Takt Time = (Available Time à 60) / Customer Demand
Available Time: min/day | Demand: units/day
Result: seconds/unit Maximum allowable cycle time to meet customer demand.
đĻ Total Lead Time
LT = ÎŖ (CT_i / 60)
Sum of all station Cycle Times converted to minutes. Total time a unit spends in the value stream.
â Total VA Time
VA Time = ÎŖ (PT_i) / 60
Sum of all station Process Times (PT) converted to minutes. Only value-adding touch time counts.
đ PCE â Process Cycle Efficiency
PCE = (VA Time / Lead Time) Ã 100
Both in the same unit (minutes).
Target: PCE > 25% (Lean benchmark). Ratio of value-added time to total lead time.
đ Flow Efficiency
Flow Eff. = (VA Time / Lead Time) Ã 100
Same calculation as PCE in this model. Can be extended to include wait/queue times in future versions.
đ Daily Throughput
Throughput = (Available Time à 60 / CT_bottleneck) à Uptime_min
CT_bottleneck = max CT across all stations (constraint).
Uptime_min = min Uptime% across all stations / 100. Max units per day limited by the bottleneck station.
đ¯ Rolled Throughput Yield (RTY)
RTY = Î (1 â Scrap_i / 100) Ã 100
Product of first-pass yields across all stations.
e.g. 98% Ã 97% Ã 99% Ã 96% = 90.3% Probability a unit passes all stations without defects.
đ Station Lead Time
LT_station = (WIP Ã Takt / 60 + CT / 60) / Available Time
WIP: units in buffer upstream of station.
Result in days. Little's Law applied per station.
đ Pcs/Cycle (Bin Consumption)
Bin consumed = Pcs/Cycle per completed cycle
Station needs Pcs/Cycle pieces available in bins to start a cycle.
Consumed from Bin 1 first, then Bin 2 for remainder. Models assembly operations requiring multiple input parts.
đ VSM Timeline â Lead Time & Avg Cycle Time per Station