Abstract
Sheet structure can be fully described in terms of(i) the distribution of fine material, (ii) the degree of fibre orientation and (iii) the degree of fibre flocculation throughout the sheet thickness.
The physical characteristics of common forming processes are discussed-those of the Technical Section sheetmachine, the Fourdrinier machine, uniflow and contraflow vats . The major characteristics of these processes are relative movement between stock and wire, drainage forces, stock concentration, recirculation of fines, manner of metering stock in relation to area of the formed sheet, conditions under which the forming process ends.
The effects of these physical process characteristics on the structure of the sheet are discussed and available evidence is presented.
It is concluded that all common forming processes can be described by means of component unit processes, which are orienting, continuous draining, intermittent draining, fractionating, emerging and flocculating . The manner in which these unit processes affect the sheet structure is described. Internal sheet structures typical of the common forming processes are presented schematically.
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