Keep Improving the System

Every system has one constraint — the bottleneck that governs the whole output. Improving anything that isn't the constraint doesn't speed up the system.

The leap: you manage bottlenecks on the production line every day. A project has them too — but they're usually a handoff between departments, not a machine.

Mỗi tô phở trải qua 3 bước:

• Trần bánh phở: 1 phút
• Xếp thịt và chan nước dùng: 30 giây
• Mang tô ra cho khách: 3 phút

Có 1 người trần bánh phở, 1 người xếp thịt và chan nước dùng, và 2 người phục vụ khách.

Changing most variables produces only small global impact. A few — the constraints — move everything. Don't spread improvement thin.

Five focusing steps:

• 1Identify the constraint
• 2Exploit it — get the most from it as-is
• 3Subordinate everything else to it
• 4Elevate it — add capacity if still needed
• 5Repeat — the constraint will move

Kanban is not the sticky notes — it is a strategy for optimizing the flow of value through a process, built on three practices that only work in tandem:

• 1Define and visualize a workflow
• 2Actively manage items in the workflow
• 3Improve the workflow

Together, these three practices form a Kanban system.

Taiichi Ohno (1912–1990) was a Toyota executive who created the Toyota Production System (TPS) — the foundation of both Lean and Kanban.

• →Designed Kanban as a pull signal: produce only what the next stage needs, when it needs it.
• →Treated the factory floor as a living system — go see the bottleneck, don't manage from a desk.
• →His discipline: stop the line the moment a defect appears — fix it now, don't let it flow downstream.

Each group takes a real project.

• 1Visualize the workflow — columns To Do · In Progress · Done (add real stages: Design, Approve, Build, QA). Put this week's real items on cards.
• 2Set a WIP limit — cap each column. Notice what you must stop starting.
• 3Find the bottleneck — where do cards pile up / wait longest? That's your constraint.
• 4Make policies explicit — one rule for how a card moves to the next column.

PDCA (Plan–Do–Check–Act) — also called the Deming cycle — is the engine that makes improvement continuous instead of a one-time event.

• PPlan — pick one change to relieve the bottleneck (a handoff policy, a WIP limit, a clearer owner).
• DDo — run the change next week on the same real project.
• CCheck — did the pile shrink? Did wait time at that stage drop?
• AAct — if yes, keep it and find the next constraint. If no, adjust and loop again.

Deming insisted the two are not the same. PDSA swaps step 3 — Check becomes Study — and that one word changes the intent.

• CCheck (PDCA) — did it pass or fail? A quick inspection against the target.
• SStudy (PDSA) — why did we get this result? Compare against your prediction and build lasting knowledge.