Ropes are actions taken to tie the rate at which material is released into the plant
(at the first operation) to the production rate of the constrained resource. The objective
of a rope is to ensure that the work-in-process inventory will not exceed the level
needed for the time buffer. Thus, the drummer rate is used to limit the rate of material
release and effectively controls the rate at which the first operation produces. The rate
of the first operation then controls the rates of subsequent operations. The TOC inventory
system is often called the drum-buffer-rope (DBR) system. Exhibit 21-10
illustrates the DBR structure for a general setting.