The hot sealing process is critical to ensuring the airtightness, strength, and safety of airbags, primarily achieved through high-frequency welding (RF welding) or thermal press welding. Below are the workflows and technical principles:
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High-Frequency Welding (RF Welding)
Principle
A high-frequency electromagnetic field (typically 27.12 MHz or 40.68 MHz) excites polar molecules (e.g., in PVC, TPU, or PU-coated fabrics), generating heat via molecular friction. Under pressure, the melted surfaces fuse into a durable weld after cooling.
Workflow
1. Material Preparation
- Airbag layers (e.g., PVC-coated fabric, TPU films) must be clean, free of oil, and contaminants.
- Pre-cut materials to required shapes with weld allowances.
2. Mold Design
- Design upper and lower molds to precisely match the airbag’s geometry, including weld zones and air chambers.
- Polish mold surfaces to prevent burrs or burns during welding.
3. Welding Operation
- Place materials on the lower mold and align with the upper mold.
- Activate the RF welder:
- Apply high-frequency electromagnetic fields via electrodes to melt material surfaces.
- Simultaneously apply pressure (via hydraulic/pneumatic systems) to ensure fusion.
- Cool the welded area to finalize sealing.
4. Quality Testing
- Airtightness test: Inflate or vacuum-check for leaks.
- Strength test: Conduct tensile/peel tests on welded joints.
- Visual inspection: Ensure smooth, bubble-free welds with no burn-through.
Advantages
- High-speed welding with excellent efficiency.
- High bond strength and airtightness.
- Suitable for complex geometries (e.g., multi-chamber designs).
