Takt time
Takt time = Total work time available / Units required
Staffing a work cell to demand. It is the drumbeat the customer sets.
- Total work time available
- Scheduled production time in the period
- Units required
- Demand for the same period
Workers required
Workers required = Total operation time required / Takt time
After takt time, to staff the cell. A fractional answer is rounded up when staffing.
- Total operation time
- Sum of all operation times for one unit, from the work balance chart
- Takt time
- Available time per unit required
Cycle time and output rate
Cycle time = Operating time per day / Desired output rate
Output rate = Operating time per day / Cycle time
Pacing a line. Check that no single task exceeds the cycle time before going further.
- Operating time per day
- Minutes or seconds the line runs
- Desired output rate
- Units required per day
Theoretical minimum stations
N(min) = Sum of task times / Cycle time (round up)
Before assigning tasks, to know the floor. Precedence often forces one or two more.
- Sum of task times
- Total work content of one unit
- Cycle time
- Maximum time per station per unit
Balance delay and efficiency
Balance delay % = (N(actual) x CT - Sum of task times) / (N(actual) x CT) x 100
Efficiency % = 100 % - Balance delay
= Sum of task times / (N(actual) x CT) x 100
After the assignment, to judge it. Always use the actual number of stations.
- N(actual)
- Stations the assignment really used
- CT
- Cycle time
Ranked Positional Weight
PW(task) = own time + SUM of the times of ALL following tasks
Rank descending by PW, then assign the highest-ranked available task that fits
A line-balancing heuristic that favours tasks with the most work behind them. Section B works two problems on it; Section A only names it.
- own time
- The task's own processing time
- following tasks
- Every task downstream of it, not only its immediate successors
Maximum output of a line
Minimum cycle time = longest single task time
Maximum output = Operating time / Longest task time
When asked how fast a line could possibly run, or whether a target rate is feasible at all.
- Longest task time
- The bottleneck task; it cannot be split across stations
- Operating time
- Available time in the period