Statistical Process Control in the wet end: The basics
This is the first in a series of columns on statistical process control (SPC) as it applies to paper chemistry. At the risk of being too simplistic, I felt it important to summarize basic SPC concepts before considering this topic in greater depth.
Papermaking quality has undergone a revolution in the past decade. In the past, the production department made paper and quality control tested it. Problems were traced to their source and corrected. However, this once pervasive attitude has changed.
Today's goal is zero defects. The emphasis is on process control rather than final inspection, on prevention rather than detection. This approach, called SPC, extends from raw materials to final product. It calls for cooperation with suppliers, to ensure raw material quality and consistency; and with customers, to gain feedback on …