HYDRAULICS PROVIDES TIGHT CONTROL OF PAPER COATINGS.

Once paper comes off the mill on bulk rolls, it often requires some type of coating to serve a specific application. The most important obstacle to overcome in obtaining the full benefits of modern computer control in coating applications has been actuator performance. Modern computer-based gauging systems can measure coatings with better than 1% accuracy and provide a variety of sophisticated control schemes. However, the coater actuator presented a unique mechanical problem: a load weighing several thousand pounds needed to be moved in precise increments of less than 100 mu m. The problem was solved using multi-piston pump and cylinders which offer more precise control than screw mechanisms.