Analysis of Fiber Orientation of Paper Using Pilot Machine with Open Headbox (3) - Effect of Stock Concentration and Feeding Speed

This study investigated the potential to improve fiber orientation in paper by controlling stock concentration and feed speed during papermaking, using a pilot-scale wet-web forming machine equipped with an opentype headbox.To regulate jet velocity at the slice outlet of the headbox, stock concentration was varied, and the pumping speed of the stock supply was adjusted accordingly.Paper sheets were then fabricated under each condition, and their physical properties, including grammage, formation, and tensile strength in both the machine direction (MD) and cross direction (CD), were quantified and compared.The results revealed that increasing both stock concentration and jet velocity raised grammage and thickness by increasing the amount of stock delivered per unit area of the wire, thereby enhancing sheet-forming capacity.At higher stock concentrations, faster consolidation reduced fiber non-uniformity in the CD, which led to a notable increase in tensile strength in the CD and, consequently, a higher CD/MD tensile index ratio.Furthermore, higher jet velocity intensified turbulence from the stock's impact on the turbulence plate in the headbox, which suppressed excessive fiber alignment in the MD and further improved CD tensile strength.These findings demonstrate that appropriate control of stock concentration and jet velocity during the forming process can effectively regulate fiber orientation and improve sheet uniformity inpapermaking.