⚙ Controls
1 Adjust setup time and batch size
2 Watch effective rate and WIP change
3 Try SMED: cut setup, shrink batch, keep rate!
💼 Interview Tip
SMED (Single-Minute Exchange of Die) reduces setup time so you can run smaller batches economically. Smaller batches = less WIP = shorter lead time (by Little's Law). The formula: Effective Rate = Batch / (Setup + Batch × Unit Time). Be ready to explain why big batches seem efficient but actually inflate lead time and hide quality problems.
Instructor Notes
- Challenge: hit demand with the lowest WIP. What batch and setup combo wins?
- Show SMED: reduce setup from 30 to 10, drop batch from 20 to 8. Rate stays above demand but WIP drops dramatically.
- Discuss: at bottlenecks, larger batches save setup time and increase throughput. At non-bottlenecks, smaller batches reduce WIP.
📊 Results
One Batch Cycle:
Setup + Processing = one cycle
Effective Rate (u/hr)
Demand
Batch Size →
Eff. Rate
-
Meets Demand?
-
Cycle Time
-
Lead Time
-
Avg WIP
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Utilization
-
Effective Rate = Batch ÷ (Setup + Batch × tunit), converted to units/hr.
Lead Time ≈ WIP ÷ Throughput (Little's Law).
Key insight: Cutting setup lets you shrink batches while keeping rate above demand.
Lead Time ≈ WIP ÷ Throughput (Little's Law).
Key insight: Cutting setup lets you shrink batches while keeping rate above demand.