Friction Stir Spot Welding Temperature Control via Speed and Plunge Depth
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Solution Overview
Problem
Conventional friction stir spot welding methods face challenges in accurately controlling the welding temperature, leading to either excessive heat causing material brittleness or insufficient heat resulting in reduced joint strength, due to the correlation between tool plunge depth and welding temperature, and the lack of a control method to manage these parameters simultaneously.
Innovation Solution
A friction stir spot welding device with a controller that adjusts the tool's rotational speed and plunge depth to maintain the welding temperature within a predetermined range by increasing or reducing the welding pressure, allowing for precise temperature control and preventing material transformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the plunge depth of the tool is increased to obtain strength, then the joint strength is improved, but the welding temperature becomes excessively high causing material brittleness
Solution Approach 1:
The invention applies dynamics by making the rotational speed of the tool variable during the welding process. The controller dynamically adjusts the rotational speed based on real-time temperature feedback from the tool, allowing the system to adapt to changing thermal conditions. This enables maintaining optimal stirring effect while preventing excessive temperature rise that would cause material brittleness
Solution Approach 2:
The invention implements feedback control by using a temperature sensor to continuously monitor the tool temperature during welding. The controller receives this temperature information and adjusts the rotational speed accordingly, creating a closed-loop control system. This feedback mechanism ensures the welding temperature remains within the optimal range to prevent material transformation and brittleness
2Temperature
If the plunge depth of the tool is reduced to lower welding temperature, then material brittleness is prevented, but the fluidity of plasticized material is reduced and adequate welded spot is not formed
Solution Approach 1:
The invention makes the rotational speed dynamic rather than fixed. By adjusting rotational speed in real-time based on temperature feedback, the system can maintain sufficient material fluidity for adequate welding even when plunge depth is reduced to control temperature. The dynamic speed adjustment compensates for the reduced plunging effect
Solution Approach 2:
The invention changes the operational parameters by adjusting rotational speed based on temperature conditions. Instead of maintaining a fixed high rotational speed that would cause excessive heating, the system varies the speed parameter to match the actual thermal state, enabling temperature control while maintaining welding quality
3Ease of operation
If the tool stays at a specified position for spot welding, then spot welding is achieved, but the welding temperature is significantly increased
Solution Approach 1:
The invention uses feedback control to monitor tool temperature during stationary spot welding and adjusts rotational speed in response to temperature changes. This allows the tool to remain at the specified position for spot welding while preventing excessive temperature accumulation through real-time speed adjustment
Solution Approach 2:
The invention changes the rotational speed parameter dynamically during the spot welding process to compensate for the stationary nature of the operation. By varying speed based on temperature feedback, the system maintains effective spot welding without the excessive temperature rise that would occur with constant high-speed rotation
4Strength
If the rotational speed is increased to stir material better, then material stirring is improved, but the tool temperature and welding temperature deviate from each other
Solution Approach 1:
The invention implements feedback control where the controller continuously monitors tool temperature and adjusts rotational speed based on the actual thermal state. This closed-loop control ensures that the rotational speed is optimized for material stirring while keeping the tool temperature aligned with the welding temperature, preventing deviation between the two temperature measurements
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 enables high-accuracy control of the welding temperature, preventing material brittleness while achieving a high enough temperature for effective material stirring, resulting in improved joint strength and reproducibility.
Implementation Method 1
a tool having a projection at a tip end is rotated and plunged into lapped portions of the plate members, to soften the lapped portions by friction heat
Implementation Method 2
friction stir spot welding, in which a plurality of plate materials are lapped to each other and spot welded to each other
Implementation Method 3
thereafter is pulled out (drawn out), and the lapped portions are cooled so that the plate materials are joined (welded) to each other
Data Source
AI summary
During friction stir spot welding, a controller executes a temperature holding control in which the controller controls a rotation driving unit so that a rotational speed of a tool is set to a value which is equal to or lower than a predetermined rotational speed at which a temperature of the tool is regarded as being equal to a welding temperature of lapped portions, and in which the controller controls a displacement driving unit to increase and reduce a welding pressure or plunge depth of the tool so that the temperature of the tool is held in a predetermined set range.