Drum-Buffer-Rope Scheduling

Key Concepts

Drum-Buffer-Rope scheduling is a method for scheduling and managing operations that have a consistent internal constraint or capacity-constrained resource

  • The "Drum" represents the capacity-constrained resource that limits the amount of throughput for the company. The Drum sets the pace for the rest of the non-constrained resources.
  • The "Buffer" is a time-based work backlog that is purposefully maintained before the Drum resource to avoid starving it. As the Drum is the limiting factor in the chain, it is desirable that it is always running to maximize the throughput.
  • The "Rope" represents the information flow from the Drum to the front of the material release line which regulates the release of materials to match the flow through the constraints. This avoids the unnecessary buildup of work-in-progress inventory beyond what is required to protect and feed the Drum. The Rope is automatically calculated for each manufacturing order to that materials are released at the right time to reach the Drum buffer and allow the finished goods to be ready on time for delivery.

This scheduling method can be used by selecting the "Drum-Buffer-Rope" release rule option of the Optimize dialog:

Setting Up DBR Scheduling

To use Drum-Buffer-Rope scheduling, users must first choose it as the Release Rule to use during optimization. Then, users must define which resource is capacity-constrained, or the "Drum". To do this, double-click on the Drum resource to open the Resource Properties Options dialog. In the "Advanced Rules" tab, check the "Drum" box and specify the Drum Buffer span from the drop-down menu. This buffer will be applied in front of the operation scheduled on the Drum resource and indicates when the predecessor operation (or materials) must be available to supply the drum resource operation. 

  • Each manufacturing order is released on its DBR Release Date minus the JIT Slack Days specified in the Optimize Settings. This is the EARLIEST that the optimize will start the manufacturing order. It can start later if there are other constraints or if other manufacturing orders are scheduled ahead of it. 
  • DBR Release Date: If the manufacturing order uses a Drum resource, then this is the Drum Due Date minus the Drum Buffer. Otherwise, it is the JIT Start Date minus the manufacturing order Shipping Buffer. 
  • Drum Due Date: The JIT Start Date of the Drum operation minus the manufacturing order Shipping Buffer. This is only valid for manufacturing orders scheduled on a Drum. Manufacturing orders must be completed by this time for them to be shipped and delivered on time. 


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