Abstract: To fully leverage the automation advantages of welding robots, improve product quality and efficiency, enhance process equipment, and reduce worker labor intensity, a robotic flexible welding workstation was designed. This paper introduces the technical solution of the robotic flexible welding workstation and the design of key components such as the positioner, intelligent transporter, and workpiece positioning fixture. Through the design, technical challenges such as high positioning accuracy requirements for the positioner, communication between the control system and the robot, the picking action of the intelligent transporter, and rapid workpiece positioning and clamping were solved.
Keywords: welding robot; positioner; servo control; intelligent transporter
With the popularization and development of industrial automation, the application of welding positioners has also gradually become widespread, mainly in welding in the fields of automobiles, electronics, and machinery. Welding positioners combined with welding robots to form a small production line can better save energy and improve production efficiency.
1 Technical Solution
The robotic flexible welding workstation is designed for small-scale automated production line operations, capable of welding various workpieces up to 2.5 meters in length. It integrates automatic feeding, semi-automatic positioning and clamping, automatic welding, and automatic unloading, thereby reducing worker labor intensity and improving production efficiency. To meet the overall design requirements, a suitable technical solution was developed. The equipment mainly consists of workpiece positioning fixtures, intelligent conveyors, positioners, component turnover racks, stacking racks, feeding mechanisms, electrical and pneumatic systems, forming a small-scale production line, as shown in Figure 1.
Figure 1. Layout of the robot flexible welding workstation
Main process: 1) The feeding mechanism transports the raw materials to station one; 2) Manual assistance for clamping and positioning; 3) The positioner rotates the clamped workpiece to station two; 4) Robot welding position 1; 5) The tilting axis rotates 90 degrees; 6) Robot welding position 2; 7) The tilting axis rotates 180 degrees; 8) Robot welding position 3, workpiece welding completed; 9) The positioner rotates the welded workpiece back to station one; 10) The intelligent transporter retrieves the workpiece from station one and transports it to the pallet rack. This completes the process. The clamping area at station one and the welding area at station two operate simultaneously, greatly improving welding efficiency.
2. Design of the positioner
The positioner is the core component of the robotic flexible welding workstation, mainly composed of a steel structure, a rotating axis, a tilting axis, guide rails, quick-release shackles, etc., as shown in Figure 2.
Figure 2 Plan view of the positioner
The main functions of each part are: (1) The steel structure is the supporting component; (2) The rotating shaft allows the positions of station 1 and station 2 to be interchanged, so as to achieve the purpose of welding, unloading and clamping; (3) The two flipping shafts are for the displacement of station 1 or station 2, so that the robot can weld and clamp the workpiece in the position most conducive to weld formation; (4) The guide rail is to guide the intelligent transporter to move laterally to the positioner to pick up the goods; (5) The quick clamping ring is mainly used to quickly change the tooling when welding different workpieces.
The welding accuracy of the robotic flexible welding workstation is mainly determined by the accuracy of the positioner. Since the welding accuracy of the robotic flexible welding workstation is within 0.5mm, this means that the positioning accuracy of the 3.8-meter diameter turntable after rotating 180 degrees must be within 0.5mm, and the flipping positioning accuracy must also be within 0.5mm. To achieve these requirements, a servo motor + compound live gear reducer is used for the transmission, achieving a transmission accuracy of 0.01mm.
3. Design of Intelligent Transporter
The intelligent handling device mainly consists of a lifting frame, a lateral frame, a guide sleeve, lateral wheels, and a telescopic fork arm. Through the operation of three motors, it can simultaneously perform lifting, lateral movement, and telescopic movements to achieve the purpose of unloading, as shown in Figure 3.
Figure 3 Three-view drawing of the intelligent transporter
Intelligent transporters are an important component of robotic flexible welding workstations for realizing assembly line operations. Their main function is to transport welded workpieces from positioners to pallet racks via guide rails, reducing the labor intensity of workers and improving palletizing efficiency.
4. Design of workpiece positioning fixture
The workpiece positioning fixture mainly consists of a fixture support, a positioning hook, a positioning frame, and a cylinder. The fixture support is universal, and different positioning frames are installed on the fixture support according to different workpieces. The entire workpiece positioning fixture is connected to the positioner via a quick-release clasp; as shown in Figure 4.
Figure 4 Elevation view of workpiece positioning fixture
To simultaneously position and clamp the workpiece, the extension and retraction of a cylinder is cleverly utilized, along with a spring and a pull hook, to achieve both positioning and clamping actions. Through variations, this mechanism has been widely applied to the positioning and clamping of other workpieces.
5 Control System Design
Figure 5 Control System Diagram
The control system integrates mainstream automation control components such as human-machine interface, servo closed-loop drive, and PLC positioning module, ensuring accuracy, making operation more convenient, and maintenance simpler.
6. Conclusion
This paper presents the design and analysis of a flexible robotic welding workstation, including key components such as the positioner, intelligent transporter, and workpiece positioning fixture. The control system design integrates mainstream automation control components such as human-machine interface, servo closed-loop drive, and PLC. Furthermore, seamless connection between the welding positioner and the welding robot is achieved through communication between the PLC and the welding robot. The following key technologies were solved:
(1) The transmission adopts a servo motor + compound gear reducer, which solves the high positioning accuracy requirements of the positioner;
(2) The communication problem between the control system and the robot was solved;
(3) It solved the problem of rapid positioning and clamping of the workpiece;
The design and implementation of the robotic flexible welding workstation has greatly improved production efficiency. Compared with manual welding, the efficiency has increased by more than three times, and the labor intensity of workers has been greatly reduced.
About the author: Cai Senhua; born in October 1975; male; master's degree; chief designer at Huixin Branch of Changzhi Qinghua Machinery Factory;
Research topic: Positioner and workstation;
Mailing address: P.O. Box 6, Qinghua Street, Changzhi, Shanxi Province;
Postal code: 046012
Contact numbers: 15035532388, 0355-3912621
Email address: [email protected]
