Stock Concentration
Mass fraction measurement indicates the percentage of solid material in the aqueous suspension just before it is discharged onto the forming wire. A precise headbox consistency is necessary to control the final basis weight and the formation quality of the paper. This value usually ranges from 0.2 to 1.0 percent depending on the grade being produced and the machine speed.
Formation Quality
The distribution of fibres across the width of the machine depends on the turbulence and flow velocity within the delivery system. High headbox consistency can lead to flocking, where fibres clump together and create an uneven appearance in the finished sheet. Maintaining the correct ratio between water and solids allows the fibres to orient themselves randomly, which provides isotropic strength properties.
Operators adjust the slice opening and the total flow to maintain this balance during production changes.
Drainage Rate
The volume of water that must be removed on the forming table is a direct function of the initial dilution level. When the headbox consistency is low, the machine must handle larger amounts of white water, which can limit production speed. Increasing the solids content can speed up the process but may compromise the internal bond strength if the fibres are not properly dispersed.
Monitoring this variable in real time allows for immediate corrections to the chemical dosing and refining stages. Accurate control of this ratio is the foundation of a uniform paper web.
