Friction Stir Welding Distance Sensing for Shoulder Depth Control

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Solution Overview

Problem

Existing methods for controlling the insertion depth of the shoulder surface of the joining tool in friction stir welding, especially for workpieces with large surface height variations, are either costly and complex or face difficulties in detecting torque fluctuations with small-diameter tools, leading to potential joining failures or excessive burrs.

Innovation Solution

A distance measuring device comprising a measuring tool with an abutment portion, a freely movable tip portion, detectors, and an output unit, which calculates the distance between the shoulder surface of the joining tool and the workpiece surface, allowing for precise control of the joining tool's motion trajectory and amount of pushing into the workpiece.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If laser light measurement method is used to control shoulder surface insertion depth, then measurement precision is improved, but device complexity and cost increase

Engineering Contradiction:

Improveworkpiece height measurement precisionVSAvoidmeasurement device complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

A measuring tool serving as an intermediary device is introduced between the joining tool and workpiece. This measuring tool includes a tip portion that contacts the workpiece surface, an abutment portion that contacts the shoulder surface, and a detector that measures the distance between them. The intermediary measuring tool simplifies the measurement system compared to direct laser measurement while maintaining adequate precision for controlling insertion depth

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces complex optical measurement systems (laser) with a simpler mechanical measurement approach. The measuring tool uses mechanical contact between the tip portion, abutment portion, and detector to measure distance, substituting the need for sophisticated laser measurement equipment while achieving the required measurement precision

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If torque fluctuation detection is used to control joining height, then device complexity is reduced, but measurement precision deteriorates for small-diameter tools

Engineering Contradiction:

Improvecontrol system complexityVSAvoidjoining height control precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The measuring tool acts as a direct intermediary measurement device that physically measures the insertion depth of the shoulder surface. By using a detector that directly contacts the shoulder surface through the abutment portion, the system achieves accurate measurement without relying on indirect torque detection, which is particularly beneficial for small-diameter joining tools where torque fluctuations are difficult to detect

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The measuring tool creates a physical copy or representation of the insertion depth condition by mechanically contacting both the workpiece surface and the shoulder surface. This direct mechanical copying of the geometric relationship provides accurate measurement data without the limitations of torque-based indirect measurement

Inventive Principle:

Principle #26Copying

3Manufacturing precision

If worktable height is controlled by cylinder to maintain constant load, then manufacturing precision is improved, but device complexity and loss of time increase

Engineering Contradiction:

Improvejoining quality consistencyVSAvoidworktable control system complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The measuring tool serves as an intermediary that directly measures the insertion depth condition at the joining interface. This eliminates the need for complex worktable height control systems with cylinders, as the measuring tool provides direct feedback on the actual insertion depth regardless of worktable position, simplifying the overall control system while maintaining joining quality

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the mechanical worktable height control system (using cylinders) with a measurement-based approach. Instead of actively controlling worktable position to maintain constant load, the system uses the measuring tool to monitor insertion depth and control the joining process based on actual measurements, reducing mechanical complexity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11331745B2Distance measuring device, friction stir welding apparatus, and friction stir welding method

Publication Date: 2022.05.17 KK TOSHIBA

AI summary

The abutment portion touches with a shoulder surface of a joining tool for friction stir welding. The tip portion is freely movable in a first direction connecting a surface of the workpiece and the shoulder surface in a state of contacting the surface of the workpiece. The detector is configured to detect a position of the tip portion in the first direction. The output unit is configured to output a data of the position of the tip portion in the first direction detected by the detector. The controller is configured to calculate a position of the tip portion to the abutment portion from the data of the position output from the output unit, and to calculate a distance between the shoulder surface of the joining tool and the surface of the workpiece.