Friction Stir Spot Welding (FSSW) & Refill Tooling Vector Prepress Guide
Manufacturing guide for solid-state spot joining of aluminum alloys, tool geometry selection, stir zone recrystallization, and robotic spot vector planning.
1. Principles of Solid-State Friction Stir Spot Welding
Friction Stir Spot Welding (FSSW) and Refill FSSW are revolutionary solid-state spot joining technologies that eliminate melting, toxic fumes, and distortion in automotive aluminum sheet structures. By plasticizing metals below their liquidus temperature, FSSW avoids solidification defects like hot cracking in 2xxx and 7xxx aerospace alloys.
2. Conventional FSSW vs. Refill FSSW Comparison
| Characteristic | Conventional Pin FSSW | Refill FSSW (RFSSW) |
|---|---|---|
| Exit Hole Keyhole | Leaves central probe keyhole | 100% Flush refilled joint (Zero exit hole) |
| Lap Shear Strength | Baseline (4.5 – 7.0 kN) | +20% to +35% higher (6.0 – 9.5 kN) |
| Corrosion Resistance | Requires sealing plug | Excellent natural hermetic seal |
| Aerodynamic Flushness | Non-flush | Aerodynamically smooth (aerospace skins) |
3. Robotic Vector Prepress & CAM Layout Rules
- Edge Margin Safety: Maintain spot center-to-edge distance $E \ge 1.5 D_s$ to prevent lateral plastic flash blowout.
- Spot Pitch Spacing: Maintain inter-spot pitch $P \ge 3.0 D_s$ to prevent thermal degradation of adjacent heat-affected zones (HAZ).
- Clamping Foot Clearances: Define annular pneumatic clamping clearance zones on CAD vector layers.
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