show:

Fig. 1A, 1B

Two oblique views of an embodiment of an inventive Graviereinheit for generating embossing and gravure structures;

Fig. 1C

a plan view of the embodiment;

Fig. 2

a schematic representation of the control of the inventive Graviereinheit;

Fig. 3A, 3B

a Querhhittdarstellung a suitable for the inventive engraving unit stylus and a recess produced therewith as part of an embossed structure;

Fig. 4A-D

a schematic representation of the processing of an image signal to a drive signal for generating embossed structures in a die and a male;

Fig. 4E

a cross section through the template produced by the drive signal or male; and

Fig. 5A-E

a schematic representation of an inventive multi-stage process for producing an embossed structure.

Basically, the same parts are provided with the same reference numerals in the figures.

Ways to carry out the invention

The FIG. 1 shows an embodiment of an inventive engraving unit, which is suitable for both the engraving and the embossing mode. The engraving unit is mounted in a conventional manner on a carriage, by means of which can be moved relative to a cylinder 5 to be machined, for example, with a surface to be machined from copper 5a. The engraving unit comprises a lower mounted engraving system 1. This is arranged pivotably about an axis 1a on a base plate 1b. At the engraving 1 a sliding foot 2 is adjustably attached. The adjustment takes place via an adjusting mechanism 3 with an adjusting spindle 3a. Also on the engraving an electrically operated stylus 4 is attached. The deflection of the stylus in a direction perpendicular to the surface 5a of the cylinder 5 takes place in a manner known in electromechanical engraving systems. The stylus is arranged in particular on a lever which is mounted on a torsion spring, and which can be deflected by overcoming the spring force by means of an electromagnet.

The lowering of the engraving system 1 by pivoting about the axis 1a is effected by an electric feed unit. This comprises a mounted on the base plate 1b electric motor 6 and connected to the drive axle of the motor 6, also fixed to the base plate 1 b transmission 7. The output shaft of the transmission 7 is connected to a feed spindle 8 with external thread on which a spring mechanism 9 hinged is. For this purpose, the spring mechanism 9 comprises a nut segment 9a with an internal thread, which cooperates with the external thread of the feed spindle 8 such that the nut segment 9a can be moved forward or backward in a direction substantially perpendicular to the surface of the cylinder 5. On the nut segment 9a, the rear end of a lever 9b is articulated with integrated spring elements. The length of this lever 9b can be reduced by overcoming the spring force. The lever 9b is hinged at its front end to the back of the engraving system 1. The spring mechanism 9 thus provides the necessary contact pressure of the engraving system 1 on the surface 5 a of the cylinder 5 ready.

In the engraving mode, the sliding foot 2 is presented with the aid of the adjusting mechanism 3 so far that a predetermined basic distance between the stylus 4 and the surface 5 a of the cylinder 5 is defined. The engraving system 1 with the present in Engraving position Gleitfuss 2 can then by the electric Be completely lowered delivery unit on the cylinder surface 5a, so that the prescribed for the engraving contact pressure is achieved. Thereafter, the engraving of the printing cylinder is possible, wherein the basic distance between engraving 1 and cylinder surface 5a is continuously tracked using the supported on the cylinder surface 5a Gleitfusses 2.

The production of an embossed structure takes place in the illustrated embodiment in several steps, i. H. The desired depth of the structures is achieved by repeated processing, wherein the processing depth is increased in each case from one processing step to the next. As a result, the load on the cutting tool can be kept below a maximum load. After performing the first processing step, the surface is due to the already introduced structure such that the Gleitfuss 2 can not be used for the determination of the distance between the cylinder surface 5a and 4 Stichel, since it penetrates into the previously introduced embossed structure, which is the distance to Cylinder surface 5a changed and may even lead to damage of the cylinder 5 or the Gleitfusses 2.

If an embossed structure is to be introduced instead of gravure engraving, the use of the sliding foot 2 is thus completely dispensed with. In order to introduce the stylus 4 in a precise manner to the cylinder surface 5 a, a fine delivery mechanism 10 for the engraving system 1 is used instead. This mechanism comprises a frame 11 which is fixedly mounted on the engraving system and extends rearwardly. In a frame 11, the rear traversing cross member a through opening is formed with internal thread, which receives a precision feed spindle 12 with external thread. At the rear end of the feed spindle 12, an adjustment handle 13 is attached. At the front end of the feed spindle 12, a ball is attached. This ball acts on a pressure plate 14, which is firmly connected by means of a yoke 15 with the base plate 1 b of the engraving unit. The feed spindle 12 and the pressure plate 14 together form a stop, by means of which the movement of the engraving system 1 on the surface 5 a of the cylinder 5 can be limited. By turning the feed spindle 12, the stop and thus finely adjust the front end position of the engraving 1. In addition, a bracket 16 for holding a scraper on the engraving system 1 is rotatably mounted. The attached to the bracket 16 diamond scraper is pressed by arranged at the lateral attachment points of the bracket 16 springs and by the weight of the bracket 16 on the surface 5 a of the cylinder 5 and serves unwanted, over the surface 5 a protruding structures by the Engraving process have been created to remove. The scraper is not used in embossing mode.

In the embossing mode, the sliding foot 2 is pulled back by an adjusting device (not shown). The feed spindle 12 is then pre-rotated until the engraving system 1 is retained so far that the stylus 4 remains just as far removed from the cylinder surface 5a when lowered by the feed unit that he does not touch it. By turning the adjusting handle 13, the cutting depth can now be determined very precisely and increased accordingly in each subsequent processing step.

In favor of a simpler representation was in connection with the FIG. 1 an embodiment described in which the adjustment of the basic distance of the engraving system is done manually. However, electric drives are preferably present for all adjustable axes, so that the setting of the engraving system can be carried out automatically.

In a preferred variant of the engraving unit according to the invention, the adjustment of the basic distance takes place with the aid of a video detection system which can optically detect the depressions generated in the cylinder surface. For this purpose, the engraving system is first to be moved onto the cylinder with a coarse feed mechanism. Subsequently, the surface of the cylinder is scribed with the tip of the stylus, wherein only that portion of the stylus penetrates into the material, which has a clearly defined and constant tool angle with respect to the stylus tip. This ensures that the engraving depth can be calculated directly from the width of the recess produced optically by means of the video acquisition system using the tool angle. Depending on the engraving depth determined in this way, the distance between the engraving system is then determined with the aid of the fine-feed mechanism and cylinder surface corrected to the specified basic distance. The increase in the cutting depth between subsequent processing steps is carried out by the precisely actuated Feinzustellungsmechanismus, without further distance measurements are performed.

The FIG. 2 shows a schematic representation of the control of the inventive engraving unit for generating embossing and gravure structures. The base plate 1 b of the engraving unit is attached to the carriage 20, by means of which it can be moved relative to the cylinder 5, in particular along a direction 21 parallel to the cylinder axis. The engraving system 1 is moved by the force acting on the spring mechanism 9 drive 6 along a direction 22 to the cylinder 5 and away from it. Arranged on the engraving system 1 is the stylus 4, which can be actuated by a drive 23 in a manner known per se electromechanically, in particular electromagnetically, so that it penetrates into the surface 5 a of the cylinder 5 for engraving.

Also arranged on the engraving system 1 is the Gleitfuss 2, which by another drive 24 in small steps from a front (in the FIG. 2 shown) position can be moved to a rear position. Further arranged on the engraving system 1 is a distance sensor 25 with a mechanical contact element 26, which can contact the surface 5 a of the cylinder 5 with its free front end. The contact element 26 can be withdrawn if necessary.

On the base plate 1 b of the engraving unit, a further actuator 27 is also arranged. This cooperates with a stop 28 on the engraving system 1, so that the movement of the engraving system in the direction 22 is limited to the surface 5a of the cylinder, while a movement away from the cylinder surface 5a is not affected by this device rearward.

The above-described drives are controlled by a controller 40. This comprises an input interface 41 for receiving input data, a central processing unit (CPU) 42 which receives data from the input interface, a memory 43 which cooperates with the CPU 42, a peripheral interface 44, for communication with the distance sensor 25 and the drives 6, 24, 27, a signal processor 45 and a drive signal generator 46, the signal processor 45 receives an input signal and control commands from the CPU 42 and passes the signal to the drive signal generator 46 after processing. The latter generates a signal which is suitable for direct control of the drive 23 for the stylus 4.

For generating embossed structures in the surface 5a of the cylinder 5, the sliding foot 2 is first retracted by the CPU 42 controlled by the drive 24 to the rear. Subsequently, the engraving system 1 is moved so far on the surface 5a of the cylinder 5 that the tip of the stylus 4 in its rest position from the axis of rotation of the cylinder 5 has a distance which the average diameter of the cylinder 5 plus the expected diameter tolerance and a maximum axis error equivalent.

Subsequently, the carriage 20 is moved to an axial initial position, after which the contact element 26 of the distance sensor 25 travels through the entire cylinder surface 5a by rotating the cylinder 5 and moving the carriage 20 axially. In this case, the distance between the engraving system 1 and the cylinder surface 5a is measured continuously or stepwise, transmitted via the peripheral interface 44 to the CPU 42 and stored by the latter in the memory 43. In the final result, the memory contains a distance profile of the entire cylinder surface 5a, in which both local deviations of the cylinder diameter and non-circularities due to axis errors are taken into account.

The contact element 26 of the distance sensor 25 is now withdrawn, and the carriage 20 is moved back to its initial position. The basic distance of the engraving system 1 from the cylinder surface 5a is now adjusted depending on the recorded distance profile and the received via the input interface 41 and stored in the memory 43 pressure data by the drive 27 at stop 28 so that to be generated in a first engraving recesses optimally, ie with the best possible quality and lowest possible wear of the stylus 4, can be engraved. During the engraving, the distance of the engraving system 1 from the cylinder surface 5a becomes continuous by the servo trained drive 27 depending on the recorded distance profile readjusted. As a result, surface inaccuracies and axis errors of the cylinder bearing are compensated.

The engraving itself can be done in a conventional manner along a helix (helical), or adjacent tracks are engraved (ring engraving).

After completion of the first engraving process, the carriage 20 is moved with the engraving unit back to its initial position. Subsequently, a new basic distance between the engraving system 1 and the cylinder surface 5a is set by the drive 27. In the determination of the new basic distance, in turn, the distance profile and the pressure data are used, whereby it is also taken into account which depressions have already been generated in the surface 5a during the first engraving process. In the context of the second engraving process on the one hand further, previously unprocessed locations of the cylinder surface 5a are processed, on the other hand recesses in already previously processed areas of the cylinder 5 - as necessary - further deepened.

Depending on the necessity, further engraving processes may follow this second engraving process, whereby the basic distance is adjusted in each case between two successive processes.

The FIG. 3A shows an embodiment of a stylus 4, which is suitable for use in the inventive engraving unit for the production of embossed structures. The stylus 4 is formed by a diamond, which is prismatic ground. It comprises a shank 4a, which is adjoined by a front cutting edge 4b in the working direction and a free edge 4c in the working direction. Both the cutting edge 4b and the free edge 4c each comprise a rear portion and a front portion adjoining therefrom, wherein the two front portions of the cutting edge 4b and the free edge 4c converge at a tool angle a. The cutting lines between the cutting edge 4b and the free edge 4c form the cutting tip 4d of the stylus 4. The rear portions include an angle β, which is smaller than the tool angle α.

The FIG. 3B shows one with the stylus 4 according FIG. 4A According to the geometry of the stylus 4, the recess 5b with a minimal areal extent has walls which, starting from the surface 5a of the cylinder 5, initially run steeply inwards. This is followed by converging wall sections. By means of the stylus 4, the illustrated recess 5b can be made even deeper in a further engraving process, wherein the area claimed by the recess 5b on the cylinder surface 5a will increase only insignificantly. It can thus be generated with the illustrated stylus 4 deep embossed structures with small surface area. Accordingly, embossing cylinders, which are produced according to the method according to the invention, can be used to produce embossments with high detail resolution while at the same time having a large embossing depth or height.

The FIGS. 4A-4D schematically illustrate the processing of an image signal to a drive signal for generating embossed patterns in a die and a male. The image signal 50 corresponds to an image signal as provided for driving engraving machines. It has an amplitude A (t) variable with time t, a high amplitude representing a high color density, the amplitude zero corresponding to full white (no color output and thus no engraving). The image signal 50 is a halftone signal and includes portions corresponding to an intermediate tone between white and full black. The image signal 50 comprises a plurality of temporally successive sections 50.1... 50.8, with sections 50.2, 50.4, 50.6, 50.8 of constant amplitude A alternating with sections 50.1, 50.3, 50.5, 50.7, in which the amplitude A changes at a constant rate, ie decreases or increases.

As part of the processing of the image signal 50, an inverted image signal 51 is first generated (see FIG. 4B The amplitude A '(t) of the inverted image signal 51 is calculated as A' (t) = 1-A (t), where the value A (t) = 1 is fully black, ie, white portions of the original image signal 50 are written in fully black portions of the inverted image signal 51, solid black portions of the original image signal 50 into white portions of the inverted image signal 51. The intermediate tones are correspondingly inverted, 40% becomes fully black, for. B. 60% full black.

Next, the image signal 50 and the inverted image signal 51 are subjected to further transformation (see FIG FIG. 4C ), wherein in the case of the original image signal 50, transitions to darker sections (greater values of A) are temporally advanced by a predetermined offset t _o1 , transitions to lighter sections (smaller values of A) are delayed in time by the predetermined offset t _o1 . In contrast, in the case of the inverted image signal 51, transitions to brighter sections (smaller values of A ') are delayed in time by the predetermined offset t _o1 , transitions to darker sections (larger values of A') are delayed in time by the predetermined offset t _o1 . The transformed signal 52 obtained from the original image signal 50 thus has a higher black content than the original image signal 50, whereas the transformed signal 53 obtained from the inverted image signal 51 has a higher white content compared to the inverted image signal 51. Due to the symmetry of the transformations made, the image size of the embossed structure is maintained in comparison with the original image signal 50. The transformation can be realized, for example, with algorithms for compressing fonts. Such algorithms are well known from the pre-press or from existing controls for engraving machines and can be used in this field for the application according to the invention.

The transformed signals 52, 53 are finally subjected to a blur transformation. The sections 52.1, 52.3, 52.5, 52.7; 53.1, 53.3, 53.5, 53.7 with alternating amplitude A at the expense of sections 52.2, 52.4, 52.6, 52.8; 53.2, 53.4, 53.6, 53.8 is extended with constant amplitude A, ie the beginning of the rise or fall of the signal is advanced by a predetermined offset t _o2 and the section is also extended by this offset. In addition, the transitions between constant and alternating sections are rounded off by inserting intermediate values that create a smooth transition. The drive signals 54, 55 generated by the described transformations for producing embossed structures in a die or patrix are disclosed in US Pat Figure 4D shown. They are particularly suitable for operating an engraving machine, which has large continuous surfaces composed of several tracks, contiguous areas can engrave. Such a system is as mentioned above, for example in the EP 0 805 957 B1 (MDC Max Dätwyler AG).

The Figure 4E The elevations of the male 61 are narrower than the corresponding recesses of the die 60. Accordingly, the material to be embossed between the die 60 and the male 61 is not crushed during the embossing process, but can be conveniently accommodated between the opposing surfaces. The rounding of the transitions also reduces the risk of damaging the material to be embossed during the embossing process.

The Figures 5A-5E show a schematic representation of a novel multi-stage process for producing an embossed structure. As an example of the structure to be produced, those in the die 60 are shown in FIG Figure 4E used to be prepared wells. In order to be able to produce good embossing, embossing structures with depths of 100-300 μm are advantageously produced.

The FIG. 5A shows the still unprocessed portion of the die 60. Dotted the structure to be generated is drawn. The process will take place in several stages, whereby material will be removed up to a certain maximum depth (levels 70.1 ... 70.4). In the example chosen, the distances of the first plane 70.1 to the surface 60a of the die 60 and adjacent planes 70.1... 70.4 are each selected to be the same size. The planes 70.1... 70.4 have, for example, a distance of 55, 110.165 or 220 μm from the original cylinder surface.

The Figures 5B, 5C, 5D each show the partially machined portion of the die 60 after the first, second and third engraving operations. The same drive signal is used for each engraving process, only the distance of the engraving system from the (original) cylinder surface is changed. The respectively removed material 71.1, 71.2, 71.3 is shown with a wide hatching. The processing takes place in each case up to a depth specified by the corresponding level 70.1... 70.3. The maximum processing depth that the used burin has to perform thus corresponds to the distance between two levels 70.1 ... 70.3, namely 55 microns, and is thus fixed.

The FIG. 5E shows the final result. After removal of the material 71.4 in the fourth engraving step, the predetermined shape is reached.

As an alternative to the illustrated procedure, the planes to which engraving may also be selected depend on the recesses to be produced, or so that the material to be abraded in each engraving process remains approximately constant from step to step.

The multi-stage engraving may comprise a plurality of successive engraving operations, wherein in each process by a helical or circular engraving in a conventional manner substantially the entire cylinder surface is processed (with the exception of those points that are not to edit or where the desired engraving depth already is reached). It is also possible, however, in connection with the Figures 5A-E in each case a circular line is processed completely and if necessary in several stages (that is, during several revolutions of the cylinder) and the engraving system is subsequently moved axially to the adjacent circular line. This allows a multi-stage engraving even when using a supporting mechanism for adjusting the base distance, such as a sliding foot. The sliding foot (or a contact element of another supporting mechanism) is supported on the still unprocessed area of the cylinder surface.

By changing the drive signal, the working depth of the stylus is gradually increased from handling to handling in the same track. The drive signal can be superimposed with a correspondingly rising signal or amplified with a stepwise increasing gain factor. If the full engraving depth is not required along a certain ring line, then the maximum number of engraving processes does not have to be carried out there, but after reaching the desired depth along the entire ring line, the engraving system can be moved to the next line and start processing there.

Depending on the geometry of the embossed structure to be produced, under certain circumstances, this can also be produced in just one engraving step.

After the embossing structures have been produced by means of the sequence of engraving processes, the surface of the embossing cylinder can, for example, be provided with a layer of chromium for greater durability. Subsequently, the cylinder is ready for use. It can be used in particular in a conventional printing press, as it is used for gravure printing. The gravure printing and the embossing can be performed in the same printing press, but with separate cylinders, in particular by directly successively arranged printing units. This allows for efficient printing and embossing, where desired, the printed pixels and imprints can be precisely registered.

In summary, it should be noted that an apparatus and a method are provided by the invention, which allow a simple, fast and cost-effective production of embossing cylinders.

Claims (29)

1. Device for producing embossed structures in a surface (5a) of a cylinder (5), comprising an electromechanical engraving unit with

   a) a burin (4), which is movably mounted on a base of the engraving unit, for machining the surface (5a);

   b) a drive (23) for moving the burin (4) in relation to the base, in a direction perpendicular to the surface (5a) of the cylinder;

   c) a mechanism (10) for setting and maintaining a basic spacing between the base of the engraving unit and the surface (5a) of the cylinder (5);

   d) a controller (40) for controlling the drive (23) for moving the burin (4) on the basis of input data (50),

   characterized in that
   the controller (40) is formed in such a manner that embossed structures can be produced in a plurality of successive engraving procedures, wherein material (71,1...71.4) is removed from the surface (5a, 60a) at the same position of the surface of the cylinder (5) in the successive engraving procedures.
2. Device according to Claim 1, characterized in that the mechanism (10) for setting the basic spacing is formed without any support with regard to the surface (5a) of the cylinder (5).
3. Device according to Claim 2, characterized in that the mechanism (10) for setting the basic spacing comprises an adjustable stop (28), which limits a spring-driven advance movement of the base of the engraving unit in the direction of the surface (5a) of the cylinder (5).
4. Device according to Claim 2 or 3, characterized in that the mechanism for setting the basic spacing comprises a device (25) for measuring a spacing between the base of the engraving unit and the surface (5a) of the cylinder (5), and also a drive (27) for setting the basic spacing between the base of the engraving unit and the surface (5a) of the cylinder (5) on the basis of the measured spacing.
5. Device according to one of Claims 2 to 4, characterized by a slide foot (2), wherein the device is formed in such a manner that the basic spacing between the base of the engraving unit and the surface (5a) of the cylinder (5) can optionally be set and maintained using the mechanism (10) for setting the basic spacing, without any support, when producing embossed structures and using the slide foot (2) when producing structures in a gravure printing cylinder.
6. Device according to Claim 1, characterized in that it is formed in such a manner that circular line engraving can be carried out, in which the same track is machined during at least two complete cylinder revolutions, wherein a working depth of the burin (4) is increased from a first run to a second run in the same track.
7. Device according to one of Claims 1-6, characterized in that the controller (40) can produce a drive signal for the drive for moving the burin (4), which produces embossed structures that comprise one or more substantially continuous engraved marks composed of a plurality of adjacent tracks.
8. Device according to Claim 7, characterized in that the controller (40) is formed in such a manner that a pulse-width-modulated drive signal can be produced, wherein in particular an amplitude of the drive signal is additionally also modulated.
9. Device according to one of Claims 1 to 8, characterized in that the controller (40) comprises calculation means (42) for processing the input data (50), such that, as input data, conventional image data (50) for engraving printing cylinders, in particular halftone data, can be received and transformed in such a manner that the drive signal (54, 55) suitable for producing the embossed structures can be produced on the basis of the transformed data,
10. Device according to Claim 9, characterized in that the calculation means are formed and controlled in such a manner that data for producing structures for breaking a chip produced during the engraving are automatically incorporated in the transformed data.
11. Device according to one of Claims 1 to 10, characterized in that the controller is formed in such a manner that burnishing engraving can be carried out, wherein at least a significant part of the surface of the cylinder (5) is machined with a constant spacing between the burin (4) and an axis of rotation of the cylinder (5).
12. Device according to one of Claims 1 to 11, characterized in that the burin (4) has a tool angle (α) of 90-140°, preferably of 90-120°.
13. Device according to Claim 12, characterized in that the burin (4) has a lower part (4b, 4c) which tapers to a point and an upper part (4a) which adjoins the lower part above, wherein delimiting edges of the upper part include an angle (β) which is smaller than the tool angle (α) included by edges in the lower part (4b, 4c) which tapers to a point.
14. Device according to one of Claims 1 to 13, characterized by a device for removing chips by suction, wherein a suction removal opening is arranged in the region of the burin on the base of the engraving unit.
15. Device according to one of Claims 1 to 14, characterized by receptacles for the cylinder, which are formed so as to be adjustable such that it is possible to minimize a circularity error of the cylinder.
16. Process for producing embossed structures in a surface (5a) of a cylinder (5), comprising the following steps:

    a) input data (50) are received;

    b) a drive signal (54, 55) is produced on the basis of the input data (50);

    c) a burin (4) of an electromechanical engraving unit is driven with the drive signal (54, 55) in order to machine the surface (5a) of the cylinder (5);

    wherein the drive signal (54, 55) is produced in such a manner that it is suitable for producing embossed structures in the surface (5a) of the cylinder (5) by means of the burin (4),
    characterized in that
    at least one of the embossed structures is produced in a plurality of successive engraving procedures, wherein material (71.1...71.4) is removed from the surface (5a, 60a) by the burin (4) at the same position of the surface (5a, 60a) of the cylinder (5) in the successive engraving procedures.
17. Process according to Claim 16, characterized in that a spacing between a base of the engraving unit, with regard to which the burin can be moved in order to machine the surface of the cylinder, and the surface of the cylinder is continuously measured in a contactless manner, and a basic spacing between the base of the engraving unit and the surface of the cylinder is continuously and automatically adjusted on the basis of the measured spacing.
18. Process according to Claims 16 and 17, characterized in that a removal of material which has already taken place at the position currently being machined is taken into account during the adjustment of the basic spacing in that the adjustment is also made on the basis of the input data.
19. Process according to Claims 16 and 17, characterized in that a profile of the surface (5a) of the cylinder (5) is measured and stored before or during a first of the engraving procedures, and in that the basic spacing is also adjusted on the basis of the stored profile.
20. Process according to Claim 16, characterized in that a basic spacing between the base of the engraving unit and the surface (5a, 60a) of the cylinder (5) is respectively reduced by a predefined value, in particular on the basis of the input data, between successive engraving procedures.
21. Process according to Claim 16, characterized in that circular line engraving is carried out, wherein the same track is machined during at least two complete successive cylinder revolutions, wherein a working depth of the burin (4) is increased from a first run to a second run in the same track.
22. Process according to Claim 21, characterized in that a basic spacing between the base of the engraving unit and the surface (5a, 60a) of the cylinder (5) is set by means of a slide foot (2) supported on a still unmachined region of the surface (5a, 60a), wherein the basic spacing is maintained and a maximum deflection of the burin (4) is increased from the first run to the second run.
23. Process according to one of Claims 16 to 22, characterized in that the production of the embossed structures in the surface of the cylinder is preceded by burnishing engraving, by at least a significant part of the surface of the cylinder being machined by the burin with a constant spacing between the burin and an axis of rotation of the cylinder.
24. Process according to one of Claims 16 to 23, characterized in that embossed structures are produced, comprising one or more substantially continuous engraved marks composed of a plurality of tracks lying adjacent to one another on the surface of the cylinder.
25. Process according to Claim 24, characterized in that the drive signal produced is pulse-width-modulated in order to produce the continuous engraved marks, wherein in particular an amplitude of the drive signal is additionally also modulated.
26. Process according to one of Claims 16 to 25, characterized in that, during the production of the drive signal (54, 55) on the basis of the input data, the input data (50) which represent an image are modified in terms of smoother transitions between regions of the image with differing brightness values, in particular by diffusion transformation.
27. Process according to one of Claims 16 to 26, characterized in that a male mould (61) interacting with a female mould (60) or a female mould interacting with a male mould is produced by inverting the input data (50) in order to produce the drive signal (54, 55) and/or in that the input data which represent an image are modified in such a manner that the image is compressed and/or stretched.
28. Process according to one of Claims 16 to 27, characterized in that structures for breaking a chip produced during the machining of the surface of the cylinder are produced in the surface of the cylinder, in particular small-area structures having a depth which is less than the depth of the surrounding embossed structure.
29. Process according to Claim 28, characterized in that, during the production of the drive signal, the input data are automatically supplemented with data for producing the structures for breaking the chip.

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