As operations proceed, it soon emerges that the process is unable to produce 100 percent good work. Figure 4.1 shows that over 20 percent of the work usually has to be redone due to quality deficiencies. This waste is chronic as it goes on and on.
The reason for this chronic waste is the wrong planning of operating process. Under conventional responsibility patterns, the operating forces are unable to get rid of this planned chronic waste. What they can do is to carry out quality control, i.e. to prevent things from getting worse. Figure 4.1 also shows a sudden sporadic spike that has raised the defect level to over 40 percent. This spike might result from some unplanned event such as a power failure, process breakdown, or human error. As a part of their job of quality control, the operating forces converge on the scene and take action to restore the status quo. This is often called “corrective action,” “troubleshooting,” “putting out the fire” and so on. The end result is to restore the error level back to the planned chronic level of about 20 percent.
The figure also shows that, in due course, the chronic waste was driven down to a level far below the original level. This gain came from the third process in the trilogy–quality improvement. In effect, it was seen that the chronic waste was an opportunity for improvement and steps were taken to make that improvement.
The Trilogy Diagram and Product Deficiencies
The trilogy diagram relates to product deficiencies. The vertical scale exhibits units of measure such as the cost of poor quality, error rate, percent defective, service rate and so on. On this same scale, perfection is at zero and what goes up is bad. The results of reducing deficiencies are the reduction of the cost of poor quality, meeting more delivery promises, reduction of customer dissatisfaction and so on.
The Trilogy Diagram and Product Features
When the trilogy diagram is applied to product features, the vertical scale changes. Now, the scale may exhibit units of measure, such as millions of instructions per second, mean time between failures, percent on-time deliveries and so on. For such diagrams, what goes up is good and a logical, generic vertical scale is “product salability.”