JP2003103746A - Gravure printing plate engraving stylus monitoring device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gravure printing plate engraving stylus monitoring device as a means to objectively judge a gravure printing plate engraving abnormality attributed to a stylus abnormality, by which a variability of judgement which is unavoidable in empirical judgement through a conventional visual observation, is eliminated and the timing of replacing a stylus is forecast and a monitoring method. SOLUTION: This gravure printing plate engraving stylus monitoring device comprises at least an image photographing means for photographing engraving cells formed on the surface of a gravure printing plate and obtaining image data and a cell-shape arithmetic means which seeks the ratio between the peripheral length and the area of a cell based on the image data and compares the obtained ratio to a normal value and judges the comparison results and the monitoring method is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for monitoring an abnormality such as abrasion of an engraving needle when engraving a plate for gravure printing.

[0002]

2. Description of the Related Art In gravure printing, a cylinder having a large number of depressions called cells formed on the surface of a base material such as copper is used as a printing plate. The method of forming the cell is roughly classified into a method by chemical etching and a method by mechanical engraving, and the latter method has been popularized in recent years because of its stability and easy management. In mechanical engraving, the surface of the substrate to be engraved is engraved with a diamond needle (hereinafter referred to as a stylus) to form a large number of cells at positions corresponding to the pattern. The depth of this cell is not generally constant, but the mechanism is such that the density of the printed matter is made to match the original by changing the engraving voltage according to the density of the corresponding picture.

If the shape of the stylus is constant, it is considered that the depth of the cell and the volume of the depression of the cell portion are uniquely determined by the planar dimension of the cell opening, that is, the cell width and the length. Is easy. However, since the diamond stylus is worn during use and its shape changes, there is a case in which a difference from the density of the printed matter occurs in the above determination. Therefore, there has been a demand for a method of objectively determining the degree of wear of the stylus.

Regarding the abnormality such as abrasion or chipping of the stylus up to now, it is general to judge the degree of abnormality by observing the shape of the enlarged image of the engraved cell and empirically comparing with the shape of the normal cell. It was However, in this method, not only the individual difference due to experience is large, but also the judgment experience is not accumulated as objective data, so it is difficult to grasp the correlation between the degree of abnormality and the change in print density. Therefore, it was not possible to judge the stylus replacement time by predicting a change in print density due to a stylus abnormality that cannot be captured only by measuring and managing the width of the cell opening. When the degree of abnormality is significant, the gloss of the engraved surface may be visually observed to determine the difference, but in that case it is almost too late.

[0005]

SUMMARY OF THE INVENTION The present invention provides a means for objectively determining an engraving abnormality caused by a stylus abnormality, which is unavoidable in the conventional empirical determination by visual observation. (EN) A gravure plate engraving needle monitoring device and method for eliminating variations and predicting when to replace a stylus.

[0006]

A first aspect of the present invention for solving the above-mentioned problems is to provide an image pickup means for picking up image data by picking up an image of an engraving cell formed on a gravure plate surface and a cell from the previous term image data. A gravure plate engraving needle monitoring device comprising at least a cell shape calculating means for determining a ratio of a perimeter to an area and making a comparison determination with a normal value. This makes it possible to quantitatively monitor the degree of wear and chipping of the gravure engraving needle, and stabilize the quality of gravure printing.

A second aspect of the present invention is to engrave the gravure plate surface with an engraving needle, image the engraved gravure plate surface to obtain image data of an engraving cell, and obtain image data of a large number of engraving cells from this image data. It is a gravure plate engraving needle monitoring method characterized by obtaining a ratio of a perimeter and an area and making a comparative judgment with a normal value. This enables stable management of the gravure engraving needle, such as exchanging the needle or polishing the gravure engraving needle according to the degree of wear or chipping of the gravure engraving needle.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an example in which a gravure plate engraving needle monitoring device is installed in a gravure plate engraving device. The configuration of the device of the present invention is such that a CCD camera 5 equipped with a necessary light source and a magnifying lens as an imaging means
The image data input / output device and the image processing device 6 having the area measuring and perimeter measuring functions are used as the cell shape calculating means. In FIG. 1, the printer 7 is also provided so that an image can be output. In addition, a camera fixing device, a display device, and a storage device are provided as needed.

The type and performance of the CCD camera, the light source and the magnifying lens can be appropriately selected depending on the surface gloss and size of the object to be measured and the required accuracy. For example,
For mechanically engraved cells with engraved cell openings of 200 μm or less, this is a 350,000 pixel monochrome CCD camera equipped with an LED epi-illuminator and a 40 × magnification lens.

As the image data input / output device, known boards depending on the camera and the image processing device can be used. The image processing device can be appropriately selected from devices having necessary processing speed and capacity. Another requirement of the image processing device is that it has an algorithm to measure the area and perimeter of the image, and if necessary, it has a filter morphology that removes noise from the original image and an automatic binarization function. As a matter of fact, these requirements can be easily selected from commercially available image processing programs.

Next, the determination of needle abnormality by the device of the present invention will be described in detail. For mechanical engraving of a plate used for rotary gravure printing, an iron or aluminum cylinder plated with hard copper of about 100 μm is used as a substrate to be engraved. The cell is intermittently engraved with a diamond stylus while rotating this cylinder. The stylus is polished so that the angle of the cross section perpendicular to the cylinder rotation direction is usually 120 to 150 degrees, and the cross section of the engraved cell is determined corresponding to the cross section of the stylus.

The section of the engraving cell immediately after polishing of the diamond stylus, which is perpendicular to the cylinder rotation direction, is the same as the section of the corresponding depth of the stylus, and two straight lines determined by the straight lines of the stylus cross the top. It has a triangle. The entry and exit of the stylus with respect to the substrate to be engraved is repeated at intervals of several KHz per second under the specific conditions determined by the mechanical engraving device, so that the cell bottom (corresponding to the top of the stylus) is smooth in the cylinder rotation direction. Form a depth curve. When the stylus in the state immediately after polishing is used, the contour of the engraved cell opening also draws a smooth curve corresponding to the stylus angle, and the ratio of the cell opening area and the contour is constant under the same engraving conditions. FIG. 2 shows an example of an image of an engraving cell obtained by enlarging and photographing a gravure plate with a CCD camera. (A) is an engraving cell when the stylus is normal, and (b) is an engraving cell when the stylus is abnormal.

The shape of the stylus changes with the time of use, and the portion that comes into contact with the base material during cutting gradually or rapidly wears. This wear usually does not occur uniformly, presumably in the form of localized chip stacking due to non-uniformity of the crystal structure. As a result, the section perpendicular to the direction of rotation of the portion that contacts the substrate during cutting changes from a smooth straight line to a jagged line. At this time, the contour of the engraved cell opening is not a smooth curve but a jagged curve corresponding to the stylus cross section of the substrate surface at the stylus penetration depth.

As a result of earnest studies, the present inventor has conducted a thorough study on a method of quantifying the degree of this jaggedness to simply quantify the degree of wear or chipping of the stylus. The inventors have found that this is possible by adopting it as a value and have completed the present invention. That is, the abnormality of the stylus is determined or predicted based on the degree of deviation from the ratio of the perimeter and area of the engraving cell opening under each engraving condition when a normal stylus is used. At this time, the allowable range of the degree of deviation is determined corresponding to the allowable range of the actual print density.

[0015]

The gravure plate engraving needle monitoring device of the present invention comprises:
Each engraving condition when a normal stylus is used by monitoring the change in the ratio of the perimeter to the area among the shape factors of the engraving cell in order to detect the abnormality of the engraving needle during engraving of the gravure plate. It becomes possible to judge or predict the abnormality of the stylus based on the ratio of the perimeter of the engraving cell opening to the area of the engraving cell as a reference, and to quantitatively monitor the degree of wear and chipping of the gravure engraving needle. It has become possible to perform stable control of gravure engraving needles such as needle replacement and polishing.
In addition, since the engraving needle for the gravure plate can be managed, the quality of the gravure printing can be stabilized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example in which a gravure plate engraving needle monitoring device is installed in a gravure plate engraving device.

FIG. 2 is an example of an image of an engraving cell obtained by enlarging and photographing a gravure plate with a CCD camera. (A) is normal, (b) is abnormal.

[Explanation of symbols]

1 ... Gravure engraving device 2 ... Gravure version 3 ... Engraving head 4 ... Coupling 5 ... CCD camera 6 ... Image processing device 7 ... Printing device 10 ... Engraving cell

Claims (2)

[Claims] 1. A cell shape calculation for picking up an image of an engraving cell formed on a gravure printing plate to obtain image data and a ratio of a perimeter of the cell to an area from the image data of the previous period and for making a comparison judgment with a normal value. A gravure plate engraving needle monitoring device comprising at least means. 2. A gravure plate surface is engraved with an engraving needle, the engraved gravure plate surface is imaged to obtain image data of an engraving cell, and the ratio of the perimeter and area of a large number of engraving cells is obtained from this image data. A gravure plate engraving needle monitoring method characterized by making a comparison judgment with a normal value.