Friction Stir Spot Welding with Two-Stage Shoulder Force Control
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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 shoulder to reach a predetermined position corresponding to 46% or more of the workpiece thickness at a constant speed and surface pressure of 200.71 to 254.65 MPa during the welding process.
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 capability 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 quality for thick workpieces
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 rapid press-in and a second pressing force (lower) for controlled welding, the system resolves the contradiction between speed and quality
2Volume of moving object
If the press-in depth of the shoulder is increased to weld thick workpieces, then the welding capability is improved, but the welding time increases
Solution Approach 1:
The dynamic adjustment of pressing force enables faster processing of thick workpieces by using a higher pressing force during press-in to reduce the time required to reach the target depth, then switching to a lower force for the welding phase
Solution Approach 2:
By changing the pressing force parameter through two distinct stages with different force values, the patent reduces overall welding time while maintaining the capability to weld thick workpieces effectively
3Speed
If the pressing force is increased to maintain constant press-in speed, then the press-in speed is stabilized, but the surface pressure increases excessively
Solution Approach 1:
The patent uses dynamic pressing force adjustment where a first pressing force maintains constant press-in speed during the press-in phase, then switches to a second pressing force during the welding phase to control surface pressure and prevent excessive stress on the workpiece
Solution Approach 2:
By changing the pressing force parameter from a single high value to a two-stage system, the patent achieves constant press-in speed without excessive surface pressure, as the force is reduced after the press-in phase completes
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 the welding time from increasing and ensures a consistent press-in speed even when welding thick workpieces, thereby improving efficiency and quality.
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.