Press brake and press brake control method

Abstract

[Problem] Known press brakes have a higher possibility of experiencing an error relative to a true movement target position of a slide as a difference between a target bending angle of a workpiece and an actual bending angle thereof decreases. [Solution] A first aspect of the present invention provides a press brake to be used for bending a workpiece. The press brake is provided with a slide fitted with an upper die and performing a reciprocating motion. The press brake is provided with a control device that controls movement of the slide. The press brake is provided with an angle sensor that detects the bending angle of a workpiece. The control device converts a target angle during pressing of the workpiece into a movement target position of the slide. The control device converts a detection angle detected by the angle sensor into the current position of the slide corresponding to the detection angle. The control device executes feedback control of comparing the target position with the current position, and correcting a stroke length so as to move the slide to a position corresponding to a difference between the target position and the current position.

Description

Press brake and press brake control method

[0001] The present invention relates to a press brake and a method for controlling a press brake.

[0002] A press brake is a machine used to bend workpieces. Bending using a press brake causes springback of the metal workpiece. Springback can lead to poor accuracy and processing defects, so measures to prevent it are essential.

[0003] The technology described in Patent Document 1 relates to a bending device that bends a workpiece by placing the workpiece between dies consisting of a punch and a die and moving the dies toward and away from each other. The bending device includes a die drive means, an angle detection means, a target angle command means, and a fuzzy control means. The die drive means moves the dies toward and away from each other. The angle detection means detects the bending angle of the workpiece being bent between the dies. The target angle command means outputs a final bending angle that is preset so that the bending angle of the workpiece becomes the product angle after springback as the target angle. The fuzzy control means inputs the target angle output by the target angle command means and the bending angle of the workpiece detected by the angle detection means, determines a command value increase amount according to the deviation between the two angles, and controls the die drive means so that the bending angle of the workpiece becomes the target angle.

[0004] Patent No. 2859689

[0005] As described above, the technology described in Patent Document 1 inputs a target angle and a workpiece bending angle, determines a command value increment based on the deviation between the two angles, and controls a die driving means so that the workpiece bending angle becomes the target angle. Here, the deviation between the target angle and the workpiece bending angle becomes smaller as the workpiece bending angle approaches the target angle. The command value increment determined based on the deviation between the target angle and the workpiece bending angle becomes smaller as the deviation between the two angles becomes smaller. Therefore, as the workpiece bending angle approaches the target angle, an error may occur in the command value increment relative to the true increment that should be commanded.

[0006] In a first aspect of the present invention, there is provided a press brake for use in bending a workpiece. The press brake includes a slide that reciprocates to which an upper die is attached. The press brake includes a control device that controls the movement of the slide. The press brake includes an angle sensor that detects the bending angle of the workpiece. The control device converts a target angle when pressurizing the workpiece into a target position to which the slide should be moved. The control device converts the detected angle detected by the angle sensor into a current position of the slide that corresponds to the detected angle. The control device compares the target position with the current position and performs feedback control to correct the stroke length so as to move the slide to a position that corresponds to the difference between the target position and the current position.

[0007] In a second aspect of the present invention, there is provided a method for controlling a press brake used to bend a workpiece. The method for controlling the press brake includes controlling the movement of a slide that reciprocates to which an upper die is attached. The method for controlling the press brake includes detecting the bending angle of the workpiece using an angle sensor. The method for controlling the press brake converts a target angle when pressurizing the workpiece into a target position to which the slide should be moved. The method for controlling the press brake converts the detected angle detected by the angle sensor into a current position of the slide that corresponds to the detected angle. The method for controlling the press brake compares the target position with the current position and performs feedback control to correct the stroke length so as to move the slide to a position corresponding to the difference between the target position and the current position.

[0008] The press brake of the above aspect converts the target angle into a target position, converts the detected angle into a current position, and compares the target position with the current position, so that even if the difference between the target angle and the detected angle is small, the accuracy of the feedback control is high.

[0009] The control device may convert the target angle to a target position using a specific function. The control device may convert the detected angle to a current position using a specific function. In this aspect of the press brake, the accuracy of converting the target angle to a target position and the accuracy of converting the detected angle to a current position are the same, thereby improving the accuracy of feedback control.

[0010] The control device may perform feedback control at specific time intervals. This type of press brake repeatedly performs feedback control, resulting in higher accuracy.

[0011] The control device may execute feedback control each time the amount of change in the detected angle reaches a specific angle. This type of press brake repeatedly executes feedback control, thereby further improving accuracy.

[0012] The control device may execute control to move the slide toward the initial target position until the upper die contacts the workpiece. The control device may start feedback control after the upper die contacts the workpiece. This type of press brake shortens the slide movement time until the upper die contacts the workpiece, thereby improving processing efficiency.

[0013] The control device may execute control to move the slide toward the initial target position until the detected angle reaches a predetermined angle. The control device may start feedback control after the detected angle reaches the predetermined angle. In this aspect of the press brake, the slide movement time until the detected angle reaches the predetermined angle is shortened, thereby improving processing efficiency.

[0014] The above summary of the invention does not list all of the necessary features of the present invention, and subcombinations of these features may also constitute inventions.

[0015] 1 is a front view showing an example of the configuration of the press brake 100. FIG. 2 is a functional block diagram showing an example of the functional configuration of the control device 160. FIG. 3 is a side view showing the workpiece W1 pressed by the press brake 100. FIG. 4 is a side view showing the workpiece W1 unloaded by the press brake 100. FIG. 5 is a flowchart showing an example of the processing of the control device 160. FIG. 6 is a functional block diagram showing another example of the functional configuration of the control device 160. FIG. 7 is a flowchart showing another example of the processing of the control device 160. FIG. 8 is a diagram showing the distribution of the bending angle of the workpiece W1 bent by feeding back the position of the slide 130. FIG. 9 is a diagram showing the distribution of the bending angle of the workpiece W1 bent by feeding back the bending angle of the workpiece W1. FIG. 10 is a diagram showing the distribution of the bending angle of the workpiece W1 bent by feeding back the position of the slide 130. FIG. 11 is a diagram showing the distribution of the bending angle of the workpiece W1 bent by feeding back the bending angle of the workpiece W1. 1 is a diagram showing the distribution of bending angles of a workpiece W1 bent by feeding back the position of the slide 130. FIG. 2 is a diagram showing the distribution of bending angles of a workpiece W1 bent by feeding back the bending angle of the workpiece W1. FIG. 3 is a diagram showing the distribution of bending angles of a workpiece W1 bent by feeding back the position of the slide 130. FIG. 4 is a diagram showing the distribution of bending angles of a workpiece W1 bent by feeding back the bending angle of the workpiece W1.

[0016] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0017] 1 is a front view showing an example of the configuration of a press brake 100. The press brake 100 is a press machine used for bending a workpiece W1. The press brake 100 includes a frame 110, a drive unit 120, a slide 130, a back gauge 140, an angle sensor 150, and a control device 160.

[0018] The frame 110 includes a crown 111, an upright 112, and a bed 113. The crown 111 houses the drive unit 120. The drive unit 120 is a mechanism that drives the slide 130. The drive unit 120 includes, for example, a servo motor, a servo valve, a servo amplifier, a feedback detector, and an electric braking device that operate the slide 130. The upright 112 holds the sliding portion of the slide 130. The bed 113 is a base that receives press pressure. The upper surface of the bed has a structure that allows a bolster BP to be attached. The bolster BP is attached to the upper surface of the bed 113 and serves as a base plate on which the lower mold LT is attached. The upper surface of the bolster has a structure that allows the lower mold LT to be attached. The lower mold LT is a tool that is combined with the upper mold UT to machine the workpiece W1.

[0019] The slide 130 is a part that reciprocates and to which the upper die UT is attached. The slide 130 is also called a ram. The upper die UT is a tool that processes the workpiece W1 in combination with the lower die LT.

[0020] The back gauge 140 is a tool that determines the position of the workpiece W1 at the rear side of the portion where the workpiece W1 is to be bent. The back gauge 140 is also called a butt. The back gauge 140 is provided so as to be movable in the X direction in the XY plane, for example, by a mechanism not shown.

[0021] The angle sensor 150 is a sensor that detects the bending angle of the workpiece W1. For example, the angle sensor 150 is provided at a position closer to the front than the lower mold LT and at a position farther back than the lower mold LT when viewed from the front. Furthermore, the angle sensor 150 is provided so as to be movable in the X direction in the XY plane by a mechanism (not shown), for example.

[0022] The control device 160 is a device that controls the movement of the slide 130. The control device 160 is electrically connected to the drive unit 120 and the angle sensor 150. The control device 160 receives a detection signal from the angle sensor 150 that can identify the bending angle of the workpiece W1. The control device 160 transmits a command signal to the drive unit 120 to drive the drive unit 120 to move the slide 130 to the target position.

[0023] 2 is a functional block diagram showing an example of the functional configuration of the control device 160. The control device 160 includes a target angle information acquisition unit 161, a target position calculation unit 162, a detected angle information acquisition unit 163, a current position calculation unit 164, and a control unit 165.

[0024] The target angle information acquisition unit 161 is a module that acquires information about the target angle when pressurizing the workpiece W1. The target angle information acquisition unit 161 acquires information about the target angle that is input using, for example, the input device 170. The input device 170 is a device that provides data, information, instructions, etc. to a device such as a computer.

[0025] The target position calculation unit 162 is a module that calculates a target position to which the slide 130 is to be moved. The target position calculation unit 162 uses information on the target angle acquired by the target angle information acquisition unit 161 to convert the target angle when pressurizing the workpiece W1 into a target position to which the slide 130 is to be moved.

[0026] The detected angle information acquisition unit 163 is a module that acquires information related to the detected angle detected by the angle sensor 150. The detected angle information acquisition unit 163 acquires information related to the detected angle by, for example, sampling the output signal of the angle sensor 150.

[0027] The current position calculation unit 164 is a module that calculates the current position of the slide 130. Using the information related to the detected angle acquired by the detected angle information acquisition unit 163, the current position calculation unit 164 converts the detected angle detected by the angle sensor 150 into the current position of the slide 130 corresponding to the detected angle.

[0028] The control unit 165 is a module that controls the movement of the slide 130. The control unit 165 sends a command signal to the servo amplifier of the drive unit 120 to move the slide 130 to the target position. The control unit 165 shown in FIG. 2 references a feedback signal output from a feedback detector of the drive unit 120, which indicates the position result when the slide 130 is controlled. The control unit 165 executes a first feedback control to move the slide 130 toward the initial target position until a specific condition is met. After the specific condition is met, the control unit 165 executes a second feedback control to correct the stroke length to move the slide 130 to a position corresponding to the difference between the target position and the current position. The stroke length is the movement distance of the slide 130 in one stroke. The second feedback control is an example of the "feedback control" defined in this invention.

[0029] Fig. 3 is a side view showing the workpiece W1 pressed by the press brake 100. Fig. 4 is a side view showing the workpiece W1 unloaded by the press brake 100.

[0030] The workpiece W1 is bent by the slide 130 moving in the downward direction LD and being sandwiched between the upper die UT and the lower die LT and pressed. When the slide 130 moves in the upward direction UD and the load is removed, the workpiece W1 springs back to the outside O1. Springback is a warp that occurs when the workpiece W1 is bent.

[0031] The bending angle of the workpiece W1 after bending is changed due to springback when the load is removed. Therefore, the target angle when pressurizing the workpiece W1 is set in anticipation of the change in angle due to springback.

[0032] 5 is a flowchart showing an example of processing by the control device 160. When bending the workpiece W1, the worker inputs information about the target angle using the input device ID in order to set a target angle when pressurizing the workpiece W1.

[0033] First, the target angle information acquisition unit 161 of the control device 160 acquires information about the target angle input using the input device ID (S101). In S101, the target angle information acquisition unit 161 acquires, as information about the target angle, for example, a parameter indicating the target angle when pressurizing the workpiece W1.

[0034] Next, the target position calculation unit 162 of the control device 160 converts the target angle when pressurizing the workpiece W1 into a target position to which the slide 130 should be moved (S102). In S102, the target position calculation unit 162 identifies the target angle based on the information about the target angle acquired by the target angle information acquisition unit 161. Then, the target position calculation unit 162 converts the target angle into a target position using, for example, a specific function. The target position calculation unit 162 uses, for example, the function disclosed in Japanese Patent No. 5737657 as the specific function.

[0035] Next, the control unit 165 of the control device 160 executes a first feedback control to move the slide 130 toward the initial target position (S103). In the first feedback control, the control unit 165 transmits a command signal to the servo amplifier of the drive unit 120 to move the slide 130 toward the initial target position.

[0036] When the control unit 165 starts the first feedback control, it determines whether the upper mold UT attached to the slide 130 has hit the workpiece W1 (S104). In S104, the control unit 165 receives, for example, a feedback signal indicating the position result when controlling the slide 130 from the feedback detector of the drive unit 120. Then, the control unit 165 determines whether the upper mold UT has hit the workpiece W1 by referring to, for example, the predicted position of the slide 130 when the upper mold UT hits the workpiece W1 and the feedback signal.

[0037] If the upper die UT is not in contact with the workpiece W1 (S104; NO), the control unit 165 repeatedly executes the process of S104 every time a certain time elapses, for example, by using an interval timer. The interval timer is a mechanism that notifies the user that a certain time has elapsed.

[0038] If the upper die UT hits the workpiece W1 (S104; YES), the control unit 165 ends the first feedback control (S105).

[0039] Next, the control device 160 starts the second feedback control (S106).

[0040] In the second feedback control, the detected angle information acquisition unit 163 of the control device 160 acquires information related to the detected angle detected by the angle sensor 150 (S107). In S107, the detected angle information acquisition unit 163 acquires, as the information related to the detected angle, for example, a parameter indicating the detected angle detected by the angle sensor 150.

[0041] Next, the current position calculation unit 164 of the control device 160 converts the detected angle into a current position of the slide 130 corresponding to the detected angle (S108). In S108, the current position calculation unit 164 converts the detected angle into a current position using, for example, a specific function. For example, the current position calculation unit 164 uses, as the specific function, the same function as the function used by the target position calculation unit 162.

[0042] Next, the detected angle information acquisition unit 163 determines whether the current position of the slide 130 has reached the target position (S109).

[0043] If the detected angle is not the target angle (S109; NO), the control unit 165 compares the target position with the current position and calculates the difference between the target position and the current position (S110). In S110, the control unit 165 compares the target position calculated by the target position calculation unit 162 with the current position calculated by the current position calculation unit 164 and calculates the difference between the target position and the current position.

[0044] Here, the bending angle of the workpiece W1 is determined by the stroke length of the slide 130. However, even if the stroke length of the slide 130 is the same, the bending angle of the workpiece W1 varies due to differences in the plate thickness, material, and size of the workpiece W1. Furthermore, even if the stroke length of the slide 130 is the same, the bending angle of the workpiece W1 varies due to deflection of the frame 110, the upper mold UT, and the lower mold LT.

[0045] Therefore, the control unit 165 corrects the stroke length so as to move the slide 130 to a position corresponding to the difference between the target position and the current position (S111).

[0046] Next, the control unit 165 moves the slide 130 using the corrected stroke length as a target (S112). In S112, the control unit 165 transmits a command signal to the servo amplifier of the drive unit 120 to move the slide 130 using the corrected stroke length as a target.

[0047] Next, the control unit 165 determines whether a specific time has elapsed (S113). In S113, the control unit 165 determines whether a specific time has elapsed after starting control to move the slide 130 with the latest corrected stroke length as the target.

[0048] If the specific time has not elapsed (S113; NO), the control unit 165 repeatedly executes the process of S113 every time a certain time elapses, for example, using an interval timer.

[0049] If the specific time has elapsed (S113; YES), the control device 160 executes the processes from S107 onwards again. The control device 160 repeatedly executes the processes from S107 to S113 until the current position of the slide 130 reaches the target position.

[0050] When the current position of the slide 130 reaches the target position (S109; YES), the control device 160 ends the second feedback control (S114) and ends the control shown in the flowchart of FIG.

[0051] As described above, the press brake 100 of the above embodiment is used to bend the workpiece W1. The press brake 100 is equipped with a slide 130 that reciprocates to which an upper die UT is attached. The press brake 100 is equipped with a control device 160 that controls the movement of the slide 130. The press brake 100 is equipped with an angle sensor 150 that detects the bending angle of the workpiece W1. The control device 160 converts a target angle when pressurizing the workpiece W1 into a target position to which the slide 130 should be moved. The control device 160 converts the detected angle detected by the angle sensor 150 into a current position of the slide 130 that corresponds to the detected angle. The control device 160 compares the target position with the current position and performs second feedback control to correct the stroke length so as to move the slide 130 to a position corresponding to the difference between the target position and the current position. The press brake 100 of this embodiment converts the target angle into a target position, converts the detected angle into a current position, and compares the target position with the current position, so that the accuracy of the second feedback control is high even if the difference between the target angle and the detected angle is small.

[0052] Furthermore, the control device 160 of the above embodiment converts the target angle into a target position using a specific function. The control device 160 of the above embodiment converts the detected angle into a current position using a specific function. The press brake 100 of this aspect has the same accuracy in converting the target angle into a target position and the same accuracy in converting the detected angle into a current position, thereby improving the accuracy of the second feedback control.

[0053] Furthermore, the control device 160 of the above embodiment executes the second feedback control at specific time intervals. The press brake 100 of this aspect repeatedly executes the second feedback control, which further improves accuracy.

[0054] Furthermore, the control device 160 of the above embodiment executes first feedback control to move the slide 130 toward the initial target position until the upper die UT attached to the slide 130 hits the workpiece W1. The control device 160 executes second feedback control after the upper die UT hits the workpiece W1. The press brake 100 of this aspect shortens the movement time of the slide 130 until the upper die UT hits the workpiece W1, thereby improving processing efficiency.

[0055] Fig. 6 is a functional block diagram showing another example of the functional configuration of the control device 160. The control device 160 shown in Fig. 6 has the same functional configuration as the control device 160 shown in Fig. 2, except that the control unit 165 refers to the detected angle acquired by the detected angle information acquisition unit 163.

[0056] Fig. 7 is a flowchart showing another example of the processing of the control device 160. The processing of the flowchart shown in Fig. 7 is common to the processing of the flowchart shown in Fig. 5 except that the detected angle is referenced when the processing from S107 onwards is executed again.

[0057] After executing the process of S112, the control unit 165 determines whether the amount of change in the detected angle has reached a specific angle (S213). In S213, the control unit 165 determines whether the amount of change in the detected angle has reached a specific angle by referring to the detected angle acquired by the detected angle information acquisition unit 163. For example, the control unit 165 determines whether the amount of change in the detected angle has reached a specific angle after starting control to move the slide 130 with the latest corrected stroke length as a target.

[0058] If the amount of change in the detected angle has not reached the specific angle (S213; NO), the control unit 165 repeatedly executes the process of S113 every time a certain period of time elapses, for example, using an interval timer.

[0059] If the change amount of the detected angle reaches the specific angle (S213; YES), the control device 160 executes the processes from S107 onwards again. The control device 160 repeatedly executes the processes from S107 to S213 until the current position of the slide 130 reaches the target position.

[0060] As described above, the control device 160 of the above embodiment executes the second feedback control each time the change in the detected angle reaches a specific angle. The press brake 100 of this aspect repeatedly executes feedback control, thereby further improving accuracy. Figure 8 is a flowchart showing another example of processing by the control device 160. The flowchart shown in Figure 8 is the same as the flowchart shown in Figure 5 in terms of processing, except that the detected angle is referenced when terminating the first feedback control.

[0061] When the first feedback control is started, the control unit 165 determines whether the detected angle has reached a predetermined angle (S304). In S304, the control unit 165 determines whether the detected angle has reached a predetermined angle, for example, by referring to the detected angle acquired by the detected angle information acquisition unit 163.

[0062] If the detected angle is not the predetermined angle (S304; NO), the control unit 165 repeatedly executes the process of S304 every time a certain time period elapses, for example, using an interval timer.

[0063] When the detected angle reaches the predetermined angle (S304; YES), the control unit 165 ends the first feedback control (S105).

[0064] As described above, the control device 160 of the above embodiment executes control to move the slide 130 toward the initial target position until the detected angle reaches a predetermined angle. The control device 160 starts the second feedback control after the detected angle reaches the predetermined angle. The press brake 100 of this aspect shortens the movement time of the slide 130 until the detected angle reaches the predetermined angle, thereby improving processing efficiency.

[0065] FIG. 9 is a diagram showing the distribution of bending angles of the workpiece W1 bent by feedbacking the position of the slide 130. FIG. 10 is a diagram showing the distribution of bending angles of the workpiece W1 bent by feedbacking the bending angle of the workpiece W1. The distributions shown in FIGS. 9 and 10 are both distributions of bending angles when 30 steel workpieces W1 of the same thickness and width are bent using a straight-sword-shaped upper die UT with a target angle of 90 degrees. In the following description, control for bending by feedbacking the position of the slide 130 is referred to as position control. On the other hand, control for bending by feedbacking the bending angle of the workpiece W1 is referred to as angle control.

[0066] As shown in Figure 9, of the 30 workpieces W1 bent using position control, the number of workpieces W1 whose bending angle was approximately the target angle was 10. As shown in Figure 10, of the 30 workpieces W1 bent using angle control, the number of workpieces W1 whose bending angle was approximately the target angle was 18. As is clear from the distributions shown in Figures 9 and 10, when bending an iron workpiece W1 using a straight-sword shaped upper die UT, bending using angle control is more accurate than bending using position control.

[0067] Fig. 11 is a diagram showing the distribution of bending angles of the workpiece W1 bent by position control. Fig. 12 is a diagram showing the distribution of bending angles of the workpiece W1 bent by angle control. The distributions shown in Fig. 11 and Fig. 12 are both distributions of bending angles when 30 aluminum workpieces W1 of the same thickness and width were bent using a straight-sword shaped upper die UT with a target angle of 90 degrees.

[0068] As shown in Figure 11, of the 30 workpieces W1 bent using position control, the number of workpieces W1 whose bending angle was approximately the target angle was 4. As shown in Figure 12, of the 30 workpieces W1 bent using angle control, the number of workpieces W1 whose bending angle was approximately the target angle was 15. As is clear from the distributions shown in Figures 11 and 12, when bending an aluminum workpiece W1 using a straight-sword shaped upper die UT, bending using angle control is more accurate than bending using position control.

[0069] Fig. 13 is a diagram showing the distribution of bending angles of workpieces W1 bent by position control. Fig. 14 is a diagram showing the distribution of bending angles of workpieces W1 bent by angle control. The distributions shown in Figs. 13 and 14 are both distributions of bending angles when 15 iron workpieces W1 with the same plate thickness and plate width are bent using a gooseneck-type upper die UT. The target angle in bending by position control is 90.3 degrees. The target angle in bending by angle control is 90 degrees.

[0070] As shown in Figure 13, of the 15 workpieces W1 bent using position control, the number of workpieces W1 whose bending angles were approximately the target angle was 2. As shown in Figure 14, of the 15 workpieces W1 bent using angle control, the number of workpieces W1 whose bending angles were approximately the target angle was 9. As is clear from the distributions shown in Figures 13 and 14, when bending is performed using a gooseneck-shaped upper die UT, bending using angle control has higher accuracy than bending using position control.

[0071] Fig. 15 is a diagram showing the distribution of bending angles of workpieces W1 bent by position control. Fig. 16 is a diagram showing the distribution of bending angles of workpieces W1 bent by angle control. The distributions shown in Fig. 15 and Fig. 16 are both distributions of bending angles when 20 workpieces W1 are bent along the roll marks of the workpieces W1 with a target angle of 90 degrees. The roll marks are the rolling direction in the process of turning the workpieces W1 into plate material.

[0072] As shown in Figure 15, of the 20 workpieces W1 bent using position control, the number of workpieces W1 for which the bending angle was approximately the target angle was 2. As shown in Figure 16, of the 20 workpieces W1 bent using angle control, the number of workpieces W1 for which the bending angle was approximately the target angle was 10. As is clear from the distributions shown in Figures 15 and 16, when bending the workpiece W1 along the roll grain, bending using angle control has higher accuracy than bending using position control.

[0073] Fig. 17 is a diagram showing the distribution of bending angles of workpieces W1 bent by position control. Fig. 18 is a diagram showing the distribution of bending angles of workpieces W1 bent by angle control. The distributions shown in Fig. 17 and Fig. 18 are both distributions of bending angles when 20 workpieces W1 are bent in a direction intersecting the roll grain of the workpieces W1 with a target angle of 90 degrees.

[0074] As shown in Figure 17, of the 20 workpieces W1 bent using position control, the number of workpieces W1 for which the bending angle was approximately the target angle was 0. As shown in Figure 18, of the 20 workpieces W1 bent using angle control, the number of workpieces W1 for which the bending angle was approximately the target angle was 7. As is clear from the distributions shown in Figures 17 and 18, when bending along the roll grain of the workpiece W1, bending using angle control has higher accuracy than bending using position control.

[0075] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0076] In the above embodiment, the backgage 140 is provided so as to be movable in the X direction in the XY plane by a mechanism not shown. However, the backgage 140 may be immovable. For example, the press brake 100 may be provided with a plurality of backgages 140 that are immovable in the X direction in the XY plane.

[0077] In the above embodiment, the angle sensors 150 are provided at a position in front of the lower mold LT and a position behind the lower mold LT in a front view. However, the angle sensors 150 may be provided at either a position in front of the lower mold LT or a position behind the lower mold LT.

[0078] In the above embodiment, the angle sensor 150 is provided so as to be movable in the X direction in the XY plane by a mechanism not shown. However, the angle sensor 150 may be immovable. For example, the press brake 100 may be provided with multiple angle sensors 150 that are immovable in the X direction in the XY plane. When multiple angle sensors 150 are provided, the control device 160 may send different command signals to the left and right control units 120 to drive the left and right crankshafts individually. The crankshafts are axes that convert rotational motion into reciprocating motion of the slide 130. Here, when bending the long workpiece W1, there is a possibility that the bending angle at one end may differ from the bending angle at the other end. For example, the control device 160 may control the crankshaft at one end using the detection result of the angle sensor 150 provided at one end, and control the crankshaft at the other end using the detection result of the angle sensor 150 provided at the other end. The press brake 100 of this aspect can prevent the bending angle at one end from misaligning with the bending angle at the other end when bending a long workpiece W1.

[0079] In the above embodiment, the target angle information acquisition unit 161 acquires, as information regarding the target angle, a parameter indicating the target angle when pressurizing the workpiece W1. However, the information acquired by the target angle information acquisition unit 161 may be information regarding the target angle when pressurizing the workpiece W1, and is not limited to a parameter indicating the target angle when pressurizing the workpiece W1. For example, the target angle information acquisition unit 161 may acquire, as information regarding the target angle, a parameter from which the target angle when pressurizing the workpiece W1 can be calculated.

[0080] In the above embodiment, the detected angle information acquisition unit 163 acquires, as information about the detected angle, a parameter indicating the detected angle detected by the angle sensor 150. However, the information acquired by the detected angle information acquisition unit 163 may be information about the detected angle detected by the angle sensor 150, and is not limited to a parameter indicating the detected angle detected by the angle sensor 150. For example, the detected angle information acquisition unit 163 may acquire, as information about the detected angle, a parameter from which the detected angle detected by the angle sensor 150 can be calculated.

[0081] In the process shown in FIG. 7, the control unit 165 may refer to the detected angle when ending the first feedback control, similarly to the process shown in FIG.

[0082] In the above embodiment, the control device 160 repeatedly executes the second feedback control. However, the control device 160 only needs to execute the second feedback control, and may execute the second feedback control only once.

[0083] The order of execution of each process, such as operations, procedures, steps, and stages, in the apparatus and methods shown in the claims, specifications, and drawings, is not specifically indicated as "before," "prior to," or the like. It should also be noted that the order of execution of each process can be any order, as long as the output of a previous process is not used in a subsequent process. Regarding the operational flow in the claims, specifications, and drawings, descriptions using "first," "next," etc. for convenience do not imply that the process must be performed in this order. Furthermore, to the extent permitted by law, the disclosure of Japanese Patent Application No. 2023-103495 is incorporated herein by reference.

[0084] 100 Press brake, 110 Frame, 111 Crown, 112 Upright, 113 Bed, 120 Drive unit, 130 Slide, 140 Back gauge, 150 Angle sensor, 160 Control device, 161 Target angle information acquisition unit, 162 Target position calculation unit, 163 Detected angle information acquisition unit, 164 Current position calculation unit, 165 Control unit, 170 Input device, BP Bolster, LD Downward direction, LT Lower die, O1 Outer side, UD Upward direction, UT Upper die, W1 Work

Claims

1. A press brake used for bending a workpiece, comprising: a slide to which an upper die is attached that moves back and forth; a control device that controls the movement of the slide; and an angle sensor that detects the bending angle of the workpiece, wherein the control device converts a target angle when pressurizing the workpiece into a target position to which the slide is to be moved, converts the detected angle detected by the angle sensor into a current position of the slide corresponding to the detected angle, compares the target position with the current position, and performs feedback control to correct the stroke length so as to move the slide to a position corresponding to the difference between the target position and the current position.

2. The press brake according to claim 1, wherein the control device converts the target angle into the target position using a specific function, and converts the detected angle into the current position using the specific function.

3. The press brake according to claim 1, wherein the control device executes the feedback control at specific time intervals.

4. The press brake according to claim 1, wherein the control device executes the feedback control each time the amount of change in the detected angle reaches a specific angle.

5. A press brake as described in claim 1, wherein the control device executes control to move the slide toward the initial target position until the upper die contacts the workpiece, and executes the feedback control after the upper die contacts the workpiece.

6. The press brake as described in claim 1, wherein the control device executes control to move the slide toward the initial target position until the detected angle becomes a predetermined angle, and starts the feedback control after the detected angle becomes the predetermined angle.

7. A method for controlling a press brake used in bending a workpiece, comprising: controlling the movement of a slide that reciprocates to which an upper die is attached; and detecting the bending angle of the workpiece by an angle sensor; converting a target angle when pressurizing the workpiece into a target position to which the slide is moved; converting the detected angle detected by the angle sensor into a current position of the slide corresponding to the detected angle; comparing the target position with the current position; and initiating feedback control to correct the stroke length so as to move the slide to a position corresponding to the difference between the target position and the current position.