Lean, Six Sigma, and Theory of Constraints

Learning objectives

• Compare Lean, Six Sigma and Theory of Constraints.
• Identify the true constraint of a garment operation.
• Choose an integrated improvement strategy.

Three complementary lenses

Lean removes non-value work and creates flow. Six Sigma validates causes of variation. Theory of Constraints (TOC) raises total throughput by focusing on the limiting step through five steps: identify, exploit, subordinate, elevate, then repeat.

Garment-factory example

Adding operators everywhere does not raise output when buttonholing is the constraint. Protecting and improving buttonholing, balancing upstream release and reducing its defect variation improves the entire line.

Method

1. Map flow and inventory.
2. Locate the true constraint using data, not the biggest queue.
3. Protect the constraint's time and reduce its variation.
4. Reassess — after elevation the constraint moves.

Common mistakes

• Optimizing every operation independently.
• Assuming the largest visible queue is always the constraint.