Production line efficiency is a fairly easy concept to grasp; however, like so many things, the devil is in the details. Simply stated, it is the percentage of productive hours realized within a scheduled period of time; the percentage results from dividing productive time by scheduled time, such as the graphic represents.
So where does the devil lurk?
First you must define “scheduled time.” Keep it simple; it is the hours the line is scheduled to run at the divider, depositor, sheeter, etc. Too often, changeover times are subtracted, as are scheduled breaks; count these for what they are: non-productive times.
Next, define “productive time.” Plain and simple, this is the time when the line is running and producing saleable, specification product.
Third, define “non-productive time.” Downtime, both mechanical and operational (changeovers, running out of dough, employee breaks and lunch, the time non-saleable product is produced, time spent reworking products, QA sampling, etc.), is to be included. Base non-productive hours on make-up time; don't get caught in the trap of confusing machine downtime with line downtime; there is a difference.