... steel fan blade 2. High quality Power 3. Energy conservation 4. Low noise 1. The outline border adopt advanced automatic process, ... and close, windproof, rainproof and dustproof 5. Newly punch forming fan blade, reasonable angel and reach the max. Air flow, ... tear down 8. Strictly quality test process: Noise test, vibration test, concentric performance test, fan blade turning speed test, input air ...