The ingenious mechanical arm design can easily realize the reciprocation of the workpiece between the conveyor belt and the machine tool

The ingenious mechanical arm design can easily realize the reciprocation of the workpiece between the conveyor belt and the machine tool

Abstract : On the basis of absorbing the knowledge about industrial robot system, the design of industrial robot arm is introduced. The manipulator adopts a stepping motor to control the precision and stability of the telescopic arm, and the hydraulic control wedge drives the connecting rod, which has a large clamping force and is light.

　　Robots are mechanical devices that automatically complete tasks and perform tasks that assist or replace humans. At present, it has important uses in the fields of industry, medicine, and military. The main contradiction in industrial production prompted the adoption of new technical equipment, namely operating machines (operating tools). The loading and unloading of the machine, especially the machine tool, the transfer of some workpieces during the operation, the storage and retrieval of the workpieces, the installation of components, welding, forging, pressing, painting and many other technological operations, etc., these operating surfaces do not seem to be complicated and usually not Workers with special skills are required, but they must be operated by a combination of human hands and arms. Therefore, all countries are studying the automated industrial manipulator of the program control system-the manipulator.

　　The main content of this design includes the design of electric telescopic arm and hydraulic control gripper . Using a stepping motor as the power source of the telescopic arm, the biggest advantage of the stepping motor is that it can be accurately positioned, instead of the previous method of positioning by positioning posts. The clamp adopts a hydraulic drive wedge to drive the linkage mechanism. The advantage of the linkage mechanism is light wear and easy processing.

1. General design plan

　　The manipulator is generally composed of an actuator, a driving mechanism, a control mechanism, and a position detection mechanism. The driving mechanism can take the forms of hydraulic transmission, pneumatic transmission, electric transmission and mechanical transmission, and most of them use motor-hydraulic combined transmission.

　　This manipulator is a special manipulator that clamps cylindrical parts from the conveyor belt to a special machine tool, and then clamps back to the conveyor belt after the processing is completed. The manipulator is divided into four parts: gripper, telescopic arm, lifting arm and base, as shown in Figure 1. The clamper is installed on the telescopic arm, the telescopic arm is installed on the lifting arm, and the lifting arm is installed on the base. The connection method is flange bolt connection.

　　The manipulator completes a transfer and retrieval process as follows: from the original position, when the workpiece is transferred to the specified position via the conveyor belt, the manipulator executes the command through the pre-edited program , the lifting arm is lowered, and the gripper clamps the workpiece, the lifting arm Ascend, after reaching the specified height, the base quickly rotates, and then the base slowly advances to the processing machine tool of the workpiece, and the telescopic arm extends to the designated position, the clamp is released, the workpiece is placed in the corresponding position of the machine tool, and then the telescopic arm retracts; After the processing is completed, the telescopic arm extends again, the gripper clamps the finished workpiece, the telescopic arm retracts, the base rotates, the base slowly retracts to the side of the conveyor belt to the specified position, the lifting arm begins to descend, and reaches the top of the conveyor belt. After the gripper is released and the workpiece is placed on the conveyor belt, the lifting arm rises to the original position and stops, ready for the next cycle.

Figure 1 The overall scheme of the manipulator

1. Gripper 2. Telescopic arm 3. Lifting arm 4. Base

2. The design of the holder

　　The wedge lever type rotary gripper (see Figure 2) is composed of a piston rod, a wedge, a roller, an auxiliary rod, a gripper claw, a gripper arm, and a spring. When working, the wedge block 2 is pushed forward by the piston rod 1 of the hydraulic cylinder, so that the two rollers 3 at the left end of the gripper arm 6 are separated from each other, so that the gripper claw can be clamped, and the gripper is in a clamping state ; The piston rod retracts, and under the action of the spring, the holder opens.

Figure 2 Structure diagram of the holder

1. Piston rod 2. Wedge 3. Roller 4. Auxiliary rod 5 Gripper claw 6. Gripper arm 7. Spring

　　According to the principle that the driving force of the gripper is provided by the hydraulic cylinder, the hydraulic cylinder is selected to meet the use of the work occasion . This program uses the W70/140L-1 series of light tie rod hydraulic cylinders. Compared with hydraulic cylinders of the same pressure level, this hydraulic cylinder has the characteristics of simple structure, high degree of commonality of parts and various installation forms. This hydraulic cylinder conforms to the structure of this program. Compact and light design concept. The gripper part uses a pair of main gripper arms and a pair of auxiliary arms to ensure that the working surface of the gripper is always on the same plane as the workpiece during work, which improves the safety of the machine.

　　The gripper's claw adopts a V-shaped claw structure, and the material is aluminum alloy, so the V-shaped claw is not easy to deform and break, and is light in weight. The processing method is casting. The structure is shown in Figure 3.

Figure 3 Schematic diagram of gripper claw

　　Strip groove marks are machined on both insides of the V-shaped jaws to increase the friction when clamping the workpiece and make the workpiece stronger. In addition, in order to prevent the V-shaped jaw from clamping and damaging the surface of the workpiece, it can also be used in the V-shaped jaw. Paste a rubber sheet with rough corrugations on the working surface, which can play a protective role. The mucosa at the joint between the rubber sheet and the V-shaped jaw is required to be firm to prevent the rubber sheet from falling off.

3. Design of electric telescopic boom

　　The manipulator telescopic arm, the bottom plate is fixed on the boom, and the front flange is installed with the manipulator to complete the linear telescopic action. The electric telescopic arm mainly consists of a motor, a transmission gear, a bearing set, a ball screw and a guide rail. The AC torque motor drives the ball screw through the transmission gear to push the guide rod to move. The motor is used to rotate forward and backward to achieve expansion and contraction. The two-way thrust bearing combination ensures the stability of the lead screw. This is achieved by the impact block on the guide rod hitting the limit switch. Maximum telescopic positioning, when the striker hits the right end switch to reach the maximum extension displacement, when the striker strikes the left end to reach the maximum contraction displacement.

　　The telescopic arm is driven by an AC torque motor. The torque motor changes the size of the locked-rotor torque by adjusting the working voltage to achieve the requirements of stable operation, fast action and accurate positioning . The telescopic arm of the transmission part is driven by a ball screw. Compared with other transmission parts such as a trapezoidal thread screw, the obvious advantage of the ball screw is that the manipulator has precise control, stable and flexible contraction, quick action and coordinated work. The extension and retraction movement of the telescopic arm of the executive part is realized by the expansion and contraction of the guide rod, and the guide rod part adopts a double guide rod design, which can further improve the mechanical performance and accuracy requirements of the telescopic arm.

Figure 4 Schematic diagram of electric telescopic mechanism

1. Motor 2. Transmission gear 3. Two-way thrust bearing assembly 4. Cushion spring 5. Ball screw 6. Bearing 7. Flange 8. Limit switch 9. Linear guide 10. Strike block 11. Connecting plate 12. Base plate

   
   

4. Conclusion

　　The task to be completed in this design is to transfer the workpiece from the conveyor belt to the machine tool, and then put the workpiece back on the conveyor belt after the processing is completed. After the robotic arm is put into production, the first thing is to improve production efficiency , reduce labor costs, and make production The process is more smooth and orderly. At the same time, it also effectively avoids the potential safety hazards caused by the manual handling process, reduces the occurrence of work-related injuries and the probability of the workpiece bumping during the handling process, which is of great help to the enterprise to improve economic benefits.