CROSS- DIRECTION CONTROL

摘要

The subject of cross-direction control was born in 1954 when someone other than the backtender officially noticed the problem of basis weight variation. Burkhard and Wrist [1] declared that there would be three components to basis weight variation:rn1. Machine direction (MD)rn2. Cross-direction (CD)rn3. Random (R)rnCuffey [2] gave us a picture of basis weight variation in 1957 by staggering successive CD weight profiles to produce a "topographical" map (Fig. 611). Prior to this, the only methods of sensing CD variation in weight, moisture or caliper were lab tests or the backtender. Control was exercised by chokers on the branched manifold entering the headbox, flow obstructions placed in the headbox. slice spindles, air nozzles in dryer pockets, and air nozzles or friction pads at the calender stack.rnThe industry discovered how bad CD variation really was when on-machine traversing weight and moisture gauges became commercially available in the early Sixties. Most of the early development effort went into troubleshooting machine faults rather than control actuators.