Friction Stir Spot Joining Tool Cooling Before Retraction
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Solution Overview
Problem
The surface temperature of tools used in friction stir spot joining can lead to oxidation when retracted, reducing tool durability and service life due to atmospheric exposure.
Innovation Solution
A friction stir spot joining apparatus with a control device that reduces the rotation speed and pressurization force of the tool after joining, ensuring the surface temperature drops below the oxidation onset temperature before tool separation, thereby preventing oxidation and maintaining tool durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the tool is retracted immediately after friction stir spot joining, then the joining process is completed quickly, but the tool surface temperature remains high causing oxidation and reducing tool durability
Solution Approach 1:
The control device performs preliminary cooling action by reducing rotation speed and pressurization force before tool retraction, ensuring the tool surface temperature drops below the oxidation onset temperature. This preliminary temperature reduction prevents oxidation damage to the tool surface, thereby maintaining tool durability and service life while still achieving efficient joining production
2Reliability
If the tool rotation speed and pressurization force are reduced for heat dissipation, then the tool surface temperature decreases preventing oxidation, but the joining work efficiency is reduced
Solution Approach 1:
The control device dynamically adjusts the rotation speed and pressurization force based on the real-time temperature state of the tool surface. During the heat dissipation phase, both parameters are reduced to cool the tool; during the joining phase, they are increased to ensure efficient joining. This dynamic parameter adjustment allows the system to optimize both tool protection and joining efficiency at different stages of the process
3Reliability
If the tool remains in contact with plate members longer for cooling, then oxidation is prevented, but the cycle time increases reducing productivity
Solution Approach 1:
The control device changes the operational parameters (rotation speed and pressurization force) from high values during joining to low values during heat dissipation. This parameter change enables effective heat dissipation and temperature control during the tool-plate contact period, allowing the tool to be cooled sufficiently without requiring excessively long contact time, thus balancing tool protection with production efficiency
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 approach effectively prolongs the service life of the tool by preventing oxidation and maintaining its durability, while minimizing the time required for heat dissipation without reducing work efficiency.
Implementation Method 1
a heat dissipation step of reducing at least one of a rotation speed and a pressurization force of the tool than in the joining step while the tool is rotated and the pin portion is kept pushed into the plate members
Implementation Method 2
a friction stir spot joining method of joining a pair of plate members by friction stirring with a pin portion of a tool
Data Source
AI summary
A friction stir spot joining apparatus for spot-joining a pair of plate members by friction stirring with a tool's pin portion includes an advancing and retracting driving device configured to advance and retract the tool to and from plate members, a rotationally driving device configured to rotate the tool, and control device configured to control advancing and retracting driving device and rotationally driving device. The control device executes joining control of pushing pin portion into plate members while the tool is rotated and causing pin portion to pressurize plate members, and executes heat dissipation control of reducing at least one of a rotation speed and a tool's pressurization force more than in the joining control while tool is rotated and pin portion is kept pushed into plate members after joining control and separating tool from plate members after the pin portion's surface temperature becomes less than an oxidation onset temperature.