The headbox takes in stock at roughly 0.2 to 1 percent consistency, breaks up flocs with turbulence and discharges it through an adjustable slice opening onto the wire. Jet speed relative to wire speed, called the jet-to-wire ratio or rush and drag, controls fiber orientation and formation. Slice adjustments across the width trim the basis weight profile.
Headbox pressure was swinging all night with the fan pump drive acting up, and formation went wild for three reels.
Also heard as
- flow box
- HB
Related terms
Formation
How evenly fibers are spread through a paper sheet, judged by small-scale variation in mass.
Floc
Clump of entangled fibers in stock or in the finished sheet, the building block of poor formation.
Wire
Endless woven plastic fabric on which the paper web is formed and drained.
Wet end
Front section of a paper machine, where stock is formed into a sheet and most of the water is drained and pressed out.
Grain
The main direction in which fibers in a paper sheet are aligned, almost always the machine direction.