What is Drum Buffer Rope (DBR) & Theory of Constraints (TOC) in Lean Manufacturing  ?
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What is Drum Buffer Rope (DBR) & Theory of Constraints (TOC) in Lean Manufacturing ?

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.

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. 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.

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

This video help you understand the concept of Drum Buffer Rope of Theory of Constraints (TOC) in Lean Manufacturing.

Girish Kumar

Technology Adviser at Resilient Leadership & Change Masters

1y

Well explained!

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Girish Kumar

Technology Adviser at Resilient Leadership & Change Masters

1y

Well explained!

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Reply

Thanks Steven Hajec, MBB, LMBB. DBR is not TOC, DBR is only one of the methods, solutions developed by Dr. Goldratt to improve operations flow. Usually companies doing Lean Manufacturing are not doing or implementing DBR, as it does challenge several deep rooted paradigms. Lean even though is not originally built or proposed this way it is wrongly practiced as a cost reduction methodology, and second to promote flow. Alas, all of TOC and thus DBR focus is to manage and improve flow systemically. TOC challenges the very core of the Cost reduction framework, as it clearly ignores the fundamental tenet: Any flow is driven by dependency + variability.

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Steven Hajec, MBB, LMBB

Business Transformation & OpEx, Business Operations Expert, Transition Management,

1y

So, the thesis posed is, "What is Drum Buffer Rope (DBR) & Theory of Constraints (TOC) in Lean Manufacturing?" Let me preference this reply with my belief that knowledge of tools (Lean, TOC, 6 Sigma) coupled with excellent project management management skills are the measurement of a process excellence practitioner. TOC isn't part of Lean; Kanban and Heijunka are. I'd even concede TOC can be superior, but to do either one somewhat precludes the other. For instance TOC reduces precursor parts inventory requirements and WIP in low mix manufacturing, but has little to say when product mixes increase. Granted, the serial approach of breaking constraints is compelling. The complete TOC methodology is much richer than represented. Also, the article describes DBR, but doesn't answer the question of how it fit's in with Lean manufacturing. It doesn't even discuss how DBR fits into TOC, or even what TOC is. I don't want to come off as a purist or premadonna (too late). I believe that a good practitioner constantly learns and applies the best tool(s) for each challenge. I also recognize an article that addresses my comments would be be a lot longer. Overall keep up the good work. just watch the Click Bait titles.

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