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Calculations Reference

Manufacturing Throughput Time Calculations

Manufacturing throughput time is the total duration required for a product to move through the entire manufacturing process, transforming from raw materials into finished goods. This concept also extends to the processing of raw materials into components or sub-assemblies.

#Effective Cycle Time

Average time it takes to produce one good part/batch

Using OEE (Overall Equipment Effectiveness) :

Effective Cycle Time=Designed Cycle TimeOEE\text{Effective Cycle Time} = \frac{\text{Designed Cycle Time}}{\text{OEE}}

The above formula can be reduced to:

Effective Cycle Time=Actual Cycle TimeUptime Percent×Yield Percent\text{Effective Cycle Time} = \frac{\text{Actual Cycle Time}}{\text{Uptime Percent} \times \text{Yield Percent}}

#Processing (value-add) time

Total of the node effective cycle times

Processing Time=EffectiveCycleTime1+EffectiveCycleTime2+…+EffectiveCycleTimen\begin{aligned} \text{Processing Time} = {} & \text{EffectiveCycleTime}_1 \\[1em] & + \text{EffectiveCycleTime}_2 \\[1em] & + \ldots \\[1em] & + \text{EffectiveCycleTime}_n \end{aligned}

#Inventory (queue) time

Total time it takes to process the inventory held between nodes

InventoryTimedays=Inventory HeldDaily Customer Requirement\text{InventoryTime}_{\text{days}} = \frac{\text{Inventory Held}}{\text{Daily Customer Requirement}}

where

Daily Customer Requirement=Units Per WeekOperating Days Per Week\begin{aligned} \text{Daily Customer Requirement} = {} & \frac{\text{Units Per Week}}{\text{Operating Days Per Week}} \\[2em] \end{aligned} InventoryTimedays=Inventory Held×Operating Days Per WeekUnits Per Week\begin{aligned} \text{InventoryTime}_{\text{days}} = {} & \frac{\text{Inventory Held} \times \text{Operating Days Per Week}}{\text{Units Per Week}} \\[2em] \end{aligned}
This is an approximate inventory time based on the value stream target performance. The actual inventory time will be closer to the number of units in inventory times the longest effective cycle time of any node in the system.
Units per week is defined at the value stream level. Operating days per week can be defined for the downstream node of the edge/relationship. Otherwise it falls back to the operating days per week defined at the value stream level.

#Manufacturing Throughput Time

Average total time it takes to produce one good part from start to finish

MTT=Processing Time+Inventory TimeMTT = \text{Processing Time} + \text{Inventory Time}

#Units

The standard unit used for these calculations is seconds. However as times increase seconds becomes less helpful and moving to larger units is needed.

Example: 34,567 seconds is difficult to comprehend. Converting this to 9.6 hours is more helpful.

#Larger units (future)

For longer manufacturing throughput times we may want to also display days or weeks, taking into account the shift duration for each node.

SecondsPerDayn=(ShiftLengthn−BreakTimen)×ShiftsPerDayn\begin{aligned} SecondsPerDay_n = {} & (ShiftLength_n - BreakTime_n) × ShiftsPerDay_n \\[2em] \end{aligned} MTTdays=EffectiveCycleTime1(1+InventoryHeld1)SecondsPerDay1+EffectiveCycleTime2(1+InventoryHeld2)SecondsPerDay2+…+EffectiveCycleTimen(1+InventoryHeldn)SecondsPerDayn\begin{aligned} MTT_{\text{days}} = {} & \frac{\text{EffectiveCycleTime}_1(1+\text{InventoryHeld}_1)}{\text{SecondsPerDay}_1} \\[2em] & + \frac{\text{EffectiveCycleTime}_2(1+\text{InventoryHeld}_2)}{\text{SecondsPerDay}_2} \\[2em] & + \ldots \\[2em] & + \frac{\text{EffectiveCycleTime}_n(1+\text{InventoryHeld}_n)}{\text{SecondsPerDay}_n} \end{aligned}

Then the weeks can be calculated by dividing by the number of operating days per week:

MTTweeks=MTTdaysOperating Days Per WeekMTT_{\text{weeks}} = \frac{MTT_{\text{days}}}{\text{Operating Days Per Week}}
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