Tail Fin Barrel Robotic TIG Filler Wire Welding Process

Literature Overview

This technical paper by Li Weiqing, Hu Zhenhai, and Li Boqi from Shaanxi Weishi Electromechanical Technology Co., Ltd. (2006, Hot Working Technology, Vol. 35, No. 7) documents the development and commissioning of a robotic TIG welding system with automatic filler wire feeding for tail fin barrel manufacturing. The paper addresses practical engineering problems encountered during system integration and debugging, making it a valuable reference for engineers involved in robotic welding system implementation.

Technical Background

Tail fin barrels are structural components in aerospace and defense applications that require high-integrity welds with consistent quality. The robotic TIG welding with filler wire approach combines the advantages of robotic precision and repeatability with the penetration characteristics of TIG welding enhanced by filler metal deposition. The system described in this paper incorporates several sophisticated control features that are critical for achieving production-quality welds.

Key System Features and Technical Solutions

The paper identifies several critical technical challenges and their solutions during the commissioning process:

Automatic Arc Voltage Control

The automatic arc voltage control system is perhaps the most critical feature of this robotic welding setup. In TIG welding, the arc voltage is directly related to the arc length, which in turn affects the heat distribution and penetration characteristics. During robotic welding of curved surfaces such as tail fin barrels, the torch-to-workpiece distance may vary slightly due to part positioning tolerances or thermal distortion of the workpiece. The automatic arc voltage control system compensates for these variations by adjusting the torch height in real time, maintaining a consistent arc length throughout the weld.

Address Register for Wire Feed Control

The use of an address register for filler wire feed control is a sophisticated approach that allows precise control of the wire feed rate at different stages of the welding cycle. This is particularly important for:

• Setting the wire feed rate during the start of the weld to ensure proper root formation
• Adjusting the feed rate during the main welding pass for optimal deposition
• Reducing or stopping the feed rate at the end of the weld to prevent excess metal buildup
• Coordinating wire feed with torch travel speed to maintain the proper wire-to-travel speed ratio

Brake Mechanism and Re-Burn Function

The brake mechanism ensures that the torch maintains proper contact and positioning throughout the welding cycle, which is essential for arc stability. The re-burn function addresses a common quality issue in TIG welding: the crater at the end of the weld. Without proper re-burn, the rapid cooling of the crater can lead to hot cracks, shrinkage porosity, and insufficient weld cap formation. The re-burn function applies additional heat input at the weld termination point to allow proper solidification and crater filling.

Engineering Practice Integration

For engineers involved in robotic welding system implementation, this paper provides practical insights that are often not covered in academic literature:

1. System Integration Challenges: The commissioning process reveals that robotic welding systems require careful calibration of multiple subsystems (torch height control, wire feed, travel speed, gas flow) that must work in concert. Any mismatch in timing or rate between these subsystems can result in weld defects.
2. Process Window Development: The paper implicitly demonstrates the need for establishing robust process windows that can accommodate variations in part geometry, material properties, and environmental conditions. The automatic arc voltage control system is a key enabler of process robustness.
3. Quality Assurance Considerations: The re-burn function highlights the importance of addressing weld termination quality, which is often overlooked in favor of optimizing the main weld pass. Crater defects are a common cause of weld rejection in critical applications.

Critical Analysis

The paper is primarily a practical engineering document rather than a fundamental research study. Its value lies in the specific technical solutions it documents, which can serve as a reference for engineers developing similar robotic welding systems. However, several aspects could benefit from further elaboration:

• The specific welding parameters (current, voltage, travel speed, wire feed rate, gas flow rate) are not provided in detail
• The material being welded and the specific geometric requirements of the tail fin barrel are not fully described
• The quality assessment methodology and acceptance criteria for the welded joints are not discussed
• The comparison between the robotic process and manual TIG welding in terms of productivity and quality consistency is not provided

From a process engineering perspective, the described system represents a well-integrated approach to automated TIG welding. The combination of arc voltage control, address register-based wire feed, brake mechanism, and re-burn function demonstrates a systematic approach to addressing the key quality challenges in robotic TIG welding. This integrated approach is consistent with the PDCA (Plan-Do-Check-Act) methodology: the system is planned with specific quality objectives, the parameters are set and executed, the results are monitored through arc voltage feedback, and adjustments are made through the control system.

Summary

This paper provides valuable practical insights into the development and commissioning of a robotic TIG welding system with automatic filler wire feeding for tail fin barrel production. The documented solutions for arc voltage control, wire feed management, torch positioning, and weld termination represent a comprehensive approach to achieving consistent weld quality in automated production. Engineers developing similar systems should pay close attention to the integration of all subsystems and the importance of addressing weld termination quality through re-burn functions.