Friction Stir Spot Welder Timing Control for Second-Workpiece Contact
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Solution Overview
Problem
Existing different-metals welding methods face challenges in accurately determining when the tip of a shoulder or pin has reached the contact surface of a second workpiece, due to instantaneous changes in current supply.
Innovation Solution
A friction stir spot welder that includes a pin and a cylindrical shoulder, operated by a rotary driver and an advance-retract driver, with circuitry that determines the tip's reach by elapsed time and speed criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If current change amount threshold determination is used to detect pin penetration, then welding process automation is achieved, but detection accuracy deteriorates due to instantaneous current changes
Solution Approach 1:
The patent replaces the electrical measurement method (current monitoring) with a mechanical measurement method (load cell force monitoring). The load cell detects the axial force when the pin penetrates the second workpiece, providing a more stable and measurable signal than instantaneous current changes. This substitution resolves the contradiction by maintaining automation while significantly improving detection accuracy through a more reliable physical measurement principle.
2Productivity
If high rotation speed is used to reduce welding time, then productivity improves, but measurement of axial speed becomes more difficult
Solution Approach 1:
The patent introduces a load cell as an intermediary measurement device between the driving source and the workpiece. Instead of directly measuring the axial speed of the pin or shoulder at high rotation speeds, the load cell measures the axial force generated during penetration. This intermediary measurement approach allows indirect detection of penetration events without being constrained by the high speed rotation, thus maintaining both high productivity and measurement capability.
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
The system provides clearer determination of the tip's reach, improving the accuracy and reliability of the welding process.
Implementation Method 1
a friction stir spot welder that softens a workpiece including a first workpiece and a second workpiece by frictional heat to weld the workpiece
Data Source
AI summary
A friction stir spot welder includes a pin, a shoulder, a rotary driver, an advance-retract driver, and circuitry. When a preset and predetermined first period of time has elapsed in a state where a speed of the rotating shoulder in an axial direction or a speed of the pin in the axial direction is a preset and predetermined first speed, the circuitry determines that the tip of the shoulder or the tip of the pin has reached a contact surface of a second workpiece which is in contact with a first workpiece.