Figure 9: Integrated function model of a pressure reducing valve.
Problem statements and discussion
In order to formulate problem statements from the function structure of the pneumatic valve the standard problem formulator was used, as described by Terninko [2].
In the following example only the hatched area of the integrated function model will be examined. From the functions of this area more than 30 problem statements could be derived [2]. For the sake of clarity we use 6 problem statements to demonstrate the relations between them and how this can be used as decision support by product reengineering.
Find an alternative way of (define pressure reducing level) that (provides control force) and does not cause (leak), (single-level control) and (rapid discharge of control pressure).
Find a way to resolve CONTRADICTION: (control pressure) provides (control force) and does not cause (leak), (single-level control) and (rapid discharge of control pressure).
Find a way to eliminate, reduce or prevent (rapid discharge of control pressure) under the condition of (control pressure).
Find a way to eliminate, reduce or prevent (leak) under the condition of (control pressure).
Find a way to eliminate, reduce or prevent (single-level control) under the condition of (control pressure).
Find a way to eliminate, reduce or prevent (increase installation space) under the condition of (provide pressure chamber).
Figure 10 shows the hierarchical structure of the derived problem statements, which is corresponds to the hierarchical function structure. A problem statement derived from a function exhibits the same hierarchical level and solution dependency. The problem statements are therefore arranged and interrelated according to their abstraction level and to the solution dependency they feature.