Friction Stir Spot Welding Backing Piece Tilting Mechanism
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Solution Overview
Problem
Friction stir spot welding techniques often result in a triangular gap between work-pieces and the backing piece, leading to an uneven back surface finish and potential degradation of welding reliability due to tilting angles.
Innovation Solution
A friction stir spot welding device with a backing piece that tilts with the work-pieces, featuring a curved or spherical crown shape bearing surface, ensuring the back surface remains smooth and preventing gap formation, while maintaining the intersection of the rotary tool's axis and shoulder surface on the work-piece front surface at maximum tilting angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If work-pieces are placed on the backing piece in a tilting state to promote plastic flow, then welding reliability is improved, but a triangular gap is formed between the back surface of work-pieces and the backing piece causing poor surface finish
Solution Approach 1:
The backing piece is designed to be movable rather than fixed, allowing it to tilt dynamically in response to the work-pieces during welding. This dynamic adjustment eliminates the triangular gap formation while maintaining the necessary tilting angle for reliable welding, thus resolving the contradiction between welding reliability and surface finish quality.
Solution Approach 2:
The invention changes the parameter of the backing piece from fixed position to variable position, enabling it to adapt its tilting angle according to the work-pieces orientation. This parameter change allows the system to maintain optimal welding conditions without creating gaps that would compromise surface finish.
2Manufacturing precision
If the backing piece is made movable to tilt with work-pieces, then surface finish quality is improved, but device complexity increases
Solution Approach 1:
The backing piece utilizes the weight and orientation of the work-pieces themselves to induce the necessary tilting motion. The system serves itself by using the work-pieces as both the object being welded and the actuating force, eliminating the need for complex external actuation mechanisms and reducing overall device complexity.
Solution Approach 2:
By making the backing piece dynamically adjustable through a simple support structure, the invention achieves improved surface finish without requiring complex active control systems. The dynamic capability is implemented through a straightforward mechanical design that allows passive adaptation to work-pieces orientation.
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 solution allows for a smooth finish of the back surface of work-pieces and prevents degradation of welding reliability even at maximum permissible tilting angles, ensuring reliable and uniform friction stir spot welding.
Implementation Method 1
performing welding of the work-pieces by the plastic flow caused by the frictional heat that is generated between the rotary tool and the work-pieces
Implementation Method 2
the backing piece tilts with the tilting of the work-pieces
Data Source
Figure 1
Figure 2(A)~2(B)
Figure 3~4
AI summary
The member support (30) of a friction stir spot welding device has: a backing piece (31) having a bearing surface (33) that contacts a member (10) being welded; and a supporting body (35) that supports the backing piece (31) such that the backing piece tilts in a slaved tracking manner in response to the tilting of the member (10) being welded, which is in contact with the bearing surface. With the backing piece (31), the amount of change (δ) in the position of the bearing surface on the line extension of the central axis of rotation, when the bearing surface is in the reference state perpendicular to the central axis of rotation (Ac) of a rotary tool (20) and when the bearing surface tilts in a slaved tracking manner in response to the tilting of the member being welded, is equal to or less than a predetermined dimension (ds) with which the shoulder part (25) of the rotary tool is embed-ded with respect to the part being welded.