Trade-off curves are a powerful tool for understanding the performance limits of a design. They visualize the relationship between two or more key parameters that directly affect customer needs and the choices made during the design process. A classic example is the relationship between the diameter and wall thickness of a pipe (design decisions) and the fluid pressure and velocity expected by the customer (customer needs).

Elements of a Trade-off Curve

A complete trade-off curve consists of the following elements:

• Visual representation: An image of the product or process being analyzed.
• Description of failure mode: A detailed explanation of how the product or service may fail, including its causes.
• Root Cause Analysis: A thorough analysis of why a failure or inefficiency occurs.
• Possible countermeasures: A list of possible solutions or improvements that can be implemented to correct the problem.
• Graphical representation: A graph that clearly shows the conditions under which the failure mode occurs. This graph charts the relationship between the various parameters.
• Description of relationships: An explanation of the relationships between key parameters, reflecting the "trade-off" or compromise of the design.

Based on this comprehensive analysis, the design team creates an engineering check sheet. This is a compact and efficient summary of key findings, which is then used in design reviews. The goal is to find a balance between functionality and efficiency, without losing sight of quality or customer satisfaction.

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