Transfer Point
Critical junctions in the papermaking process occur where the wet fibre mat leaves the forming wire to enter the first press nip. The couch interface marks the transition from a supported slurry to a self-supporting web capable of withstanding tension. Vacuum pressure at this location removes the final portion of free water before mechanical compression begins.
Moisture Regulation
Suction couch rolls use internal vacuum boxes to pull air through the holes in the shell and the pores of the forming fabric. This action compacts the sheet at the couch interface and increases the solids content to approximately twenty percent. Proper vacuum levels prevent the sheet from sticking to the wire or delaminating during the transfer.
Operators adjust the take-off angle to manage the release of the web from the mesh surface. Precise control of the vacuum capacity is essential for preventing crushing in the subsequent press.
Mechanical Stress
Inadequate dewatering at this stage leads to web breaks and reduced machine efficiency. Excess moisture weakens the hydrogen bonds between fibres and prevents the couch interface from functioning at higher speeds. This weakness limits the maximum velocity at which the machine can operate without risking a failure at the open draw.
