This can occur if the spinner that holds the blade is not tightly fastened. Turn off your product and remove the front grill. Place one hand on the spinner and the other on the blade. Turn the blade clockwise without moving the spinner. This will tighten the spinner and prevent the blade from bumping against the spinner.
This can also happen if the blade itself is out of balance. Try removing the blade and running the fan motor without the blade to see if the motor shaft wobbles when running. If it does, the motor shaft may be bent. If it does not, the blade may be out of balance.
If your fan continues to vibrate after trying this troubleshooting, please contact our Customer Support Specialist for further assistance