Basic Term 1

Perforated plates (drawing 2) are classified in four main categories: perforated plates with round, square, oblong or slotted holes.

Basic Terms 2

The hole pattern differs as follows (drawing 3 and drawings to 4.1 up to 6.3):

Round and square holes:
straight rows (Rg), diagonally staggered rows (Rd), 60° staggered rows (RV).

Oblong or slotted holes:
straight rows (Lg), staggered rows (Lv) diagonal rows, herringbone patters, checker board pattern.

The hole pattern is very important with screening plates. The best results are achieved if the holes are staggered across the feed direction (drawing 1).

Drawing 1: definition of the feed direction

Basic term 3

Width of edge e1, e2 or f1, f2 is the distance from the edge of the plate to the first holes (drawing 2). Usually a blank margin is required to manufacture perforated plates.

Plates without blank margin (throughout punched) may be cheaper than plates with blank margin provided they can be cut out of standard plates. Perforation will cause unavoidable surface tensions resulting in negative impacts with wide blank margins.

Drawing 2: definition of the feed direction

Basic term 4

Width of hole w is (drawing 3): diameter of the round hole, edge length of the square hole, the smaller dimension of the oblong or slot hole.

Basic term 5

Length of hole l is (drawing 3): the larger hole size of the oblong or slot hole.

Basic term 6

Width of bridge c ist the smallest unperforated space between round or square holes in adjacent rows (drawing 3).

Width of side bridge c1 is the smallest unperforated space between the broadsides (w) of oblong or slot holes in adjacent rows.

Width of end bridge c2 is the smallest unperforated space at the longitudinal axis between oblong or slot holes in adjacent rows (drawing 3).

Basic term 7

Pitch t is defined as the distance from the centre of two adjacent round or square holes or rows of holes (drawing 3).

Side pitch t1 is the distance on the broadside of two adjacent oblong or slot holes.

End pitch is the distance in longitudinal direction of two adjacent oblong or slot holes.

Basic term 8

The relative open surface or screening area is the percentage of the open surface (holes) in relation to the whole screening area. It is important for determination of the rate of flow and the calculation of the load-bearing capacity of the perforated sheet.

Drawing 3: Definition of the position of holes, width of edge e, f, width of hole w, pitch t, width of bridge c etc.