Editing Theory of constraints (section)

===Operations===
Within manufacturing operations and [[operations management]], the solution seeks to pull materials through the system, rather than push them into the system. The primary methodology used is drum-buffer-rope (DBR)<ref name=race>{{cite book |author1=Goldratt, Eliyahu |author2=Fox, Robert |title=The Race |publisher=North River Press |location=[Croton-on-Hudson, New York] |year=1986 |pages=[https://archive.org/details/race00gold/page/179 179] |isbn=978-0-88427-062-1 |url=https://archive.org/details/race00gold/page/179 }}</ref> and a variation called simplified drum-buffer-rope (S-DBR).<ref name=sdbr>{{Cite journal |author1=Eli Schragenheim  |author2=H. William Dettmer  |name-list-style=amp | title = Simplified Drum-Buffer-Rope: A Whole System Approach to High Velocity Manufacturing | year=  2000 | url = http://www.goalsys.com/books/documents/S-DBRPaper.pdf | access-date = 8 December 2007}}</ref>

Drum-buffer-rope is a manufacturing execution methodology based on the fact the output of a system can only be the same as the output at the constraint of the system. Any attempt to produce more than what the constraint can process just leads to excess inventory piling up.<ref>{{Cite book|title=The Race|last=Goldratt|first=Eliyahu M.|publisher=North River Press|year=1986|isbn=9780884270621|location=Croton-on Hudson, New York|pages=[https://archive.org/details/race00gold/page/77 77–97]|url=https://archive.org/details/race00gold/page/77}}</ref> The method is named for its three components. The ''drum'' is the rate at which the physical constraint of the plant can work: the work center or machine or operation that limits the ability of the entire system to produce more. The rest of the plant follows the beat of the drum. Schedule at the drum decides what the system should produce, in what sequence to produce and how much to produce.<ref>{{cite book|last1=Goldratt|first1=Eliyahu|title=The Haystack Syndrome:: Sifting Information out of the Data Ocean|url=https://archive.org/details/haystacksyndrome00gold|url-access=registration|date=1990|publisher=New York: North River Press|location=New York|isbn=9780884270898}}</ref> They make sure the drum has work and that anything the drum has processed does not get wasted.

The ''buffer'' protects the drum, so that it always has work flowing to it. Buffers in DBR provide the additional lead time beyond the required set up and process times, for materials in the product flow. Since these buffers have time as their unit of measure, rather than quantity of material, this makes the priority system operate strictly based on the time an order is expected to be at the drum. Each work order will have a remaining buffer status that can be calculated. Based on this buffer status, work orders can be color coded into Red, Yellow and Green. The red orders have the highest priority and must be worked on first, since they have penetrated most into their buffers followed by yellow and green. As time evolves, this buffer status might change and the color assigned to the particular work order change with it.<ref>{{cite book|last1=Shri Shrikanth|first1=M|title=DBR, Buffer Management, and VATI flow classification|date=2010}}</ref><ref>{{cite book|last1=J. F. Cox III & J. J. Schleier|title=Theory of Constraints Handbook|publisher=McGraw Hill|location=New York|pages=175–210}}</ref>

Traditional DBR usually calls for buffers at several points in the system: the constraint, synchronization points and at shipping. S-DBR has a buffer at shipping and manages the flow of work across the drum through a load planning mechanism.<ref>{{cite book|last1=Schragenheim|first1=e|last2=Dettmer|first2=H. W|last3=Patterson|first3=J. W.|title=Supply Chain Management at Warp Speed|date=2009|publisher=Auerbach publications|location=Boca Raton}}</ref>

The ''rope'' is the work release mechanism for the plant. Orders are released to the shop floor at one "buffer time" before they are due to be processed by the constraint. In other words, if the buffer is 5 days, the order is released 5 days before it is due at the constraint. Putting work into the system earlier than this buffer time is likely to generate too-high work-in-process and slow down the entire system.<ref name="International Journal of Production Research">{{cite book|last1=Russell|first1=G. R.|last2=Fry|first2=T. D|title=Order review/release and lot splitting in drum-buffer-rope|date=1997|pages=35:827–845}}</ref>