JPH091770A - Gravure engraving system - Google Patents

Abstract

PURPOSE: To provide a gravure engraving system wherein an area of cells to be engraved actually is linearly proportional to a gradation to be designated by an original image data. CONSTITUTION: A density signal whose level changes dependent on a gradation to be designated by an image data (i.e., density of image to be printed) is superimposed on a carry signal having a shape of sine wave at an adding section 105, and applied to an engraving head 21 as an engraving signal. A stylus included in the engraving head 21 vibrates in a reciprocating manner according to the engraving signal to be applied, so as to engrave cells on a gravure cylinder which rotates in the horizontal scanning direction. A vertical scanning motor 107 sends the engraving head 21 in the vertical scanning direction intersecting the horizontal scanning direction every time engraving of the cells for one row on the gravure cylinder is completed. A data creating device 201 corrects a gradation of an original image data such that an area of the cells is linearly proportional to change of the gradation of the inputted original image data. Thereafter, it is sent to a density signal generating section 101.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gravure engraving system, and more particularly to a gravure engraving system for producing an intaglio plate for gravure printing by engraving a plurality of cells on the surface of a gravure cylinder.

[0002]

2. Description of the Related Art A gravure engraving system is an intaglio plate for gravure printing, in which minute cavities called cells are formed on the surface of a gravure cylinder while rotating a cylindrical gravure cylinder whose surface is plated with copper. Is a system for making. Then, the amount of ink filled in the cell is controlled by the depth and width (area) of the cell, and the print density is expressed. An engraving head is used to form cells on the surface of the gravure cylinder. The engraving head is provided with a stylus having a diamond needle (bite) at its tip, and the stylus is vibrated at a frequency of several KHz for engraving.

FIG. 17C shows the waveform of an engraving signal applied to the engraving head in the conventional gravure engraving system, which corresponds to the stylus displacement waveform. This signal waveform is obtained by superimposing the density signal waveform as shown in FIG. 17B on the high frequency carry signal waveform as shown in FIG. 17A (that is, modulating the carry signal with the density signal). It is a thing. By applying such an engraving signal to the engraving head, cells having a depth and a width corresponding to the density signal can be engraved on the surface of the gravure cylinder. The alternate long and short dash line R in FIG. 17C corresponds to the surface of the gravure cylinder, and the hatched portion in the drawing corresponds to the cell.

FIG. 18 is a diagram showing an example of a top surface shape of a cell engraved by a conventional gravure engraving system and an arrangement state thereof. As shown in FIG. 18, conventional cells are regularly arranged. The shape of each cell is approximate to a rhombus, as shown in FIG.

[0005]

By the way, the level of the density signal changes according to the gradation specified on the image data, that is, the print density. Then, the level of the density signal appears as the width of the cell (width in the sub-scanning direction). Therefore, the gradation specified on the image data corresponds to the lateral width of the cell, and the cell area is proportional to the square of the lateral width of the cell. The area is, as shown in FIG.
It changes like a quadratic function. As described above, in the conventional gravure engraving system, since the cell area is not linearly proportional to the gradation on the image data, the density of the printed matter cannot be accurately controlled as it is. Therefore, conventionally, there has been a problem that it takes time to make the adjustment because the conventional engraving is performed to observe the density change of the actual printed matter and the image data is corrected based on the observation result.

Therefore, an object of the present invention is to provide a gravure engraving system in which the area of the cell actually engraved is linearly proportional to the gradation specified by the original image data. is there.

[0007]

The invention according to claim 1 is
A gravure engraving system for producing an intaglio plate for gravure printing by engraving a plurality of cells on the surface of a gravure cylinder, which has a rotating means for rotating the gravure cylinder in a main scanning direction and a constant frequency and a constant amplitude. Carry signal generating means for generating a sine wave carry signal, density signal generating means for generating a density signal whose level changes according to the gradation of image data provided, and by superposing the density signal on the carry signal, An engraving signal generating means for generating an engraving signal and a stylus for engraving cells with respect to a gravure cylinder rotating in the main scanning direction by reciprocating vibration according to the engraving signal, and a sub-scanning element for making the stylus orthogonal to the main scanning direction The stylus feeding means for feeding in the scanning direction and the cell area is linear with respect to changes in the gradation of the original image data. As proportional, after correcting the gradation of the image data of the original, and a gradation correction means for providing a density signal generating means.

According to a second aspect of the present invention, in the first aspect of the present invention, the gradation correction means determines the area of a cell engraved when the original image data is directly applied to the density signal generation means for each gradation. A first calculating means for calculating; a second calculating means for calculating a cell area for each gradation when linearly proportional to a change in gradation of the original image data;
And a third calculation means for calculating a correction value for each gradation value of the original image data based on the calculation result of the second calculation means.

[0009]

According to the first aspect of the invention, the gradation correction means corrects the gradation of the original image data so that the cell area is linearly proportional to the change of the gradation of the original image data. After that, it is applied to the density signal generating means. As a result, since the area of the cell actually engraved is linearly proportional to the change in the gradation of the original image data, it is possible to accurately control the print density without performing trial engraving. .

According to the second aspect of the invention, the gradation correcting means calculates the area of the cell engraved for each gradation when the original image data is given to the density signal generating means as it is, and the original image data of the original image data is calculated. The cell area when linearly proportional to the change in gradation is calculated for each gradation, and the correction value for each gradation value of the original image data is calculated based on these calculation results.

[0011]

1 and 2 are a front view and a plan view, respectively, of a gravure engraving machine used in a gravure engraving system according to an embodiment of the present invention. 1 and 2, the gravure engraving machine 100 includes a bed 1, a headstock 2 fixed to the upper surface of the bed 1, a tailstock 3 arranged to face the headstock 2, and a table 4. Is equipped with. The tailstock 3 is movable in the left-right direction of the apparatus along a pair of guide rails 6 arranged on the upper surface of the bed 1. The tailstock 3 can be moved toward or away from the headstock 2 by a drive mechanism 9 including a motor and a belt provided on the side of the bed. The center 12 of the tailstock 3 can be retracted by a cylinder 13. The table 4 is movable in the left-right direction along a pair of guide rails 7 arranged on the upper surface of the bed 1. The table 4 is movable along the guide rails 7 by the ball screw 15 arranged between the pair of guide rails 7 and the drive motor 16 for driving the ball screws 15. The spindle 10 of the spindle stock 2 is rotated by a drive mechanism 11 including a drive motor and a belt. In such a configuration, the gravure cylinder 14 is supported between the main shaft 10 and the center 12 as shown by the chain double-dashed line in FIG.

An engraving head 21 is provided on the table 4 so as to be movable in the front-rear direction of the apparatus (direction perpendicular to the paper surface of FIG. 1). A guide rail 20 is provided on the upper surface of the table 4, and the engraving head 21 is moved by a drive mechanism including a ball screw 22 and a drive motor 23.

FIG. 3 is a perspective view showing a stylus provided on the engraving head 21 and its drive mechanism. In FIG. 3, the stylus 30 is fixed to the tip of a torsion shaft 31, and a diamond bite 32 is attached to one end thereof. The other end of the torsion shaft 31 is fixed to the fixed portion 33. In addition, a rotor 34 having a diamond shape in plan view is fixed to an intermediate portion of the torsion shaft 31. A laminated magnetic body (stator) 35 is arranged around the rotor 34 so as to sandwich the rotor 34, and a permanent magnet 36 for giving a magnetic force to the stator 35 is arranged on a side portion of the stator 35. . In addition, the rotor 34
A coil 37 is arranged around the rotor between the rotor 34 and the stator 35. In such a configuration, the coil 3
When the engraving signal is applied to 7, the stylus 30 vibrates in the direction of arrow B in the figure according to the frequency of the engraving signal.

FIG. 4 is an external view of the diamond cutting tool 32. In particular, FIG. 4 (a) is its front view, FIG. 4 (b) is its left side view, and FIG. 4 (c). It is the bottom view. As shown in FIG. 4, diamond bite 32
Has the shape of a triangular pyramid, and the vertex 32a of this triangular pyramid is
The surface of the gravure cylinder 14 is carved with.

The gravure engraving machine of the first embodiment constructed as described above engraves cells along the main scanning direction (circumferential direction of the gravure cylinder 14) shown in FIG. The engraving head 21 is fed at a predetermined pitch in the sub-scanning direction (direction parallel to the rotation axis of the gravure cylinder 14) to engrave cells in the next row. By repeating this,
An intaglio formed of a plurality of cells is formed on the surface of the gravure cylinder 14.

FIG. 6 is a block diagram showing an electrical configuration of a gravure engraving system using the gravure engraving machine 100 shown in FIGS. 1 and 2. In FIG. 6, the gravure engraving machine 100 is connected to a data creation device 201 including a personal computer or the like. The data creating device 201 includes a reading device 202 such as a scanner.
The other image system 203, an external storage device 204 such as a hard disk device, and an operation unit 205 such as a keyboard and a mouse are connected. Data creation device 20
1 creates image data for gravure plate making based on data read from a predetermined document by the reading device 202 and data obtained from other image systems 203. For example, the data creation device 201 obtains offset image data from another image system and performs offset / gravure conversion to create image data. The operator operates the operation unit 205 to input various data or instructions (for example, engraving conditions such as the number of lines and cell patterns (elongate, compressed, etc.)) to the data creating apparatus 201. Based on the input data or instruction from the operation unit 205, the data creating device 201 generates carry command data, sub-scanning command signal, and main scanning command signal together with the image data. These data and signals are given to the gravure engraving machine 100.

The gravure engraving machine 100 includes a density signal generating section 101, a carry signal generating section 102, a sub-scanning motor 103, a main scanning motor 104, an adding section 105, an engraving head 21, and a sub-scanning motor 107. , And a main scanning motor 108. The density signal generator 101 generates a density signal based on the image data provided from the data creation device 201. Carry signal generator 102
Determines the amplitude and the offset amount based on the carry command data given from the data creating device 201, and generates a carry signal. The density signal from the density signal generator 101 and the carry signal from the carry signal generator 102 are added by the adder 105 and then applied to the engraving head 21 as an engraving signal. The sub-scanning motor 107 is a motor for moving the engraving head 21 in the sub-scanning direction. The main scanning motor 108 is a motor for rotating the gravure cylinder 14. Sub-scanning motor controller 1
No. 03 changes the feed amount of the engraving head 21 in the sub-scanning direction according to engraving conditions such as the number of lines.
1 based on the sub-scanning command signal from the sub-scanning motor 10
7 is controlled. The main scanning motor control unit 104 changes the rotation speed of the gravure cylinder 14 according to the difference in the cell pattern and the number of lines, and thus controls the main scanning motor 108 based on the main scanning command signal from the data creation device 201. .

In this embodiment, as shown in FIG.
Among the values 0-256 that can be represented by 8 bits, the values 29-22
8 is used to express gradation. Here, the value 29 corresponds to the minimum density gradation and the value 228 corresponds to the maximum density gradation. Therefore, between the minimum density gradation and the maximum density gradation,
It is expressed by 199 gradation values.

Further, in the present embodiment, when engraving a large size cell, a part which communicates with each other, that is, a channel C (see FIG. 8A) is formed between the cells adjacent to each other in the main scanning direction. ing. By forming such a channel C, the flow of ink in the main scanning direction is improved,
The efficiency of filling the ink in each cell is improved. In order to form the channel C, as shown in FIG. 9, the level of the apex portion K of the engraving signal corresponding to the maximum density cell is set lower than the reference level R corresponding to the surface of the gravure cylinder. As a result, the width of the cell is widened, and a channel appears between cells adjacent in the main scanning direction.

FIG. 10 is a flow chart showing the operation of the gravure engraving system according to the above embodiment. This figure 1
The operation of 0 is mainly executed by the data creation device 201 of FIG. The operation of the above embodiment will be described below with reference to FIG.

First, the data creating device 201 selects and inputs a parameter required for correction from various preset parameters (step S1). The parameters input at this time are the maximum cell width W _MAX and the minimum cell width W _MAX.
And _MIN, and the maximum channel width C _{MA X,} a cell pitch P ₁ in the sub-scanning direction, a cell pitch P ₂ Doo in the main scanning direction. Here, the maximum cell width W _MAX is the maximum density gradation 228.
Is the width in the sub-scanning direction of the cell corresponding to, that is, the maximum density cell (see FIG. 7). The minimum cell width W _MIN is the width in the sub-scanning direction of the cell corresponding to the lowest density gradation 29, that is, the lowest density cell (see FIG. 7). Further, the maximum channel width C _MAX is the width of the channel C in the sub-scanning direction that occurs when engraving the maximum density cell (the maximum width of the channel C; FIG. 8).
(See reference).

Next, the data creation device 201 calculates a predetermined value necessary for area correction described later based on the various parameters input in step S1 (step S2).
Hereinafter, the predetermined value will be described in detail.

1. γ_C Calculation of this γ_C Is the gradation of the smallest cell when channel C appears
Value. FIG. 8A shows the top surface shape of the maximum concentration cell.
doing. In this case, the cell shape is the maximum cell width W_MAX 
And the maximum channel width C_MAX And On the other hand, FIG.
(B) Top view of the smallest cell when channel C appears
Shape. The cell width in this case is W _MAX -C_MAX 
Becomes Here, in general, the cell width W (W_MAX ≧ W ≧ W
_MIN ) Is proportional to the gradation γ (228 ≧ γ ≧ 29)
Therefore, the cell width W is calculated by the following equation (1). The following formula
In (1), (W_MAX -W_MIN ) / 199 is the unit
The cell width increment per gradation is shown.

[Equation 1]

Here, the minimum cell width W _MAX -C _MAX when the channel C appears is obtained by substituting γ _C (gray scale of the minimum cell when the channel C appears) into the above equation (1). It is calculated by the following equation (2).

[Equation 2]

When the gradation γ _C is obtained by modifying the above equation (2), the following equation (3) is obtained.

(Equation 3)

2. Calculation of f / e This value f / e is frequently used for calculation of area correction performed later. Therefore, by obtaining the value f / e in advance, the subsequent correction calculation is simplified. Where f
Is 1/2 of the cell width W when the channel C does not appear (when γ <γ _C ), and is calculated by the following equation (4).

(Equation 4)

On the other hand, e is 1/2 of the total amplitude α of the carry signal (see FIG. 9 (a)) and is calculated by the following equation (5).

(Equation 5)

Therefore, f / e is obtained by the following equation (6) from the above equations (4) and (5).

(Equation 6)

3. Calculation Formula of Cell Area A First, the cell area when the channel C does not appear (when γ _C > γ ≧ 29) will be described. Now, the cell width W (=
Considering the area of the cell having 2f), the cell area A
Is four times as large as the shaded area in FIG. In FIG. 11, the equation of the outer curve φ of the cell is expressed by the following equation (7).

(Equation 7)

The coordinate of the point x ₀ in FIG. 11 is obtained as the value of x when y = 0 in the above equation (7) and is represented by the following equation (8).

(Equation 8)

Therefore, the cell area A is obtained by the following equation (9).

[Equation 9]

Next, when channel C appears (228 ≧
The area of the cell in the case of γ ≧ γ _C ) will be described. In this case, as shown in FIG. 12, the cell area A is the sum of the cell original area (hatched area area) A ₃ and the channel area (dotted rectangular area) A _4. Become.
Here, the area A ₃ is obtained by substituting f = 2e into the above equation (9), and A ₃ = 2eP ₂ . On the other hand, the channel portion has a rectangular shape with one side length P ₂ and the other side length C, and the area A ₄ is A ₄ = P ₂ C. Therefore, the total cell area A is obtained by the following equation (10).

(Equation 10)

A cell area A having a predetermined cell width W (= 2f) is obtained by the above equations (9) and (10). Note that the gradation γ
Since the cell width W is determined by the cell area A,
Can be determined by

4. Calculation of Area Increment per Unit Gradation ΔA When the maximum cell area is A _MAX and the minimum cell area is A _MIN , the area increment ΔA per unit gradation is given by the following equation (11).
Is required.

[Equation 11]

In the above equation (11), the maximum cell area A _MAX is obtained by the following equation (12) by substituting W = W _MAX into the above equation (10).

(Equation 12)

Further, the minimum cell area A _MIN is _calculated by the following equation (1) by substituting f = f _MIN into the above equation (9).
Required in 3).

(Equation 13)

In the above equation (13), f _MIN / e
Is calculated by the following equation (14).

[Equation 14]

As described above, in step S2, the gradation γ _C of the minimum cell when the channel C appears, f / e,
Calculation formula of cell area A and area increment per unit gradation Δ
A and are required.

Next, the data creation device 201 creates a data conversion table for making the gradation of the original image data and the cell area into a linear relationship (step S3). The operation of creating the data conversion table will be described first by giving specific numerical values. In addition, each numerical value shown below is
It is pointed out in advance that the present invention is merely an example and the present invention is not limited to these numerical values.

As shown in FIG. 13, the gradation specified on the original image data (the image data fetched from the reading device 202 or the other image system 203) is 29 to 228.
Change to 199 steps. When the density on the original image data is not corrected and is given to the density signal generation unit 101 as it is, the cell area is 841 (= 29 ² ) to 51.
It changes in the range of 984 (= 228 ² ). If the cell area increases or decreases by (51984-841) / 199 = 257 per unit gradation, the cell area ideally changes with respect to the gradation of the original image data, as shown in FIG. That is, it is linearly proportional. For example, if the gradation of the original image data is 100, the ideal cell area is 841 + 257 (100-29) = 19088. The gradation of the original image data for this ideal area 19088 is 138, as shown in FIG.
In step S3, a table for performing such gradation conversion is created.

In step S3, the data creating device 2
01 is, first, by using the equations (9) and (10) obtained in step S2, each gradation γ = 29 of the original image data.
The cell areas A (29) to A (228) with respect to .about.228 are calculated to create a first list as shown in FIG. Next, the data creation device 201 calculates ideal cell areas A ′ (29) to A ′ (228) for each gradation γ = 29 to 228 of the original image data by using the following equation (15). , A second list as shown in FIG. 16 (b) is created. A ′ = ΔA (γ−29) + A _MIN (15) Next, the data creation device 201 outputs the corrected gradation value corresponding to each ideal cell area on the second list from the first list. By searching, a conversion table of gradation data as shown in FIG. 16C is created.

Next, the data creating device 201 inputs image data from the reading device 202 or another image system 203, and uses the data conversion table (see FIG. 16C) created in step S3 to create the image data. The gradation value is converted (step S4). As a result, the data creation device 2
From 01 to the density signal generation unit 101, gradation-corrected image data is output. Therefore, the cell area is linearly proportional to the gradation on the original image data.

The density signal generator 101 is based on the image data supplied from the data generator 201, and
A density signal as shown in (b) is generated. This density signal is added by the adder 105 to the carry signal generator 102.
Is added to the carry signal (see FIG. 9A) and applied as an engraving signal (see FIG. 9C) to the engraving head 21. The engraving head 21 reciprocally rotates the stylus 30 in the direction B of FIG. 3 according to the engraving signal supplied. At this time, the main scanning motor 108 rotates the gravure cylinder 14 in the main scanning direction. by this,
One row of cells are engraved along the main scanning direction. The sub-scanning motor 107 moves the engraving head 21 in the sub-scanning direction by a predetermined pitch P ₁ each time the engraving of cells for one row is completed. By repeating such an operation, a plurality of rows of cells are engraved on the gravure cylinder 14.

In the above embodiment, the cell area for each gradation when the original image data is not corrected is obtained by calculation. However, the cell area is measured by trial engraving in advance, and this measurement is performed. The value may be registered in the system and used.

In the above embodiment, the data conversion table is created in advance, and when the actual image data is input, the data conversion table is searched to obtain the corrected gradation. However, when the data creation device 201 is equipped with a high-speed CPU, it is possible to obtain the corrected gradation only by calculation when inputting image data without using such a data conversion table. Is also good.

Further, in the above-described embodiment, the stylus 30 is fed at a predetermined pitch in the sub-scanning direction every time the engraving of one row of cells in the main scanning direction is completed. However, the stylus 30 is always kept at a constant speed. The cells may be engraved in a spiral shape on the gravure cylinder 14 by sending the cells in the sub-scanning direction.

[0047]

According to the first aspect of the present invention, since the gradation of the original image data is corrected and then applied to the density signal generating means, it is possible to cope with the change in the gradation of the original image data. The cell area can be linearly proportional. As a result, it is possible to accurately control the print density without performing trial engraving as in the conventional case.

According to the second aspect of the present invention, when the original image data is directly applied to the density signal generating means, the area of the engraved cell and the gradation of the original image data change linearly. Since the gradation of the original image data is corrected based on the calculation result with the area of the engraved cell when proportional, the gradation of the original image data can be corrected easily and accurately.

[Brief description of the drawings]

FIG. 1 is a front view of a gravure engraving machine used in a gravure engraving system according to an embodiment of the present invention.

FIG. 2 is a plan view of a gravure engraving machine used in the gravure engraving system of one embodiment of the present invention.

3 is a perspective view showing a stylus provided on the engraving head 21 of FIG. 1 and a drive mechanism thereof.

4 is an external view of the diamond bite 32 of FIG.

FIG. 5 is a diagram for explaining a main scanning direction and a sub scanning direction with respect to a gravure cylinder.

6 is a block diagram showing an electrical configuration of a gravure engraving system using the gravure engraving machine shown in FIGS. 1 and 2. FIG.

FIG. 7 is a diagram for explaining gradation expression of image data adopted in the gravure engraving system of the present embodiment.

FIG. 8 is a diagram showing a relationship between a channel and a cell width generated between cells adjacent to each other in the main scanning direction in the present embodiment.

FIG. 9 is a waveform chart of various signals used in the gravure engraving system of the present embodiment.

FIG. 10 is a flowchart showing the operation of the gravure engraving system of this embodiment.

FIG. 11 is a diagram for explaining how to determine the cell area when the channel C does not appear.

FIG. 12 is a diagram for explaining how to determine the area of a cell when a channel C appears.

FIG. 13 is a diagram showing a state in which the cell area changes non-linearly with respect to the gradation of image data before correction.

FIG. 14 is a diagram showing a state in which the cell area changes linearly with respect to the gradation of the corrected image data.

FIG. 15 is a diagram showing a method for obtaining the gradation of image data after correction from the relationship between the gradation of image data before correction and the cell area.

FIG. 16 is a diagram showing a procedure of creating a conversion table of gradation data in the present embodiment.

FIG. 17 is a waveform diagram of various signals used in the conventional gravure engraving system.

FIG. 18 is a diagram showing a top surface shape of a cell engraved by a conventional gravure engraving system and an arrangement state thereof.

FIG. 19 is a view showing a top surface shape of a cell carved by a conventional gravure engraving system in a pseudo equivalent to another geometrical figure.

FIG. 20 is a diagram showing that the gradation of original image data and the cell area have a non-linear relationship.

[Explanation of symbols]

 14 ... Gravure cylinder 21 ... Engraving head 30 ... Stylus 32 ... Diamond bite 100 ... Gravure engraving machine 101 ... Density signal generating section 102 ... Carry signal generating section 103 ... Sub scanning motor control section 104 ... Main scanning motor control section 105 ... Addition section 107 ... Sub-scanning motor 108 ... Main-scanning motor 201 ... Data creation device

Claims (2)

[Claims] 1. A gravure engraving system for producing an intaglio plate for gravure printing by engraving a plurality of cells on the surface of a gravure cylinder, comprising: rotating means for rotating the gravure cylinder in a main scanning direction; Carry signal generating means for generating a sinusoidal carry signal having a frequency and a constant amplitude; density signal generating means for generating a density signal whose level changes according to the gradation of image data provided; By engraving the density signal, engraving signal generating means for generating an engraving signal, and by reciprocating vibration according to the engraving signal, with respect to the gravure cylinder rotating in the main scanning direction, a stylus for engraving cells, Stylus feeding means for feeding the stylus in the sub-scanning direction orthogonal to the main scanning direction, and original image data A gravure engraving system comprising: a gradation correcting unit that corrects the gradation of the original image data so that the area of the cell is linearly proportional to the change of the gradation and then supplies the density signal generating unit with the gradation correcting unit. . 2. The gradation correcting means comprises first calculating means for calculating, for each gradation, an area of a cell engraved when the original image data is given to the density signal generating means as it is, Second calculation means for calculating the cell area for each gradation when linearly proportional to the change in the gradation of the original image data, and based on the calculation results of the first and second calculation means hand,
The gravure engraving system according to claim 1, further comprising a third calculation unit that calculates a correction value for each gradation value of the original image data.