Abstract
The course of the papermaking process, as it occurs on a Fourdrinier machine, is analysed to illustrate how each functional operation performed by the machine influences the final product. The analysis starts with the role played by the slice and its approaches and special emphasis is given to the many compromising factors that determine holey roll design and behaviour. The effect of slice design on orientation, flocculation and jet delivery is also considered. It is shown that the concept of a fibre network structure for the stock with a strength that varies with fibre consistency, length and type explains many of the observations .
The distinction between macro- and microformation is defined and the relative effects of the head box and table suction on these properties are illustrated. It is concluded that gross relative motion of stock on the wire is detrimental to macroformation, but that short range relative motion is beneficial to microformation and results in a more uniform fibre distribution than is possible by random turbulent diffusion processes in the head box alone.
The variation of sheet properties across the sheet thickness are discussed and it is concluded that selective filtration that occurs during the forming operation is the principal cause, not the backwashing of the sheet by inflow of water at table rolls, as is ,frequently reported.
A brief speculation on the construction of the `idealised’ machinemade paper sheet is presented.
Download PDF