Factors Affecting Blade Buildup on a High Speed Production Coater, 1997 Coating Conference Proceedings

Over a two-month period, visual observations of coating buildup on the blade were made and corresponding process data was collected. This problem is called by many names and is often referred to as “weeping”, “bleeding” or “stalagmiting”. The coater observed, applied coat weights ranging from 10 to 13.5 g/m 2 with a rigid blade at speeds between 1100 and 1200 m/min. Both wood-free and wood-containing grades were observed in a basis weight range from 65-90 g/m 2 . A preliminary study found that for a .38 mm (.015 in) thick blade, blade wear accounted for a reduction in blade length of 0.09 mm (.0035 in) and an increase in blade angle of just less than 1 degree/hr. A system was developed for visually ranking blade buildup on a l-10 scale. For each observation, corresponding values were recorded for grade, basis weight, coater speed, coating solids, coating temperature, blade angle, blade load, coat weight, sheet temperature both entering and exiting, time since a splice, and time since a web break. Only about 50-65% of the variability of the blade buildup could be accounted for by the monitored variables. The remaining variability is due to experimental error, variability in the coating supply system and rawstock variability. In all, 36 observations of both heads were made. 15 of these were for wood-free grades and 21 were wood-containing.