Bending angle measuring device and bending angle measuring method

Abstract

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

[0002] A press brake has an upper table on which a punch is attached and a lower table on which a die is attached, and the upper table is lowered onto the lower table to sandwich and bend a workpiece placed on the die between the punch and the die. Press brakes are sometimes equipped with 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] Japanese Patent Application Publication No. 2019-10666 Summary of the Invention [Problem 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 device measures the bending angle of the workpiece based on the angle of the linear image formed by the captured reflected light. The linear image is formed by multiple pixels on each line within a frame. The bending angle measuring device selects one pixel from the multiple pixels on each line and calculates the angle of the line image by connecting the selected pixels on the multiple lines.

[0005] In Patent Document 1, the angle of a line image is calculated by selecting the central pixel in the luminance distribution of the line image for each line. Through verification by the inventors, it became clear that the method of calculating the angle of a line image by selecting the central pixel in the luminance distribution may not be able to accurately measure the bend angle of a workpiece. Therefore, there is a need for a bend angle measurement device and a bend angle measurement method that can accurately measure the bend angle of a workpiece. [Means for solving the problem]

[0006] a camera that captures images of the reflected light of the laser light irradiated to the first and second flanges; an exposure time adjustment unit that adjusts an exposure time when the camera captures the reflected light of the laser light; an image angle calculation unit that extracts pixels in a line image formed by the reflected light included in the captured image for each line within a frame of the image captured by the camera and calculates an image angle of a line obtained by linearly approximating the pixels of the extracted multiple lines; and a bend angle conversion unit that converts the image angle into a bend angle of the workpiece, wherein the exposure time adjustment unit adjusts the exposure time so that a luminance distribution of the reflected light for each line falls within a reference range, and the image angle calculation unit extracts the pixels in the line image with the exposure time adjusted so that the luminance distribution of the reflected light falls within the reference range.

[0007] A second aspect of one or more embodiments is a method for forming a film sandwiched between a punch and a die. , so that the target bending angle is achieved.The present invention provides a bending angle measurement method that irradiates a linear laser beam onto a first flange on the front side of the punch and the die and a second flange on the rear side of the bent workpiece, captures the reflected light of the laser beam irradiated onto the first and second flanges with a camera, adjusts the exposure time of the camera so that the luminance distribution of the reflected light on each line within a frame of the image captured by the camera falls within a reference range, extracts pixels from a line image of the reflected light included in the captured image for each line in a state in which the exposure time has been adjusted so that the luminance distribution of the reflected light falls within the reference range, calculates an image angle of a straight line obtained by linearly approximating the pixels of the extracted multiple lines, and converts the image angle into a bending angle of the workpiece. [Effects of the Invention]

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

[0009] [Figure 1] FIG. 1 is a diagram showing 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] FIG. 2 is a perspective view showing angle sensors disposed in front of and behind the punch and die. [Figure 3] FIG. 3 is a block diagram illustrating a bend angle measurement device according to one or more embodiments. [Figure 4] FIG. 4 is a block diagram showing a specific example of the configuration of an operation instruction unit and an image angle calculation unit included in the bending angle measurement device according to one or more embodiments. [Figure 5] FIG. 5 is a diagram showing an example of an exposure time setting table before and after updating set in the exposure time setting table provided in the operation instruction unit shown in FIG. [Figure 6] FIG. 6 is a diagram showing an example of a line image in which the bending angle of the workpiece cannot be measured with high accuracy due to a short exposure time. [Figure 7] FIG. 7 is a characteristic diagram showing the luminance distribution formed by the horizontal pixel position and luminance value of a line at a certain vertical position in the line image shown in FIG. [Figure 8] FIG. 8 is a diagram showing an example of a line image in which the bending angle of the workpiece cannot be measured with high accuracy due to a long exposure time. [Figure 9] FIG. 9 is a characteristic diagram showing the luminance distribution formed by the horizontal pixel position and luminance value of a line at a certain vertical position in the line image shown in FIG. [Figure 10] FIG. 10 is a diagram showing an example of a line image that allows the bending angle of a workpiece to be measured with high accuracy by optimizing the exposure time. [Figure 11] FIG. 11 is a characteristic diagram showing the luminance distribution formed by the horizontal pixel position and luminance value of a line at a certain vertical position in the line image shown in FIG. [Figure 12] FIG. 12 is a diagram schematically showing the luminance distribution of a line image that changes depending on the exposure time. [Figure 13] FIG. 13 is a diagram showing a state in which the pixel extracting unit shown in FIG. 4 extracts pixels of each line from the line image shown in FIG. [Figure 14] FIG. 14 is a diagram showing a straight line obtained by linear approximation of the plurality of pixels shown in FIG. 13 by the straight line approximation unit shown in FIG. [Figure 15] FIG. 15 is a diagram showing the image angle of the straight line approximated in FIG. [Figure 16A] FIG. 16A is a partial flow chart illustrating the operation of one or more embodiments of a bend angle measurement device and one or more embodiments of a bend angle measurement method. [Figure 16B] Following FIG. 16A, FIG. 16B is a partial flowchart illustrating the operation of one or more embodiments of a bend angle measurement device and one or more embodiments of a bend angle measurement method. DETAILED DESCRIPTION OF THE INVENTION

[0010] Bending angle measuring devices and bending angle measuring methods according to one or more embodiments will be described below with reference to the accompanying drawings.

[0011] First, an example of the overall configuration and schematic operation of a press brake 100 equipped with a bending angle measuring device according to one or more embodiments will be described using Figure 1. As shown in Figure 1, the press brake 100 is equipped with an NC (Numerical Control) device 10 that functions as a control device for controlling the press brake 100. The parts excluding the NC device 10 and the bending angle measuring device (described later) will be referred to as a press brake main body 101. The press brake 100 is equipped with 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 be raised and lowered by hydraulic cylinders 6L and 6R provided on the left and right sides. 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 also be configured with actuators other than the hydraulic cylinders 6L and 6R. The table lifting mechanism lowers the upper table 1 so that it approaches the lower table 3, or raises it so that it moves away from the lower table 3.

[0013] A punch Tp, which is an upper die, is attached to the upper die holder 2, and a die Td, which is a lower die, is attached to the lower die holder 4. Fig. 1 shows a modular type in which the upper die holder 2 is attached integrally along the entire length of the lower end of the upper table 1, but it may also be an intermediate plate type in which multiple intermediate plates for attaching punches Tp are attached in the longitudinal direction of the lower end of the upper table 1. The intermediate plates are also upper die holders.

[0014] Mounting a punch Tp on the upper table 1 means mounting the punch Tp on the upper die holder 2 or 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 disposed on the rear side of the lower table 3. The back gauge 40 has stoppers 42a and 42b that move left and right along a back gauge carriage 41. Here, there are two stoppers, 42a and 42b, but the number of stoppers is not limited to two. The stoppers 42a and 42b are configured to move in the height direction and the front and rear directions as well.

[0016] The operator places the metal sheet W, which is the workpiece to be processed, on the die Td, and before sandwiching and bending the metal sheet W between the punch Tp and the die Td, the butts 42a and 42b move to positions corresponding to the die Td. The operator places the metal sheet W on the die Td so that the rear end of the metal sheet W butts against the butts 42a and 42b. In other words, the butts 42a and 42b act to determine the position of the metal sheet W in the front-to-rear direction when the metal sheet W is placed on the die Td.

[0017] An operation pendant 7 having a display unit 71 and an operation unit 72 including a plurality of operation buttons is attached via an arm 7a to the left side of the press brake 100. The operation pendant 7 is connected to an NC device 10. The NC device 10 is connected to a foot switch 8 having an open foot switch 81 that raises the upper table 1 and a close foot switch 82 that lowers the upper table 1. When the operator steps on the close foot switch 82, the upper table 1 lowers and the metal sheet W is sandwiched between the punch Tp and the die Td and bent. When the operator steps on the open foot switch 81, the upper table 1 rises and the bent metal sheet W can be removed.

[0018] The bending angle measuring device is not shown in FIG. 1. As shown in FIG. 2, angle sensors 30F and 30R, which constitute part of the bending angle measuring device, are arranged in front of and behind the die Td, respectively. The punch Tp is not shown in FIG. 2. The front-side angle sensor 30F and the rear-side 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 FIG. 3, the angle sensor control device 20 and the angle sensor 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 a computer device.

[0019] 3, the angle sensor 30 includes 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 FIG. 2, the housing 301 of the angle sensor 30 (30F and 30R) has a first storage section 315 that stores the sensor board 31 and the camera 35, and a second storage section 340 that stores the laser diode 34.

[0020] The laser diode 34 of the angle sensor 30F is housed in the second housing section 340 and oriented toward the metal sheet W so as to irradiate the lower surface of the front flange Wf (first flange) of the metal sheet W with a linear laser beam (hereinafter referred to as "line laser beam") indicated by the dashed dotted line. The laser diode 34 of the angle sensor 30R is housed in the second housing section 340 and oriented toward the metal sheet W so as to irradiate the lower surface of the rear flange Wr (second flange) of the metal sheet W with a line laser beam. In FIG. 2, the line laser beam irradiated onto the rear flange Wr by the laser diode 34 of the angle sensor 30R is not shown. The laser diode 34 is an example of a laser beam irradiator.

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

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

[0023] Furthermore, the measurement instruction unit 21 transmits a threshold value according to the workpiece material information to the image angle calculation unit 33 of the sensor board 31. The threshold value according to the workpiece material information will be described in detail 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 emit a line laser beam and instructs the camera 35 to capture the reflected light.

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

[0026] Since the reflectance of line laser light differs between mirror-finished stainless steel and non-mirror-finished stainless steel, the exposure time setting table holding unit 322 holds separate exposure time setting tables for mirror-finished stainless steel and non-mirror-finished stainless steel.

[0027] If the target bend angle is large, for example, less than 180 degrees but not less than 170 degrees, assuming that the state of the metal sheet W before bending is 180 degrees, the distance from the laser diode 34 to the metal sheet W is short, and therefore the intensity of the line laser light irradiated onto the front flange Wf and the rear flange Wr is high. If the target bend angle is small, for example, less than 100 degrees but not less than 90 degrees (not shown), the distance from the laser diode 34 to the metal sheet W is long, and therefore the intensity of the line laser light irradiated onto the front flange Wf and the rear flange Wr is low. Therefore, the initial value of the exposure time is set longer for angle groups with smaller target bend angles.

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

[0029] FIG. 6 shows frame F of a captured image of the reflected light of a line laser beam when the metal sheet W is a mirror-finish stainless steel and the exposure time is 2 ms at a predetermined target bending angle. Frame F includes a high-brightness line RL2 as a line image formed by the reflected light. The brightness distribution of the horizontal pixel position and brightness value of a line at a certain vertical position in frame F is as shown in FIG. 7. Assume that the captured image is converted into an 8-bit digital signal by an A / D converter (not shown). Through verification by the inventors, it was found that the high-brightness line RL2, which has the brightness value characteristics shown in FIG. 7, is thin and cannot be used to measure the bending angle of the metal sheet W with high accuracy. The exposure time of 2 ms in this case is too short.

[0030] FIG. 8 shows frame F of an image captured by capturing reflected light of a line laser beam 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 the line at a certain vertical position in frame F at this time is as shown in FIG. 9. Through verification by the inventors, it was found that the high-brightness line RL8 having the brightness value characteristics shown in FIG. 9 is thick, and that the bending angle of the metal sheet W cannot be measured with high accuracy using the high-brightness line RL8. In this case, the exposure time of 8 ms was too long.

[0031] FIG. 10 shows frame F of an image captured by capturing reflected light of a line laser beam when the exposure time is 4 ms. Frame F includes a high-brightness line RL4 as a line image formed by the reflected light. The brightness distribution of the line at a certain vertical position in frame F at this time is as shown in FIG. 11. Through verification by the inventors, it was found that the high-brightness line RL4 having the brightness value characteristics shown in FIG. 11 has an appropriate thickness, and that the bending angle of the sheet metal W can be measured with high accuracy using the high-brightness line RL4. In this case, the exposure time of 4 ms is actually the optimal value. Let us refer to any high-brightness line as RL.

[0032] The optimum exposure time varies depending on the material of the workpiece. Even if the material of the workpiece is the same, the optimum exposure time may differ depending on 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 on each line in the frame F falls within a reference range. The image angle calculation unit 33 extracts pixels from the line image (high-luminance line RL) with the exposure time adjusted so that the luminance distribution of reflected light falls within the reference range. A luminance distribution falling within the reference range means that the shape or size (particularly the horizontal width) of the portion of the luminance distribution with a luminance value equal to or greater than a threshold value TH (described later) falls within the reference range. In this way, the bending angle measurement device can accurately measure the bending angle of the metal sheet W.

[0034] In detail, the image angle calculation unit 33 measures the bending angle of the metal sheet W as follows. As shown in FIG. 4 , the image angle calculation unit 33 includes an extracted pixel position determination unit 331, a pixel extraction unit 332, a linear approximation unit 333, and a linear angle calculation unit 334. The extracted 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 extracted pixel position determination unit 331 controls the exposure time adjustment unit 321 as follows to optimize the exposure time when the camera 35 captures the reflected light of the line laser beam. Furthermore, the extracted pixel position determination unit 331 determines an extracted pixel position for extracting one pixel from a high-luminance line RL for each line in the frame F while controlling the exposure time adjustment unit 321 to optimize the exposure time.

[0035] FIG. 12 schematically shows the luminance distribution of the high-luminance line RL, which changes depending on the exposure time as shown in FIGS. 7, 9, and 11. The luminance integrated value calculation unit 3311 calculates an integrated value by integrating luminance values ​​equal to or greater than a threshold value TH, using a predetermined luminance value in the luminance distribution of each line as a threshold value TH. If the metal sheet W is a stainless steel mirror-finish material, the threshold value TH should be set to 75% of the maximum luminance value, and if the workpiece material is other than that, the threshold value TH should be set to 50% of the maximum luminance value. The reason why a relatively high luminance value is set as the threshold value TH when the metal sheet W is a stainless steel mirror-finish material is that the luminance of the high-luminance line RL becomes very high.

[0036] As shown in Fig. 12, the brightness value of the brightness distribution changes from a brightness value less than the threshold value TH to the threshold value TH at the first pixel Px1, and from a brightness value exceeding the threshold value TH to the threshold value TH at the second pixel Px2. The first pixel Px1 is at the first pixel position P1, and the second pixel Px2 is at the second pixel position P2. The integrated value of the brightness values ​​equal to or greater than the threshold value TH corresponds to the area of ​​the hatched region Aac shown in Fig. 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 the vertical line Lv, which divides the integrated value into halves on the left and right, is located. The area Aac is divided by the vertical line Lv into a first area Ar1 and a second area Ar2, each of which has 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 based on the first pixel position P1 and calculate the half-width HW, as shown in FIG. 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 based on the second pixel position P2 and calculate the half-width HW, which is the opposite of FIG. 12.

[0038] The high brightness line RL2 shown in Figure 7, which does not allow for high-accuracy measurement of the bending angle of the sheet metal W, has a narrow half-width HW. The high brightness line RL8 shown in Figure 9, which does not allow for high-accuracy measurement of the bending angle of the sheet metal W, has a wide half-width HW. The high brightness line RL4 shown in Figure 11, which allows for high-accuracy measurement of the bending angle of the sheet metal W, has a moderate half-width HW that is neither too narrow nor too wide.

[0039] The inventor's verification revealed the following. The half width HW, obtained by dividing the area of ​​the region Aac, which is the integrated value obtained by integrating the brightness values ​​above the threshold TH in the brightness distribution of each line of the high-brightness line RL, in half, affects whether the bending angle of the sheet metal W can be measured with high accuracy. If the half width HW is within a reference range obtained by adding a positive or negative error to a predetermined reference value, the high-brightness line RL will have 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 the number of pixels from the first pixel position P1 or the second pixel position P2 to the third pixel position P3 on each line is within a predetermined range.

[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. When the half width calculation unit 3312 calculates a half width HW within the reference range as a result of the half width adjustment unit 3313 controlling the exposure time adjustment unit 321, the extraction pixel position determination unit 331 determines the third pixel position P3 as the extraction pixel position within the high-luminance line RL. The half width adjustment unit 3313 instructs the pixel extraction unit 332 about the extraction pixel position. The pixel extraction unit 332 extracts a pixel at the instructed extraction pixel position (third pixel position P3).

[0041] FIG. 13 shows the state in which pixels at the third pixel positions P3 of each line in the high-luminance line RL4 shown in FIG. 10 have been extracted. In FIG. 13, the high-luminance line RL4 is shown in black, and the extracted pixels Pxe are shown as white circles. In FIGS. 13 and 14, for simplicity, the number of lines from which the extracted pixels Pxe are extracted is shown to be smaller than the actual number. As shown in FIG. 14, the linear approximation unit 333 linearly approximates all of the extracted pixels Pxe of the multiple lines extracted from the high-luminance line RL4 using, for example, the least squares method, to generate a straight line Ls. In FIG. 14, the extracted pixels Pxe are shown as black circles. As shown in FIG. 15, the straight line angle calculation unit 334 calculates the image angle φ of the straight line Ls with respect to the horizontal direction.

[0042] Returning to FIG. 3 , the image angle calculation units 33 of the angle sensors 30F and 30R transmit 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 units 33 of the angle sensors 30F and 30R into the bending angle θ of the metal sheet W shown in FIG. 2 and transmits it to the NC device 10. The NC device 10 compares the target bending angle with the bending angle θ, which is the measured actual bending angle of the metal sheet W bent to the target bending angle. Based on the comparison result, the NC device 10 can control the press brake main body 101 to bend the metal sheet W so that it is closer to the target bending angle. Furthermore, the NC device 10 can control the press brake main body 101 to bend the metal sheet W so that it is closer to the target bending angle during subsequent bending processes of the metal sheet W.

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

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

[0045] As described above, the optimum value of the exposure time may differ depending on the influence of factors such as the environment in which the press brake 100 is installed. Therefore, it is preferable that an exposure time setting table for each user who uses the press brake 100 is set in the exposure time setting table storage unit 322. It is preferable that an exposure time setting table for each factory in which the press brake 100 is installed is set in the exposure time setting table storage unit 322. 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 metal sheet W has a protective film attached, the metal sheet W may be bent by the press brake 100 with the protective film facing downward, or may be bent by the press brake 100 with the protective film facing upward. 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 on which no protective film is attached. Therefore, it is preferable that the exposure time setting table holding unit 322 has set therein not only an exposure time setting table for the metal surface but also an exposure time setting table for the protective film surface.

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

[0048] If a bending angle measurement request is made from the NC device 10 in step S1 (YES), the angle sensor control device 20 instructs the angle sensor 30 to irradiate and photograph a line laser light in step S2. In step S3, the angle sensor 30 irradiates the metal sheet W with a line laser light and photographs the reflected light. In step S4, the brightness integrated value calculation unit 3311 in the image angle calculation unit 33 of the angle sensor 30 calculates an integrated value by integrating brightness values ​​equal to or greater than the threshold value TH in each line. In step S5, the half width calculation unit 3312 calculates the areal 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), in step S7, the half width adjustment unit 3313 controls the exposure time adjustment unit 321 to adjust the exposure time of the camera 35. The half width adjustment unit 3313 repeats the processes of 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 a pixel at the pixel position of the half width HW (third pixel position P3) on each line in step S8. In step S9, the linear approximation unit 333 linearly approximates the multiple pixels extracted in step S8.

[0050] In FIG. 16B, in step S10, the straight line angle calculation unit 334 calculates the image angle φ of the straight line that has been approximated. 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 a bending angle θ of the metal sheet 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 the 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] In step S14, the table update unit 323 updates the exposure time in the exposure time setting table in accordance with instructions from the NC device 10. Thereafter, the process proceeds to step S15. If the bending angle is not within a predetermined error range with respect to the target bending angle in step S13 (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 bend angle measuring device determines whether or not to end the operation of the bend angle measuring device by, for example, turning off the power to the press brake 100. If the operation is not to be ended (NO), the bend angle measuring device repeats the processing from step S1 onwards. If the operation is to be ended (YES), the bend angle measuring device ends the processing.

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

[0054] In the configuration example of the bending angle measuring device shown in Fig. 3, an image angle calculation unit 33 is provided on a sensor substrate 31 in an angle sensor 30. The image angle calculation unit 33 may be provided in an angle sensor control device 20. Furthermore, a function similar to that of the angle sensor control device 20 may be provided in an NC device 10, or a function similar to that of the angle sensor control device 20 and the image angle calculation unit 33 may be provided in an NC device 10. The function of the operation instruction unit 32 may be provided in the NC device 10.

[0055] The present invention is not limited to one or more of the above-described embodiments, and various modifications can be made without departing from the spirit of the present 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 cylinder 7 Operation pendant 8 Footswitch 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 Backgauge 41 Backgauge carriage 42a, 42b butt 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 storage 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 (workpiece) Wf Front flange (first flange) Wr Rear flange (second flange)

Claims

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

2. The image angle calculation unit a predetermined luminance value in the luminance distribution for each line is set as a threshold, and an integrated value is calculated by integrating luminance values ​​equal to or greater than the threshold; calculate a half width from a first pixel position where the luminance value of the luminance distribution changes from a luminance value less than the threshold value to the threshold value, or a second pixel position where the luminance value changes from a luminance value exceeding the threshold value to the threshold value, to a third pixel position where a vertical line dividing the integrated value into 1 / 2 on the left and 1 / 2 on the right is located; controlling the exposure time adjustment unit so that the exposure time is such that the half width falls within a reference range; As a pixel in the line image, a pixel at the third pixel position obtained in a state where the exposure time is adjusted so that the half width is within the reference range is extracted. The bending angle measuring device according to claim 1 .

3. 3. The bending angle measuring device according to claim 1, 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 a group of angles obtained by dividing the target bending angle into predetermined angles, and adjusts the exposure time of the camera so that the exposure time is the exposure time selected based on the exposure time setting table.

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

5. A linear laser beam is irradiated onto a first flange on a front side of the punch and a second flange on a rear side of the punch and the die in a workpiece that is sandwiched between the punch and the die and bent to a target bending angle; Photographing the reflected light of the laser light irradiated on the first and second flanges with a camera; adjusting an exposure time of the camera so that the luminance distribution of the reflected light on each line within a frame of the image captured by the camera falls within a reference range; extracting pixels in a line image formed by the reflected light included in the captured image for each line in a state in which the exposure time is adjusted so that the luminance distribution of the reflected light falls within the reference range; Calculate the image angle of a straight line that is a linear approximation of the pixels of the extracted lines; The image angle is converted into a bending angle of the workpiece. Bending angle measurement method.

6. A predetermined luminance value in the luminance distribution for each of the lines is set as a threshold, and an integrated value is calculated by accumulating luminance values ​​equal to or greater than the threshold; calculate a half width from a first pixel position where the luminance value of the luminance distribution changes from a luminance value less than the threshold value to the threshold value, or a second pixel position where the luminance value changes from a luminance value exceeding the threshold value to the threshold value, to a third pixel position where a vertical line dividing the integrated value into 1 / 2 on the left and 1 / 2 on the right is located; adjusting the exposure time so that the half width falls within a reference range; As a pixel in the line image, a pixel at the third pixel position obtained in a state where the exposure time is adjusted so that the half width is within the reference range is extracted. The bending angle measuring method according to claim 5.

7. A bending angle measurement method as described in claim 5 or 6, which refers to an exposure time setting table in which the exposure time of the camera is set to correspond to the material of the workpiece and a group of angles obtained by dividing the target bending angle into predetermined angles, and adjusts the exposure time of the camera so that it becomes the exposure time selected based on the exposure time setting table.

8. A bending angle measurement method as described in Claim 7, wherein when the exposure time of the camera is adjusted to be different from the exposure time pre-set in the exposure time setting table, the pre-set exposure time in the exposure time setting table is updated to the different exposure time.

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