The control sieve is used to eliminate small brokens and lumps of material which form during the processing of the rice.
The machine consists of a wooden case normally containing two perforated metal work surfaces. The upper one has holes which allow the rice to pass but withhold lumps which are then discharged down a chute. From the first level the rice falls through to the second one where it is stopped by the holes and led to the download chute. The collection box rests on special suspension springs fixed to the frame. The movement is alternating and is produced by an eccentric camshaft linked to the box by a connecting rod.