Whirlers

            Plate whirler are still needed for conventional deep-etch and bi-metal plates.

            The plate whirler is designed to coat lithographic plates. The whirler is actually an oversized turntable. The plate is fastened or mounted on the turntable, the sensitized coating is poured on and centrifugally distributed over the plate while it is turning. The whirler should be equipped with a positive variable speed drive and accurate controls for setting and measuring whirler speed. The coating is dried by heat and/or forced air as the plate revolves.

            There are two types of whirlers in general use:-

            Horizontal and Vertical.  The horizontal whirler distributes the coating solely by centrifugal force. The Vertical whirler which has the turntable placed at an angle of 15° to the perpendicular, distributes the coating by a combination of centrifugal force and the gravity. There is little difference in the quality of the coatings produced by these two types of whirler neither produces a perfectly even coating over the entire plate. Coatings are generally slightly b   thicker in the centres and on the edges of the plates. The vertical whirler has the advantage of taking up less space. The horizontal whirler is better suited for coating fragile materials such as plastics and glass.