Abstract: A process and a corresponding device for filtering plastics in an injection molding machine having a plasticizing unit and a mold cavity. A slide having a receptacle for a filter element is arranged between the plasticizing unit and the mold cavity. A piston cylinder displacing unit is mounted parallel to a principal axis of the plasticizing unit so as to be slideably contactable by the slide holding the filter element. The displacement unit has a filter holder surrounded by a filter preheater for the insertion and preheating of a fresh filter element. The slide is displaced so that the filter receptacle in the slide corresponds to the filter holder in the displacement unit thereby enabling a spent filter element to be ejected while simultaneously inserting the fresh filter element into the receptacle. The slide is then returned to its operating position in which the filter element is acted upon by the plastic casting substance.