FAST CD AND MD CONTROL IN A SHEETMAKING MACHINE

摘要

A system and method of providing fast machine direction (MD) and cross direction (CD) basis weight adjustments using a simultaneous multi-point water weight sensors (21, 22) which provides independent MD and CD measurements is described. The water weight sensors (21, 22) are placed under the wire (12) of the sheetmaking machine and provide fast wet end water weight measurements which are converted into predicted dry end basis weight information and used to control operating variables of machine elements in the sheetmaking machine to compensate for high frequency process variations. MD wet end measurements are used to control operating variables of machine elements that influence the MD dry end basis weight and CD wet end measurements are used to control operating variables of machine elements that influence CD dry end basis weight. The fast control information provided by the non-scanned water weight sensor can be used in a fast control loop which provides feedback information to wetstock source (10), headbox (11) and forming elements and which can be used with a slower response control loop including a dry end sensor which provides a slower basis weight measurement and which controls system variables to compensate for larger basis weight fluctuations.