Performance compares what the line actually produced during run time against what it could have produced at its ideal speed. Ideal cycle time is the fastest time per unit the machine was designed for, with no slowdowns. On a bottling line this is normally stated as a rate, such as 250 bottles per minute, which is an ideal cycle time of 1 ÷ 250 = 0.004 minutes per bottle.
Performance = (Ideal Cycle Time × Total Count) ÷ Run Time. The top of the fraction is the time the output should have taken at ideal speed. If the line produced 85,800 bottles and that should have taken 343.2 minutes, but run time was 390 minutes, the missing 46.8 minutes were lost to reduced speed and minor stops that nobody logged.
Minor stops are the silent killer here. A filler that pauses for 20 seconds every few minutes because a bottle tips over never shows on the downtime log, but it steals output all shift long. Running the line at 220 instead of 250 bottles per minute "to be safe" has the same effect. Both losses land in Performance, which is why Performance is often the hardest factor to explain to a supervisor who only sees a clean downtime log.
Standard Procedure
- 1Confirm the ideal cycle time or ideal rate from the machine's design specification, not from recent average speed.
- 2Read the total count from the line counter, including rejects.
- 3Multiply total count by ideal cycle time (or divide by ideal rate) to get ideal production time.
- 4Divide ideal production time by run time; a result above 1.0 means the ideal rate is set wrong.
Lesson Summary
- ✓Use the design speed as ideal, never the comfortable speed, or Performance will flatter the line.
- ✓A clean downtime log with a low Performance figure points to micro-stops and slow running.