Variant diversity Structural analysis Product FMEA

The first step of a product FMEA is usually the structural analysis.

In a structural analysis, the product is divided into system elements, which are usually hierarchically related. This article is intended to give an overview of the different possibilities for structuring a product FMEA.

The goals of a structural analysis are:

  • Representation of structural relationships
  • definition of the scope of analysis
  • a modular structure for reuse
  • structural basis for function and fault networks
  • structure according to responsibilities

    Assembly/component structure

    The classic structure of a product FMEA is based on the bill of materials structure - breakdown into assemblies to components (see Figure 1).

    This division has advantages:

  • participants find their way around the structure
  • each system element exists only once (requirement VDA)
  • fast implementation without having to think much about it

    Interface system elements

    Interfaces are mapped via functions in an FMEA. In the classical structure, functions of the interface BG Steering Arm/ BG Axle would be described in both system elements BG Steering Arm and BG Axle. Extra system elements for the interface allow a focusing and simplification or reduction of function networks. The functions of the interface would only be described once more in the system element, for example, BG Handlebar/BG Axle interface. An exemplary structure with interface as system element is shown in Figure 2. When separating out interfaces, it is important that the functions do not now appear in the assembly system elements and in the interface, but that a clear boundary is drawn between the system elements.

    The separate listing of interfaces in system elements would most likely not be done for the Bobby Car. Here are two useful examples from practice:

  • Truck body (interfaces consist of several components)
  • Dashboard (interfaces are especially important for trims)

    Function-oriented structure

    Products are becoming increasingly complex. Electronics, software and also mechanical systems such as lubrication or cooling systems can run through the entire product. If work were now purely assembly/assembly/component oriented, this would lead to complicated and duplicate function networks. An organization of the structure according to function groups allows:

  • to arrange the system elements hierarchically and to create a basis for function and fault networks consisting of sequence-fault-cause
  • generate a modular structure for reuse
  • to organize the system elements according to responsibilities.

    As an example, a functional structure is shown in Figure 3.
    Practical examples of a function-oriented structure analysis:

  • wind turbine (lubrication system, cooling system, control system, etc.)
  • Car