Friction Stir Spot Welding with Constant Shoulder Press-In Speed
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Solution Overview
Problem
The friction stir spot welding method disclosed in PTL 1 often results in increased welding time and decreased press-in speed when welding thick workpieces due to the increase in press-in depth of the shoulder.
Innovation Solution
A friction stir spot welder and method that maintains a constant press-in speed of the shoulder by controlling the rotary driver and tool driver to press the pin and shoulder into a workpiece at a predetermined first position, corresponding to 46% or more of the workpiece thickness, with a surface pressure of 200.71 to 254.65 MPa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the press-in depth of the shoulder is increased to weld thick workpieces, then the welding depth is improved, but the press-in speed decreases and welding time increases
Solution Approach 1:
The patent applies dynamics by making the pressing force adjustable during different stages of the welding process. The pressing force is set to a first value during the press-in phase and a second value during the welding phase, allowing optimization of both press-in speed and welding depth without compromise
Solution Approach 2:
The patent changes the parameter of pressing force from a static single value to a dynamic two-stage value system. By switching between a first pressing force (higher) for press-in and a second pressing force (lower) for welding, the system achieves both fast press-in and adequate welding depth
2Volume of moving object
If the press-in depth of the shoulder is increased to weld thick workpieces, then the welding depth is improved, but the welding time increases
Solution Approach 1:
The patent uses dynamic control of the pressing force to reduce welding time. By applying a higher first pressing force during press-in to achieve faster engagement, and then switching to a lower second pressing force for the welding phase, the overall welding time is reduced while maintaining adequate welding depth
Solution Approach 2:
The patent performs preliminary action by applying a higher pressing force during the press-in phase before the actual welding phase. This preliminary high-force action ensures rapid engagement and positioning, reducing the time required for the subsequent welding phase
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 prevents an increase in welding time and maintains a consistent press-in speed when welding thick workpieces, ensuring efficient and effective friction stir spot welding.
Implementation Method 1
a method (friction stir spot welding method) of joining metal materials by utilizing frictional heat
Data Source
AI summary
A friction stir spot welder includes: a pin; a shoulder; a rotary driver; a tool driver; and circuitry that performs an operation of driving the rotary driver and the tool driver such that the pin and the shoulder press a workpiece by a first pressing force while rotating at a first rotational frequency, and after the operation, performs an operation of driving the rotary driver and the tool driver such that a tip of the shoulder in a rotating state is pressed in to a first position. The first position is a position corresponding to 46% or more of a thickness of the workpiece from a front surface of the workpiece. A press-in speed of the shoulder until the shoulder reaches the first position is a constant speed.