What is Drum Buffer Rope?

Drum Buffer Rope (DBR) is the Theory of Constraints scheduling process focused on increasing flow and Throughput by identifying and leveraging the system constraint. DBR was developed by Eliyahu M. Goldratt (Eli Goldratt), the father of Theory of Constraints.

Where should the constraint be?

Where should you strategically place your constraint? Where do you want it to be? Before we answer those questions, let's talk about where you don't want your constraint to be. Non-constraints by definition have excess capacity. The rule of thumb is that you'll need 25-30% excess capacity at non-constraints. But I prefer to call this PROTECTIVE capacity. Excess implies that it should be eliminated. Which resources are easier to hire, less expensive to buy? The answer to those questions will give you an idea of which resources you want to be non-constraints. Since some of this capacity may not be used or used as much, you don't want protective capacity for expensive, hard to hire resources. So that means that you would want to strategically place your constraint at the resource that is hardest or most expensive to get more of. Often this resource is the essence of what you do. Now, if you could put your constraint anywhere because all your resources were equal in terms of adding more, then I'd put the constraints at the beginning of your process. More on that below.

In Drum Buffer Rope what provides the schedule?

In Drum Buffer Rope the schedule is created for the constraint resource, the drum. Since all other resources have more capacity relative to the constraint, the only resource that you need to schedule is the constraint. If you know what the constraint's capacity is per day, you can schedule or sequence which jobs will be on the constraint each day. This is much easier than trying to schedule every job at every resource.

What is Simplified Drum Buffer Rope (sDBR)?

Simplified Drum Buffer Rope (sDBR) is Traditional DBR without the constraint buffer. Simplified Drum Buffer Rope just has a shipping buffer. The market is considered to be the constraint and the drum is set to meet all the due dates, so the shipping buffer is buffering the due dates. When you have a market constraint, you need to exploit that constraint by making sure you're on time to all customers. In the case of sDBR the drum is the due date. Therefore there is no need to sequence jobs at the constraint or the "would be" capacity constrained resource (CCR) since the constraint is the market. Raw materials are released on the job due date minus the shipping buffer. Releasing the right jobs in the right order is critical. If priorities are out of sequence due date performance is put in jeopardy. sDBR is easier to implement since there is only one buffer. But the challenge can be in exploiting capacity to ensure Throughput is maximized.

What is the BUFFER in Drum Buffer Rope?

The buffer is measured in time. It's the amount of work expressed in time (like days worth) prior to the constraint. We control this amount of work with the rope. By having a buffer of work in front of the constraint, we can ensure the constraint does not run out of work. The constraint is the only place where 100% utilization is a good thing! The buffer's job is to absorb variability. In traditional Drum Buffer Rope there are 2 buffers - one for the constraint and a shipping buffer. The one before the constraints is there to protect the constraint and the shipping buffer protects the due date. Simplified Drum Buffer Rope just has a shipping buffer. The market is considered to be the constraint and the drum is set to meet all the due dates, so the shipping buffer is buffering the due dates. When you have a market constraint, you need to exploit that constraint by making sure you're on time to all customers.

What is the DRUM in Drum Buffer Rope?

The drum is the constraint. The resource that is limiting your output. Also called the Capacity Constrained Resource (CCR). Most shops typically only have one constraint at any point in time, but the issue is that for many custom job shops and machine shops the constraint can move as the mix changes. And in custom job shops and machine shops the mix can change dramatically and often. A constraint is any resources that has demand greater than its available capacity. Any time lost on the constraint is output lost by the entire system. An hour lost on the constraint is an hour lost for the output of the entire system. Increasing output at the constraint, increases overall output. If you increase the output of the constraint to the point that another resources has become constrained, the constraint/drum has moved. The constraint is called a drum because it sets the pace for the operation like a drum sets the pace for solders marching. The rate of output is equal to the output of the constraint. This concept was illustrated in The Goal with boy scouts going on a hike. The slowest hiker, Herbie, set the pace. In The Race (also by Goldratt), it was illustrated with solders marching to the beat of the drum. Improving non-constraints has no effect on overall output. This is why measuring utilization everywhere makes no sense. Trying to 100% utilize non-constraints just results in too much Work in Process (WIP) and the many issues associated with that. We see a moving constraint most often in situations where shops have balanced capacity, meaning that the amount of capacity needed at each resource is close to exactly what is needed. The capacity everywhere is balanced to the demand. The Theory of Constraints diagram above would show balanced capacity if all circles had the capacity at 20. In job shops and machine shops that have changing mix, this balancing of capacity has the detrimental effect of lowering output. The exact opposite of what it was supposed to do. It is a common misconception that you should constantly be eliminating your constraint. This would be an unending, ever changing process. For example, the Drum Buffer Rope policies procedures and measures would need to adjust each time your constraint moved. How do you leverage or maximize the output of an ever moving and changing target? It would be difficult. It would be far better to be strategic about the placement of your drum. And for it to be a business decision if the drum moved. After all, the drum dictates the output of your entire organization.

What are the different types of capacity in Theory of Constraints?

Theory of Constraints identifies three types of capacity: productive capacity (actively used to generate throughput), protective capacity (planned excess at non-constraints to absorb variability), and excess capacity (beyond what is needed). Non-constraints need approximately 25-30% protective capacity to ensure the constraint never starves for work.

Theory of Constraint, Lean and Six Sigma. Lean tells us to reduce waste everywhere. Six Sigma tells us to reduce variability everywhere. The Theory of Constraints methodology, Drum Buffer Rope buffer statistics shows us WHERE to improve to have the biggest impact on our output and Throughput.

What is the ROPE in Drum Buffer Rope?

The rope is how we control the release of new work. The idea is that if the constraint sets the pace, the drum beat, for the entire operation, then we should only release work at the rate that the constraint can consume it. Rope buffers drum. If we release work faster than the constraint can consume it, then WIP (work in process) piles up and bad things begin to happen. (See Little's Law <- click for an explanation of why too much WIP is a bad thing.) A common theme among job shops and machine shops is too much WIP. And this increase in WIP happens in an attempt to keep all resources busy in an environment where mix changes, cross training is limited, certain jobs have to run on certain machines, emergency orders, customer changes and ISO or other tracking requirements.

What is the difference in Drum Buffer Rope vs Kanban?

DBR is a pull system. When the constraint finishes one, one is released into the system. Whereas, Kanban is a don’t push system. If the kanban is full don’t push (release) more in. In DBR the buffer is time. In Kanban the buffer is space. Also see this article ,"Does Lean Manufacturing Work in Job Shops?".

What is the difference in push vs pull?

Theory of Constraints drum buffer rope is a pull system. When the constraint finishes one, one is released into the system. Whereas, Kanban is a don’t push system. If the kanban is full don’t push (release) more in. In DBR the buffer is time. In Kanban the buffer is space. Also see this article ,"Does Lean Manufacturing Work in Job Shops?".

Are there any Drum Buffer Rope Games or Simulations

There are several games / simulations you can run to better understand DBR and the benefits. Here are two of them: The Job Shop Game Game from The Goal by Eliyahu Goldratt

Is there Drum Buffer Rope software?

You can find information on drum buffer rope software (https://www.velocityschedulingsystem.com/blog/drum-buffer-rope-software/)<-- here. While there are several companies that have built DBR software, Velocity Scheduling System is a manual visual system where you can get results BEFORE you'd have any software implemented. VSS now includes iVSS software.

Are there any Drum Buffer Rope case studies?

You can find tons of case studies on this page: https://www.velocityschedulingsystem.com/blog/velocity-scheduling-system-case-studies/

what does "drum-buffer-rope" mean in the theory of constraints?

The drum stands for the schedule. The buffer is the time buffer of work at or on the way to the constraint. And the rope times the release of new work with the consumption of work at the constraint.

If I learn DBR from a seminar or workshop, why can't I just implement it myself?

You can implement standard DBR principles yourself in a relatively simple production environment where the constraint is stable. The challenge is that most job shops and machine shops have a moving constraint - the bottleneck shifts depending on the job mix that week. Standard DBR does not give you a mechanism to handle that gracefully. Shops that attempt a DIY implementation in a high-mix environment typically get the principles right but struggle to make the scheduling hold when the constraint moves. That is where structured coaching makes the difference.

What is the difference between standard DBR and the Velocity Scheduling System?

The core difference is how each handles the constraint. Standard DBR assumes the constraint is stable - you identify it, build your drum-buffer-rope system around it, and manage to it. That works well in traditional production environments. In high-mix job shops and machine shops, the constraint often moves week to week depending on the mix of work. Standard DBR policies, procedures, and measures cannot adapt to that without constant re-engineering. VSS was built specifically for managing moving constraints. It adapts the drum-buffer-rope logic to an environment where the bottleneck is not fixed, using the Velocity Board to keep the system visual and manageable even as the constraint shifts.

How do the five focusing steps apply to DBR scheduling?

The five focusing steps - Identify, Exploit, Subordinate, Elevate, Repeat - are the strategic framework that DBR operates within. You identify the constraint (the drum), exploit it by scheduling it fully and protecting it with a buffer, subordinate all other resources to its schedule, elevate it if you need more throughput, and then repeat when the constraint moves. In a job shop with changing mix, that "Repeat" step happens often. VSS gives you the system to cycle through those steps without rebuilding your scheduling from scratch each time.

What are obstacles to flow and how does DBR help identify them?

Obstacles to flow are anything that disrupts work moving through your constraint on schedule - missing materials, quality holds, equipment downtime, vendor delays. DBR makes these visible through buffer penetration. When your buffer enters the red zone, you investigate why. Tracking those "why" reasons over time gives you a Pareto of your biggest obstacles to flow. You then use Lean or Six Sigma tools to eliminate them. This is how DBR drives continuous improvement: not by chasing waste everywhere, but by focusing improvement energy where it actually affects throughput.

Drum Buffer Rope (DBR): The Complete Implementation Guide

By Dr Lisa Lang, TOCICO Certified Expert and developer of the Velocity Scheduling System

Originally published December 13, 2023 | Updated September 2026

Newsweek has named Dr Lisa a “Manufacturing Champion” for helping custom job shops improve flow; her work has also been featured in USA Today, CNBC, and MarketWatch.

Drum buffer rope (DBR) is a Theory of Constraints scheduling method that controls production by synchronizing all work to the pace of the shop’s bottleneck constraint. The drum is the constraint’s schedule, the buffer is a time cushion protecting the constraint from disruptions, and the rope is the signal that controls when new work enters – creating a pull-based system that reduces WIP and improves on-time delivery.

TL;DR: Drum buffer rope is a Theory of Constraints method that controls manufacturing flow by synchronizing work to your constraint (the drum), protecting it with a time buffer, and releasing new work at the right pace (the rope). It works well in stable production environments – but if your constraint moves with job mix, standard DBR breaks down. That’s the challenge most job shops face, and it’s exactly what the Velocity Scheduling System was built to solve.