Theory of Constraints: what is limiting your operation?

Rising work in progress, repeated expediting and idle downstream capacity can share a common cause: work reaches one step faster than it can leave. Theory of Constraints helps leaders focus improvement where it can change overall performance.

A simple flow example

Imagine four production steps with capacities of 100, 80, 40 and 90 units per hour. Customers need 70. In this simplified example, with no downtime or quality losses, the third step limits the line to 40 units per hour. Running the earlier steps faster builds queues without increasing deliveries.

Raising that step to 70 units per hour gives the line enough capacity to meet demand. Release work to match that pace and customer need. Continuing to maximise every department’s output would keep adding inventory.

Five steps to focus improvement

1. Identify: Find the resource, process or policy that limits performance today. Follow the work and verify the constraint with evidence.
2. Exploit: Make better use of the capacity already available. Protect the constraint from avoidable downtime, missing materials and defective work.
3. Subordinate: Align priorities and work release across the operation with the constraint’s pace.
4. Elevate: If the shortfall remains, consider additional capacity or other changes at the constraint.
5. Repeat: Reassess the whole flow after improvement. The limiting factor may have moved, so yesterday’s priorities may no longer apply.

Keep the flow under control

Drum, Buffer, Rope turns this into a scheduling discipline. The constraint sets the pace: the drum. A time buffer protects it against disruption. The rope controls when new work enters the system, helping prevent excess work in progress.

Start with one product family and trace its journey from demand to delivery. Establish the current output, inventory and service position, then agree who owns the first changes. Use a short weekly review to check whether deliveries improve and queues shrink, alongside the effect on operating expense.