Screens are used to classify chips, sawdust, "flakes" and other wood products into various sizes to meet market requirements.

Rotary, or shaker, chip screens have decks of screens with different size openings in each deck to screen out overs, accepts and fines.  The top screen would typically have 50 mm (2") to 60 mm (2-1/2") openings.  Chip material larger than this would cascade over the screen and be directed to rechipping.  The bottom screen would have openings that represent the fines classification.  These openings would typically be 6 mm (1/4") to 10 mm (3/8").  Chip material that drops through the top screen and is retained on the bottom screen is acceptable chip material (accepts).  Chips and sawdust that falls through the bottom screen is classified as fines.

Thickness chip or particleboard screens are designed to specifically screen out over thick chips.  A typical thickness screen would consist of a series of rolls with spaces between them set to represent maximum chip thickness.  As the chip material passes over the rolls, any material that is thinner than the opening between the rolls would fall through as acceptable chips.  The over thick chips would cascade over the rolls for further processing.

Fines chip or particleboard screens are designed to screen out chips that are too thin (fines).  A typical fines screen would consist of a series of rolls with spaces between them set to represent unacceptable thin chips.  As the chip material passes over the rolls, any material that is thinner than the opening between the rolls would fall through as fines.  The acceptable chips would cascade over the rolls.

English Terminology: Screens, screen, screening, shaker, rotary, disc, disk, chips, sawdust, bark, sawmill, planer mill, plywood plant, oriented strand board, medium density fibre board, pulp, paper, wet mill, dry mill.