In conducting the activities of quality maintenance in a broad sense, initial-phase control activities must be conducted in stages from product planning, development and design to full- scale production after start-up. Initial-phase control activities consist of activities to reinforce the development management and activities to reinforce the development system. The “figure 8 development” method comprised of seven items shown in Table 1 will help understand the initial-phase control activities.
If there are less novelties in a certain development program, activities conducted to reinforce the development system, i.e., activities described at (3), (4) and (5) in the stage of initial-phase control will overlap activities conducted to reinforce the improved system which are activities of quality maintenance in a narrow sense. Therefore, it is important that activities based on the “figure 8 development” of quality maintenance in a narrow sense and activities based on the “figure 8 development” of initial-phase control be conducted simultaneously.
To increase the effectiveness and efficiency of quality maintenance, routine management tasks shall be performed and the status of improvements made shall be monitored (activities of quality maintenance in a narrow sense) according to the “figure 8 development” method while initial- phase control activities shall be conducted at the same time according to the “figure 8 development” method so that quality maintenance activities are conducted in the form of “double figure 8 development,” the quality maintenance system in its broad sense can be established and improved, and a company-wide quality assurance system can be operated effectively and efficiently.
The approach of robust design can be effectively used to identify and clarify unclear process conditions as against clear, ideal process conditions when performing tasks specified in steps (3), (4) and (5) of initial-process control activities of quality maintenance in a narrow sense.
Robust design will also provide concepts and techniques essential in increasing the efficiency of development and design work and cutting down on the development period in steps (3), (4) and (5) of initial-phase control activities of quality maintenance in a broad sense.
Initial-process control activities involve new work methods, new equipment, unknown techniques, and other novelties. Because new process techniques and other unique techniques must be developed in the stage of initial-process control, robust design can be used as an effective tool to produce good results out of initial-process control activities.
1.2 Quality Maintenance in a Narrow Sense and Robust Design
In seven steps of quality maintenance in a narrow sense, ability needed to perform the task specified in step (3) is analysis ability. It is the ability to identify factors by reasoning based on a knowledge of theories, principles and mechanisms. Training in the concept of PM analysis will produce good results for personnel who wan to acquire this ability. It is important to identify requirements and sufficient conditions through PM analysis and to define an ideal state of things.
An ideal state of equipment, materials, personnel, etc., can be identified through PM analysis. On the other hand, an ideal state of process conditions cannot always be identified from a physical standpoint and therefore past experience is usually given higher priority in determining an ideal state of process conditions.
To optimize the process conditions, robust design can be used as a very effective approach.
In the step (6) where conditions are to be controlled, a small number of rules must be observed in a short time over a long period. Therefore, conditions easy to maintain and control must be established as conditions to be controlled in the step (6). These conditions, however, depend on the conditions determined in the above step (3). It is important, therefore, that conditions easy to maintain and control are established in steps (3) and (4).
Robust design can be used as a tool for quality maintenance in a narrow sense to optimize unclear conditions, to create an ideal state of things, and to upgrade conditions to conditions easy to maintain and control.