A robot-assisted sheet metal bending process

Abstract

This invention relates to a robot-assisted sheet metal bending process, comprising the following steps: a robot picks up the sheet metal and moves it to the centering table's unloading point to achieve physical centering; the robot picks up the sheet metal and moves it to the initial bending position of the bending machine; a pre-tilt angle is added between the sheet metal and the lower die of the bending machine; the robot's action start signal is a speed conversion point with an interval time; the robot grips the sheet metal and moves it horizontally, cooperating with the upper die to complete the bending follow-up process; the upper die of the bending machine begins to move rapidly downwards, and the robot grips the sheet metal synchronously, completing the bending follow-up process. The robot-assisted sheet metal bending process of this invention adds a pre-tilt angle design, increasing the robot's acceleration time, allowing the robot to have an initial speed at the beginning of the bending process, better cooperating with the bending machine for bending, and maximizing the bending machine's performance. A parametric model is used to simulate the sheet metal bending process, obtaining more accurate end-point trajectory results.

Description

Technical Field

[0001] This invention relates to the field of industrial robot technology, and in particular to a robot-assisted sheet metal bending process. Background Technology

[0002] Currently, automated sheet metal bending using robots in conjunction with bending machines is gradually replacing manual bending. Robotic automated bending not only ensures stable bending quality but also greatly improves production efficiency. Especially when bending large plates, robotic automated bending significantly reduces labor intensity and eliminates safety hazards.

[0003] like Figure 8-11 As shown, one of the most critical technologies in robot-assisted sheet metal bending is the bending follow-up process. This means that when the bending machine bends the sheet metal, the robot's end effector must move synchronously with the sheet metal to complete the bending. Currently, the bending follow-up process in sheet metal bending is as follows: First, the upper die of the bending machine is at the top dead center position. The robot grips the sheet metal and places it above the lower die of the bending machine, ensuring complete contact. Simultaneously, the sheet metal contacts the rear sensor, and the upper die of the bending machine begins to move rapidly downwards, stopping at the clamping point. It then moves downwards to the bottom dead center to bend the sheet metal. The robot grips the sheet metal and moves synchronously, completing the bending follow-up process.

[0004] During the real-time interpolation process of sheet metal bending, the robot's end-effector suction cup will make an approximately circular arc motion around the bending edge of the sheet metal. The trajectory of the robot's end point is quite complex. At the same time, different materials and thicknesses of the sheet metal will have different effects on the bending.

[0005] It mainly has the following defects:

[0006] 1. During the bending process, the speed of the robot's end suction cup may be unable to keep up with the bending speed of the sheet metal, resulting in dragging and deformation or detachment from the sheet metal, which limits the performance of the bending machine.

[0007] 2. The mathematical model's calculation of the end trajectory may deviate from the actual bending process.

[0008] 3. Due to the setting of the clamping points, when the robot delivers the sheet metal to the bending machine processing area, it needs to pause and wait for the sheet metal to be clamped before bending can be performed. Summary of the Invention

[0009] Therefore, the technical problem to be solved by the present invention is to overcome the problem in the prior art that when the sheet metal is bent with robot assistance, the sheet metal rotates around the dynamic contact point between the robot and the bending machine to form the sheet metal. Because the movement of the robot's end suction cup and the upper die of the bending machine is not synchronized or accurate, the robot's end suction cup pulls the sheet metal, resulting in large deformation of the sheet metal, or even making it a defective product.

[0010] To solve the above-mentioned technical problems, the present invention provides a robot-assisted sheet metal bending process, comprising the following steps:

[0011] S1. The robot moves from the gripping preparation point to the gripping point. The end suction cup on the robot adsorbs the sheet metal and moves it to the centering platform unloading point. The end suction cup on the robot releases air, allowing the sheet metal to slide freely on the centering platform to achieve physical centering.

[0012] S2. The robot moves to the gripping point of the centering platform, and the end suction cup on the robot adsorbs the sheet metal and moves it to the initial bending position of the bending machine.

[0013] S3. Before the bending process of the bending machine begins, the robot grips the sheet metal at a certain angle to the horizontal plane, that is, a pre-tilt angle is added between the sheet metal and the lower die of the bending machine.

[0014] S4. Adjust the robot motion start signal command from the clamping point to the speed conversion point and leave an interval time to ensure that the robot moves in sync with the sheet metal.

[0015] S5. When the upper die of the bending machine reaches the robot to pick up the sheet metal and moves it to the initial bending position (horizontal position) of the bending machine, the robot grabs the sheet metal and moves it to the horizontal position. Then the robot works with the upper die to complete the bending follow-up process.

[0016] S6. The upper die of the bending machine begins to move downward rapidly, and the robot grasps the sheet metal in sync, completing the bending and following process.

[0017] In one embodiment of the present invention, before step S1, a parametric model of the sheet metal bending process is established. The parametric model consists of the upper and lower dies of the bending machine and the sheet metal, wherein the upper die performs a downward pressing motion and the lower die is fixed. A user coordinate system for the bending machine is established, and the position coordinates of the robot end-effector gripping point during the bending process are represented by points. The parametric model of sheet metal bending is thus established.

[0018] In one embodiment of the present invention, after the above-mentioned sheet metal bending parametric model is established, the parametric model is then set. First, the spatial positions of the upper and lower dies of the bending machine are set and their material properties are defined. Then, the upper and lower dies of the bending machine and the sheet metal are meshed and constraints are applied. Finally, sheet metal bending simulation is performed to obtain real-time trajectory data of the gripping points and export them. The end trajectory of the robot bending process is obtained from the exported data.

[0019] In one embodiment of the present invention, in step S5 above, when the upper die of the bending machine reaches the clamping point position, the sheet metal also reaches the clamping point position at the same time, realizing real-time interpolation movement of the two devices, and then bending is performed.

[0020] In one embodiment of the present invention, in step S3 above, the sheet metal on the side where the gripping point between the robot and the sheet metal is located is lower than the horizontal plane.

[0021] In one embodiment of the present invention, in step S4 above, the robot action start signal command is adjusted from the clamping point to the speed conversion point with an interval time, so that the sheet metal has a certain initial speed and acceleration when it reaches the clamping point position, in order to adapt to the trajectory of the acceleration phase of the gripping point trajectory, reduce the peak value of speed change, so that the robot can better cooperate with the bending machine to ensure that the robot and the sheet metal move synchronously.

[0022] In one embodiment of the present invention, in step S3 above, the method for establishing a certain angle between the sheet metal and the horizontal plane is as follows: the end suction cup on the robot adsorbs the sheet metal and moves it to the lower die of the bending machine, the sheet metal is placed on the lower die of the bending machine, the sheet metal and the lower die of the bending machine are attached together, and one end of the end suction cup on the robot adsorbs the sheet metal and descends below the horizontal plane, thereby making the sheet metal tilted.

[0023] In one embodiment of the present invention, during the tilting process of the end suction cup on the robot adsorbing the sheet metal, the lower die of the bending machine rotates with the contact point between the edge of the robot and the sheet metal gripping point and the sheet metal as the fulcrum.

[0024] In one embodiment of the present invention, in step S6 above, the upper die of the bending machine moves downward to bend the sheet metal, and the robot grasps the sheet metal synchronously. The robot grasps the sheet metal and moves along an arc-shaped trajectory with the bending point of the upper die of the bending machine as the center.

[0025] In one embodiment of the present invention, in step S6 above, the robot picks up the bent sheet metal and moves it to the unloading point. The end suction cup on the robot releases air, allowing the bent sheet metal to be placed on the unloading table. The robot returns to the picking preparation point, ready to perform the next sheet metal bending process.

[0026] Compared with the prior art, the above-mentioned technical solution of the present invention has the following advantages: Compared with the conventional robot-assisted bending process:

[0027] 1. The robot's acceleration gradient has been reduced, and the robot's following speed has been increased, which allows it to better adapt to the bending machine's feed speed and bring out the bending machine's greater performance.

[0028] 2. Using a parametric model yields a more general model than a mathematical model, and the resulting real-time interpolation trajectory is also more accurate.

[0029] 3. The bending cycle has been shortened, and there is no longer a pause at the clamping point, which indirectly improves the bending efficiency of sheet metal.

[0030] The robot-assisted sheet metal bending process described in this invention applies the bending follow-up process with added tilt angle to the overall process of robot-assisted sheet metal bending. Combined with the simulation of the sheet metal bending process by a parametric model, the real-time interpolation trajectory of the robot end effector is obtained. While ensuring product requirements, it improves the overall efficiency of sheet metal bending, maximizes the performance of the bending machine, and increases the continuity of the entire processing (eliminating the pauses at the clamping points that cause discontinuous speed). Attached Figure Description

[0031] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0032] Figure 1 This is a schematic diagram of the robot-assisted sheet metal bending process of the present invention. Figure 1 ;

[0033] Figure 2 This is a schematic diagram of the robot-assisted sheet metal bending process of the present invention. Figure 2 ;

[0034] Figure 3 This is a schematic diagram of the robot-assisted sheet metal bending process of the present invention. Figure 3 ;

[0035] Figure 4 This invention relates to the principle of robot-assisted sheet metal bending process. Figure 1 ;

[0036] Figure 5 This invention relates to the principle of robot-assisted sheet metal bending process. Figure 2 ;

[0037] Figure 6 This is a robot end effector trajectory diagram of the robot-assisted sheet metal bending process of the present invention;

[0038] Figure 7 This is a prior art diagram of the robot's end effector trajectory.

[0039] Figure 8 This is a diagram showing the position of the upper die of the bending machine at the top dead center in the prior art of this invention;

[0040] Figure 9 This is a diagram showing the position of the upper die of the bending machine at the clamping point in the prior art of this invention;

[0041] Figure 10 This is a position diagram of the bending stage of the upper die pressing down in the prior art of the present invention;

[0042] Figure 11 This is a diagram showing the position of the upper die of the bending machine at the bottom dead center in the prior art of this invention;

[0043] Figure 12 This is a diagram of the relative position data of the upper die read by the bending machine system of the present invention;

[0044] Figure 13 This is a real-time position data diagram of the upper die of the bending machine according to the present invention;

[0045] Figure 14 This is a line graph of the feed distance of the upper die of the bending machine according to the present invention;

[0046] Figure 15 This is a simulation result diagram of the sheet metal bending process of the present invention;

[0047] Figure 16 This is a graph showing the relationship between the horizontal coordinate of point W and the bending time in this invention.

[0048] Figure 17 This is a graph showing the relationship between the vertical coordinate of point W and the bending time in this invention. Detailed Implementation

[0049] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0050] Example 1

[0051] Reference Figure 1-7 As shown, the robot-assisted sheet metal bending process of the present invention includes the following steps:

[0052] S1. The robot moves from the gripping preparation point to the gripping point. The end suction cup on the robot adsorbs the sheet metal and moves it to the centering platform unloading point. The end suction cup on the robot releases air, allowing the sheet metal to slide freely on the centering platform to achieve physical centering.

[0053] S2. The robot moves to the gripping point of the centering platform, and the end suction cup on the robot adsorbs the sheet metal and moves it to the initial bending position of the bending machine.

[0054] S3. Before the bending process of the bending machine begins, the robot grips the sheet metal at a certain angle to the horizontal plane, that is, a pre-tilt angle is added between the sheet metal and the lower die of the bending machine.

[0055] S4. Adjust the robot motion start signal command from the clamping point to the speed conversion point and leave an interval time to ensure that the robot moves in sync with the sheet metal.

[0056] S5. When the upper die of the bending machine reaches the clamping point, the robot grabs the sheet metal and moves it to a horizontal position. Then the robot works with the upper die to complete the bending and following process.

[0057] S6. The upper die of the bending machine begins to move downward rapidly, and the robot grasps the sheet metal in sync, completing the bending and following process.

[0058] Example 2

[0059] Reference Figure 1-7 As shown, the robot-assisted sheet metal bending process of the present invention includes the following steps:

[0060] S1. In sheet metal bending, the sheet metal material and its dimensional parameters, as well as the upper and lower dies of the bending machine, all have a certain impact on the real-time interpolation trajectory of the robot's end effector suction cup gripping point. Therefore, a parametric model of the sheet metal bending process is first established. This parametric model consists of the upper and lower dies of the bending machine and the sheet metal, where the upper die performs a downward pressing motion and the lower die is fixed. A user coordinate system for the bending machine is established, and the position coordinates of the robot's end effector suction cup gripping point during the bending process are represented by points. After establishing the sheet metal bending parametric model, the following steps are taken... The parametric model is set up by first setting the spatial positions of the upper and lower dies of the bending machine and defining their material properties. Then, the upper and lower dies of the bending machine and the sheet metal are meshed and constraints are applied. Finally, the sheet metal bending simulation is performed to obtain and export the real-time trajectory data of the gripping point. The end trajectory of the robot bending process is obtained from the exported data. The robot moves from the gripping preparation point to the gripping point. The end suction cup on the robot adsorbs the sheet metal and moves it to the centering table unloading point. The end suction cup on the robot releases air, allowing the sheet metal to slide freely on the centering table to achieve physical centering.

[0061] S2. The robot moves to the centering platform gripping point, the end suction cup on the robot adsorbs the sheet metal and moves it to the initial bending position of the bending machine, i.e., the horizontal position.

[0062] S3. Before the bending process of the bending machine begins, the robot grips the sheet metal at a certain angle to the horizontal plane. That is, a pre-tilt angle is added between the sheet metal and the lower die of the bending machine. At this time, the sheet metal on the side where the gripping point between the robot and the sheet metal is located is lower than the horizontal plane. The method of pre-leaving the tilt angle in advance not only ensures that the clamping point position can be removed to improve efficiency, but also ensures that the robot speed does not change suddenly, the sheet metal bending quality is not affected, and there is no impact on the robot.

[0063] S4. Adjust the robot motion start signal command from the clamping point to the speed conversion point and leave an interval time so that the sheet metal has a certain initial speed and acceleration when it reaches the clamping point position, in order to adapt to the trajectory of the acceleration phase of the gripping point trajectory, reduce the peak value of speed change, so that the robot can better cooperate with the bending machine to ensure that the robot and the sheet metal move synchronously.

[0064] S5. When the upper die of the bending machine reaches the clamping point, the robot grabs the sheet metal and moves synchronously. The sheet metal also reaches the clamping point at the same time, realizing real-time interpolation movement of the two devices. The robot grabs the sheet metal and moves it to the horizontal. Then the robot works with the upper die to complete the bending follow-up process.

[0065] S6. The upper die of the bending machine begins to move downward rapidly, bending the sheet metal. The robot grips the sheet metal synchronously, following the arc trajectory centered on the bending point of the sheet metal by the upper die of the bending machine. After the sheet metal is bent, the robot moves to the unloading point. The end suction cup on the robot releases air, allowing the bent sheet metal to be placed on the unloading table. The robot returns to the gripping preparation point, ready to perform the next sheet metal bending and forming process.

[0066] In step S3 above, the method for establishing a certain angle between the sheet metal and the horizontal plane is as follows: the end suction cup on the robot adsorbs the sheet metal and moves it to the lower die of the bending machine. The sheet metal is placed on the lower die of the bending machine, and the sheet metal and the lower die of the bending machine are in contact. The end suction cup on the robot adsorbs the sheet metal and descends below the horizontal plane, thereby making the sheet metal tilted.

[0067] During the tilting process of the sheet metal being adsorbed by the end suction cup on the robot, the lower die of the bending machine rotates around the contact point between the edge of the robot and the sheet metal gripping point and the sheet metal.

[0068] Experimental verification was conducted: At the same feed speed of 10mm / s on the bending machine, the bending process with the added tilt angle was compared to the conventional bending process. Under normal circumstances, the sheet metal had already detached from the suction cup. After adding the tilt angle, the sheet metal did not detach, and the bent sheet metal met production requirements. Data from the bending machine control system showed that the improved bending cycle was shortened by approximately 10% compared to the previous method.

[0069] The robot-assisted sheet metal bending process of this invention incorporates a pre-tilt angle design, increasing the robot's acceleration time and ensuring it has an initial velocity at the start of the bending process. This allows for better coordination with the bending machine, maximizing its performance. A parametric model is used to simulate the sheet metal bending process, yielding more accurate end-point trajectory results. The elimination of clamping points shortens the bending cycle and improves bending efficiency while meeting product manufacturing requirements.

[0070] Example 3

[0071] Based on Embodiment 2, the robot-assisted sheet metal bending process of the present invention includes the following method for establishing a parametric model:

[0072] This invention uses the APDL language in ANSYS software to implement secondary development, establish a parametric model of the robot bending process, and then perform steps such as mesh generation, applying constraints and solving to finally obtain real-time trajectory data of the gripping points.

[0073] In sheet metal bending, the sheet metal material and its dimensional parameters, as well as the upper and lower dies of the bending machine, all influence the real-time interpolation trajectory of the robot's end effector suction cup gripping point. To ensure the versatility and accuracy of sheet metal bending, secondary development of ANSYS software using APDL language allows for the creation of a parametric model of the sheet metal bending process. This model consists of the upper and lower dies of the bending machine and the sheet metal, where the upper die performs a downward pressing motion, and the lower die remains stationary. A user coordinate system for the bending machine is then established. k x k y k z k During the bending process, the coordinates of the robot's end-effector gripping point are represented by point W(x). w ,y w The parametric model of sheet metal bending is represented by ) Figure 5 As shown.

[0074] The parametric model setup process involves a series of steps to ensure its accuracy and reliability. First, the spatial positions of the upper and lower dies of the bending machine are set, and their material properties are clearly defined. Second, the upper and lower dies and the sheet metal are meshed, and appropriate constraints are applied. Meshing aims to divide the object into smaller units for more accurate simulation of its movements. Constraints are set to simulate constraints in the processing environment, ensuring the simulation results match reality. Finally, the sheet metal bending process is simulated. During the simulation, real-time trajectory data of the gripping points is acquired and exported for further analysis and application.

[0075] To facilitate parameter setting and simulation operations, a visual parameter interface was designed using the APDL language. This interface allows users to manually set parameters such as sheet metal dimensions and material properties. Figure 12 The table shows the meanings of relevant parameters for sheet metal bending. The ANSYS software automatically models the sheet metal using the APDL language program, acquiring real-time trajectory data of the grab points.

[0076] The bending distance refers to the distance from the gripping point of the robot's end effector suction cup to the bending edge. By setting the upper and lower die parameters, sheet metal material properties, bending angle, and bending speed of the bending machine's CNC system, the real-time feed distance curve of the upper die under these parameters can be obtained in the system software. Figure 14As shown. In the sheet metal bending process, the upper die of the bending machine first moves rapidly from its initial position to the clamping point position and undergoes speed conversion. Then, the sheet metal bending process is performed; the upper die changes speed from the clamping point position to the bottom dead center position to maintain pressure. Finally, the upper die returns to the bending return point from the bottom dead center position. The motion data of the upper die is extracted in MATLAB software based on the upper die feed motion curve in the bending machine system software. Simultaneously, relevant parameters are set in ANSYS software to establish a parametric model, completing the simulation process and acquiring relevant data.

[0077] A specific calculation example is as follows:

[0078] First, a parametric model is established, setting the lower die slot width to 10mm, sheet metal thickness to 1.5mm, bending radius to 1.5mm, sheet metal material elastic modulus to 200GPa, yield strength to 205MPa, and tangent modulus to 2000N / m. 2 The shear modulus is 79 GPa and the tensile strength is 520 MPa. Next, MATLAB software was used to read the motion curve of the upper die pressing down on the bending machine, such as... Figure 15-17 As shown, the data was then imported into ANSYS software for simulation, and the simulation results are as follows. Figure 15 As shown.

[0079] Simulations yielded the spatial position of point W, the robot's end-effector gripper point, during sheet metal bending in the user coordinate system of the bending machine, as shown in Table 16. MATLAB software was used to analyze the spatial position of point W and plot a curve, as shown in the figure below. Figure 16 , 17 As shown.

[0080] The results obtained from the simulation parameterized model show that during the bending process, the upper die feed motion of the bending machine is a variable speed motion. The initial speed of the robot end suction cup gripping point (point W) is relatively slow, and then it performs variable speed motion within the set bending speed range, and finally decelerates and stops. The trend of the change of the horizontal and vertical coordinates of point W and the bending angle is the same as that of point W.

[0081] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A robot-assisted sheet metal bending process, characterized in that, Includes the following steps: S1. The robot moves from the gripping preparation point to the gripping point. The end suction cup on the robot adsorbs the sheet metal and moves it to the centering platform unloading point. The end suction cup on the robot releases air, allowing the sheet metal to slide freely on the centering platform to achieve physical centering. S2. The robot moves to the gripping point of the centering platform, and the end suction cup on the robot adsorbs the sheet metal and moves it to the initial bending position of the bending machine. S3. Before the bending process of the bending machine begins, the robot grips the sheet metal at a certain angle to the horizontal plane, that is, a pre-tilt angle is added between the sheet metal and the lower die of the bending machine. At this time, the sheet metal on the side where the gripping point between the robot and the sheet metal is located is lower than the horizontal plane. S4. Adjust the robot motion start signal command from the clamping point to the speed conversion point and leave an interval time so that the sheet metal has a certain initial speed and acceleration when it reaches the clamping point position, in order to adapt to the trajectory of the acceleration phase of the gripping point trajectory, reduce the peak value of speed change, so that the robot can better cooperate with the bending machine to ensure that the robot and the sheet metal move synchronously. S5. When the upper die of the bending machine reaches the clamping point, the robot grabs the sheet metal and moves it to a horizontal position. Then the robot works with the upper die to complete the bending follow-up process. When the upper die of the bending machine reaches the clamping point, the sheet metal also reaches the clamping point at the same time, realizing real-time interpolation movement of the two devices, and then bending is performed. S6. The upper die of the bending machine begins to move downward rapidly, and the robot grasps the sheet metal in sync, completing the bending and following process.

2. The robot-assisted sheet metal bending process according to claim 1, characterized in that: Before step S1, a parametric model of the sheet metal bending process is established. The parametric model consists of the upper and lower dies of the bending machine and the sheet metal. The upper die performs a downward pressing motion, while the lower die is fixed. A user coordinate system for the bending machine is established. During the bending process, the position coordinates of the robot's end-effector gripping point are represented by points. The parametric model of sheet metal bending is thus established.

3. The robot-assisted sheet metal bending process according to claim 2, characterized in that: After the above-mentioned sheet metal bending parametric model is established, the parametric model is then set. First, the spatial positions of the upper and lower dies of the bending machine are set and their material properties are defined. Then, the upper and lower dies of the bending machine and the sheet metal are meshed and constraints are applied. Finally, the sheet metal bending simulation is performed to obtain the real-time trajectory data of the gripping points and export it. The end trajectory of the robot bending process is obtained from the exported data.

4. The robot-assisted sheet metal bending process according to claim 1, characterized in that: In step S3 above, the method for establishing a certain angle between the sheet metal and the horizontal plane is as follows: the end suction cup on the robot adsorbs the sheet metal and moves it to the lower die of the bending machine. The sheet metal is placed on the lower die of the bending machine, and the sheet metal and the lower die of the bending machine are in contact. The end suction cup on the robot adsorbs the sheet metal and descends below the horizontal plane, thereby making the sheet metal tilted.

5. The robot-assisted sheet metal bending process according to claim 4, characterized in that: During the tilting process of the sheet metal being adsorbed by the end suction cup on the robot, the lower die of the bending machine rotates around the contact point between the edge of the robot and the sheet metal gripping point and the sheet metal.

6. The robot-assisted sheet metal bending process according to claim 1, characterized in that: In step S6 above, the upper die of the bending machine moves downward to bend the sheet metal, and the robot grasps the sheet metal in a synchronous motion. The robot grasps the sheet metal and moves along an arc-shaped trajectory with the bending point of the upper die of the bending machine as the center.

7. The robot-assisted sheet metal bending process according to claim 1, characterized in that: In step S6 above, the robot picks up the bent sheet metal and moves it to the unloading point. The end suction cup on the robot releases air, allowing the bent sheet metal to be placed on the unloading table. The robot then returns to the pick-up preparation point, ready to perform the next sheet metal bending process.

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