The internal customer philosophy has proven to be a powerful tool to improve quality and productivity in the modern quality movement. It has given great personal satisfaction to those individuals who have learned to use it. The principle is simple: We in the project are all, one way or another, each other's customer. This is best explained in the following project management setting:
An engineering group begins a project to build, for example, a control system, by creating a design. The manufacturing department reviews the design and makes suggestions about manufacturability; they then pass the design onto the shop floor where it is created. Manufacturing personnel then may suggest changes to the engineers. From there, it goes to testing and the testers determine whether the system actually works. So far, no one has simply passed or rejected the project, they have made evaluations and suggestions. The design then returns to engineering to be refined and finalized. The persons in each group do not just "do it and dump it" on the next group: They discuss each other's needs as they go along. By doing good work, each group helps the next group down the line, and together they proceed to produce an excellent control system.
When team members begin thinking in these terms, they will seek out the best way to help each other do a good job. If I, as a team member, explain my tasks to the "customers" who receive the outputs, I will discover how to time task processing to best serve them. However, I, too, am a "customer" to my "customers," and for me to better serve them, they must inform me of their needs. At this point, my "customer" who has supplied me with information becomes my "supplier," and this information enables me do a better job of performing my tasks.
This is a powerful concept. Convincing team members to adopt it will improve project quality and productivity, but it will not be easy. The project manager must explain, demonstrate, advise, and coach the team. It will take time to make their responses automatic. This concept will be revisited again at the project launch meeting where task execution begins.