EP1386727A1 - Process for improving the quality of an image engraved in a printing cylinder - Google Patents

Abstract

The method involves engraving small indentations by taking into account geometrical data, both indentation geometry data and tool (4) geometry data, which can vary with tool wear, for corrective adaptation of the actual indentation volume to the desired volume corresponding to a required shade value An especially two-dimensional image of the tool used is formed, from which the geometry is determined. An independent claim is also included for the following: (a) an arrangement for improving the quality of an image engraved on a print forme cylinder.

Description

The invention relates to a method and a device for improving the Quality of engraved from an engraving machine in a printing plate cylinder Image.

In an electronic engraver, an engraver moves with a, Also referred to as a stylus engraving stylus as a cutting tool in the axial Direction along a rotating printing forme cylinder along. The one by one Engraving control signal controlled engraving stylus cuts a sequence of, in one Low pressure grid arranged recesses, wells called, in the lateral surface of the plate cylinder. The engraving control signal is in a signal conditioning stage by overlaying one of the tonal values between "black" and "White" representing engraving signal with a periodic raster signal (Vibration) formed. The engraving signal corresponds to the values of stored Engraving data that gives each point of a picture to be engraved a specific one Assign tonal value. While the raster signal vibrates a vibrating stroke causes the engraving stylus to generate the grid controls the Engraving signal corresponding to the tonal values to be reproduced the cutting depths the in the lateral surface of the plate cylinder engraved wells.

Thus, the engraved in the printing forme wells the wells through the engraving data correspond to predetermined tonal values, the engraving control signal must be calibrated become. This is a trial engraving before the actual engraving, or Also called Probeschnitt, carried out, for the given tones, For example, for tonal values "light", "medium" and "low", wells are engraved.

After the sample engraving, the actual geometries of the engraved wells, for example the well diagonals Q and the cell lengths L ₁ , or, in the case of "deep" wells, the diagonal Q and, alternatively, the puncture width S are measured. These dimensions can be detected, for example, with the support of a CCD camera, or even a correspondingly enabled, analogue camera. These are each properties of the wells on the surface of the printing forme cylinder.

The actual values are stored with stored nominal value specifications of the well geometries compared for the sample cut. The comparison becomes setting values obtained with which the engraving control signal is calibrated such that at the later engraving actually produced wells, tonal values, which at least come closer to those specified in the engraving data.

From WO-98/55302 it is e.g. known, engraved on a sample cut To measure wells in a video image taken with a video camera.

Depending on the actual values of the well geometries from the sample cut, the Engraving control signal calibrated. The basis of the procedure presented here for the calibration of the engraving control signal is the assumption that two-dimensional Data, such as the base of the wells, or even one-dimensional Information such as the cup diagonal or the cell length, about the well-known "ideal" engraving geometry directly with the volume of the wells correlate.

But if one assumes on its own that the cups are replaced by one, a diamond Generous gravers are produced, and that diamond is included has an "ideal" pyramid shape, e.g. in DE 10051736, so Such a procedure can no longer be completely higher on the requirements Image quality of an image generated by a real grader suffice. A real one Stichel may deviate from this ideal form even before the first use, at least he will do it at the latest after his first use. The For example, wear of the stylus may deviate from the pyramidal shape Contours of the stylus result. It may then be possible that at one certain penetration depth z of the stylus in the plate cylinder, although the actual values the well geometries match the setpoint default, the actual reached tonal value of that given in the engraving date but deviates because the volume of wells actually produced, due to the different stylus geometry, the requirements, no longer enough.

The object of the present invention is therefore to improve the quality of a Engraving machine on a printing plate cylinder engraved image to improve.

The object is achieved according to the invention in process view that Engraving control signals used to engrave cups in a printing form cylinder by consideration of geometric data, both from the well geometry, as well as the geometry of the used stylus, each through Abrasion of the used stylus can be changed for correcting Adjustment of the actual actual well volume to that specified Tonwert corresponding nominal cup volume, to be changed.

This method according to the invention makes it possible to adjust the tonal values of the at least to preserve engraved wells over a longer period of time, because the wear of the stylus is taken into account by its measured geometries can be. Unwanted chromatic variations in, with the same engraved engraved, different pressure cylinders, can thereby be counteracted. The tonal values of the engraved wells remain over constant for a longer period of time.

Since the stylus replaced in normal use due to wear must be when the tonal values of the engraved wells to can greatly change, by the inventive method the service life The stylus used can advantageously be extended as it passes through the Compensation according to the invention not so fast to corresponding changes the tonal values comes.

Conveniently, by the method also strand differences by different pricks engraved wells are at least reduced. The Differences in the tonal values of different strands come at least partly due to the varying geometries of, in different strands used gravers. By considering the stylus geometries for providing the engraving control signals used in the individual strands, can the different Stichelgeometrien according to the invention be compensated, so that a more uniform printed image, the engraved by different pricks strands results.

Overall, the alignment of the tonal values of different strands, the more accurate adjustment of the wells to the desired hues and the receipt these tones over a longer period of time, to an increase in quality of the picture engraved by one or more engravers.

In a procedural development of the invention, it is provided that a particular two-dimensional image of the used, if necessary used to be used.

The production of an image of the prick has the advantage that directly a statement can be taken about the Stichelgeometrie. The dimensions of the Probes can e.g. can be read directly from this image and can then used to correct the change in the engraving control signal. This evaluation of the image may e.g. done manually by one person be done automatically or automatically. It may also be due to the picture To decide whether the burin is too worn and therefore exchanged must be, or whether a grave break may be imminent and the machine must be switched off and the graver removed.

In a further advantageous embodiment of the invention, it is provided that from the image of the prick, the prick geometry, preferably its contour descriptive functions are determined.

These functions may e.g. be a function A (z), or D (z). A (z) describes while the two-dimensional surface of the stylus within the printing forme cylinder, up to a depth z, measured from the Stichelspitze, in the printing form cylinder has penetrated. D (z) is the corresponding width of the bur at the depth z.

If functions are known, the geometry of the stylus, at least in Describe the dependence of the penetration depth z of the stylus in the plate cylinder, so with the knowledge of the penetration depth of the burin a statement about the volume occupied at that moment by the stylet in the cup to be hit. An arithmetical juxtaposition of the thus recognized Volumes can be when all of the graver traversed in the cup Way is known, the well volume result.

bestimmt werden. L₁ ist dabei die Näpfchenlänge und l ist der Punkt in Längsrichtung, an dem sich gerade der Stichel, entgegengesetzt der Rotationsrichtung des Druckformzylinders, befindet.This volume can also be calculated, for example via an integral

be determined. L ₁ is the cup length and l is the point in the longitudinal direction at which just the stylus, opposite to the direction of rotation of the plate cylinder, is located.

beschrieben werden. Der Abstand z₀ ergibt sich aus der Überlagerung des Graviersignals für ein bestimmtes Näpfchen und dem Ruheabstand des Stichels von der Druckformzylinderoberfläche. Dieser Ruheabstand ergibt sich aus dem Abstand des Stichels im stromlosen Zustand. Er ergibt sich aus der Einstellung des Gleitfußes. Das Graviersignal variiert zwischen Werten für "Schwarz" und "Superweiß". "Schwärzeren" Werten entsprechen geringere Abstände Z₀.des Stichels von der Oberfläche. Der Abstand z_o wird hier auch Offset genannt.z itself describes the picking movement relative to the pressure cylinder surface and can be expressed by the equation:

to be discribed. The distance z ₀ results from the superposition of the engraving signal for a specific well and the rest distance of the stylus from the printing form cylinder surface. This rest distance results from the distance of the stylus in the de-energized state. It results from the adjustment of the Gleitfußes. The engraving signal varies between values for "black" and "super white". "Blacker" values correspond to smaller distances Z _{0 of the} stylus from the surface. The distance z _o is also called offset here.

Z and the amplitude of the Stichelschwingung and the offset is superimposed. It is constant during the engraving process. L _R indicates the grid length of the engraving. It depends on the desired print image and is fixed.

In a further embodiment of the invention, it is provided that at least the data of the well diagonals Q and the cell lengths L _{1 are} determined from a sample cut.

Advantageously, the geometry of the cup can be determined via this data become. If additional functions are known, the geometry of the Completely describing a stylus, it may result from the combination of this information to be closed, at which place of the engraved cup the engraver during the engraving which volume has taken. About the addition of this individual volumes, the whole cell volume can be determined.

Conveniently, functions can also be determined via the trial cut the exact contour of the cell boundary and thus the describe complete well geometry. This can then be a complete Determination of the well volume may be possible.

It is also advantageously possible via these data parameters of the stylus movement read.

In a further embodiment of the invention, it is provided that from a Pro cut at least the data of the well diagonals Q and the puncture widths S be determined.

In wells that correspond to a tone "low", a puncture between two successive wells may occur. In this case, it is not possible to determine a well length L ₁ . Conveniently, then the puncture width S should be determined in addition to the Näpfchendiagonalen Q. As a second parameter it provides information about the exact well geometry. From the knowledge of the piercing widths, for example, further parameters of the stylus movement and / or the stylus geometry can be determined. For example, the course of the Stichelbreit depending on the penetration depth, or the amplitude Z and .

In addition, it is favorable to pay special attention to the puncture width, since with too large widths, which correlate at least with the partial depth, problems can occur when the voltage, it can thus according to the invention allows be to ensure a constant puncture width S.

According to the invention, it is further provided that the actual values of the cell geometry data are compared with setpoint specifications. In this case, for example, the well diagonals Q and the cell lengths L ₁ or the puncture widths S can be compared.

In the event of deviations, the engraving control signals can then be adapted, for example be that the resulting well geometries below the correspond to desired tonal values. In particular, correction data can be used be used on the basis of the known Stichelgeometrie.

For example, it may be known which cell volume corresponds to which tone value. The engraving date of a cup can then be assigned a desired volume as the desired value. After measuring the cup geometry, taking into account the stylus geometry, an actual value for the cup volume can be determined and compared with the target value. If it does not match, then the engraving control signal can be adjusted so that the corrected engraving control signals subsequently produce tonal-correct cells. Next can also Näpfchendiagonalen Q and lengths L ₁ be assigned as setpoint specifications, the achievement of which is desired in the engraving.
In a further embodiment of the method according to the invention, it is provided that the setpoint specifications are corrected taking into account the Stichgegeometriedaten.

It is conveniently not necessary here the engraving control signal directly to change it generates a target volume. It is simply necessary pay attention to easily determinable well geometries. Fulfill these actual values the corrected setpoint specifications for the well geometry, so it is automatic also reached the right volume. A conversion to a volume does not take place.

It is conveniently possible to continue an already existing and proven method for correcting the engraving control signal to use. That already proven methods can be used e.g. adjust the engraving control signal so that actual values of the well geometries correspond to predetermined setpoint specifications. Of course, there is little need to interfere in this process in which the existing setpoint specifications by corrected setpoint specifications be replaced. These new setpoint specifications should be determined in this way be that they represent cups, taking into account the geometry of the stylus, which have a volume corresponding to the tone value of the engraving date.

In a further development of the invention, it is provided that the adjustment of the setpoint values for wells which correspond to a tonal value "low" take place while maintaining the well length L ₁ .

Advantageously, thus preserving the shape of the wells at least almost possible.

In a continuation of the invention, it is provided that the adaptation of Target values for wells that correspond to a tone "low", under conservation the puncture width S done.

Advantageously, it is thus given that the amount of chips in the engraving of the puncture when changing the setpoints does not change. It is thus Ensures that it does not cause hue fluctuations or disabilities the engraving comes through a too long span.

It is further advantageously provided that when adjusting the setpoint values for wells which correspond to the tonal value "low", both the oscillation amplitude Z and the rest position Z _{0 of} the stylus movement are changed.

While by a sole change in the rest position Z ₀ both the Stichelbreite, and the cell length, or the puncture width is changed, it is possible by an additional change in the oscillation amplitude Z and the change of the puncture width or the cell length again compensate, so that a Adjustment of the setpoints to the desired volume is done mainly by changing the depth of the wells. The remaining well geometry is essentially retained, and it is possible to proceed in such a way that, if unavoidable, the cell cross-section alone changes. The average width is maintained in any case.

Advantageously, it is provided according to the method that the adaptation of the setpoint values for wells which correspond to one of the tonal values "average" or "light" take place while maintaining the oscillation amplitude Z and .

Offset-dependent changes in the oscillation amplitude would be the engraving accuracy not conducive, since different thermal developments in the Engraving head arise that can cause thermal drift.

It is therefore advantageously provided that the oscillation amplitude during the entire calibration procedure alone to set the setpoints of the well "low" is varied in other settings and calibrations, preceded or followed by the method described here, it may usually be provided that the amplitude only for "depth" wells is varied so as to be kept constant at the other tone values.

The change in the setpoint specifications for "middle" and "light" wells is therefore limited solely to a change in the intended rest position Z _{0 of} the stylus.

In a continuation of the method according to the invention, it is favorable provided that the adjustment taking into account the actual

Vibration amplitude Z and _{is (L 1 )} , while the engraving of wells of the variety "light" or "medium" occurs.

Since the oscillation amplitude Z and in a real engraving method depends on the offset z ₀ , as described in the cutting characteristic of an engraving head, the movement of the stylus, and thus also the cell volume, is thus dependent on the offset.

Since the amplitude is adjusted for a "Low" tone value, it is not necessary to adjust it here: For the "Medium" and "Light" tonal values, comparison of the setpoint specifications and the actual values of the cell geometry in conventional methods assumes a constant amplitude therefore according to the invention advantageously provided to adjust the set points so that the change in the oscillation amplitude is considered Z and already in them. in this way we would obtain from the setpoints tone can be better adapted to the engraving data. the oscillation amplitude Z and is therefore a Istschwingungsamplitude Z and _{is assigned (M, L} ).

The object of the invention is in device view by a camera for Measurement of, the printing form cylinder engraving stylus solved.

Using such a camera, that can be a CCD camera, a CMOS camera or another camera with a suitable magnification can be an image of the prick can be generated by which one is able to become to be clear about the wear and tear of the burin, then take appropriate action to take. It is then possible to use either parameters of the engraving control signal to create a well that matches the desired tonal values corresponds, or it can also be decided whether the Stichelverschleiß is too big and the stylus must be replaced. Furthermore you can Based on the Stichgegeometriedaten new setpoint specifications for the cup engraving be determined, which allow a total tonwertrichtigere well volumes.

It can be provided that the camera outside of the engraving machine provided in a special device.

Conveniently, it can also be provided that the camera within the Engraving machine is provided and the image of the prick while, or at least before an engraving can take. In particular, it is possible that an existing camera that has the appropriate requirements fulfilled is used for this task.

The determined contour parameters can e.g. in a store in the engraving head get saved.

In a further favorable development of the invention it is device-wise provided that at least one image processing unit of the invention is included.

It is then possible that parameters are recorded directly by means of this unit, describing the Stichelgeometrien, at least in the required frame. So may it be possible to gain functions that describe the stylus geometry, e.g. can be a function A (z) of the effective gauge area depending on be created by the penetration depth of the stylus in the printing form cylinder. Thus, a statement about the cell volume can be made. On Because of these statements, the tone value of the well can then be assessed and consequences can be drawn.

In an advantageous development of the invention are device-wise Comparative organs for comparing the measured geometries of the wells with Setpoints and to calculate the resulting, together with the Stichelgeometrien provided devoted well volumes.

Advantageously, by means of the organs according to the invention, the volume the wells are determined directly.

The knowledge about the well volume thus obtained can e.g. be used to judge whether the corresponding tone value of the well sufficiently with matches the desired one, or otherwise the stylus is replaced, but at least the engraving control signals should be corrected accordingly. These comparative organs can according to the invention also be present in an already existing Control unit to be integrated.

So that the engraving control signals can be corrected so far that the, the Wells corresponding to the actual tonal values according to the specifications from the engraving data, It is further provided according to the invention that a device for Adjustment of setpoint specifications is provided. Here are the reasons the wear of the stylus necessary corrections to the setpoint specifications either directly from the measured geometry data of the stylus and / or wells determined, or at least with the help of iteratively determined. These organs could also be integrated in an existing control unit.

The thus corrected setpoint specifications for the engraving parameters lead to the wells engraved on the basis of these parameters at least better with the match the required tone value. This then results in an increase in Quality of the engraved image by the engraver.

Fig. 1

ein prinzipielles, eine erfindungsgemäße Vorrichtung umfassendes Ausführungsbeispiel für eine elektronische Graviermaschine zur Gravur von Druckformen,

Fig.2

Eine graphische Darstellung eines Näpfchens,

Fig. 3

Eine graphische Darstellung eines Videobildes eines verwendeten Stichels

Fig. 4

Ein Blockdiagramm eines Verfahrens zur Steigerung der Qualität eines, durch eine Graviermaschine gravierten Bildes,

Fig. 5

Ein weiteres Blockdiagramm eines weiteren Verfahrens zur Steigerung der Qualität eines, durch eine Graviermaschine gravierten Bildes.

Embodiments from which further inventive features may result but to which the invention is not limited in its scope are shown in the drawing. Show it:

Fig. 1

an exemplary embodiment of an apparatus according to the invention for an electronic engraving machine for engraving printing plates,

Fig.2

A graphic representation of a cup,

Fig. 3

A graphic representation of a video image of a used stylus

Fig. 4

A block diagram of a method for enhancing the quality of an image engraved by an engraver,

Fig. 5

Another block diagram of another method for enhancing the quality of an image engraved by an engraver.

Fig. 1 shows a basic embodiment of an electronic engraving machine for engraving printing forms for gravure printing. The engraving machine is, for example, a HelioKlischograph® from Hell Gravure Systems GmbH, Kiel, DE.

A printing cylinder 1 is driven in rotation by a cylinder drive 2. The Engraving on the printing cylinder 1 by means of an engraving element 3, for example as an electromagnetic engraving organ with a engraving stylus 4 as Cutting tool is formed.

The engraving element 3 is located on an engraving carriage 5, which by means of a Spindle 6 of a engraving trolley drive 7 in the axial direction of the printing cylinder 1 is movable.

The engraving stylus 4 of the engraving element 3 cuts a sequence of in an engraving grid arranged wells 8 in the lateral surface of the rotating pressure cylinder 1, while the engraving 5 with the engraving element 3 in the feed direction moved along the printing cylinder 1 along.

The engraving stylus 4 of the engraving element 3 is replaced by an engraving control signal 9 controlled. The engraving control signal 9 is in a signal conditioning stage 32nd by superposition of a periodic raster signal 10 with engraving data, the via a line 11 at the signal conditioning stage 32 are formed. The engraving data includes values for the engraving, e.g. Electricity or Tension values, which are the tonal values of the wells to be engraved between Represent "light" (white) and "depth" (black). While the periodic Raster signal 10 a vibrating lifting movement of Engierstichels 4 for generating of the engraving screen, determine the engraving data according to the to gravitational tonal values the respective dimensions of the engraved wells such as penetration depth, transverse diagonal and longitudinal diagonal. The graver movement is by the raster signal 10 and by, the engraving data corresponding Control signals completely determined.

The engraving data are stored in an engraving data memory 12, from which they Engraving line for engraving line to be read out. Every engraving place for a cup 8 is assigned an engraving date which is e.g. two or four bytes can. This date can be the grave value of the well to be engraved 8 include. The assignment of an engraving date to a well 8, can be done in such a way that the tonal values between "light" and "depth" each value between 255 and 1 is assigned. This digital Value can then be assigned an analog value. In the signal conditioning stage 32 can this assignment also taking into account any Calibration parameters are made. Any additional Components or devices for such a calibration of the tonal values are not here shown.

The engraving data and the raster signal 10 are then passed through the signal conditioning stage 32 combined to the engraving control signals 9. The engraving data can be converted into analog data. A transformation in analog data can also in an analog-to-digital converter, not shown here take place, which may be preceded by the signal conditioning stage 32.

The printing cylinder 1 is associated with an XY coordinate system whose X-axis in the axial direction and its Y-axis in the circumferential direction of the impression cylinder. 1 are oriented. The X coordinate of a well 8 to be engraved becomes direct generated by the engraving carriage drive 7. The y-coordinate by a position sensor 13, which is coupled to the cylinder drive 2. Via lines 14, 15 The XY coordinates are fed to a control unit 16.

The control unit 16 controls the addressing and the reading of the engraving data from the engraving data memory 12 in dependence on the XY location coordinates of the current engraving locations via a line 54. The control unit 16 also generates the raster signal 10 with the frequency required for the generation of the engraving screen, a control command (S ₁ ) on a line 18 to the engraving drive 7 for setting the relevant for generating the engraving grid feed increment and to control the incremental feed of the engraving 3 during the engraving, and another control command (S ₂ ) on a line 19 to the cylinder drive 2 for setting the required for the generation of the engraving screen peripheral speed of the printing cylinder 1. The engraving itself itself can be stored in the engraving data memory 12 and transmitted via a line 50 to the control unit 16.

To carry out a test cut, the engraving data required for the sample cups are kept available. This can be done either in the engraving data memory 12, but it may also be the case that an extra computer is kept for this purpose, which is not shown here. Each engraving datum represents a predetermined nominal tonal value, to which respective desired nominal cell geometries, such as well diagonal Q _nominal and cell length L ₁ , are assigned. For "depth" wells, instead of the well length L ₁ , values for a puncture width S, if present, may also be provided.

To measure the sample cups 8 engraved in the sample section, a measuring carriage 20 which can be displaced in the axial direction of the printing cylinder 1 is provided with a video camera 21 for recording a video image of the sample cups 8 and an image evaluation stage 23 connected to the video camera 21 via a line 22 and also integrated into the video camera 21 may be provided for measuring the Probenäpfchen 8 in the video image. The measuring carriage 20 can be automatically moved via a spindle 24 by a measuring carriage drive 25 to the required axial measuring position in the individual engraving lines. The measuring carriage drive 25 is controlled by a control command (S ₃ ) on a line 26 from the control unit 16.

Alternatively, the video camera 21 can also be arranged in the region of the engraving element 3 be, wherein the recording of the video image, for example via a not shown light guide can be done.

The cell geometry data obtained by the image evaluation stage 23 are passed via a line 27 to the control unit 16. In the control unit 16, the geometric actual values are then compared with the predetermined setpoint values and, on the basis of this comparison, necessary setting values for calibrating the engraving control signals 9 are obtained. The comparison of the actual and desired values can also be done outside the control unit 16 in comparison organs not shown here. However, these organs are integrated here in the control unit 16. The calibration of the engraving control signals can take place via a control of the screen signal 10, the engraving data or both together. A regulation of the engraving data takes place via a control signal of the control unit 16 that is sent via the line 54 to the engraving data memory 12. The calibration of the engraving control signals 9 can also take place via an external computer, not shown, which can then also regulate the calibration directly via the signal conditioning stage 32. The calibration should be such that the cells 8 actually produced later during the engraving at least come closer to the cups 8 required for a tone-true engraving. For this purpose, it is provided that the parameters of the movement of the stylus 4, in particular the offset Z ₀ and the oscillation amplitude Z and be adjusted so that in a renewed passage of the test section, the cell geometries correspond to the corresponding setpoint specifications. A corresponding method belongs to the prior art, see, for example, WO 98/55302, and will not be explained further.

After a possible match of setpoint specifications and actual cup geometry can in the control unit 16, an assignment of between the Well values "deep" and "light" digital engraving data, to analogue Control data done. The assignment can be done with the support of Tonal "Medium" done. The assignment thus determined can then be sent to the signal conditioning stage 32 are given. A corresponding method of Midtone correction is generally state of the art and will not be explained further here become. This correction can also be done in a computer, not shown or in the signal conditioning stage 32.

For more accurate calibration of the engraving is on the engraving 5 a further camera 28 is provided, which is mounted so that it forms an image of Tip of Engierstichels 4 can record.

It may also be provided that this camera 28 is not on the engraving cart 5 is attached. In this case, the camera 28 may be e.g. not in one here be shown in the particular shown before or to be measured after an engraving of the engraver 4

Furthermore, it can also be provided that instead of the camera 28 another, already existing, but not shown here camera for recording a suitable image is used.

The thus obtained image of Engierstichels 4 is connected via a line 29 to a Image processing device 30 passed, there can from the image of the stylus. 4 the different properties of its geometry, such as a surface function A (z) or a diagonal function D (z) can be determined. These properties of the stylus can then via another line 31 to the control unit 16 are sent. Here can then be obtained by means of shortcuts Geometry data of the stylus 4 with, via the camera 21, in conjunction with the Bildauswertestufe 23 known Well geometries, the volumes the generated and measured stylus are calculated.

The image evaluation stage 23 and the image processing device 30 can thereby also be combined in an arrangement, in particular, a device be provided with a corresponding arithmetic unit, the same time can fulfill both tasks.

In the case that the camera 21 is arranged in the region of the engraving element 3, Alternatively, it may also be possible that instead of the cameras 21 and 28 only one single camera, e.g. exactly pivotable is movable, for recording both the images of the wells 8, as well as the images of the stylus 4, used becomes.

Next, according to the invention within the control unit 16 an adaptation made the setpoint specifications for the cup geometry. there taking into account the stylus geometries, the setpoint specifications are determined that wells 8 that meet these specifications, just those of the Engraving data required tone values correspond.

It may in particular between the adjustment of the wells 8 for tonal values "Depth" and the well 8 for tonal values "medium" and "light", distinguished become.

First, an adjustment of the setpoint specifications for "depth" wells should be done. In particular, the parameters for the stitch offset Z ₀ and the vibration amplitude Z and are adapted to these cups. By means of a corresponding calculation or at least iteratively, it is determined which parameters must be used in the existing stylus 4 in order to achieve a desired well volume. Next, then, these parameters are assigned to well geometry data. These data can easily be determined using the existing functions for the stylus geometry. For example, the function D (z) provides information about the well diagonal Q and / or the puncture width S as a function of the penetration depth z of the stylus 4. The cell geometry data can also be determined optionally with the area function A (z) of the stylus.

Since the vibration amplitude Z and depends on the cutting characteristic of the stylus 4 of the offset z _{0 of} the stylus movement, this dependence should be taken into account before a final adjustment of the setpoint specifications for "light" and "middle" wells 8, since this is a change in the offset require. The measured geometries of the sample cups 8 are first converted according to the cutting characteristics of the stylus 4 to values corresponding to the oscillation amplitude Z and the "depth" wells. Since the amplitude Z and was set just for these cups 8, it is naturally preserved here. For the comparison of the actual values of the cup geometry with the setpoint specifications, wells 8 which correspond to the tonal values "light" and "mean" are not used the actually measured geometry data. They are first adjusted for the comparison so that they correspond to a vibration amplitude Z and as in the engraving of the "depth" wells. The lstschwingungsamplituden Z and _{is (L, M)} for "light" - and "agent" -Näpfchen 8 is determined from the measured actual values of the well profiles, whereby in particular the puncture width S and the transverse diagonal Q takes into account the "depth" -Näpfchen with become.

After determining the well geometry data for the "deep" wells of the test section and deriving the corresponding setpoint specifications, the adjustments to the setpoint values of the well geometry for "light" and "center" wells are determined. According to the invention, the procedure is such that the parameters of the stylus movement, which are necessary to achieve the volumes corresponding to the given tonal values, are calculated such that the oscillation amplitude remains constant. That is, it is determined for each of these Probenäpfchen 8, the Sticheloffset Z ₀ so that it can achieve the appropriate well volume taking into account the Stichelgeometrie. A change in the oscillation amplitude does not take place, but its change due to the cutting characteristic is taken into account. From the value for the necessary offset Z ₀ and the vibration amplitude

Z and _{is (L, M)} then the new setpoint specifications for the cell geometry are determined. For "light" and "middle" wells this means an adjustment of the values for the now required well width Q and the well length L ₁ . See also Fig. 2.

In Fig. 2, a cup 8 is shown symbolically in plan view. The cup geometry can be described, for example, by the information about the cup length L ₁ and the cup diagonal Q.

In Fig. 3, a contour 33 of the point of a stylus 4 is shown, e.g. after processing of the image obtained by the camera 28 by the image processing device 30 can result.

The penetration depth z of the stylus 4 in a printing form cylinder 1 results from the Top 34 of the real engraver.

The contours of the ideal burin or the contours that the burin 4 before his Having exhibited use arise as tangents 35, 36 at the contour 33 of the stylus 4 at the points 37, 38, where the contour of the Grave 4 deviates from a straight line.

The original point 34 '4 is the result of the intersection of the two Tangents 35, 36.

The course of the contour 33 can be achieved by means of the image processing device 30 describe, at least in part, functions 39 and 40 that make up then at least approximately the stylus geometry descriptive functions A (z) and let D (z) be determined.

FIG. 4 shows a flowchart which shows the sequence of adaptation of the engraving control signal 9 to achieve a better match of the actual tonal values explained with the target tonal values of the engraved wells.

The procedure starts with an engraving of Probenäpfchen after block 41. Thereafter With the first camera 21, an image of the wells 8 thus engraved is taken. As an image of a well 8, e.g. a representation, as in Fig. 2 is shown result. The image will then be in the image processing stage 23 evaluated according to 42. According to Box 42, the Geometry data of the stylus 4 is determined. The Stichgegeometriedaten be with Help the camera 28 and with the image processing device 30 detected and processed. In this case, a function A (z) is determined, which is the area of the stylus. 4 determined within the plate cylinder 1.

In this method further characteristic cell geometries, such as the cell length L ₁ and the well diagonal Q are measured. For the case of "depth" wells, if necessary, also the puncture width S can be determined. As shown in block 43, a cell assignment will next occur. For a query of the engraving data memory 12 is performed by the control unit 16. Thereby, a check takes place, which tonal range "low", "medium" or "light" correspond to the respectively engraved wells 8.

This assignment can also be made so that the place is known on the the respective wells 8 are to be engraved. This place does not need it can be achieved exactly by the cup engraving, it can be provided that small deviations of the wells 8 from this engraving location in the assignment the wells 8 can be tolerated. Thus, for example, if at least in the vicinity the place for a provided "depth" well a well 8 within the Tolerance detected by the camera 21, then the following procedure also assumed a cup 8 of the tonal range "low".

The continuation of the method now depends on the respectively recognized tonal range. In the tonal ranges "medium" and "light", provision is made for the actual oscillation amplitudes Z and _{(L, M) of} the vibration of the stylus for these wells 8 to be ascertained first in accordance with box 44. The actual amplitudes

Z and _is can be determined via the cup geometries or also via a known cutting characteristic of the stylus 4.

Next, a computational projection 45 of the setpoint default values for the well geometry of "center" and "light" wells, on a geometry at the adjusted amplitude Z and takes place.
From the projection of the well geometry at 45 for "middle" and "light" wells 8 and the geometric data of the stylus 4, taking into account the stylus geometry data of Figure 42, a volume of wells 8 is calculated which they would reach for the existing setpoint specifications.

For the wells 8, which correspond to a tone value "low", alone the Setpoint specifications considering the random geometry data according to 42 used to calculate therefrom a corresponding volume of wells 8, whose geometries correspond to the setpoint specifications.

At 46, a comparison is made between the volumes that are achieved to give the desired tonal value and those that are achieved taking into account the actual values of the stylus geometry and the well geometry according to the existing setpoint presupposes.

If the required volumes are equal to the volumes according to the setpoint specifications, become the known from 42 actual values of the cell geometry with the Set point specifications at 47 compared.

If the actual values of the well geometries match the setpoint specifications for all three tonal values "low", "medium" and "light" is of a correct Assignment of the engraving control signals 9 to the required tonal values went out.

48, the settings for the three tonal values "low", "average" and "light" and the oscillation amplitude Z and from the digital engraving data of the engraving data memory 12 are used to determine the analog engraving control signals 9. This determination can be made directly in the signal conditioning stage 32. It may also be possible, for example, for an engraving preamplifier (not shown) to be interposed between the signal conditioning stage 32 and the engraving data memory 12, which performs this combination and then forwards the analog data thus obtained to the signal conditioning stage 32, where they are then amplified. After the determination of the analog engraving control signals 9, the engraving of the desired image can be started in the printing form cylinder 1 corresponding to 49.

If at 47 no agreement of the actual values of the cell geometry with the setpoint specifications are found, so after block 50 is a calibration the engraving control signals 9 instead. At this time, the engraving control signals 9 become so readjusted that they, taking into account the actual Stichelgeometrie Engrave wells 8 whose geometries match the setpoint specifications.

If, according to 46, the volumes that would result from the existing set value specifications for the wells 8 do not all coincide with the volumes which are necessary for a tone-true engraving, then after the volume comparison 46 an adaptation takes place, both of the offset z ₀ , as well as the vibration amplitude Z and for "depth" wells 8, to 51 instead. Here, the amplitude Z and is set so that together with the newly calculated offset z ₀ for the "depth" wells 8 a new function the stitching movement z, which, in conjunction with the area function A (z) of the stylus 4, results in a computational well volume for the "depth" wells 8 corresponding to the volume required for the desired tone value.

It should be determined at this time both the amplitude Z and as well as the offset z _o for the "depth" well. This determination should be made so that the puncture width S is maintained in the resulting engraving. This adaptation only occurs if the "depth" well does not have the right volume. With a volume match according to 46 for "depth" wells 8, 51 is skipped insofar that an adaptation does not occur. If there is no puncture, then the cell length L _{1 should be} preserved.

Next, after 52, an adjustment of the offsets Z ₀ for the "middle" and "light" wells 8 is performed. There are no further adjustments to the vibration amplitude Z and be made. It is determined solely by the adjustment for "depth" wells and adopted for all varieties of wells 8, wherein after 44 and 45 the actual oscillation amplitudes Z and _{is (L, M)} for the determination of the different offsets z ₀ for the, different Tonal corresponding wells 8, are taken into account.

After 53, a determination of new setpoint presets for the well geometries will next take place. The setpoints can be calculated in a computer not shown further or directly in the control unit 16. They are calculated from the picking movement z for the different tone values, taking into account the new values for the amplitude Z and and the different offsets z ₀ and the area function A (z) of the stylus.

For further test cuts, these new setpoint specifications will be compared used with the actual values of the well geometries.

Next, at 41, a re-run of the method begins with a Test cut.

In Fig. 5 is a further procedural embodiment of the invention shown as a block diagram.

After the determination of the stylus geometry 42a, the trial section 41 and the determination of the cell geometry 42b, the actual volume V _{ist of} the wells 8 is first calculated or determined after 58 from the cell geometry and the stylus geometry.

After 54, in addition, the respective offset z _{0 of} the different wells 8 and the respective vibration amplitudes Z and _{is (, M, L)} determined. Thereafter, an adaptation of the oscillation amplitude for the "deep" wells 8 should take place according to 55, so that the actual oscillation amplitude coincides with that from the setpoint specifications. From this oscillation amplitude Z and 57, a calculation of a volume V ₁ engraved by the stylus 4, assuming a non-worn stylus 4, should then take place as a function of a variable offset Z ₀ , var.

From the 54 and 55 known actual values of the vibration amplitudes Z and _{is (M, L} ) and Z and for "middle", "light" and "depth" wells and the corresponding offsets z _o , then a volume V ₂ for the respective wells 8, assuming a non-worn stylus 4.

From the data of the engraving data memory 12 V _soll for the volumes of the respective wells 8 are determined according to 59 setpoint specifications.

Next, the offsets z _o for the engraving of the respective wells 8 to 60 are corrected to such an extent that the new offsets z ₀ 'take those values which result in volumes which correspond to the respective set values according to FIG.

For this, the actual volume value V _{is determined} to 58 for the respective wells 8, using the values V ₂ , which was calculated for the actual vibration amplitudes and V ₁ , which is a volume at the setpoint Z and the vibration amplitude as a function of the offset z ₀ ' describes, adapted to a volume V _var , which is directly comparable to the volume V _soll , since it was brought to a value for the target value of the vibration amplitude Z and . Now, with changes of the offset z ₀ ', this can be adjusted for the respective wells 8 so that the two volumes V _soll and V _var match. This can be done either computationally or iteratively.

After the correction of the offsets 60, the engraving control signals for the respective wells 8 to 61 are corrected from these values for Z and and z ₀ 'to 60 and 55, respectively.

At 62, the size of the offset correction is queried. If the distances of the new values z ₀ 'from the old offsets z _{0 are} each smaller than a predetermined limit value W, the engraving of the plate cylinder 1 starts after 63. It may also be required that the distances on average and the limit value W lie.

In the other case, a trial cut 41 is made again and the procedure begins the loop from 41 to 62 again.

Claims (16)

Method for improving the quality of an image engraved by an engraving machine in a printing form cylinder (1), characterized. in that engraving control signals (9) used to engrave cups (8) on the printing form cylinder (1) are changed by taking account of geometric data, both from cup geometry data and from the geometry of the stylus (4) used, in each case by wear of the used stylus (4) may be changed for corrective adjustment of the actual actual well volume to the desired well volume corresponding to the predetermined tone value. A method according to claim 1, characterized in that one, in particular two-dimensional image of the used optionally used burin (4) is generated. A method according to claim 2, characterized in that from the image of the stylus (4) the stylus geometry, preferably its contour descriptive functions are determined. A method according to claim 1, characterized in that from a sample cut at least the data of the well diagonals Q and the cell lengths L _{1 are} determined. A method according to claim 1, characterized in that from a sample cut at least the data of the well diagonals Q and the puncture width S are determined. Method according to one of claims 1 to 5, characterized. that the measured Well geometry data are compared with setpoint specifications. Method according to one of claims 1 to 6, characterized. that the setpoint specifications are corrected taking into account the Stichgegeometriedaten. Method according to one of claims 1 to 7, characterized. in that the adjustment of the nominal values for wells (8) which correspond to a tone value "low" takes place while maintaining the well length L ₁ . Method according to one of claims 1 to 7, characterized. take place that the adaptation of the desired values for wells (8) corresponding to a tone value "depth" while preserving the puncture width S. Method according to one of claims 8 or 9, characterized. that when adapting the set values for wells (8) corresponding to the tone value "depth", both the oscillation amplitude Z and, and the rest position z of the Stichelbewegung be changed _0th Method according to one of claims 1 to 10, characterized. in that the adjustment of the nominal value specifications for wells (8) which correspond to one of the tonal values "medium" or "light" takes place while maintaining the oscillation amplitude Z and the stylus movement. A method according to claim 11, characterized in that the adjustment taking into account the actual oscillation amplitude Z and _{is (L, M)} during the engraving of wells (8) of the "light" or "medium" type. Device for improving the quality of an image engraved by an engraving machine in a printing form cylinder (1), for carrying out the method according to one of the preceding claims, characterized by a camera (28) for measuring the stylus (4) engraving the printing form cylinder (1) , Apparatus according to claim 13, characterized in that the device comprises at least one image processing unit (30). Device according to one of claims 13 and 14, characterized in that comparative organs for comparison of the measured geometries of the wells with set values and for calculating the resulting therefrom, together with the Stichelgeometrien, cell volumes are kept ready. Device according to one of claims 13 to 15, characterized by a device for adapting setpoint specifications.

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