Comprehensive Guide to Welding Robot Operation
A welding robot consists of two parts: the robot itself and the welding equipment. Using welding robots not only stabilizes and improves welding quality and increases production efficiency, but also reduces the skill requirements for welders, thereby shortening the preparation cycle for product upgrades and reducing corresponding equipment investment.
Welding Robot Requirements for Welding Wire
Robots can use either drum-type or reel-type welding wire as needed. To reduce the frequency of wire changes, drum-type welding wire should be used. However, due to the long wire feeding hose, resistance is high, requiring higher quality wire stiffness and other properties. When using welding wire with slightly lower copper plating quality, the copper plating on the wire surface may rub off due to friction, reducing the internal volume of the guide tube. This increases resistance during high-speed wire feeding, causing the wire to not be fed smoothly, resulting in vibration, unstable arc, and affecting weld quality. In severe cases, jamming may occur, causing the robot to stop. Therefore, the welding wire guide tube must be cleaned regularly.
Analysis and Handling Methods of Welding Defects in Welding Robots
Robot welding uses argon-rich mixed gas shielded welding. Common welding defects include weld misalignment, undercut, and porosity. Specific analyses are as follows:
(1) Weld misalignment may be due to incorrect welding position or problems with the welding torch's positioning. In this case, check the accuracy of the TCP (center point position of the welding torch) and adjust it accordingly. If this occurs frequently, check the zero position of each robot axis and recalibrate.
(2) Undercut is characterized by groove-like depressions at the weld edge of the base material, often appearing on both sides of the cap weld. The main causes include excessive welding speed, excessive oscillation amplitude, insufficient dwell time on both sides, or excessive welding current. Handling methods include appropriately reducing the welding speed, decreasing the oscillation amplitude, increasing the dwell time on both sides, and using a push welding method with a forward tilt angle of 5-10°. Lack of fusion and incomplete penetration are serious internal defects, usually caused by insufficient welding current, excessive welding speed, excessive bevel angle, welding torch centering deviation, or incomplete interlayer cleaning. To address these defects, the welding current should be increased, the welding speed reduced, and the oscillation amplitude increased to ensure coverage of both sides of the bevel. Interlayer cleaning should also be strengthened. For multi-layer, multi-pass welding of thick plates, special attention should be paid to the fusion at both sides of the bevel and at the interlayer junctions.
(3) Porosity occurs. Porosity is mainly related to the shielding gas, including improper gas flow rate, insufficient gas purity, nozzle blockage, gas line leakage, and oil or rust on the workpiece surface or moisture on the welding wire. To address this, gas parameters should be optimized to 15-25 L/min, the gas system checked, nozzles cleaned, and the working environment improved to control the wind speed below 2 m/s. The workpiece surface should be thoroughly cleaned before welding. Excessive spatter usually stems from mismatched welding parameters, excessively long extension length, or poor welding wire quality. This can be improved by adjusting voltage and current matching, controlling the extension length to 10-15 mm, using copper-free or high-quality copper-plated welding wire, and using an Ar+CO₂ mixture.
(4) Excessive spatter may be due to improper welding parameter selection, gas composition issues, or excessively long welding wire extension. Adjusting the power output can change the welding parameters, adjusting the gas mix ratio can correct the mixed gas proportions, and adjusting the relative position of the welding torch and the workpiece can also help.
(5) An arc crater forms at the end of the weld after cooling. Adding a crater filling function during programming can fill this crater.
Common Welding Robot Faults and Solutions
(1) Torch collision. This may be due to workpiece assembly deviation or inaccurate welding torch TCP. Check the assembly or correct the welding torch TCP.
(2) Arc failure, unable to ignite the arc. This may be due to the welding wire not contacting the workpiece or the process parameters being too low. Manually feed the wire, adjust the distance between the welding torch and the weld, or adjust the process parameters appropriately.
(3) Shielding gas monitoring alarm. This indicates a fault in the cooling water or shielding gas supply. Check the cooling water or shielding gas pipelines.
How to Ensure Workpiece Quality
As a teach-and-reproduce robot, the assembly quality and precision of the workpiece must be consistent.
The application of welding robots requires strict control over the quality of part preparation and improvement of assembly accuracy. The surface quality of parts, bevel dimensions, and assembly accuracy will affect weld tracking performance. The following aspects can be used to improve part preparation quality and weld assembly accuracy:
(1) Develop welding processes specifically for welding robots, with strict process specifications for part dimensions, weld bevels, and assembly dimensions. Generally, part and bevel size tolerances should be controlled within ±0.8mm, and assembly size errors within ±1.5mm. This can significantly reduce the probability of welding defects such as porosity and undercut.
(2) Use high-precision assembly fixtures to improve the assembly accuracy of weldments.
(3) Welds should be thoroughly cleaned, free of oil, rust, welding slag, cutting slag, and other debris. A weldable primer is permissible. Otherwise, the success rate of arc ignition will be affected. Tack welding should be changed from electrode welding to gas shielded welding. Simultaneously, the tack welding area should be ground to avoid residual slag or porosity from tack welding, thus preventing arc instability and even spatter.
Programming Techniques Summary
(1) Choose a reasonable welding sequence. The welding sequence should be determined to minimize welding deformation and the length of the welding torch's travel path.
(2) The welding torch spatial transition requires a short, smooth, and safe movement trajectory.
(3) Optimize welding parameters. To obtain the best welding parameters, prepare workpieces for welding tests and process evaluation.
(4) Reasonable positioner position, welding torch posture, and welding torch position relative to the joint. After the workpiece is fixed on the positioner, if the weld seam is not in the ideal position and angle, the positioner needs to be continuously adjusted during programming to ensure the weld seam reaches a horizontal position sequentially. Simultaneously, the positions of each robot axis must be continuously adjusted to reasonably determine the position, angle, and wire extension length of the welding torch relative to the joint. After the workpiece position is determined, the position of the welding torch relative to the joint is difficult to determine visually by the programmer. This requires programmers to be adept at summarizing and accumulating experience.
(5) Insert the torch cleaning program in a timely manner. After writing a welding program of a certain length, a torch cleaning program should be inserted promptly. This prevents welding spatter from clogging the welding nozzle and contact tip, ensuring torch cleanliness, extending nozzle life, ensuring reliable arc ignition, and reducing welding spatter.
(6) Programming should generally not be done in one step. It requires continuous testing and modification during robot welding, adjusting welding parameters and torch posture, etc., to create a good program.
Operating Costs and Management Analysis
Learning oils with similar performance and effectiveness can be replaced at a lower price. Strengthening maintenance during the welding process extends the lifespan of consumable parts such as nozzles and contact tips. Furthermore, preventative maintenance of the robot system can effectively improve the lifespan of components.
Highly qualified managers, technicians, and operators are essential for robots to achieve maximum efficiency. The success of a company's welding robot operation largely depends on its workforce; therefore, a stable workforce is crucial.
