Understanding TOC Concepts: Buffer Management – Determine whether expediting is necessary

The TOC logistical applications are based on the existence of two facts from reality: dependency and variability. A system is under control if these are managed properly. A key element of the application’s solution to deal with the combination of dependency and variability, its effect and causes is called Buffer Management. Whether for manufacturing, healthcare, construction, product development, consumer products, or even the service industry the concept and the differences in the details of Buffer Management should be properly understood for each application, if a TOC implementation is to be successfully sustained.

The TOC Dictionary includes a whole set of clarification related to the concept of Buffer and provides a detailed description of Buffer Management as follows:

Buffer Management (BM)

A control mechanism based on the amount of time (till the due date) or stock remaining used in the execution phase of TOC applications (operations, project and distribution). Buffer management consists of four main functions:

  1. Prioritize tasks/orders based on buffer penetration / consumption.
  2. Signal when to expedite individual tasks/orders that are at risk (normally identified by penetrating the red zone of the buffer).
  3. Provide feedback to the planning process to consider changing certain parameters, like buffer sizes or even take more drastic actions like adding capacity.
  4. Identify prime causes of delay to focus ongoing improvement activity.

Usage: In make-to-order production, for example when a CCR buffer is used in DBR, work is released into the execution a specific time interval (known as the buffer) prior to its scheduled processing at the constraint. The time buffer is divided into three zones known as the green, yellow, and red zones. During the first 1/3 of the time buffer, an order is said to be “in the green zone”; during the middle 1/3 it is “in the yellow zone”; and in the final 1/3 it is “in the red zone”. Work should typically arrive at the “bank” of work in process in front of the constraint when the order is in the yellow zone. If it has not arrived when the order is in the red zone, (this is often referred to as there being a ‘hole’2 in the red zone), the job is located, usually marked in some way, such as with a red tag, and expedited if necessary. A significant increase in the number of red zone penetrations signals production planning to either change buffer parameters or take more drastic actions (e.g., add capacity at the non-constraint causing delays) before the system goes out of control. Records are kept of which work areas are causing holes in the red zone. This information is used to direct continuous improvement efforts. 

Cox III, James F., Lynn H. Boyd, Timothy T. Sullivan, Richard A. Reid, and Brad Cartier, 2012, The Theory of Constraints International Certification Organization Dictionary, Second Edition, page 14.

Directly from the source, the Goldratt Satellite Program (GSP) Series provides a clear overview of the different concepts and principles behind Buffer Management:


Operations – DBR and Buffer Management

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Project Management and Engineering – Critical Chain (CCPM) and Product Development

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Distribution and Supply Chain – Pull System and Replenishment

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Furthermore Dr Goldratt expands the knowledge of the use of BM incorporating a distinct variation for the industry, called Light Blue:


Light Blue – a Buffer Management Concept

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In the Goldratt S&T Series, Dr Goldratt shows how inventories can be managed properly in a MTA environment using Buffer Management:


Keeping correct inventory levels

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Several of the TOC Handbook chapters are devoted to the concept and the uses of Buffer Management:

 

Project Management

Chapter 3 explains the power of Buffer Management in Projects.

 

Managerial Interventions

In Chapter 4 you can learn how to use Buffers to Measure Execution, and Drive Execution Priorities and Managerial Interventions.

Expediting orders before they become late

In Chapter 7 you will find how BM is of vital importance both in expediting orders before they become late and also as the foundation of a process of ongoing improvement and the importance of the buffer manager role.

 

Controlling execution and the process to implement BM

Chapter 8 is perfect if you want a detailed explanation of controlling execution, the need for control and the need for corrective actions, the buffer as the source of Information for controlling execution and the process to implement Buffer Management.

 

Moving from DBR to S-DBR

In Chapter 9 you will know how BM becomes even more critical when moving from DBR to S-DBR, since BM becomes the only control on orders, showing a nice application example.

 

Dynamic Buffer Management

The concept of Dynamic Buffer Management is presented in Chapter 10.

Increase Your Effectiveness

And last but not least, Chapter 38 presents the approach of using Buffer Management to Increase Your Effectiveness.

Learn more about Buffer Management on TOC.tv:

Select Buffer Management from the Application Menu on TOC.tv (or click here) to find a whole array of presentations given by TOC Professionals and Practitioners on this topic. Here we offer two of the many presentations around the concept of Buffer Management:


Buffer Management in Context

by Roy Stratton


Recommendations for developing and using money buffers in TOC logistical solutions

by Oded Cohen
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