A paper machine runs continuously and winds its output onto jumbo reels at a fixed deckle width. Winders and sheeters cut those reels into the widths, diameters and sheet sizes customers ordered. Each grade has its own GSM, shade, furnish and coating, and moving from one grade to the next costs make-ready time and off-spec paper.
Orders from converters, printers and packaging makers arrive in many widths and GSMs, so the mill has to sequence grades and combine widths to fill the deckle. Fiber (wood, pulp or recovered paper), chemicals such as caustic soda, and energy dominate cost, and their prices move month to month. Steam, power and crew availability limit what each machine can run.