This article is an excerpt from the book Creating Lean Corporations
, Copyright ® 2005 Jeffrey Alan Morgan.
The starting point for the creation of a lean corporation is the development of a corporate business process model that represents all corporate activities in a common format and facilitates the implementation of the lean philosophy. A bottom-up approach is used to create this model, such that groups and departments document their processes, and these processes are combined to form larger processes. The highest-level process corresponds to the corporation's business process.
The first step in creating a corporate business process model is to determine the boundaries of the corporation. Corporations interface with external entities, so to determine the boundaries of the corporation, you must identify and manage these interfaces.
Figure 1. IDEF0 Process Model
Integration Definition for Function Modeling (IDEF0) Process Model
The lean philosophy is implemented by defining business processes in terms of process models, which are defined and managed using the fundamental features of the lean philosophy. They are created using a bottom-up approach, which means that the smallest elements of the processes are defined first. These are referred to as tasks, and the resulting models are called task models. Tasks are sequenced together to create business processes using their input-output relationships.
But defining business processes effectively requires a model - a universal way to represent tasks and processes. Many representations exist that would work well; however, we prefer the Integration Definition for Function Modeling (IDEF0). This model was developed for the U.S. Air Force and is nonproprietary and general enough to handle
The general IDEF0 process model is shown in Figure 1.
Figure 2. Sample Process
Elements of the IDEF0 Process Model
The IDEF0 process model consists of a function name, inputs, outputs, controls, mechanism and a call. These items are defined as follows.
- Function name: The verb or verb phrase placed inside an IDEF0 box to describe the modeled function.
- Inputs: The data or objects that are transformed by the function into output.
- Outputs: The data or objects produced by a function.
- Controls: Conditions required to produce correct output.
- Mechanism: The means used to perform a function; includes the special case of a call.
- Call: A type of mechanism that enables the sharing of detail between models (linking them together) or within a model.
Numerous rules surround the construction of IDEF0 models. Most are followed in this book, except that when process diagrams are presented, the inputs and outputs linkages are always shown (the controls, mechanisms, and calls sometimes are not). This is done to make the process diagrams less cluttered, so the resulting process is simply a sequence of tasks: The sequence is determined by the input-output relations between tasks. A sample process consisting of several tasks is shown in Figure 2.
Considering Processes and Tasks
The lean philosophy considers processes and tasks separately:
- Processes are the sequence of tasks used to create services or products. Processes are called vertical activities because they take low-level inputs and elevate them to higher-level outputs.
- Tasks are the standardized units of work that are performed during a process. Tasks are called horizontal activities because they span many processes, but at the same process level.
A lean manufacturing guideline is to optimize the process first and then the tasks.* Reprinted with permission from the publisher, Productivity PressFor more information, contact Productivity Press, phone (212) 686-5900 or visit www.productivitypress.com.