Robot TIG Filler Wire Welding Process for Tail Boom Barrel

Literature Overview

Published in 2006 in the journal Hot Working Technology, this paper by Li Weiqing, Hu Zhenhai, and Li Boqi from Shaanxi Weishi Electromechanical Technology Co., Ltd. presents the development and implementation of a robotized TIG welding process with filler wire for manufacturing tail boom barrels. The tail boom is a critical structural component in aerospace applications, typically fabricated from high-strength aluminum or titanium alloys, requiring precise welding procedures to ensure structural integrity and dimensional accuracy.

Technical Background and Challenges

The tail boom barrel is a thin-walled cylindrical structure that undergoes significant bending and torsional loads during flight. Welding this component presents multiple challenges including:

• Thin wall thickness (typically 2-4 mm) requiring precise heat input control
• Long seam lengths requiring consistent welding parameters over extended distances
• Cylindrical geometry requiring specialized fixture design and robot path planning
• Material sensitivity to thermal distortion and residual stress
• Stringent quality requirements for aerospace applications

The robotized approach addresses these challenges by providing consistent welding parameters, precise torch positioning, and the ability to maintain optimal travel speed and arc length throughout the weld length. The filler wire technique (as opposed to autogenous welding) allows for better control of weld geometry and mechanical properties.

Process Parameters and Configuration

The welding process employs a TIG configuration with continuous filler wire feeding. The robot system provides six-axis positioning capability, allowing the torch to maintain optimal angle and distance from the workpiece throughout the circumferential weld.

The backside shielding arrangement is critical for preventing oxide inclusion and ensuring full fusion through the wall thickness. A backpurge of argon or helium is maintained throughout the welding operation, with purge flow rates of 5-10 L/min depending on the barrel diameter and joint configuration.

Robot Path Planning and Welding Strategy

The robot path planning for circumferential welding requires careful consideration of the barrel geometry and fixture design. The barrel is typically mounted on a rotary table that rotates synchronously with the robot's motion, ensuring constant travel speed and consistent weld geometry.

The welding strategy typically involves:

1. A tack welding sequence to establish joint alignment and reduce distortion during the main weld pass
2. A root pass with reduced parameters to ensure complete backside fusion
3. Fill passes with optimized parameters for maximum deposition efficiency
4. A cap pass with surface finish optimization

Distortion control is achieved through the combination of low heat input parameters, controlled welding sequence, and strategic fixture design. The barrel is clamped at multiple points along its length to minimize radial expansion and ovality during welding.

Quality Control and Inspection

Given the critical nature of tail boom structures, comprehensive quality control measures are implemented:

• Visual inspection of weld appearance for consistent bead profile and absence of surface defects
• Radiographic testing (RT) for volumetric defect detection, particularly porosity and incomplete fusion
• Dye penetrant testing (PT) for surface-breaking crack detection
• Dimensional inspection for barrel diameter, ovality, and length tolerance
• Mechanical testing of coupon welds for tensile strength and hardness verification

Acceptance criteria typically follow aerospace standards such as AMS 2472 or equivalent, requiring 100% inspection of critical welds and sampling inspection of non-critical joints.

Engineering Practice Applications

This robotic TIG welding technology has been successfully applied to multiple aerospace programs involving tail boom manufacturing. The key advantages include:

• Consistent weld quality across multiple production units
• Reduced dependence on operator skill for critical weld operations
• Improved productivity through continuous operation capability
• Enhanced process documentation and traceability for quality assurance
• Reduced material waste through optimized filler wire consumption

The technology represents a significant advancement in automated welding of thin-walled aerospace structures, combining the precision of robotic control with the versatility of TIG welding for high-quality joint formation.

Study Insights and Reflections

This research demonstrates the successful integration of robotic automation with traditional TIG welding techniques for aerospace manufacturing. The key insight is that automation does not replace the fundamental understanding of welding metallurgy and process physics but rather enhances the precision and repeatability with which these principles are applied.

The choice of TIG with filler wire over alternative processes such as laser welding or friction stir welding reflects the need for process flexibility and the ability to handle various joint configurations and material thicknesses within a single production line. The robotic system provides the precision required for aerospace quality while maintaining the versatility needed for production flexibility.

In summary, this work provides a comprehensive framework for implementing robotic TIG welding in aerospace structural manufacturing, offering valuable guidance for engineers seeking to improve production efficiency and quality consistency in similar applications.