Friction Stir Welding Pin with Freely Rotating Shoulder
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Solution Overview
Problem
Friction stir welding devices with a bobbin configuration face high mechanical and thermal loads, limiting welding speed and quality due to the pin's need to transmit torque and frictionally heat both shoulder elements, leading to pin damage and suboptimal joint quality.
Innovation Solution
The second shoulder element is connected to the pin to rotate freely, eliminating torque transmission and using a ceramic annular spacer for thermal decoupling, reducing mechanical and thermal stress on the pin and workpieces, while allowing higher welding speeds and improved joint quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pin transmits torque to both shoulder elements for frictional heating, then welding capability is achieved, but mechanical and thermal loads increase leading to pin damage
Solution Approach 1:
The patent extracts the torque transmission function from the pin by allowing the second shoulder element to rotate freely. Only the first shoulder element transmits torque for frictional heating, while the second shoulder element serves solely as a support and alignment component, eliminating unnecessary mechanical and thermal loads on the pin.
Solution Approach 2:
Instead of having the pin drive both shoulder elements, the patent inverts the relationship by making the second shoulder element freely rotatable. This reverses the conventional approach where the pin is the active driver of both components, reducing the pin's workload and improving its durability.
2Productivity
If welding speed is increased to improve productivity, then output increases, but thermal load on pin and workpiece increases causing pin damage and reduced joint quality
Solution Approach 1:
The patent removes the source of excessive heat generation by eliminating torque transmission to the second shoulder element. This reduces overall frictional heating in the system, allowing higher welding speeds to be achieved without proportionally increasing thermal loads on the pin and workpiece.
Solution Approach 2:
The patent changes the operational parameters by decoupling the rotation of the second shoulder element from the pin's rotation. This parameter change reduces the total friction work, thereby lowering process temperatures and enabling faster welding speeds with controlled thermal exposure.
3Device complexity
If the second shoulder element is fixed to the pin for rotation, then structural simplicity is maintained, but torque transmission causes excessive frictional heating and pin damage
Solution Approach 1:
The patent introduces dynamic behavior by allowing the second shoulder element to rotate freely relative to the pin. This dynamic connection replaces the static fixed connection, enabling the system to adapt during operation by eliminating unnecessary friction and heat generation while maintaining structural simplicity.
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 design reduces thermal and mechanical stress, preventing pin damage, enhancing weld quality, and enabling faster, more efficient welding processes by allowing higher pin movement speeds and lower process temperatures.
Implementation Method 1
The material in the adjacent area of the workpieces is plasticized by the friction of the pin and shoulder element on the workpieces
Implementation Method 2
a ceramic annular spacer provided in the second abutment surface, which surrounds the engagement portion
Data Source
Figure 1
Figure 2
AI summary
Device (1) comprises: a rotatably driven pin (3) about a rotational axis (9) exhibiting a drive end (11) and a free end; a first shoulder element (5) concentrically arranged on the drive end facing side of the engaging portion relative to the rotational axis around the pin and exhibits a first abutment surface extending perpendicular to the rotational axis oriented for engaging portion; and a second shoulder element concentrically arranged on the free end facing side of the engaging portion relative to the rotational axis around the pin. Device (1) for friction stir welding comprises: a rotatably driven pin (3) about a rotational axis (9) exhibiting a drive end (11) and a free end, where a cylindrical engaging portion is provided between the drive end and the free end which extends axially in direction of the rotational axis, and a circumferential surface is provided for engaging with at least one workpiece; a first shoulder element (5) which is concentrically arranged on the drive end facing side of the engaging portion relative to the rotational axis around the pin and exhibits a first abutment surface extending perpendicular to the rotational axis oriented for engaging portion; and a second shoulder element which is concentrically arranged on the free end facing side of the engaging portion relative to the rotational axis around the pin and exhibits a second abutment surface extending perpendicular to the rotational axis oriented for engaging portion. The second abutment surface extends directly up to the engaging portion, and the first shoulder element is provided for engaging the first surface and the second shoulder element is provided for engaging the second surface, where the first opposite surface is provided on at least one workpiece. The second shoulder element is rotatably connected with the pin freely about the rotational axis.