an improved plansifter having an open trough - shaped housing on which is centrally mounted an oscillation generator having a drive motor and a rotary and balance weight for imparting oscillation movement to the housing . a pair of sieve stacks , each having a plurality of individual sieves , is mounted on the floor of the housing stradling the oscillation generator . the housing is suspended for free oscillation . in a preferred construction , the rotary unbalance weight is accelerated by the drive motor to operational speed in a short period of time in order to preclude adverse resonance effects . the deleterious effects which might occur to the structure as it goes through its resonance frequency during acceleration and deceleration of the rotary unbalance weight can be further minimized by providing a suspension means comprising an elastic suspension element at one of four positions on the housing . each element may include a plurality of circularly cylindrical plastic bars extending parallelly from a point or locus of affixation on the housing . in one preferred embodiment , first and second ends of the bars can be secured at the point or locus of affixation to the housing and an external support respectively by means of a plurality of facing clamping members with facing clamping surfaces having contours formed therein to accommodate and securely retain therebetween the plastic bars .