Drum-Buffer-Rope
also DBR
A Theory of Constraints scheduling method where the constraint sets the production tempo (drum), a buffer shields it from starvation, and a rope ties new-work release to that tempo to stop overproduction upstream.
Drum-Buffer-Rope (DBR) is Goldratt’s scheduling discipline for running a system around its constraint. It names three roles with metaphors. The drum is the constraint, whose pace sets the beat for the whole plant the way a drummer synchronizes a marching band or a rowing crew. The buffer is a stock of work held in front of the constraint so that statistical fluctuations and dependent events upstream cannot starve it; protecting the weakest link protects total throughput. The rope ties release of raw materials to the drum’s rate, so no more is started than the constraint can consume. In The Goal’s hike, putting the slowest boy at the front and forbidding anyone to pass him is the rope without literal rope.
DBR is a concrete instance of subordinating non-constraints to the constraint, and CF uses it to attack local optimization. Running a non-constraint flat-out feels productive locally but, beyond the drum’s tempo, only piles up inventory and clutters flow; it does not raise throughput. This is why CF rejects the balanced plant: you cannot abolish the weakest link, so deliberately choose where it sits and orchestrate around it.
CF’s distinctive addition treats the buffer as a precondition for error correction. Problems are inevitable, and fixing them consumes spare time, parts, and capacity; with zero slack every correction would steal resources from elsewhere. So buffers and excess capacity are not waste but the margin that lets a system absorb errors without disruption.