Friction Stir Welding Bobbin Tool Variable Thickness
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Solution Overview
Problem
Friction stir welding with a bobbin tool is limited by its inability to accommodate workpiece assemblies with variable thickness along a weld path, leading to inefficiencies and potential tool failure when encountering thicker sections, as conventional designs struggle to maintain consistent contact and generate sufficient frictional heat uniformly.
Innovation Solution
The bobbin tool incorporates radially and axially extending blades that utilize the angular velocity and torque to cut through thickness variations, allowing it to be axially plunged or extracted, ensuring consistent contact and heat distribution, thereby enabling friction stir welding of assemblies with varying thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional bobbin tool is used for friction stir welding, then uniform heat generation and consistent contact are achieved on constant thickness workpieces, but the tool fails when encountering variable thickness sections as it cannot clear thicker sections ahead
Solution Approach 1:
The bobbin tool is segmented by adding discrete cutting blades to the shoulder structure. These blades are positioned radially outwardly from the rotational axis and extend axially forward of the shoulder's leading edge, allowing them to independently cut and clear thicker sections of the workpiece ahead of the main shoulder, enabling the tool to adapt to variable thickness assemblies without failure.
2Productivity
If the bobbin tool operates at high angular velocity for efficient welding, then productivity increases, but the tool cannot maintain consistent contact on variable thickness surfaces
Solution Approach 1:
The cutting blades perform preliminary action by cutting and clearing thicker sections of the workpiece ahead of the bobbin tool's main shoulder. This pre-clearing action ensures that when the shoulder contacts the workpiece at high welding speeds, the surface is already prepared at the correct thickness, maintaining consistent contact and heat generation throughout the welding process.
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
This design allows for successful friction stir welding of assemblies with variable thickness by clearing thicker sections ahead of the tool, ensuring consistent frictional heat application and preventing tool failure, thus achieving strong and uniform weld bonds.
Implementation Method 1
Friction stir welding is a solid state joining process in which a rotating tool engages an assembly of overlapping or abutting metal workpieces to generate frictional heat
Implementation Method 2
When rotated about the axis of the axial pin, the spinning end surfaces of the top and bottom shoulders generate and introduce frictional heat into both sides of the workpiece assembly
Data Source
AI summary
A bobbin tool is disclosed that includes a top shoulder, a bottom shoulder, and an axial pin that extends between the top and bottom shoulders. The bottom shoulder has an annular shoulder end surface, a back surface opposite the annular shoulder end surface, and a side surface that joins the annular shoulder end surface and the back surface. One or more and radially-extending blades may be disposed on the side surface of the bottom shoulder and/or one or more axially-extending blades may be disposed on the back surface. The one or more blades provide the bobbin tool with an ability to friction stir weld a variable thickness workpiece assembly, axially plunged through the workpiece assembly along an axis of rotation of the bobbin tool, and/or be extracted through the workpiece assembly along an axis of rotation of the bobbin tool.