Abstract: A method for manufacturing a screen plate with screen slots from a thin plate (1), which screen slots (5, 13) are achieved by cutting. The plate is formed by bending to a screen plate of a desired shape. The screen slots (5, 13) are produced by a laser beam for cutting, which hits the plate from one of its sides, the inlet side. Focus for the beam is situated on a predetermined depth between both sides of the plate. The slot is obtained by at least two cutting operations following each other, in which the direction (3, 4) of the laser beam forms two different angles with the main plane of the plate. There is obtained a screen slot (5, 13), the cross section of which increases against the other side of the plate, the outlet side.

Abstract: In a pressure screening device for separating undesired particles from a fibre suspension a cylindrical screen (2) is provided. The screen has an outer side and an inner side and is provided with a plurality of projections (19) on the outer side of the screen (2) which extend in the circumferential direction of the screen (2), grooves (17) formed on the inner side of the screen (2) and extending in a direction having an axial component, and screening passages in the form of slots (18) disposed in the area of each groove (17) and diverging from the inner side of the screen (2) towards its outer side. According to the invention, the projections (19), grooves (17) and slots (18) of the screen (2) are produced by working of a substantially planar screen plate bent into cylindrical shape subsequent to the working. Thereby it is possible to form a screen (2) having uniform slots (18), the width of which at the inner side of the screen (2) is only about 0.1 mm.