Twinformer
Sheet formation takes place in the screen part of the paper machine. It is in fact an on-going battle between filtration and re-flocculation. The wire part can have different design features. The most common design is the endless wire con- cept. It is a universally applicable system allowing for high flexibility with regard to basic weight and sheet properties. However, these endless wire paper machines have a serious performance limitation in that they are strictly one- sided: drainage takes place only at the bottom, not at the top. And so, new designs were considered to increase drainage efficiency. This led to the development of the so-called twinformer, where additional equipment is installed on the rods of the endless wire. The twinformer is a design which provides for drainage of the suspension to the top side as well, by means of an added upper wire and a series of suction boxes. With this additional equipment, the paper stock can now be drained on both sides – from the bottom by means of gravity, and from the top, by means of suction. Drainage time is significantly reduced, which results in a far more efficient production process, with the added advantage of reduced two-sidedness of the paper.