Friction Stir Welding Depth Control Using Cross-Seam Force Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing friction stir welding methods face challenges in controlling tool depth due to nonlinear and unstable relationships between axial force and plunge depth, especially in applications with flexible parts or inconsistent material stiffness, leading to issues like material escape and inconsistent weld quality.
Innovation Solution
Implementing cross-seam force control and power control to regulate tool depth by measuring spindle torque and comparing it to a target power set point, using closed-loop control algorithms to adjust spindle motor current and maintain consistent power, thereby stabilizing the welding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If axial force control is used to manage tool depth, then tool engagement can be controlled, but the relationship becomes nonlinear and unstable when material stiffness is insufficient or parts are flexible
Solution Approach 1:
The patent implements a closed-loop feedback control system that continuously monitors axial force and adjusts tool depth in real-time. The control algorithm processes axial force signals from both upper and lower welding heads and dynamically adjusts the position of welding tools to maintain optimal engagement, resolving the instability caused by flexible parts and inconsistent material stiffness.
Solution Approach 2:
The patent introduces an intermediary control system that decouples the direct relationship between axial force and tool depth. By using a sophisticated control algorithm that considers multiple parameters (axial force, traverse rate, RPM, and material properties), the system mediates the control process to achieve stable tool depth even when material stiffness varies.
2Strength
If higher axial force is applied to ensure proper tool engagement, then material containment improves, but the tool may penetrate too deep and cause material to escape the weld zone
Solution Approach 1:
The patent employs dynamic control where axial force is not held constant but continuously adjusted during the welding process. The control system modulates axial force in real-time based on feedback signals, allowing the system to adapt to changing material properties and geometric conditions, thereby maintaining optimal material containment without excessive penetration.
Solution Approach 2:
The patent changes the control parameter from fixed axial force to dynamically adjusted axial force based on multiple input signals. By varying axial force as a function of real-time measurements and material properties, the system optimizes the balance between material containment and preventing excessive penetration that would cause material escape.
3Adaptability or versatility
If traditional force control is used in dual sided welding, then each head can be independently controlled, but crosstalk between axial force signals from upper and lower heads complicates the control process
Solution Approach 1:
The patent merges the control of upper and lower welding heads into a unified control system. By combining axial force signals from both heads and processing them through a single sophisticated control algorithm, the system eliminates crosstalk issues while maintaining independent adjustability of each head's parameters (traverse rate, RPM, axial force) for optimal dual-sided welding performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed method enhances weld consistency and stability by maintaining optimal tool engagement, even in complex geometries and varying thermal conditions, reducing the risk of material escape and ensuring high-quality welds.
Implementation Method 1
friction stir welding, a process that uses a rotating tool generating frictional heat to soften metal below the melting point
Implementation Method 2
adjust spindle motor current
Data Source
AI summary
A process is provided for controlling a friction stir welding process using one of two methods where standard depth/force control is inadequate. Both methods use sensors that are combined and compared to generate forge force, cross-seam force, and traverse forces. Cross-seam force is force perpendicular to the direction of travel and traverse force is aligned with the direction of travel. Forge force is the force applied in the depth direction. The first method uses only cross-seam force and the second method uses cross-seam force combined with traverse force as an input into a control loop that sets the tool depth command. The first method also uses spindle power to control the speed of the spindle. Both methods use forge force only as a safety limit. The control loop maintains forge depth better than forge force, temperature, or spindle power.