"Cooling Fan Manufacturer" Motor diameter: Because of the motor and bearings, the central portion of the main shaft axial fan inevitably a certain blind spot where the air flow through the spindle diameter will determine the size of this blind spot. The size of the spindle diameter depends mainly on the power of "Cooling Fan Manufacturer" motor - high power motor stator winding require larger, must take up more space, without being able to scale up (increase the height), it will had to scale (increasing the area).
"Cooling Fan Manufacturer" blade smoothness: This is a non-index design factors, basically depends on the forming mold producers and post-processing technology. In addition to the design curve is not flat blades will produce turbulence in the rotation, increasing friction, reduce fan efficiency, impairment fan performance, increased operating noise.