Date of Award

4-1995

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

First Advisor

Dr. David K. Peterson

Abstract

Introduction

Paper exhibits a wide range of physical and optical properties, all, in essence, can be said to depend on one property, its internal structure, more commonly known as its formation. Generally, the sheet structure is largely determined by the orientation and distribution of the fibers in the finished sheet, both across the sheet and through its thickness. Paper is like most other materials, it is only as strong as its weakest link. Because paper is a complex, heterogeneous material, it is extremely sensitive to the weak link concept.

Higher headbox consistencies are being used by the industry to reduce overall water handling in the paper making process. High consistencies create problems with paper formation, pushing the use of various devices to improve the drainage, orientated shear and turbulence to the pulp on the wire. As a result, improvements in formation properties, as well as fiber orientation, can be expected. Slower machines are often equipped with a shake mechanism, which improves sheet formation, but has little effect on the fiber orientation. As the machines get faster, the shake effects decrease, due to the nearly instant setting of the pulp suspension. A stationary serrated slice mechanism, designed for the faster papermachines, causes stock ridges and valleys to occur in a controlled manner as the pulp suspension leaves the headbox. Collapsing of the stock ridges and valleys occur as water is pulled from the web by gravitation and suction forces from drainage elements. Phase changes cause ridges to form valleys and valleys to form ridges. Several phase changes occur as the pulp suspension travels down the machine, until a full collapse results. The collapsing action creates a shear and turbulence to the pulp suspension resulting in improved sheet formation and fiber orientation along the direction of the collapsed ridges. Vibrating the serrated slice mechanism causes the stock ridges and valleys to oscillate back and forth down the length of the machine. The intent of this thesis is to examine the effects the vibrating serrated slice has on paper formation and fiber orientation at above normal headbox consistencies.

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