into collection chamber 120 microground product or finely ground powder 114 moves upward partially because of static electricity partially by upward movement of carrier gas 64 regulating by valve 148 and partially by the decreasing radius shape of housing 82 heavier particles work there way downward due to the shape of housing or column 82 because of gravity because of the low velocity of the fluidized bed not being able to hold larger particles in suspension and partially due to centrifugal force the centrifugal force assists in the separation because larger particles are forced to the conical inner outer surface of the microgrinder 80 whereas the microground product 114 moves upward through the center core of the microgrinder 80 therefore the three factors which affect the final grind are the impellers 98 shape design upward or downward position and speed the housing shape design and position relative gravity and the flow of carrier gas 64 in the housing 82 the impeller design 98 is primarily responsible for the creation of the vortexes in the housing 82 smaller vortexes hold smaller lighter particles for a longer amount of time in an impact zone with larger particles providing the opportunity for finer smaller particles sizes to be created the housing 82 can be matched to the impellers 98 to give some variance in the vortex size because the vortexes are formed in the space between impellers outer edges and the inner wall of the housing 82 by altering cones and rings upon the housing 82 the impact zone.