Bending angle measuring device and bending angle measuring method

Abstract

To provide a bending angle measuring device that can accurately measure the bending angle of a workpiece. [Solution] The laser beam irradiation unit irradiates a linear laser beam onto the first flange on the front side and the second flange on the rear side of the workpiece. The camera 35 captures the reflected light of the laser beam irradiated onto the first and second flanges. The exposure time adjustment unit 321 adjusts the exposure time of the camera 35 so that the brightness distribution of the reflected light in each line is within a reference range. The image angle calculation unit 33 extracts pixels in the line image with the exposure time adjusted so that the brightness distribution of the reflected light is within a reference range. The image angle calculation unit 33 calculates the image angle of a straight line by linearly approximating the pixels of the extracted multiple lines. The bending angle conversion unit converts the image angle to the bending angle of the workpiece.

Description

Technical Field

[0001] The present invention relates to a bending angle measuring device and a bending angle measuring method.

Background Art

[0002] A press brake includes an upper table on which a punch is mounted and a lower table on which a die is mounted. The upper table is lowered onto the lower table, and a workpiece placed on the die is bent by sandwiching it between the punch and the die. The press brake may include a non-contact bending angle measuring device that measures the bending angle of the workpiece (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A non-contact bending angle measuring device irradiates a linear laser beam onto a workpiece, and a camera captures the reflected light of the laser beam irradiated onto the workpiece. The bending angle of the workpiece is measured based on the angle of a line image formed by the captured reflected light. The line image is formed by a plurality of pixels in each line within a frame. The bending angle measuring device selects any one pixel from the plurality of pixels in each line, and calculates the angle of a line connecting the pixels selected in the plurality of lines as the angle of the line image.

[0005] Patent Document 1 calculates the angle of a line image by selecting the central pixel in the brightness distribution of the line image for each line. Verification by the present inventors has revealed that this method of calculating the angle of a line image by selecting the central pixel in the brightness distribution may not accurately measure the bending angle of the workpiece. There is a need for a bending angle measuring device and bending angle measuring method that can accurately measure the bending angle of a workpiece. [Means for solving the problem]

[0006] A first aspect of one or more embodiments provides a bending angle measuring device comprising: a laser beam irradiation unit that irradiates a linear laser beam onto a first flange on the front side and a second flange on the rear side of a punch and a die in a workpiece that is sandwiched between a punch and a die and bent to a target bending angle; a camera that photographs the reflected light of the laser beam irradiated onto the first and second flanges; an exposure time adjustment unit that adjusts the exposure time when the camera photographs the reflected light of the laser beam; an image angle calculation unit that extracts pixels in the line image formed by the reflected light contained in the photographed image for each line in the frame of the image taken by the camera, and calculates a linear image angle by linearly approximating the pixels of the extracted plurality of lines; and a bending angle conversion unit that converts the image angle into the bending angle of the workpiece, wherein the exposure time adjustment unit adjusts the exposure time so that the brightness distribution of the reflected light in each line is within a reference range, and the image angle calculation unit extracts pixels in the line image when the exposure time has been adjusted so that the brightness distribution of the reflected light is within the reference range.

[0007] A second aspect of one or more embodiments provides a bending angle measurement method which involves irradiating a first flange on the front side and a second flange on the rear side of a punch and a die in a workpiece that is bent by being sandwiched between a punch and a die with linear laser light, capturing the reflected light of the laser light irradiated on the first and second flanges with a camera, adjusting the exposure time of the camera so that the brightness distribution of the reflected light in each line within the frame of the image captured by the camera is within a reference range, extracting pixels in the line image of the reflected light contained in the captured image for each line while the exposure time has been adjusted so that the brightness distribution of the reflected light is within the reference range, calculating the image angle of a straight line obtained by linearly approximating the pixels of the extracted plurality of lines, and converting the image angle into the bending angle of the workpiece. [Effects of the Invention]

[0008] According to one or more embodiments of the bending angle measuring device and bending angle measuring method, the bending angle of a workpiece can be accurately measured. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows an example of the overall configuration of a press brake equipped with a bending angle measuring device according to one or more embodiments. [Figure 2] Figure 2 is a perspective view showing angle sensors positioned in front of and behind the punch and die. [Figure 3] Figure 3 is a block diagram showing a bending angle measuring device according to one or more embodiments. [Figure 4] Figure 4 is a block diagram showing a specific configuration example of an operation instruction unit and an image angle calculation unit included in a bending angle measuring device according to one or more embodiments. [Figure 5] Figure 5 shows an example of the exposure time setting table before and after the update, which is set in the exposure time setting table provided in the operation instruction unit shown in Figure 4. [Figure 6]Figure 6 shows an example of a line image in which the bending angle of the workpiece cannot be measured with high precision due to a short exposure time. [Figure 7] Figure 7 is a characteristic diagram showing the luminance distribution between the horizontal pixel position and luminance value of a line at a certain vertical position in the line image shown in Figure 6. [Figure 8] Figure 8 shows an example of a line image in which the bending angle of the workpiece cannot be measured with high precision due to a long exposure time. [Figure 9] Figure 9 is a characteristic diagram showing the luminance distribution between the horizontal pixel position and luminance value of a line at a certain vertical position in the line image shown in Figure 8. [Figure 10] Figure 10 shows an example of a line image in which the bending angle of a workpiece can be measured with high precision by optimizing the exposure time. [Figure 11] Figure 11 is a characteristic diagram showing the luminance distribution between the horizontal pixel position and luminance value of a line at a certain vertical position in the line image shown in Figure 10. [Figure 12] Figure 12 schematically shows the brightness distribution of a line image that changes with exposure time. [Figure 13] Figure 13 shows the state after the pixel extraction unit shown in Figure 4 has extracted pixels for each line from the line image shown in Figure 10. [Figure 14] Figure 14 shows a straight line obtained by linearly approximating the multiple pixels shown in Figure 13, where the linear approximation section shown in Figure 4 is a straight line. [Figure 15] Figure 15 shows the image angle of the straight line approximated by the straight line shown in Figure 14. [Figure 16A] Figure 16A is a partial flowchart illustrating the operation of a bending angle measuring device according to one or more embodiments, and a bending angle measuring method according to one or more embodiments. [Figure 16B] Figure 16B, following Figure 16A, is a partial flowchart illustrating the operation of a bending angle measuring device according to one or more embodiments, and a bending angle measuring method according to one or more embodiments. [Modes for carrying out the invention]

[0010] Hereinafter, a bending angle measuring device and a bending angle measuring method according to one or more embodiments will be described with reference to the accompanying drawings.

[0011] First, using FIG. 1, an overall configuration example of a press brake 100 equipped with a bending angle measuring device according to one or more embodiments and its schematic operation will be described. As shown in FIG. 1, the press brake 100 includes an NC (Numerical Control) device 10 that functions as a control device for controlling the press brake 100. The part excluding the NC device 10 and the bending angle measuring device described later will be referred to as the press brake main body 101. The press brake 100 includes an upper table 1, a lower table 3, and left and right side plates 5R and 5L. An upper die holder 2 is attached to the upper table 1, and a lower die holder 4 is attached to the lower table 3.

[0012] The upper table 1 is configured to move up and down by hydraulic cylinders 6L and 6R provided on the left and right. The hydraulic cylinders 6L and 6R constitute a table lifting mechanism. The table lifting mechanism may include actuators other than the hydraulic cylinders 6L and 6R. The table lifting mechanism may be configured by other components than the hydraulic cylinders 6L and 6R. The table lifting mechanism lowers the upper table 1 closer to the lower table 3 or raises it away from the lower table 3.

[0013] A punch Tp, which is an upper die, is mounted on the upper die holder 2, and a die Td, which is a lower die, is mounted on the lower die holder 4. In FIG. 1, a modular type is shown in which the upper die holder 2 is integrally attached over the entire length of the lower end of the upper table 1, but an intermediate plate type in which a plurality of intermediate plates for mounting the punch Tp are attached in the longitudinal direction of the lower end of the upper table 1 may also be used. The intermediate plate is also an upper die holder.

[0014] Mounting a punch Tp on the upper table 1 means mounting the punch Tp on the upper die holder 2 or the intermediate plate. Mounting a die Td on the lower table 3 means mounting the die Td on the lower die holder 4. Two or more punches Tp may be mounted side by side on the upper table 1, and two or more dies Td may be mounted side by side on the lower table 3.

[0015] A back gauge 40 is positioned on the underside of the lower table 3. The back gauge 40 includes abutments 42a and 42b that move left and right along the back gauge carriage 41. Here, there are two abutments, 42a and 42b, but the number of abutments is not limited to two. The abutments 42a and 42b are configured to move in the height direction and the front-to-back direction as well.

[0016] Before the operator places the sheet metal W, which is the workpiece to be processed, onto the die Td and bends the sheet metal W by sandwiching it between the punch Tp and the die Td, the abutments 42a and 42b move to positions corresponding to the die Td. The operator places the sheet metal W on the die Td so that its rear end abuts against the abutments 42a and 42b. In other words, the abutments 42a and 42b act to determine the front-to-back position of the sheet metal W when it is placed on the die Td.

[0017] An operating pendant 7 is attached to the left side of the press brake 100 via an arm 7a, and has a display unit 71 and an operating unit 72 including a plurality of operating buttons. The operating pendant 7 is connected to the NC device 10. The NC device 10 is connected to a foot switch 8 which has an open foot switch 81 for raising the upper table 1 and a close foot switch 82 for lowering the upper table 1. When the operator steps on the close foot switch 82, the upper table 1 is lowered, and the sheet metal W is bent by being sandwiched between the punch Tp and the die Td. When the operator steps on the open foot switch 81, the upper table 1 is raised, and the bent sheet metal W can be removed.

[0018] In Figure 1, the bending angle measuring device is not shown. As shown in Figure 2, angle sensors 30F and 30R, which constitute part of the bending angle measuring device, are positioned in front of and behind the die Td, respectively. In Figure 2, the punch Tp is not shown. The front angle sensor 30F and the rear angle sensor 30R have substantially the same configuration. The angle sensors 30F and 30R are collectively referred to as angle sensor 30. In the configuration example shown in Figure 3, the angle sensor control device 20 and the angle sensors 30 constitute the bending angle measuring device. The angle sensor control device 20 includes a measurement instruction unit 21 and a bending angle conversion unit 22. The angle sensor control device 20 can be configured using computer equipment.

[0019] As shown in Figure 3, the angle sensor 30 comprises a sensor board 31, a laser diode 34, and a camera 35. The sensor board 31 has an operation instruction unit 32 and an image angle calculation unit 33. As shown in Figure 2, the housing 301 of the angle sensor 30 (30F and 30R) has a first housing section 315 for housing the sensor board 31 and the camera 35, and a second housing section 340 for housing the laser diode 34.

[0020] The laser diode 34 of the angle sensor 30F is housed in the second housing 340 and oriented toward the sheet metal W so as to irradiate the lower surface of the front flange Wf (first flange) of the sheet metal W with a linear laser beam (hereinafter referred to as line laser beam), as shown by the dashed line. The laser diode 34 of the angle sensor 30R is housed in the second housing 340 and oriented toward the sheet metal W so as to irradiate the lower surface of the rear flange Wr (second flange) of the sheet metal W with a line laser beam. In Figure 2, the illustration of the line laser beam irradiated by the laser diode 34 of the angle sensor 30R onto the rear flange Wr is omitted. The laser diode 34 is an example of a laser beam irradiation unit.

[0021] Camera 35 captures the reflected light of the line laser beam irradiated onto the front flange Wf and the rear flange Wr from a predetermined distance away from the laser diode 34. The camera 35 of angle sensor 30F is located to the left of the laser diode 34 when viewed from the angle sensor 30F towards the sheet metal W. Camera 35 is tilted at a 45-degree angle and captures the front flange Wf from the left side. The camera 35 of angle sensor 30R is located to the right of the laser diode 34 when viewed from the angle sensor 30R towards the sheet metal W. Camera 35 is tilted at a 45-degree angle and captures the rear flange Wr from the right side.

[0022] In Figure 3, the NC device 10 controls the press brake body 101 to bend the sheet metal W to a predetermined target bending angle, and then transmits a bending angle measurement request signal, workpiece material information indicating the material of the sheet metal W, and the target bending angle to the angle sensor control device 20. The workpiece material information indicates the material of the workpiece (sheet metal W), such as whether the sheet metal W is stainless steel, mild steel, or sheet metal with a protective film. The measurement instruction unit 21 transmits an instruction signal to the operation instruction unit 32 of the sensor board 31 to instruct the irradiation of line laser light and the capture of reflected light. The measurement instruction unit 21 transmits the workpiece material information and the target bending angle to the operation instruction unit 32.

[0023] Furthermore, the measurement instruction unit 21 transmits a threshold value corresponding to the workpiece material information to the image angle calculation unit 33 of the sensor substrate 31. Details of the threshold value corresponding to the workpiece material information will be described later.

[0024] When the operation instruction unit 32 receives an instruction signal from the angle sensor control device 20, it instructs the laser diode 34 to irradiate with line laser light and instructs the camera 35 to capture reflected light.

[0025] As shown in Figure 4, the operation instruction unit 32 includes an exposure time adjustment unit 321, an exposure time setting table holding unit 322, and a table update unit 323. As shown in Figure 5(a), the exposure time setting table holding unit 322 holds an exposure time setting table in which initial values ​​for exposure time are set corresponding to the material of the sheet metal W and the target bending angle of the sheet metal W. Here, as an example, the target bending angle is divided into angle groups of 10 degrees each. Figure 5(a) shows only the exposure time setting table when the sheet metal W is stainless steel with a mirror finish, but the exposure time setting table holding unit 322 also holds exposure time setting tables corresponding to other materials.

[0026] The reflectivity of line laser light differs between polished stainless steel and non-polished stainless steel. Therefore, the exposure time setting table holder 322 separately holds an exposure time setting table for polished stainless steel and an exposure time setting table for non-polished stainless steel.

[0027] Assuming the initial state of the sheet metal W before bending is 180 degrees, for example, if the target bending angle is large, such as less than 180 degrees or 170 degrees or more, the distance from the laser diode 34 to the sheet metal W is short, so the intensity of the line laser light irradiated onto the front flange Wf and rear flange Wr is large. For example, if the target bending angle is small, such as less than 100 degrees or 90 degrees or more (not shown in the figure), the distance from the laser diode 34 to the sheet metal W is long, so the intensity of the line laser light irradiated onto the front flange Wf and rear flange Wr is small. Therefore, the initial value of the exposure time is set to be longer for angle groups with smaller target bending angles.

[0028] The exposure time adjustment unit 321 selects an exposure time setting table corresponding to the material of the sheet metal W according to the input workpiece material information, and reads out an initial value for the exposure time according to the input target bending angle. The exposure time adjustment unit 321 controls the camera 35 so that the time for which the shutter of the camera 35 is open is set to the read initial value for the exposure time. Although the initial value for the exposure time is set to an optimal value in advance according to the material of the sheet metal W and the target bending angle, the reflected light of the line laser beam is not always captured in an appropriate state due to influences such as the environment in which the press brake 100 is installed.

[0029] Figure 6 shows frame F of an image captured of reflected light from a line laser beam when the sheet metal W is made of mirror-finish stainless steel, at a predetermined target bending angle, and with an exposure time of 2 ms. Frame F includes a high-brightness line RL2 as a line image formed by the reflected light. The brightness distribution between the horizontal pixel position and brightness value of a line at a certain vertical position in frame F is as shown in Figure 7. The captured image is assumed to have been converted into an 8-bit digital signal by an A / D converter (not shown). Verification by the inventor revealed that the high-brightness line RL2, which has the brightness value characteristics shown in Figure 7, is thin, and that the bending angle of the sheet metal W cannot be measured with high precision using the high-brightness line RL2. This indicates that the exposure time of 2 ms is too short.

[0030] Figure 8 shows frame F of an image captured from reflected line laser light when the exposure time was 8 ms. Frame F includes a high-brightness line RL8 as a line image formed by the reflected light. The brightness distribution of a line at a certain vertical position in frame F is as shown in Figure 9. Verification by the inventor revealed that the high-brightness line RL8, which has the brightness value characteristics shown in Figure 9, is thick, and that the bending angle of the sheet metal W cannot be measured with high precision using the high-brightness line RL8. This indicates that the exposure time of 8 ms is too long.

[0031] Figure 10 shows frame F of an image captured of reflected light from a line laser beam with an exposure time of 4 ms. Frame F includes a high-brightness line RL4 as a line image formed by the reflected light. The brightness distribution of a line at a certain vertical position in frame F is as shown in Figure 11. Verification by the inventors revealed that the high-brightness line RL4, which has the brightness value characteristics shown in Figure 11, has an appropriate thickness, and that the bending angle of the sheet metal W can be measured with high precision using the high-brightness line RL4. The exposure time of 4 ms in this case is the actual optimal value. Any high-brightness line will be referred to as RL.

[0032] The optimal exposure time varies depending on the material of the workpiece. Even with the same workpiece material, the optimal exposure time may differ due to factors such as the environment in which the press brake 100 is installed.

[0033] The exposure time adjustment unit 321 adjusts the exposure time so that the luminance distribution of reflected light in each line within frame F falls within a reference range. The image angle calculation unit 33 extracts pixels within the line image (high-luminance line RL) with the exposure time adjusted so that the luminance distribution of reflected light falls within a reference range. When the luminance distribution is within a reference range, it means that the shape or size (especially the horizontal width) of the portion of the luminance distribution with a luminance value above the threshold TH described later is within the reference range. In this way, the bending angle measuring device can accurately measure the bending angle of the sheet metal W.

[0034] In detail, the image angle calculation unit 33 measures the bending angle of the sheet metal W as follows. As shown in Figure 4, the image angle calculation unit 33 includes an extraction pixel position determination unit 331, a pixel extraction unit 332, a linear approximation unit 333, and a linear angle calculation unit 334. The extraction pixel position determination unit 331 includes a brightness integrated value calculation unit 3311, a half-width calculation unit 3312, and a half-width adjustment unit 3313. The extraction pixel position determination unit 331 controls the exposure time adjustment unit 321 to optimize the exposure time when the camera 35 captures the reflected light of the line laser beam as follows. Furthermore, with the exposure time adjustment unit 321 controlled to optimize the exposure time, the extraction pixel position determination unit 331 determines the extraction pixel position for each line in the frame F to extract one pixel within the high-brightness line RL.

[0035] Figure 12 schematically shows the luminance distribution of the high-luminance line RL, which changes according to the exposure time, as shown in Figures 7, 9, and 11. The luminance integrated value calculation unit 3311 calculates an integrated value by integrating luminance values ​​that are equal to or greater than a predetermined luminance value in the luminance distribution of each line, with the threshold value TH being the threshold value. If the sheet metal W is mirror-finished stainless steel, the threshold value TH should be set to 75% of the maximum luminance value, and for other workpiece materials, it should be set to 50% of the maximum luminance value. A relatively high luminance value is used as the threshold value TH when the sheet metal W is mirror-finished stainless steel because the luminance of the high-luminance line RL becomes very high.

[0036] As shown in Figure 12, the luminance values ​​in the luminance distribution are such that the luminance value at the first pixel Px1 becomes the threshold TH from a luminance value below the threshold TH, and the luminance value at the second pixel Px2 becomes the threshold TH from a luminance value above the threshold TH. The first pixel Px1 is at the first pixel position P1, and the second pixel Px2 is at the second pixel position P2. The cumulative value of luminance values ​​above the threshold TH corresponds to the area of ​​the hatched region Aac shown in Figure 12.

[0037] The half-width calculation unit 3312 calculates the half-width HW for each line from the first pixel position P1 or the second pixel position P2 to the third pixel position P3 where a vertical line Lv is located that divides the integrated value in half horizontally. Region Aac is divided by the vertical line Lv into a first region Ar1 and a second region Ar2, both of the same area. As described above, the camera 35 of the angle sensor 30F is located to the left of the laser diode 34 and tilted to the right, so it is preferable to set the vertical line Lv with respect to the first pixel position P1 as the reference and calculate the half-width HW, as shown in Figure 12. The camera 35 of the angle sensor 30R is located to the right of the laser diode 34 and tilted to the left, so it is preferable to set the vertical line Lv with respect to the second pixel position P2 as the reference and calculate the half-width HW, the opposite of Figure 12.

[0038] In the high-luminosity line RL2, which cannot measure the bending angle of the sheet metal W with high precision as shown in Figure 7, the half-width HW is narrow. In the high-luminosity line RL8, which cannot measure the bending angle of the sheet metal W with high precision as shown in Figure 9, the half-width HW is wide. In the high-luminosity line RL4, which can measure the bending angle of the sheet metal W with high precision as shown in Figure 11, the half-width HW is neither too narrow nor too wide, but has an appropriate width.

[0039] Verification by the inventors revealed the following: The half-width HW obtained by dividing the area of ​​region Aac, which is the integrated value obtained by accumulating the luminance values ​​above the threshold TH of the luminance distribution in each line of the high-luminance line RL, into two parts affects whether or not the bending angle of the sheet metal W can be measured with high accuracy. If the half-width HW is within a reference range, which is the width obtained by adding a positive or negative error to a predetermined reference value, the high-luminance line RL becomes of an appropriate thickness, and the bending angle of the sheet metal W can be measured with high accuracy. The error may be zero. The half-width HW being within the reference range means that in each line, the number of pixels from the first pixel position P1 or the second pixel position P2 to the third pixel position P3 is within a predetermined number of pixels.

[0040] The half-width adjustment unit 3313 controls the exposure time adjustment unit 321 so that the half-width HW is within the reference range. As a result of the half-width adjustment unit 3313 controlling the exposure time adjustment unit 321, when the half-width calculation unit 3312 calculates a half-width HW within the reference range, the extracted pixel position determination unit 331 determines the third pixel position P3 as the extracted pixel position within the high-luminance line RL. The half-width adjustment unit 3313 instructs the pixel extraction unit 332 to specify the extracted pixel position. The pixel extraction unit 332 extracts the pixel at the instructed extracted pixel position (third pixel position P3).

[0041] Figure 13 shows the extracted pixels at the third pixel position P3 of each line in the high-luminance line RL4 shown in Figure 10. In Figure 13, the high-luminance line RL4 is shown in black, and the extracted pixels Pxe are shown as white circles. In Figures 13 and 14, for the sake of illustration simplicity, the number of extracted lines is shown as fewer extracted pixels Pxe than the actual number. As shown in Figure 14, the linear approximation unit 333 generates a linear line Ls by linearly approximating all extracted pixels Pxe of the multiple lines extracted from the high-luminance line RL4, for example, using the least squares method. In Figure 14, the extracted pixels Pxe are shown as black circles. As shown in Figure 15, the linear angle calculation unit 334 calculates the image angle φ of the linear line Ls with respect to the horizontal direction.

[0042] Returning to Figure 3, the image angle calculation unit 33 of angle sensors 30F and 30R transmits the calculated image angle φ of the straight line Ls to the bending angle conversion unit 22 of the angle sensor control device 20. The bending angle conversion unit 22 converts the two image angles φ calculated by the image angle calculation unit 33 of angle sensors 30F and 30R into the bending angle θ of the sheet metal W shown in Figure 2 and transmits it to the NC device 10. The NC device 10 compares the target bending angle with the actual bending angle θ of the sheet metal W bent to the target bending angle. Depending on the comparison result, the NC device 10 can control the press brake body 101 to bend the sheet metal W even closer to the target bending angle. Furthermore, the NC device 10 can control the press brake body 101 to bend the sheet metal W even closer to the target bending angle during subsequent bending operations.

[0043] If the target bending angle and the bending angle θ are within a predetermined error range, the NC device 10 may supply an update instruction signal via the measurement instruction unit 21 to the table update unit 323, instructing it to update the initial value of the exposure time in the exposure time setting table shown in Figure 5(a). As shown in Figure 4, when the update instruction signal is input to the table update unit 323, the table update unit 323 overwrites the initial value of the exposure time set in the exposure time setting table with the updated value. The updated value indicates an exposure time different from the exposure time indicated by the preset initial value. Figure 5(b) shows the state in which the initial value of the exposure time for each target bending angle has been overwritten with the updated value.

[0044] When the table update unit 323 updates the exposure time setting table, the latest exposure time is set in the exposure time setting table to obtain a bending angle θ within a predetermined error range relative to the target bending angle. Therefore, the bending angle measuring device can always accurately measure the bending angle θ of the sheet metal W.

[0045] As described above, the optimal exposure time may differ depending on the environment in which the press brake 100 is installed. Therefore, it is preferable that the exposure time setting table holder 322 has an exposure time setting table set for each user who uses the press brake 100. It is also preferable that the exposure time setting table holder 322 has an exposure time setting table set for each factory in which the press brake 100 is installed. The amount of sunlight entering the factory changes depending on the position of the sun. Even in the same factory, different exposure time setting tables may be set for different time periods. For example, an exposure time setting table for the morning and an exposure time setting table for the afternoon may be set.

[0046] When the sheet metal W has a protective film attached, the sheet metal W may be bent with the press brake 100 with the protective film facing downwards, or with the protective film facing upwards. In the former case, the high-brightness line RL is formed on the protective film surface. In the latter case, the high-brightness line RL is formed on the metal surface where the protective film is not attached. Therefore, it is preferable that the exposure time setting table holder 322 be equipped with an exposure time setting table not only for the metal surface but also for the protective film surface.

[0047] The operation of the bending angle measuring device according to one or more embodiments, and the bending angle measuring method according to one or more embodiments, will be further explained using the flowcharts shown in Figures 16A and 16B. In Figure 16A, when processing starts due to power being turned on to the press brake 100, the angle sensor control device 20 determines in step S1 whether or not a bending angle measurement request has been made from the NC device 10. If no bending angle measurement request has been made from the NC device 10 (NO), the angle sensor control device 20 repeats the process in step S1.

[0048] If the NC device 10 requests measurement of the bending angle in step S1 (YES), the angle sensor control device 20 instructs the angle sensor 30 to irradiate and capture line laser light in step S2. In step S3, the angle sensor 30 irradiates the sheet metal W with line laser light and captures the reflected light. In step S4, the luminance integration value calculation unit 3311 in the image angle calculation unit 33 of the angle sensor 30 calculates an integrated value by accumulating luminance values ​​that are equal to or greater than the threshold TH for each line. In step S5, the half-width calculation unit 3312 calculates the area-based half-width HW of the integrated value.

[0049] In step S6, the half-width adjustment unit 3313 determines whether the half-width HW is within the reference range. If the half-width HW is not within the reference range (NO), the half-width adjustment unit 3313 controls the exposure time adjustment unit 321 in step S7 to adjust the exposure time of the camera 35. The half-width adjustment unit 3313 repeats the processes in steps S6 and S7 until the half-width HW is within the reference range in step S6. If the half-width HW is within the reference range in step S6 (YES), the pixel extraction unit 332 extracts pixels at the pixel positions (third pixel positions P3) of the half-width HW in each line in step S8. In step S9, the linear approximation unit 333 linearly approximates the multiple pixels extracted in step S8.

[0050] In Figure 16B, the linear angle calculation unit 334 calculates the image angle φ of the linearly approximated line in step S10. The image angle calculation unit 33 transmits the image angle φ to the angle sensor control device 20. In step S11, the bending angle conversion unit 22 converts the image angle φ obtained by the two angle sensors 30F and 30R into the bending angle θ of the sheet metal W. In step S12, the angle sensor control device 20 transmits the bending angle θ to the NC device 10. In step S13, the NC device 10 determines whether the bending angle θ is within a predetermined error range with respect to the target bending angle. If the bending angle is within a predetermined error range with respect to the target bending angle, the NC device 10 instructs the table update unit 323 to update the exposure time setting table.

[0051] The table update unit 323 updates the exposure time in the exposure time setting table in step S14, in accordance with instructions from the NC device 10. After that, the process proceeds to step S15. If the bending angle in step S13 is not within a predetermined error range relative to the target bending angle (NO), the NC device 10 does not instruct the table update unit 323 to update the exposure time setting table, and the process proceeds to step S15.

[0052] In step S15, the bending angle measuring device determines whether or not to terminate its operation by cutting off the power to the press brake 100, etc. If it does not terminate its operation (NO), the bending angle measuring device repeats the process from step S1 onwards. If it terminates its operation (YES), the bending angle measuring device terminates the process.

[0053] As described above, according to the bending angle measuring device and bending angle measuring method of one or more embodiments, the bending angle θ of the sheet metal W can be accurately measured.

[0054] In the example configuration of the bending angle measuring device shown in Figure 3, an image angle calculation unit 33 is provided on the sensor substrate 31 within the angle sensor 30. The image angle calculation unit 33 may also be provided within the angle sensor control device 20. Alternatively, the same functions as the angle sensor control device 20 may be provided within the NC device 10, or the same functions as the angle sensor control device 20 and the image angle calculation unit 33 may be provided within the NC device 10. The NC device 10 may also have the function of the operation instruction unit 32.

[0055] The present invention is not limited to the one or more embodiments described above, and can be modified in various ways without departing from the spirit of the invention. [Explanation of symbols]

[0056] 1 Upper table 2 Upper mold holder 3 Lower table 4. Lower mold holder 5L,5R side plate 6L, 6R Hydraulic Cylinders 7 Operation Pendant 8 Footswitches 10 NC device 20 Angle sensor control device 21 Measurement instruction section 22 Bending angle conversion section 30, 30F, 30R Angle Sensor 31 Sensor board 32 Operation instruction section 33 Image Angle Calculation Unit 34. Laser diode (laser light irradiation part) 35 Camera 40 Back Gauge 41 Back Gauge Carriage 42a, 42b Nose 100 Press Brake 101 Press brake body 331 Extraction pixel position determination unit 332 Pixel Extraction Unit 333 Linear approximation part 334 Linear Angle Calculation Unit 321 Exposure time adjustment unit 322 Exposure time setting table holding unit 323 Table Update Section 3311 Luminance integrated value calculation unit 3312 Half width calculation part 3313 Half width adjustment section Td Die Tp Punch W Sheet metal (work) Wf Front flange (first flange) Wr Rear flange (second flange)

Claims

1. A laser beam irradiation unit that irradiates a linear laser beam onto the first flange on the front side and the second flange on the rear side of the punch and die of a workpiece that has been sandwiched between the punch and die and bent to a target bending angle, A camera for capturing the reflected light of the laser beam irradiated onto the first and second flanges, An exposure time adjustment unit adjusts the exposure time when the camera captures the reflected light of the laser beam, An image angle calculation unit that extracts pixels from the line image formed by the reflected light contained in the captured image for each line in the frame of the image captured by the camera, and calculates the image angle of a straight line by approximating the pixels of the extracted multiple lines with a straight line, A bending angle conversion unit that converts the aforementioned image angle into the bending angle of the workpiece, Equipped with, The exposure time adjustment unit adjusts the exposure time so that the brightness distribution of the reflected light in each line falls within a reference range. The image angle calculation unit extracts pixels within the line image when the exposure time is adjusted so that the brightness distribution of the reflected light falls within the reference range. Bending angle measuring device.

2. The image angle calculation unit, Using a predetermined luminance value in the luminance distribution of each line as a threshold, an integrated value is calculated by accumulating luminance values ​​that are equal to or greater than the threshold. In each of the lines, the half-width is calculated from the first pixel position where the luminance value of the luminance distribution changes from a luminance value below the threshold to the threshold, or from the second pixel position where the luminance value changes from a luminance value above the threshold to the threshold, to the third pixel position where a vertical line is located that divides the integrated value in half horizontally. The exposure time adjustment unit is controlled so that the exposure time becomes such that the half-width is within the standard range. The pixels at the third pixel position obtained within the line image are extracted when the exposure time is adjusted so that the half-width is within the width of the reference range. The bending angle measuring device according to claim 1.

3. The bending angle measuring device according to claim 1 or 2, wherein the exposure time adjustment unit refers to an exposure time setting table in which the exposure time of the camera is set in correspondence with the material of the workpiece and the angle group obtained by dividing the target bending angle into predetermined angle groups, and adjusts the exposure time of the camera to the exposure time selected based on the exposure time setting table.

4. The bending angle measuring device according to claim 3, further comprising a table updating unit that updates the exposure time in the exposure time setting table to the different exposure time when the exposure time adjustment unit adjusts the exposure time of the camera to an exposure time different from the exposure time preset in the exposure time setting table.

5. A linear laser beam is irradiated onto the first flange on the front side and the second flange on the rear side of the punch and die of a workpiece that has been bent by being sandwiched between the punch and die. The reflected light of the laser beam irradiated onto the first and second flanges is captured by a camera. The exposure time of the camera is adjusted so that the brightness distribution of the reflected light in each line within the frame of the image captured by the camera falls within a standard brightness range. With the exposure time adjusted so that the brightness distribution of the reflected light falls within the reference range, pixels in the line image formed by the reflected light contained in the captured image are extracted for each line. The image angle of the straight line obtained by linearly approximating the pixels of the extracted multiple lines is calculated. Convert the aforementioned image angle to the bending angle of the workpiece. Method for measuring bending angle.

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