A dandy roll has raised patterns on it. As it presses onto the wet paper at the end of the wire, it leaves impressions called watermarks. If you hold a piece of paper up to the light, you may see a pattern or wording left by a dandy roll.
A wire-covered cylinder located toward the end of the forming section of a papermaking machine that is used to squeeze excess water out of the wet paper furnish and even out the formation of the paper web. Raised designs woven into the dandy roll wire are used to add wove finish or laid finish texture to the paper, as well as a watermark.
The dandy roll was invented in 1826 in England by John Marshall, a maker of molds for watermarking handmade paper. After the invention of the papermaking machine (Fourdrinier brother), he developed the dandy roll technique as a means of watermarking machine-made paper. (Watermarks, Laid Finish, and Wove Finish.)
The dandy roll improves quality on Fourdrinier wire machines up to 1,000 m/min. The key feature is the patented self-supporting honeycomb with a large open surface. The honeycomb is easy to clean and prevents undesirable ring marks in the paper due to its special design. The dandy roll works by being immersed into the free suspension and lightly wrapped by the wire. By unwinding the dandy roll wire on the top side of the web, the latter is smoothed. The intake pressure causes the stock water to penetrate the dandy roll fabric into the interior of the dandy roll. The flow is thus oriented in such a way that freely floating fibers in the suspension reach the fabric and are deflocculated there. The combined steam-water spray tube, the simple adjusting unit, quick retraction and heated chamfers are some of the other tried and tested features of the well-engineered dandy roll device.
Water that is centrifuged out of the dandy roll into the outlet is securely caught with a drop collection device, which can easily be retrofitted onto the dandy rolls of other manufacturers.
Picture Credit : Google
