Patent Description:
Regarding offset printing machines, an offset printing machine has been known in which halftone dots according to a pattern to be printed are formed on a plate, ink is applied to the halftone dots, and the ink applied to the halftone dots are transferred to a paper so that the pattern according to the halftone dots is printed on the paper.

In such offset printing machine, print quality of a printed matter would gradually be deteriorated as proceeding printing, and the printed matter would become defective.

As one of causes of the deterioration in the print quality of the printed matter, it may be given that a halftone dot shape changes. For example, the halftone dot shape would differ from a predetermined shape due to whether the amount of dampening water supplied together with the ink to the plate is greater than or less than an appropriate value.

<CIT> discloses that an operator visually inspects the printed matter using a magnifying monitoring device such as a loupe to confirm the halftone dot shape and the like.

US patent <CIT> discloses a method of generating a halftone processing rule, in which a characteristic parameter acquisition chart including a pattern for acquiring characteristic parameters related to characteristics of the printing system is output, and the output characteristic parameter acquisition chart is read by image reading means. The characteristic parameters are acquired by analyzing the read image of the characteristic parameter acquisition chart, and halftone processing rules that define the processing contents of halftone processes used in the printing system are generated based on the acquired characteristic parameters.

Determination of the print quality of the printed matter by an operator's visual confirmation of the halftone dot shape, however, may require long work time for determining, take times to discover any sign of defective printed matter due to deterioration in the print quality of the printed matter, which would cause the defective printed matter.

In addition, for visually grasping the halftone dot shape, it is essential to acquire skills and know-how established by sufficient work experience.

Furthermore, when a roll paper is used as the paper to be printed, it is necessary to stop temporarily the offset printing machine and visually confirm the printed matter output from the offset printing machine using the magnifying monitoring device in order to confirm the halftone dot shape of the printed matter during printing, which would result in deterioration of the printing work efficiency.

The present invention has been made to solve the above problems, and its purpose is to provide a print quality control system for the offset printing machine that enables early detection of the sign of the defective printed matter due to deterioration in the print quality of the printed matter, and allows to control the print quality of the printed matter by confirming the halftone dot shape during printing while maintaining production speed without stopping or decelerating the offset printing machine, even when using the roll paper.

The present invention is related to a print quality control system for an offset printing machine which may be configured to form halftone dots for printing a pattern and a shape confirmation halftone dot on a plate cylinder of a printing unit and print a pattern and a shape confirmation halftone dot pattern on a paper, the print quality control system comprising an imaging device for capturing the shape confirmation halftone dot pattern printed on the paper and a determining device which are provided on a paper conveying path, wherein the determining device includes a calculation part configured to store the halftone dot shape on the plate of the plate cylinder as an ideal halftone dot shape of the printed halftone dot, superimpose and compare an outline of the shape confirmation halftone dot pattern captured by the imaging device with an outline of the ideal halftone dot shape during printing, and confirm a change in the halftone dot shape based on a change in outline of the halftone dot depending on whether the amount of dampening water which is supplied to the plate cylinder is greater or less than an appropriate value, and wherein the determining device is configured to perform machine learning based on information of a determination result of the change in the halftone dot shape confirmed by the calculation part, a printing condition controlled by an operator via a display part of the determining device and information of a printing result input by the operator to create a control model for predicting the change in the printing result based on the information, and notify the operator of or execute automatically a control for suppressing an occurrence of a defective printed matter, when it is confirmed from the output result of the control model that the change in the halftone dot shape is at a degree that print quality of a printed matter would be deteriorated and the defective printed matter would be caused if printing continues as it is.

According to the print quality control system for the offset printing machine of the present invention, the sign of defective printed matter due to deterioration in the print quality of printed matter can be detected at an early stage, and the halftone dot shape can be confirmed during printing while maintaining the production speed without stopping or decelerating the offset printing machine and the print quality of the printed matter can be controlled, even when roll paper is used.

An offset printing machine according to an embodiment of the present invention will be described with reference to <FIG> is an overall front view which shows an example of an offset printing machine to which a print quality control system of the present invention can be applied.

The offset printing machine <NUM> according to an embodiment of the present invention includes a paper feeding part <NUM> that feeds a paper W, a printing part <NUM> that performs printing on the paper W conveyed from the paper feeding part <NUM>, and a winding part <NUM> that winds up the paper printed by the printing part <NUM>.

The paper feeding part <NUM> may be constituted to feed the paper W rolled up in rolls, that is, a roll paper, toward the printing part <NUM>.

The paper feeding part <NUM> is not limited to this constitution and may have a constitution of a paper feeding part of a known printing machine, such as a constitution for feeding sheet.

The printing part <NUM> may be constituted of at least one or more printing units <NUM>. In each printing unit <NUM>, the printing is performed on the paper W using any ink. In the embodiment of <FIG>, four printing units <NUM> are provided, and each printing is performed using yellow (Y), cyan (C), magenta (M), and black (K) inks. All printing units <NUM> have the same constitution.

The number of printing units <NUM> used in the printing system of the present invention is not limited to that of the embodiment of <FIG>, the printing part <NUM> can be constituted of any number of printing units <NUM>, such as only one printing unit that performs the printing using black (K) ink. Further, available ink is not limited to the above yellow (Y), cyan (C), magenta (M), and black (K), and any color ink such as special color ink can be used.

The printing unit <NUM> is provided with a plate cylinder <NUM>, a blanket cylinder <NUM>, and an impression cylinder <NUM>. The plate cylinder <NUM> is provided with a plate (not shown), halftone dots (not shown) corresponding to a pattern are formed on the plate.

Rotations of the plate cylinder <NUM>, the blanket cylinder <NUM> and the impression cylinder <NUM> are controlled by drive motor (s) not shown. The paper W is conveyed between the blanket cylinder <NUM> and the impression cylinder <NUM>.

The printing is performed as in the following way. The ink and dampening water are supplied to the plate cylinder <NUM>, the ink is applied to the halftone dots on the plate, the ink is transferred from the plate cylinder <NUM> to the blanket cylinder <NUM>, and the printing is performed by transferring the ink from the blanket cylinder <NUM> to the paper W.

The winding part <NUM> winds the paper W printed by the printing part <NUM>.

The winding part <NUM> is not limited to this constitution and may have a constitution of a winding part of a known printing machine, such as a delivery device that delivers the paper W to another processing device or a sheet accumulation device.

The offset printing machine <NUM> to which the print quality control system of the present invention can be applied may not be limited to this constitution but also have any constitution, such as one in which a processing part to perform cutting and folding processing of the paper W is provided between the printing part <NUM> and the paper winding part <NUM>.

The print quality control system of the present invention can be applied regardless of types of paper W. Therefore, as the paper W, any material used in a known offset printing machine such as paper, film, or label paper can be used. Further, it can be used regardless of forms of continuous paper, sheet, or the like.

Next, an embodiment of the print quality control system of the present invention will be described.

As shown in <FIG>, a shape confirmation halftone dot <NUM> for confirming the halftone dot shape is formed on a plate <NUM> of the plate cylinder <NUM> of each printing unit <NUM>.

In the present embodiment, the shape confirmation halftone dot <NUM> is formed at a position away from halftone dots <NUM> corresponding to the pattern. For example, the halftone dots <NUM> corresponding to the pattern are formed at an axial middle portion of the plate cylinder <NUM> on the plate <NUM>, and the shape confirmation halftone dot <NUM> is formed on the plate <NUM> at an axial end of the plate cylinder <NUM>.

Then, when printing, ink is applied to the shape confirmation halftone dot <NUM> and the halftone dots <NUM> corresponding to the pattern in the same way.

In the present embodiment, the shape confirmation halftone dot <NUM> formed on the plate <NUM> of each printing unit <NUM> is formed at a position that is deviated in a rotational direction of each of plate cylinders <NUM>.

The position of shape confirmation halftone dot <NUM> is not limited to the position of <FIG>. For example, it may be formed, along the axial direction of the plate cylinder <NUM> at a position overlapping halftone dots <NUM> corresponding to the pattern in the axial direction of the plate cylinder <NUM> and a position different from the halftone dots <NUM> corresponding to the pattern in the rotational direction of the plate cylinder <NUM>.

In this case, the shape confirmation halftone dot <NUM> is printed on the printed paper W between the halftone dots <NUM> corresponding to the pattern in a paper conveying direction. Then, the shape confirmation halftone dots <NUM> formed on the plates <NUM> of each printing unit <NUM> are formed at positions deviated in the axial direction of the plate cylinder <NUM> for each printing unit <NUM>. Further, it may be formed at positions deviated in the rotational direction of the plate cylinder <NUM>.

When the label paper is used as the paper W, if the shape confirmation halftone dot <NUM> is printed on a place where stripping is performed by a stripping device provided in the processing part, it can be removed together with residue.

In the case of form printing that uses paper as the paper W, the same effect can be obtained by forming the shape confirmation halftone dot <NUM> on a part to be removed by a processing part such as a slitter or marginal hole processing device provided on a downstream side of the printing part <NUM>, or between the marginal holes.

Further, among halftone dots <NUM> corresponding to the pattern, a halftone dot at any position may be set in advance as the shape confirmation halftone dot <NUM>.

From this, since the shape confirmation halftone dot <NUM> is sequentially printed in different color at the end away from the pattern, each time when the pattern is sequentially printed on the paper W in different color at each printing unit <NUM>, a color pattern <NUM> and a plurality of shape confirmation halftone dot patterns <NUM> next to the pattern <NUM> are printed in different colors on the paper W printed as shown in <FIG>.

For example, a shape confirmation halftone dot pattern <NUM>-<NUM> printed with yellow (Y) ink, a shape confirmation halftone dot pattern <NUM>-<NUM> printed with cyan (C) ink, a shape confirmation halftone dot pattern <NUM>-<NUM> printed with magenta (M) ink, and a shape confirmation halftone dot pattern <NUM>-<NUM> printed with black (K) ink are arranged at intervals in the paper conveying direction.

As shown in <FIG>, the shape confirmation halftone dot pattern <NUM> printed on the paper W is captured by an imaging device <NUM> disposed opposite to a paper conveying path <NUM> in the winding part <NUM>.

As shown in <FIG>, the imaging device <NUM> is disposed opposite to the paper conveying path <NUM> and includes a camera <NUM> for capturing the shape confirmation halftone dot patterns <NUM> printed on the paper W, and lightings <NUM> that lighten up a portion to be captured by the camera <NUM>.

The camera <NUM> has high resolution performance. Specifically, when it has a resolution of <NUM>/pixel or higher, it can measure the halftone dot shape. In addition, when a target printing speed is set at <NUM>/min, a scan rate of about <NUM> would be required at <NUM>/pixel, so a selection of a camera and an adaption of an imaging method which satisfy this condition are required.

The image to be captured by the camera <NUM> may be a color image or a monochrome image. When it is the color image, the camera <NUM> can also be used as a density detecting camera.

When it is the monochrome image, it has smaller data amount than that of the color image, so it is capable of imaging at a high resolution even if the printing speed is high. When it becomes to be necessary to measure the density of each color in the case of the monochrome image, a density measurement camera may be provided separately from the camera <NUM> in the paper conveying path <NUM>.

An imaging direction 31a of the camera <NUM> is at a right angle to a paper surface of the paper W to be conveyed and is directed to the shape confirmation halftone dot pattern <NUM> on the paper W.

Two high-brightness lightings <NUM> that throw light on the shape confirmation halftone dot pattern <NUM> of the paper W are arranged close to the paper W, whose irradiation directions 32a are of an inverted V shape to throw light on the same position of the paper W at <NUM> degrees to the paper surface of the paper W.

The number of the high brightness lighting <NUM> is not limited to two, may be one or three or more, and the angle of the irradiation directions 32a to the paper surface of the paper W may not be limited to <NUM> degrees, it may be enough to throw light on the same position.

When the target printing speed is <NUM>/min, at <NUM>/pixel, an exposure time of 7usec or less is required, so it is necessary to select the lighting and optical conditions satisfying these conditions.

According to the imaging device <NUM> of this constitution, since the camera <NUM> is of high-resolution performance and the lightings <NUM> can realize brightness corresponding to a short exposure time due to the high resolution, the resolution of the image capturing the confirmation halftone dot pattern <NUM> of the paper W conveyed at a fast speed can become excellent.

Therefore, it can correspond to the offset printing machine <NUM> that is driven at high speed and has a high paper conveying speed.

The imaging device <NUM> is not necessary to capture the corresponding shape confirmation halftone dot <NUM> each time when the pattern <NUM> is printed. The capture timing may be set in advance, for example, such as capturing every <NUM> images, and the image may be captured at a specified timing.

A mounting position of the imaging device <NUM> may be movable in a paper width direction (axial direction of the plate cylinder <NUM>). An imaging position can be thereby adjusted according to the paper width of the paper W. Further, when the shape confirmation halftone dot <NUM> is formed along the axial direction of the plate cylinder <NUM>, the shape confirmation halftone dot <NUM> can be captured at any position in the paper width direction. Furthermore, the imaging device <NUM> can be automatically moved in the paper width direction, and the shape confirmation halftone dot patterns <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> of each color printed in the paper width direction may be captured sequentially at each set number of sheets.

A determining device for determining print quality of a printed matter based on the captured image will be described with reference to <FIG>.

As shown in <FIG>, the determining device <NUM> includes an image processing part <NUM>, a calculation part <NUM>, and a display part <NUM>.

The image of the shape confirmation halftone dot pattern <NUM> captured by the imaging device <NUM> is sent to the image processing part <NUM> for image processing. An image-processed image is sent to the calculation part <NUM> to confirm the halftone dot shape of the shape confirmation halftone dot pattern <NUM>.

Since the ink is applied to the shape confirmation halftone dot pattern <NUM> and the pattern <NUM> in the same condition, the halftone dot shapes of both would become the same, therefore, when the shape confirmation halftone dot pattern <NUM> has changed from a predetermined shape, the halftone dot shape of the pattern <NUM> would have changed as well.

When the calculation part <NUM> determines that the change in the halftone dot shape of the shape confirmation halftone dot pattern <NUM> is at a degree that the print quality of the printed matter would be deteriorated and a defective printed matter would be caused if the printing continues as it is, the display part <NUM> shows that the print quality has been deteriorated, as a sign that the defective printed matter will be caused. The display part <NUM> may be enough to be a display that allows the operator to sense the quality deterioration, such as an audio display or a character display.

According to this constitution, since the image captured by the imaging device <NUM> is processed by the image processing part <NUM> and calculated by the calculation part <NUM> to confirm a change in a halftone dot shape of the shape confirmation halftone dot pattern <NUM>, the change in the halftone dot shape can be confirmed in a short time, and from the result, since the sign can suggest that the defective printed matter will be caused, the sign of the defective printed matter due to deterioration in the print quality can be detected at an early stage.

The operator can obtain the sign of occurring of the defective printed matter from the indication of the display part <NUM>.

Moreover, since the imaging device <NUM> is provided opposite to the paper conveying path <NUM> of the offset printing machine <NUM> and the shape confirmation halftone dot pattern <NUM> of the conveyed printed matter is captured to confirm the change in the halftone dot shape, the halftone dot shape can be confirmed and the print quality of the printed matter can be determined during printing without stopping or decelerating the offset printing machine <NUM>, even when roll paper is used.

The change in the halftone dot shape of each shape confirmation halftone dot pattern <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, or <NUM>-<NUM> of each shape confirmation halftone dot <NUM> formed on the plate <NUM> of the plate cylinder <NUM> of each printing unit <NUM> is confirmed, and it is thereby determined whether the sign of occurring of the defective printed matter for each printing unit <NUM> exists, so by displaying the printing unit <NUM> in which the sign has appeared on the display part <NUM>, the operator can sense in which printing unit <NUM> the sign has appeared, and can control printing conditions such as the amount of dampening water in that printing unit <NUM> to achieve normal print quality.

For example, when it is determined that the change in the halftone dot shape of the shape confirmation halftone dot pattern <NUM>-<NUM> printed with yellow (Y) ink is the sign that the defective printed matter will be caused and it is displayed on the display part <NUM>, the printing conditions of the printing unit <NUM> printing with yellow (Y) ink is controlled.

Next, determination of the change in the halftone dot shape of the shape confirmation halftone dot pattern <NUM> will be described.

The shape confirmation halftone dot <NUM> will be described based on <FIG> schematically shows the shape confirmation halftone dot and may differ from the actual situation.

As shown in <FIG>, a plurality of shape confirmation halftone dots <NUM> are formed at intervals within a frame <NUM>. For example, the sum of the areas of all shape confirmation halftone dots <NUM> is set to be <NUM>% of the area within the frame <NUM>.

While the shape confirmation halftone dot <NUM> is a quadrangle, the control of the present invention can be performed with any shape such as a round shape or an oval shape.

The shape confirmation halftone dot pattern <NUM> printed on the paper will be described based on <FIG> schematically shows the shape confirmation halftone dot pattern and may differ from the actual situation.

As shown in <FIG>, the shape confirmation halftone dot patterns <NUM> as many as the shape confirmation halftone dots <NUM> are printed on the paper W.

Regarding the shape of the shape confirmation halftone dot pattern <NUM>, there are various shapes, such as a shape that is the same as, slightly different from, and greatly different from the shape confirmation halftone dot <NUM>.

The captured image of the imaging device <NUM> is the same as that shown in <FIG>, and the captured image is sent to the image processing part <NUM> for image processing.

The image processing part <NUM> processes the sent image to make the shape confirmation halftone dot pattern <NUM> constituted of only an outline, and sends an image of only the outline to the calculation part <NUM>.

Determination carried out in the calculation part <NUM> will be described based on <FIG>.

As shown in <FIG>, an outline 11a of the shape confirmation halftone dot <NUM> and an outline 21a of the shape confirmation halftone dot pattern <NUM> are superimposed and compared, and difference between the halftone dot shape of the shape confirmation halftone dot pattern <NUM> and the shape of the shape confirmation halftone dot <NUM>, that is, the change in the halftone dot shape of the shape confirmation halftone dot pattern <NUM> is confirmed.

When the confirmed change in the halftone dot shape is at a degree that the print quality of the printed matter would be deteriorated and the defective printed matter would be caused if printing continues as it is, it is determined as the sign that the defective printed matter will be caused. Then, the calculation part <NUM> indicates that the print quality has been deteriorated on the display part <NUM>. It should be noted that <FIG> schematically illustrates each outline 11a and 21a and may differ from the actual one.

The calculation part <NUM> performs a control for suppressing an occurrence of the defective printed matter as described later and notifies the operator of or automatically executes control contents.

The change in the halftone dot shape of the shape confirmation halftone dot pattern <NUM> is confirmed as follows.

A shape of the shape confirmation halftone dot <NUM> and a halftone dot shape of each confirmation halftone dot pattern <NUM> are compared, and a shape difference corresponding to each halftone dot is summed up, and when the summed shape differences become greater than or equal to a preset setting value, it is confirmed that the change in the halftone dot shape is the degree that the print quality of the printed matter would be deteriorated and the defective printed matter would be caused if printing continues as it is.

Numerical values obtained by capturing the shape confirmation halftone dot <NUM> include area, height, width, roundness, outline length, aspect ratio, ellipse approximation (long axis, short axis, angle), number of holes, and the like. One or more of these numerical values is used to confirm the halftone dot shape.

For example, when the halftone dot becomes to have a shape being extended in the paper conveying direction and shorten in the paper width direction, the roundness and aspect ratio becomes different, even if the area of the halftone dot is the same. Even in this case, the print quality may sometimes be deteriorated and the defective printed matter may be caused. Therefore, the occurrence of the defective printed matter can be predicted more accurately by measuring the shape other than the area of the halftone dot.

The set value may be set by experiment or experience so far, or the like.

More specifically, the area on which the shape confirmation halftone dot patterns <NUM> are printed is captured by the imaging device <NUM>.

In the example of <FIG>, while a region on which the shape confirmation halftone dot pattern <NUM> is printed is set as being at the width direction end of the paper W, it can be provided in any position. Further, it may be any region within the pattern <NUM>.

The image processing part <NUM> receives the captured image from the imaging device <NUM>, and extracts the shape confirmation halftone dot pattern <NUM> for confirming the halftone dot shape from the captured image.

Regarding the shape confirmation halftone dot pattern <NUM> to be extracted, the shape, size, density, and the like of the halftone dot to be extracted can be arbitrarily determined based on the performance of the imaging device <NUM>, printing conditions such as printing speed, and measurement data to be used for machine learning described later. By detecting more shape confirmation halftone dot patterns <NUM> and confirming changes in the halftone dot, the accuracy of the machine learning described later can be improved and the print quality of the printed matter can be determined more accurately.

Hereinafter, a determination method related to the outline of the captured shape confirmation halftone dot patterns <NUM> will be described.

The image processing part <NUM> determines the outline 21a of the shape confirmation halftone dot pattern <NUM> by binarizing the captured image. By binarization, the region on which the shape confirmation halftone dot patterns <NUM> are printed and a nonprinted region (the color region of the paper W, that is the background color) can be distinguished in the captured image.

Therefore, by binarization, the outline 21a of each shape confirmation halftone dot pattern <NUM> in the captured image can be calculated. Information of the outline 21a is used as detection data for the machine learning described later and for determining the print quality of the printed matter.

In binarizing, for distinguishing the color of any ink to be extracted from the color of the paper W that is the background color, setting values for binarization are set with respect to the RGB values or grayscale value of the extracted image, and those RGB values or grayscale value are compared with the setting values for binarization.

The setting values for binarization can be arbitrarily set according to printing conditions such as the color of any ink to be extracted and the color of paper W that is the background color.

In this embodiment, the image processing part <NUM> and the calculation part <NUM> are shown as being independent, but both processes may be performed with one device.

The resolution of the image captured by the imaging device <NUM> may be any resolution enabling to determine the outline 21a of the shape confirmation halftone dot pattern <NUM> calculated by binarizing.

The calculation part <NUM> determines the change in the shape of an arbitrary number of shape confirmation halftone dot pattern <NUM> in the image extracted by binarizing. The larger the number of the shape confirmation halftone dot pattern <NUM> to be determined becomes, the higher accuracy of the machine learning described later becomes, and the print quality of the printed matter can be determined with the more accuracy. In the present embodiment, the outline 21a is determined for all the shape confirmation halftone dot patterns <NUM> within the extracted image.

The calculation part <NUM> determines each halftone dot shape as follows.

The calculation part <NUM> stores the halftone dot shape on the plate <NUM> (the shape of the shape confirmation halftone dot <NUM>) as an ideal halftone dot shape of the printed halftone dot. The calculation part <NUM> compares the shape of each shape confirmation halftone dot pattern <NUM> determined by binarizing with the halftone dot shape on the plate <NUM>.

Measurement data to be used for comparison may be used_as follows based on the halftone dot shape to be used as the shape confirmation halftone dot pattern <NUM>.

When the halftone dot to be used is a square, as the measurement data, the area, the length (height, width) of each side, the ratio of each side, the deviation of each side to the halftone dot shape on the plate <NUM>, etc. are used as a feature amount of the outline 21a, based on the outline calculated from the captured image.

When the halftone dot to be used is circular, the area, roundness, ellipse approximation (long axis, short axis, angle), aspect ratio, outline length, etc. are used as the feature amount of the outline, based on the outline calculated from the captured image.

For the above measurement data, for example, when the halftone dot is a regular square and the deviation of each side to the halftone dot shape on the plate <NUM> is calculated as measurement data, four sides of the outline 21a calculated from the captured image are subdivided at any intervals, and the deviation from the halftone dot shape on the plate <NUM> to the outline 11a is calculated at each subdivided point. The calculated deviations are used as measurement data for determining the change in the halftone dot shape.

The determination of the halftone dot shape for the deviations means that, when any deviation exceeds a certain value, a convex change would be caused in the outline 21a and the larger the deviation value becomes, the larger the convex change becomes.

Also, a standard deviation may be calculated from the calculated deviations and the standard deviation may be compared with a set value of standard deviation. It means that the larger the value of the standard deviation becomes, the more distorted the outline 21a becomes.

For the above measurement data, for example, when the halftone dot is a perfect circle and the roundness is calculated as measurement data, the difference in outlines between the outline calculated from the captured image and the outline of the halftone dot shape of the plate <NUM>, or the distance between the two concentric geometric circles when the outline calculated from the captured image is put between the above two circles is calculated as roundness.

Calculated roundness may be used as measurement data for determining the change in the halftone dot shape. If the roundness is large, it means that the outline is out of the perfect circle and the outline is distorted.

It means that there is a tendency in which the more change in convex shape occurs and the greater the distortion of the outline 21a becomes, the lower the print quality and the defective printed matter would be resulted.

The measurement data showing the features of the above outline 21a can be used to determine the halftone dot shape by arbitrarily combining a plurality of different measurement data.

The calculation part <NUM> determines the sign of the occurrence of the defective printed matter as follows from the measurement data showing the change in the halftone dot shape calculated from the above outline 21a.

The calculation part <NUM> determines the degree of the change in the halftone dot shape using information, such as data concerning the operation status or the like of the offset printing machine <NUM> described later, information on the printing results input by the operator, and information from the machine learning described later, in addition to the measurement data.

The calculation part <NUM> determines the degree of change in the halftone dot shape for all the set shape confirmation halftone dot patterns <NUM> among the captured images. The calculation part <NUM> calculates the ratio of halftone dots whose degree of the shape change exceeds a set value for the total number of shape confirmation halftone dot pattern <NUM> that have been determined, and, when it is more than the set value of ratio, confirms that the halftone dot change has been at the degree that the print quality of the printed matter would be deteriorated and the defective printed matter would be caused, if the printing is continued as it is.

Each of the above setting values is set by experiment or experience so far, or the like. Alternatively, it can be set by learning by the machine learning described later.

In the above example, while a example is shown in which captured shape confirmation halftone dot patterns <NUM> are compared individually with the halftone dot shapes on the plate <NUM>, by taking a position of any one shape confirmation halftone dot pattern <NUM> included in the captured region as a reference and assuming the outlines of the plurality of shape confirmation halftone dot patterns <NUM> as one data, it can also be compared with the dotted shape on the plate <NUM> including a positional relationship between a plurality of halftone dots.

In this case, not only the individual shapes of the halftone dots but also the data obtained by comparing the relative position between the captured halftone dots and the relative position between the halftone dots on the plate <NUM> can be measurement data for determining the print quality. The number of the shape confirmation halftone dot patterns <NUM> that are to be assumed as one data can be set arbitrarily, and all the shape confirmation halftone dot patterns <NUM> included within the captured region can be assumed as one data.

Although the print quality has been conventionally determined by the area ratio of the halftone dot, according to the conventional determination of print quality by the area ratio of the halftone dot, for example, the determination by concentration, even if the outline of the halftone dot is distorted, it cannot be detected that the change has been caused in the halftone dot shape, if it is matched in area with the halftone dot on the plate. Thus, it could not be detected, even if there caused the change in the halftone dot shape that would affect the print quality.

According to the print quality control system of the offset printing machine <NUM> of the present invention, since the shape of each halftone dot can be accurately determined, it is possible to detect the changes in the halftone dot shapes and determine the sign of the defective printed matter accurately, that could not have been detected by conventional evaluation of print quality during printing.

Next, a control related to the machine learning will be described.

The determining device <NUM> of the print quality control system of the offset printing machine <NUM> of the present invention stores, as data for performing the machine learning, the outline of each calculated shape confirmation halftone dot patterns <NUM>, the printed halftone dot shape on the plate <NUM>, the measurement data, that are the area, the length (height, width) of each side, the ratio of each side, the deviation of each side to the halftone dot shape on the plate <NUM>, roundness, ellipse approximation (long axis, short axis, angle), aspect ratio, outline length, number of holes, etc., and the degree of change in each halftone dot shape calculated from the measurement data, the percentage of shape confirmation halftone dot patterns <NUM> whose change of degree exceeds the set value with respect to the total number, which have been used by the calculation part <NUM> as above mentioned.

Data storage may be performed by the determining device <NUM> or by any storage device provided independently of the determining device <NUM>.

As the initial stage of the machine learning, the result of the operator's determination of the occurrence of print quality deterioration of the printed matter is stored in association with the above data.

The determining device <NUM> performs the machine learning based on determination result data on the print quality input by the operator and the halftone dot shape detection data confirmed by the calculation part <NUM>, and creates and updates a control model that predicts changes in the halftone dot shape detection data and the printing result.

In other words, the determining device <NUM> confirms the change in the halftone dot shape by the image of the shape confirmation halftone dot pattern <NUM> captured by the imaging device <NUM> using the control model by the machine learning and, when the change in the halftone dot shape is at the degree that print quality of the printed matter would be deteriorated and the defective printed matter would be caused if printing continues as it is, can inform it the operator.

Further, the offset printing machine <NUM> may be configured to be automatically controlled according to the change in the halftone dot shape that would cause the defective printed matter.

Since the relationship between the change in the halftone dot shape and the printing result may be updated at any time, the sign of print quality deterioration can be detected with high accuracy.

As machine learning data, in addition to the above data concerning to the halftone dot shape and the print result data, the determining device <NUM> can further use any data from data or the like such as, paper width, paper type as the paper information, the amount of dampening water supplied at the start of printing, the amount of ink supplied at the start of printing, the information of the pattern to be printed, the printing speed during printing, the amount of dampening water supplied during printing, and the ink supply amount during printing data as an operation status of the offset printing machine <NUM>, halftone dot area ratio, ink concentration data as detection information of the printing result of the offset printing machine <NUM>, the dampening water temperature at the start of printing, the ink temperature at the start of printing, the swinging roller water flow temperature at the start of printing, the plate cylinder water flow temperature at the start of printing, the temperature in the factory at the start of printing, the humidity in the factory at the start of printing, the temperature of the dampening water during printing, the ink temperature during printing, the swinging roller water flow temperature during printing, the plate cylinder water flow temperature during printing, the temperature in the factory during printing, the humidity in the factory during printing as the information on the temperature and humidity of the offset printing machine <NUM>. Using these data on the offset printing machine <NUM> for the machine learning, influence on print quality that would change due to various environmental factors can be reflected in the control model.

The data to be used for the above machine learning are stored in associated with elapse time.

In the above description, while the control by edge AI in which the determining device <NUM> in the offset printing machine <NUM> performs the machine learning has been shown by taking as an example, the machine learning is not limited to this example but may use cloud Servers.

When using the cloud Servers, the determining device <NUM> transmits the above data to the cloud Servers via Internet.

The cloud Servers store the received data, perform the machine learning to create and update the control model, and output the result output by the control model to the offset printing machine <NUM> for the input data.

The offset printing machine <NUM> responds to the sign of the defective printed matter based on the result output from the cloud Servers.

The cloud Servers can also manage a plurality of offset printing machines <NUM> with one cloud Server. In this case, the control model can be built using the measurement data of the plurality of offset printing machines <NUM>.

The print quality control system of the present invention can be controlled using the machine learning by the above edge AI or a learnt control model prepared by the machine learning using the cloud Servers.

The determining device <NUM> does not perform the machine learning but applies data such as the outline 21a calculated by the calculation part <NUM> and operation status of the offset printing machine <NUM> to the control model, and responds to the sign of the defective printed matter that will be caused according to the output results.

Claim 1:
A print quality control system for an offset printing machine (<NUM>) which is configured to form halftone dots for printing a pattern and a shape confirmation halftone dot (<NUM>) on a plate cylinder (<NUM>) of a printing unit (<NUM>) and print a pattern and a shape confirmation halftone dot pattern (<NUM>) on a paper (W), the print quality control system comprising an imaging device (<NUM>) for capturing the shape confirmation halftone dot pattern (<NUM>) printed on the paper (W) and a determining device (<NUM>) which are provided on a paper conveying path (<NUM>),
wherein the determining device (<NUM>) includes a calculation part (<NUM>) configured to store the halftone dot shape on the plate (<NUM>) of the plate cylinder (<NUM>) as an ideal halftone dot shape of the printed halftone dot, superimpose and compare an outline of the shape confirmation halftone dot pattern (<NUM>) captured by the imaging device (<NUM>) with an outline of the ideal halftone dot shape during printing, and confirm a change in a halftone dot shape based on a change in outline of the halftone dot depending on whether the amount of dampening water which is supplied to the plate cylinder (<NUM>) is greater or less than an appropriate value, and
wherein the determining device (<NUM>) is configured to perform the machine learning based on information of a determination result of the change in the halftone dot shape confirmed by the calculation part (<NUM>), a printing condition controlled by an operator via a display part (<NUM>) of the determining device (<NUM>) and information of a printing result input by the operator to create a control model for predicting the change in the printing result based on the information, and notify the operator of or execute automatically a control for suppressing an occurrence of a defective printed matter, when it is confirmed from the output result of the control model that the change in the halftone dot shape is at a degree that print quality of a printed matter would be deteriorated and the defective printed matter would be caused if printing continues as it is.