The electric motor runs slowly with the impellor just after decelerated through the belt, decelerator and gears wheel. The sand and stone flow into washing launder from feeding launder, rolls with the impellor, and grinds each other. The impurity covering the sand is washing away. Firstly, water is removed from your sand and stone; Secondly, the water can be thoroughly used. Thirdly, the sand and stone goes for the out launder in the rotary impellor to finish the washing undertaking.