|
Context: |
|
In true twin-wire forming, the headbox slice jet impinges into the converging gap between two wires. Depending on the particular gap former design, the initial drainage can take place in one direction or in both directions. The dewatering action is due to pressure set up by the tension in the two wires and by water drainage elements outside of the wires. As fiber mats build up on both wire surfaces, the drainage resistance increases and the pressure in the fiber suspension also increases. The length of the forming zone is dependent on machine speed, basis weight, and stock freeness, as well as the tension in the two wires and the position of the dewatering elements. An even dispersion from the headbox is critical for gap formers because the sheet is set almost immediately and formation is provided by the jet. The jet impingement angle is also critical, more so than for a fourdrinier. |
|
