Sensitivity Analysis

A sensitivity analysis allows for the definition of a stable process window and is used in the conceptual design of a forming process. In the early stage of product design, for example during part design, tool design, or process engineering, engineers have to define many design parameters, such as:

  • Part radii
  • Binder geometry
  • Addendum geometry (e.g. punch and tool radii)
  • Use and position of drawbeads
  • Blankholder forces, etc.

These decisions directly influence the quality of the drawing processes and are mainly based on company standards and experience. Since changes are difficult to make in the remaining development processes, these decisions are crucial in the production process.

A sensitivity analysis can be carried out in order to support the decision-making process with facts. The analysis involves multiple simulations with automatically selected values of the design parameter. The degree to which the design parameter influences the results indicates the sensitivity. The process window for the design parameter is defined by extreme values within which a forming process can successfully take place.

A sensitivity analysis provides information on the degree to which a design parameter must be changed in order to achieve a desired quality level. If the influence and sensitivity of a design parameter is known, a better choice can be made on the particular parameter’s value. By showing which design parameter (input) influences the quality (output) and to what extent this occurs, the forming process is made transparent.

Design parameter for the sensitivity analysis
Input diagram of a design parameter for a sensitivity analysis
Robust process window for the sensitivity analysis
A sensitivity analysis allows for the definition of a stable process window

The figure shows an example of a sensitivity analysis. When observing the output across the whole process window, there are two areas in which quality criteria have been met. The left area is characterized by a relatively high peak while the right area indicates a rather steady trend. If the corresponding design parameter lies in the left area during the production phase, problems may arise. A well-defined parameter value results in good product quality. Should the value change slightly, it causes the opposite effect. The right area, on the other hand, ensures a stable production process because the desired quality level can be reached within a larger window. In this way, sensitivity analysis allows for the definition of a stable process window.

Further information on sensitivity analysis at AutoForm:

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Software for Sensitivity Analysis, Optimization and Robustness