Have you ever needed to assess how applicable a test may be to a particular design, and the environment in which the part will need to function?
Or have you needed to design a test which will give some level of confidence in the long term reliability if a part?

If so, then preparing a Parameter (P) Diagram and developing a Robustness and Reliability matrix may be an approach which you may want to consider in the future.

A P Diagram consists of the following components, the contents of which may be arranged so that any potential interactions may be assessed.

Starting from the Boundary Diagram, which is essentially a blocked out sketch of the design in question, Keltech Design can help you develop all of the components and environmental factors such as temperature and pressure which relate or interface to the design.

Using this as a reference, any interfaces or variables are assigned and arranged within the P Diagram.

Input Signal(s)

The signal which passes through the parts so that it delivers function

Control Factor(s)

Elements such as design, material or process over which we have control

Ideal Function(s)

How we want the design to perform

Noise Factor(s)

Items that can influence the design but are not under the control of the designer. These are usually assigned under the headings of Piece to Piece variation, Component changes over time or wear out, Duty cycle or customer usage, External environment and System to system interaction.

Error State(s)

Failure modes or effects of failure as defined by an end user when using the product.

The information developed within the P Diagram is then fed into the Robustness and Reliability matrix. It is here that interactions between Control Factors, Ideal Functions, Noise Factors and Error States may be assessed. These interactions may be reviewed against the current design and test assumptions, enabling the design team to assess whether all areas of potential concern have been covered or whether further work is required.

This process can also be used to support Design Of Experiment strategies or during FMEA development to determine potential failure modes and whether or not design, process or test strategies are in place to prevent potential failure.