The DBR (Drum Buffer Rope) method for production planning

Scheduling is one of the most difficult tasks manufacturing companies face, but understanding how to schedule effectively can bring great benefits. Sometimes, however, despite exploiting an ERP software, production is not as efficient as it should or could be. This is because within the production system there can be an element that creates a bottleneck, slowing everything down. The Drum Buffer Rope comes to the rescue of these situations, since it uses the constraint as a lever for the management of the entire system.


Whatis Drum Buffer Rope

The Drum Buffer Rope is a very important planning tool within the Theory of Constraints, a business management theory that is based on the search for the factors that hinder the efficient achievement of results.

Planning with the DBR allows you to identify the resource that slows down production and create a schedule taking into account this resource and its limitations, making performance more fluid.

The purpose of the Drum Buffer Rope is precisely to balance the production flow according to the rhythm of the slowest element that represents the constraint, since the performance of the system as a whole depends on the performance of the constraint. The constraint can be represented, for example, by the presence of scarce resources on which, however, the overall output depends.


How the Drum Buffer Rope works

Eliyahu M. Goldratt, an important expert in business management and creator of several theories including that of constraints, in his book The Goal describes the Drum Buffer Rope with a metaphor featuring a group of scouts.

Imagine a line of scouts hiking through the woods. In the middle of the line there is a less trained scout who goes slower and even without a backpack on his shoulders he remains the slowest. The others would like to go faster and get past it, but this way the line would no longer be respected and some scouts might get lost. The solution found is to make the slow scout play a drum to give the rhythm and tie all the scouts to each other with a string, so that no one can be left behind and no one can go too far. The Drum Buffer Rope works similarly.


The elements of the DBR

The elements of the DBR are the Drum that gives the rhythm of production according to its maximum possible speed, the Buffer that acts as a bearing to prevent production from stopping and the Rope, which guarantees regular production and controls the speed of the rest of the system.


The drum coincides with the slowest process or with the resource with limited availability, the elements that within a production system represent a bottleneck. Its task is to set the pace to tell the upstream party when to add more items or, conversely, when to slow down if there is too much activity going on at the same time and too much unnecessary stock. The pace corresponds to the maximum delivery speed, because the system can only go as fast as its slowest part. 


Buffers ensure that programming is not left behind and that production is not interrupted, preventing the process from depending in a risky way on the various parts that compose it.

A buffer is a sort of buffer, a period of time to protect against delays and problems that may occur upstream of the operation of the drum. A buffer before the drum prevents the rhythm from being interrupted due to the lack of input and causes the work to proceed at the correct pace. Otherwise, the entire downstream part of the delivery would be affected. Instead, a buffer inserted after the drum serves to limit the work in progress, slowing down the downstream part of the process from being too early compared to the rest.

The need to use buffers depends on the fluidity of the flow. A cumulative flowchart can help understand whether sections of the process are smooth or jagged and consequently whether small or large buffers are needed (the more the flow is characterized by variations, the larger the required buffer size).


Ropes are those processes that allow work and operations to proceed without interruptions, ensuring regular production. They are used to keep the other parts of the system under control, to make them go at the right speed and prevent them from being too fast, creating unnecessary stock. 


The advantages of DBR

Planning with the Drum Buffer Rope leads to numerous advantages, the main ones being:

  • Reduction of Lead Time;
  • Increase in Throughput;
  • Improved communication and priority management.

Reduce lead time

For a growing manufacturing company, keeping lead time under control is one of the most difficult tasks and often its imperfect management is the cause of some lost orders in favor of competitors, who in some cases can offer identical or not very different products, but make deliveries on time. In fact, customers want to know the delivery dates of the products they have ordered and the sales department needs to communicate them to them; however, traditional production planning tools offer very approximate estimates.

Planning with the DBR allows companies to better manage the plant and to produce while maintaining efficiency at optimal levels, this means being able to provide customers with precise dates and deliver products on time.

Instead of having firm orders due to bottlenecks in the production department, which cause chaos and delays, DBR planning prioritizes these critical areas. Jobs no longer accumulate before these critical work centers thanks to the fact that the production department is planned precisely and at a sustainable pace for the department, basically to prevent bottlenecks.

In fact, the main purpose of the DBR is to ensure that all the activities prior to the critical center are planned as a priority and that the production flow is regular, this allows production to take place smoothly and respecting delivery times, avoiding unforeseen events and accumulations, reducing the overall time needed to create a product.

Increase Throughput

This is perhaps the greatest benefit of DBR planning as it allows you to organize production in a way that produces at maximum flow (or throughput). Instead of generating a schedule based on order forecasts, the DBR is based on, and is created to support, the resources of the production department that slow it down. A DBR schedule allows you to manage your plant at the most efficient level and maximize throughput.

Throughput is one of the crucial values for the production department, but many companies interpret it incorrectly. The correct definition of throughput is the frequency with which the system generates money through sales.

Defining the scope in terms of sales ensures that the planning is carried out correctly; in fact, it does not make much sense to push production if the orders then lie in stock. We must ensure that the orders that are being carried out are those that customers are waiting for, and therefore are ordered according to a priority. 

Planning with the DBR method is specifically designed to maximize the throughput of the production plant, you just have to make sure to set priorities correctly to maximize profits.

Improved communication and priority management

Make sure you are working on the right set of priorities to ensure work is completed and delivered on time. A DBR makes it possible to avoid the continuous reshuffling of orders and plan changes and to eliminate communication difficulties. A DBR planning tool in fact creates a detailed schedule within which each task and processing is prioritised and planned.

Thanks to a DBR tool, managers and supervisors can easily set and control production priorities and scope. Production managers will always know what needs to be done and when and you will be sure that each employee will be working on what is necessary to complete the orders without having to try to understand the priorities, because they will be defined in a prudent way. Planning with DBR gives companies peace of mind knowing that the production department is working at the right pace to meet customer demand and that orders will be delivered on time.


CyberPlan and the Drum Buffer Rope

The DBR (Drum Buffer Rope) solution represents the application of the renowned method of constraint theory in CyberPlan. As we have seen, the DBR concept consists of a constant check on the maximum level of the queue allowed before a particular machining center that turns out to be a bottleneck of the system. The buffer level is established with a simulation that evaluates for each buffer the best compromise between the level of WIP and the level of customer service you want to achieve.

Benefits for the user:

  • Accurately and easily define the maximum level of WIP;
  • Avoid the variability of delivery dates;
  • Define the pace of production.

The consequent benefits for the company are:

  • Reduction of delivery times;
  • Reduction of WIP;
  • Better service level.

Get these benefits in your company too, ask the supply chain experts at your disposal for more information and download the Drum Buffer Rope brochure.


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