Design and application of automatic bending scheme of robot

introduction

Since the beginning of the 21st century, with the rapid development of the economy, metal parts have been widely used in the automotive, electricity, home appliances, chemical, food, network communications and other industries. Metal processing technology and production efficiency have affected the development of these industries to a certain extent. The forming methods of three-dimensional metal parts are mainly divided into hard mold forming and soft mold forming. Hard mold forming requires the development of special stamping dies, which is relatively expensive: soft mold forming is mainly reflected in bending forming, using simple and universal bending dies, which is relatively low in cost and can meet the processing needs of products with complex processes. With the acceleration of product replacement, the cost of hard mold development is getting higher and higher, so people prefer the bending forming processing method, but the bending process has high technical requirements for the operator, so it is particularly important to study and apply automatic bending.

1 Bending process analysis

1.1 Bending process principle

The bending process principle is shown in Figure 1. The upper and lower dies are fixed on the upper and lower workbenches of the folding machine respectively. The power generated by the motor is used to drive the workbenches to move relative to each other. Combined with the shapes of the upper and lower dies, the bending forming of the sheet metal is achieved.

1.2 Bending action analysis

When the folding machine is stationary, the upper die is at the top dead center. When bending begins, the upper die moves downward quickly to the slow point. At this time, the folding machine starts to change speed and moves to the pressure plate point according to the set bending speed. The upper die continues to press down, and the workpiece begins to bend due to extrusion. The upper die presses down to the bottom dead center, and the workpiece completes bending.

2. Selection of robots

Due to the complexity of the bending process, the robot needs to move synchronously with the workpiece during automatic bending. Following too fast or too slow will cause the workpiece to deform or even be scrapped. Therefore, the selection of the robot plays a key role in the effect of automatic bending. This solution uses the FANUC-R2000ic/165F six-axis robot, which has a large travel, strong load capacity (can meet the needs of automatic bending of large workpieces), high repeat positioning accuracy, and a bending follow-up system when adapted. It is simple to debug and is suitable for automatic bending.

3. Automatic bending scheme design

The automatic bending system is mainly composed of the following parts: bending machine, robot, gripper, gravity centering table, loading and unloading table, material separation mechanism, thickness measurement system, reversing table, encoder, etc., as shown in Figure 2.

A bending machine is automatically bent by a robot: the robot grabs the workpiece from the loading table through the gripper, moves the workpiece to the top of the centering table, puts down the workpiece, and completes the secondary positioning and grabbing of the workpiece through the gravity centering table and 2D visual inspection to improve accuracy: the workpiece is then inspected by the thickness measurement system to prevent multiple grabbing and wrong materials: after passing the inspection, the robot flips the workpiece and moves it to the top of the lower die of the folding machine for positioning: after positioning is completed, bending begins, and the robot moves upward synchronously with the workpiece until the bending is completed: the workpiece is reversed through the reversing table to ensure that the bending operation can be effectively and continuously completed when bending in different directions: finally, the bent workpiece is stacked. If the workpiece level requirements are high, it cannot be stacked. The robot can add the action of taking and placing the partition to protect the appearance of the workpiece.

The whole process is completed by the robot, which automatically picks up, places, positions, inspects, flips, and cooperates with the folding machine to bend, realizing unmanned automatic bending throughout the entire process.

4 Solution Verification

According to the design plan, the Komatsu PAs5020 folding machine and the FANUC-R2000ic/165F robot were used. The unfolded size of the workpiece was 1052.8mm×993.8mm×1.0mm, the bending angle was 90a, the bending size was (9.0±0.25)mm, (15.0±0.25)mm, and (21.0±0.25)mm. The upper die was GZJ3090 and the lower die was GV59060 for scheme verification. The robot's running points were manually calibrated, and the mold and workpiece parameter settings are shown in Table 1.

The movements of the folding machine and the robot are controlled by I/O signals. The robot moves the workpiece to the top of the lower die of the folding machine, so that the workpiece fits the die completely, and then pushes the workpiece to move until the induction switch on the rear gauge is turned on. After the folding machine receives the induction switch signal, it starts to perform the bending action. The robot obtains the tool coordinates of the upper dead center, pressure plate point, and lower dead center of the folding machine through the encoder, and calculates the movement path of the workpiece during the bending process, and moves synchronously with the folding machine along the path, thereby completing the bending follow-up action. After the folding machine is pressed down to the lower dead center, it quickly returns to the upper dead center. The robot exits the folding machine with the workpiece, completing an automatic bending. The verification process is shown in Figures 3 and 4.

200Pcs workpieces were used to verify the automatic bending effect and stability, and 10Pcs finished products were sampled to test the bending angle and size. The results are shown in Table 2. It can be seen from the test results that the angle and size of the workpiece after automatic bending by the robot are within the tolerance range, which shows that the automatic bending solution is feasible.

5 Conclusion

In this paper, based on the bending process principle, an automatic bending solution using a manipulator is designed. The automatic bending solution is verified many times using a folding machine and a robot. The results show that the robot's automatic bending effect is good and the robot can replace manual bending operations.