Disaggregating Work Center Confirmation Logs to Identify Governing Shop-Floor Bottlenecks
Disaggregating confirmation logs separates true machine constraints from reporting lags, scrap losses, and administrative batching to target capital expansion.
Inter-Arrival Variance
Meaning
Measuring the fluctuation in the elapsed time between consecutive arrivals of parts or orders at a workstation provides a critical metric for queueing performance. When inter-arrival variance is high, jobs arrive in batches or clumps rather than at steady intervals. This clustering causes temporary capacity overloads even if the average arrival rate remains well below the workstation capability.
Measuring this variability helps engineers locate the source of line instability.
Queue Creation
Unstable arrival times force downstream machines to sit idle and then experience sudden backlogs. High inter-arrival variance directly drives up the average queue length at a workstation. This occurs because the capacity that is unused during quiet periods cannot be stored to handle the subsequent rush.
As a result, the queue grows larger even when the average supply and demand are perfectly balanced.
Operational Cost
Fluctuating arrival schedules increase work-in-process inventory and prolong the lead time of manufactured items. This outcome arises because parts spend more time waiting in line than being processed. Factory managers are forced to hold larger finished goods inventories to protect their customer service levels against these delivery delays.
Mitigation Strategy
Scheduling arrivals through automated release gates can help reduce arrival volatility. This action stabilizes flow.