Friction Stir Spot Welder Contact Detection via Axial Speed
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Solution Overview
Problem
Existing friction stir spot welding methods struggle to accurately determine when the tip of the shoulder or pin has reached the contact surface of the second workpiece due to instantaneous changes in current, making precise control difficult.
Innovation Solution
A friction stir spot welder and method that includes a pin, shoulder, rotary driver, and advance-retract driver, with circuitry to control the process, determining tip contact based on a preset time and speed threshold, allowing clear detection of contact surface engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current change amount threshold is used to determine pin contact with first metal member, then welding process can be monitored, but determination becomes difficult due to instantaneous current increase
Solution Approach 1:
The patent introduces an intermediary parameter (axial speed of the pin) to detect contact between the pin and the first metal member. Instead of directly measuring the instantaneous current change, the system monitors the axial speed which changes continuously and predictably upon contact, making the detection more reliable and less prone to noise interference.
Solution Approach 2:
The patent replaces the electrical measurement approach (current monitoring) with a mechanical measurement approach (axial speed monitoring). By using the axial speed of the pin as the primary detection parameter, the system avoids the issues of instantaneous current spikes and achieves more stable and accurate contact detection.
2Productivity
If pin advances rapidly through workpiece, then welding speed increases, but current load fluctuates making control difficult
Solution Approach 1:
The patent implements a feedback control system that continuously monitors the axial speed of the pin and adjusts the driving force accordingly. When contact with the first metal member is detected through axial speed changes, the system provides feedback to maintain stable advancement, ensuring reliable process control even at high welding speeds.
Solution Approach 2:
The patent employs dynamic control of the pin advancement process, allowing the axial speed to vary naturally during different stages of welding (approach, contact, penetration) while maintaining overall process stability. The system adapts to the changing mechanical conditions rather than enforcing a rigid constant speed, improving both productivity and reliability.
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
Enhances the precision of determining tip contact, ensuring accurate welding by using a predetermined time and speed to confirm engagement, thereby improving welding control.
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 11, a shoulder 12, a rotary driver 57, an advance-retract driver 53, and circuitry 51. When a preset and predetermined first period of time has elapsed in a state where a speed of the rotating shoulder 12 in an axial direction or a speed of the pin 11 in the axial direction is a preset and predetermined first speed, the circuitry 51 determines that the tip of the shoulder 12 or the tip of the pin 11 has reached a contact surface 62a of a second workpiece 62 which is in contact with a first workpiece 61.