Friction Stir Welding L-Shaped Support Shoulder
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Solution Overview
Problem
Friction stir welding apparatuses form recesses on the front surface of weld joints due to frictional heat, regardless of the presence or absence of a gap between workpieces, leading to suboptimal weld quality.
Innovation Solution
A friction stir welding apparatus with a rotating shaft and a non-rotatable stationary shoulder that holds workpieces in a sandwiching manner, preventing frictional heat generation on the front surface and using a thread for friction stirring, along with a wire-feeding groove to manage the welding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a bobbin-type rotary tool with rotating shoulders is used to join workpieces, then the workpieces can be held and processed, but recesses are formed on the front surface side of the weld joint due to frictional heat generation
Solution Approach 1:
The patent divides the shoulder structure into two separate functional components: a rotating shoulder that contacts the back surface of the workpiece and a stationary shoulder that contacts the front surface. This segmentation allows each component to perform its specific function without causing harmful effects - the rotating shoulder provides frictional heating for material softening while the stationary shoulder prevents front surface recession without generating frictional heat
Solution Approach 2:
The patent inverts the conventional bobbin-type rotary tool design where both shoulders rotate. Instead, it makes the front surface shoulder stationary while keeping the back surface shoulder rotating. This inversion eliminates frictional heat generation on the front surface, preventing recess formation while maintaining the necessary frictional heating at the back surface for proper material softening and welding
2Manufacturing precision
If the rotation speed of the second shoulder is increased to prevent recess formation when gaps exist, then recess prevention is achieved, but the back surface becomes softened before the front surface
Solution Approach 1:
The patent segments the shoulder functions to allow independent optimization of each shoulder's rotation speed. The stationary shoulder on the front surface eliminates the need for high rotation speeds to prevent recesses, while the rotating shoulder on the back surface can operate at optimal speeds for controlled material softening without causing premature softening issues
Solution Approach 2:
The patent converts the potentially harmful frictional heat generation on the front surface into a beneficial stationary support function. By making the front shoulder stationary, it provides mechanical support and prevents recess formation without generating frictional heat that would cause unwanted premature softening, thus turning a potential source of heat into a purely mechanical support element
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
Prevents the formation of recesses on both sides of the welding trace on the front surface of the weld joint, ensuring consistent and high-quality welds regardless of the gap between workpieces.
Implementation Method 1
a thread for friction stirring is formed on a rotating shaft (2)
Implementation Method 2
a rotating shoulder (5) fixed to a distal end of the rotating shaft (2) and configured to rotate together with the rotating shaft (2) to generate frictional heat between the rotating shoulder (5) and back surfaces of the workpieces (W)
Data Source
AI summary
A friction stir welding apparatus includes: a rotating shaft, on which a thread for friction stirring is formed; and a drive unit rotatably supporting the rotating shaft. A rotating shoulder configured to rotate together with the rotating shaft to generate frictional heat between the rotating shoulder and back surfaces of workpieces is fixed to a distal end of the rotating shaft. The rotating shoulder is pushed against the back surfaces of the workpieces by a pushing mechanism. A stationary shoulder penetrated by the rotating shaft and configured to hold the workpieces in a sandwiching manner together with the rotating shoulder is non-rotatably mounted to the drive unit or a member connected to the drive unit.