Drum-buffer-rope (DBR) is a way to schedule a whole plant around the one step that limits its output. It comes from the Theory of Constraints. In plain words, it has three parts.
The drum — the bottleneck sets the pace
The step that limits output is the drum. Its schedule is the plant’s schedule: what it runs, and in what order, decides how much the plant ships. Every hour it loses is an hour lost for the whole plant.
The buffer — protection in time, not piles of stock
Things go wrong upstream: a late part, a breakdown, a quality hold. A buffer is a slice of time in front of the drum (and before shipping) so those problems don’t starve it. Each order carries its own buffer, and how much of it has been used tells you which orders need help.
- Green — less than a third of the buffer used: leave it alone.
- Amber — between a third and two thirds: watch it and plan a recovery.
- Red — more than two thirds: act today, with a named owner.
The rope — release work at the drum’s pace
The rope ties the release of new work to the drum. A job is released a buffer’s length before it is due — not because a machine upstream ran out of work. Less work in process, shorter queues, and lead times you can actually quote.
Simplified DBR for make-to-order plants
In many make-to-order plants the market, not a machine, limits output most of the time. Simplified DBR treats the order due date as the drum, uses a single shipping buffer, and still checks the load on the one internal step most likely to become a bottleneck. It is easier to run and often the right place to start.
How it compares with MRP and ERP scheduling
A scheduling module in your business system usually schedules every machine as if each mattered equally. DBR schedules one step in detail and lets the rest follow. The two work together: your business system keeps orders, routings and materials; the DBR schedule decides what to release and what needs help today.
At a hand-tool manufacturer, heat treatment was the drum. Buffer-management software and visual boards on the floor moved the plant from push to pull: work was released at heat treatment’s pace, and only when its kit was complete. The mindset changed with it — from producing as much as possible to producing what customers had ordered. At a multi-site metal fabricator, the same approach came with written rules for releasing work, a daily walk of the floor, and a habit of tracing every priority violation back to its cause.
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