"Downtime" and "Time Lost" measure different things and are easy to confuse, so we'll define them carefully and then illustrate with an example.
- "Downtime" (shown on the Performance Bar) measures the time consumed by downtime events (both automatically detected and manually reported) during the current shift.
- "Time Lost" (shown under the Job Performance panels) shows the total amount of time lost on this job during this shift to cycles that were slower than the target takt time. This includes both time lost to automatically detected downtime events and time lost due to cycles that were slower than the target takt time but not slow enough to reach the downtime detection threshold.
To make the difference clear, let's look at an example. Let's say you started a job at the beginning of the shift with target takt time 20 seconds and downtime detection threshold of 24 seconds:
- During the shift so far, you've had 10 units that took 24 or more seconds to build and were detected as downtime events. These 10 units had an average takt time of 30 seconds each, so there were 100 seconds of measured downtime during downtime events during this shift: (30 seconds average takt time during downtime events - 20 seconds target takt time) * 10 = 100 seconds.
- You also had 10 "slow cycles" that were slower than the target takt time of 20 seconds, but weren't 24 seconds or greater, so they weren't included in "downtime." These 10 slow cycles had an average takt time of 22 seconds, so there were 20 seconds lost to slow cycles so far during the shift: (22 seconds average takt time for the slow cycles - 20 seconds target takt time) * 10 = 20 seconds. Time Lost is time lost to downtime plus time lost to slow cycles, so Time Lost here is 120 seconds.
- In this example, the Performance Bar will show 100 seconds of downtime, and the "Time Lost" panel under the Job Performance panels will show 120 seconds.
Time lost actually looks at the total time taken to create all the units of the current job during the current shift. Therefore, if you have some units that were created in LESS time than the target takt time, that will reduce the "time lost" total. So if you have a series of such fast builds, you may see "time lost" decreasing during a shift.
Keep in mind that if you complete, pause, or stop one job during a shift and start another, the "time lost" total will reset for the new job, but the "downtime" total (which is for the shift) will not reset.