Control Zone
Permissible deviation ranges within automated paper machine control loops prevent continuous actuator adjustments around target basis weight or moisture setpoints. The deadband threshold defines the physical range where sensor variations do not trigger corrective control signals to headbox valves or steam controls. Establishing this zone stabilizes process controls and reduces mechanical wear on control valves.
The parameter stops governing process loops during manual override operations.
System Response
Automated quality control systems on continuous paper machines utilize deadband settings to filter short-term signal noise from scanner measurements. Applying a deadband threshold prevents steam valve hunting and stock flow instability caused by transient basis weight fluctuations. Scanner heads moving across the paper web register minor variations in thickness, density, and moisture that reflect natural fiber flocculation rather than true process drift.
Actuators respond only when measured deviations exceed the defined boundary, maintaining steady-state drying and web profile uniformity. Oversensitive control loops without adequate thresholds induce artificial profile waves, leading to caliper swings across the reel. Tuning control loop parameters ensures rapid response to genuine process upsets while ignoring statistical noise.
Stable wet-end controls improve basis weight profile uniformity and sheet runnability.
Operational Scope
Quality control limits restrict threshold width to ensure finished paperboard remains within commercial basis weight tolerances. Narrowing the deadband threshold improves profile tight-range control but increases actuator frequency and valve wear. Thick packaging board grades allow wider control bands compared to lightweight printing papers due to higher basis weight target allowances.
The setting becomes inactive during grade changes or reel turnarounds.
