⚙ Controls
1 Adjust the Drum (bottleneck) and Rope (release rate)
2 Size the Buffer to protect the bottleneck
3 Watch throughput, WIP, and service level respond
💼 Interview Tip
Drum-Buffer-Rope is the scheduling mechanism of TOC. The drum is the bottleneck that sets the pace. The buffer is inventory placed before the bottleneck so it never starves. The rope is upstream communication that limits release to match the drum. Key quote: "An hour lost at the bottleneck is an hour lost for the entire system."
Instructor Notes
- Start with "Balanced" scenario. Ask: what happens if we increase release rate above drum capacity?
- Switch to "Over-release" — WIP explodes but throughput stays flat. Why? The bottleneck caps it.
- Flip to the Economics tab: when does a bigger buffer increase profit (prevents costly stockouts) vs. just add holding cost?
- Ask: should we pace release to the BN or to market demand when revenue/unit is very high?
🎿 System View
Rope (Release)
10
➔
Buffer
15
➔
Drum (BN)
10
➔
Market
12
Throughput
-
Avg WIP
-
Service Level
-
Lead Time
-
Revenue/Hr
-
Cost/Hr
-
Profit/Hr
-
Missed Sales
-
BN Output
Buffer Level
Release In
Demand
💡 What to Look For
The rope releases work into the system. Work builds up in the buffer, and the drum (bottleneck) pulls from it at its maximum capacity. If release > drum, WIP grows without increasing throughput. If release < drum, the bottleneck starves and throughput drops below potential. The goal: pace release to the drum, size the buffer to absorb variability.