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P-Diagram  

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About P-Diagram

The P-Diagram is used to collect noise and control factors potentially affecting a system function / functional requirement.

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Identify external factors that might impact system robustness

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A P-Diagram returns a list of noise and control factors. These are intended as an input for design verification planning or Design of Experiments.

Qualica Software supports the P-Diagram by means of a specialized editor form. In addition to collecting the input and output factors, the P-Diagram form can also be used to document how the different factors are related together. This information is re-used in many other components inside the DFSS system. For printing and reporting, the form creates a graphical representation of the P-Diagram.

Information developed with a P-Diagram can be used as input for other methods.

  1. 1
    Use control and noise factors listed to plan experiments and simulations returning robust parameter settings. A Component Design Matrix can be used to support this process.
  2. 2
    Use noise factors and design verification methods to identify potential gaps in the design verification plan (DVP). The Robustness Checklist can be used to support this process.
  3. 3
    Align Noise factors and faults (error states) with FMEA:
  • Verify all faults (error states) identified on the P-diagram, together with the noise factors potentially causing them, are included in FMEA.
  • Verify all designed verification methods linked to noise factors and faults are included in FMEA as detection controls.

Worksheets

P-Diagram Form

The P-Diagram form has list box controls for the 5 types of noise factors, signal factors, CTQs, Characteristics (Control Factors), and possible Failures. In addition a box for the intended verification tests lets you edit the experiments intended to verify the reaction on the different noise factors. This information can later be used by the Robustness Checklist.

List Boxes

All list boxes work in the same way as the simple outline view of a tree or the side-by-side editor. Use the Insert buttons on the Home ribbon to add new items or click the empty last line of a list. Use drag&drop to change the tree structure.

  • Noise Factors: The first row contains list boxes for each of the 5 noise factor categories.
  • Signal Factors: located at the left middle part of the form you can enter the important signal factors here
  • Characteristics: at the lower center of the form, this is in fact the tree of design elements. Usually the top hierarchy level will show the parts and components of the system. Add the design parameters, e.g. length / height, etc. as children of the design elements.
  • CTQs: this is the tree of functional requirements as already used in the House of Quality. The CTQs are placed at the right middle of the form.
  • Failures: at the right bottom you can find the list of error states. This list is identical to the possible failures, causes, and effects used in FMEA
  • Verification Tests: located at the lower left, this is a new list of intended experiments. Each experiment should verify the system's reaction on one or more noise factors listed in the top row

Setting Relations

When you open the P-Diagram form for the first time, it is configured to set relations from a Noise Factor to a CTQ, Verification Test, or Failure Mode.

One of the 5 list controls for the noise factors is active. This status is shown by the black edges around the control. The colored arrows lead to the dependant list controls, here: CTQs, Verification Tests, and Failure Modes. List controls with grayed arrows do not have any connection in this scenario.

The dependent list controls have a first column with check-box controls. If you set a value here, it refers to the selected factor in the active list control.

Changing the active list

In order to edit relations from other sources, e.g. Signal Factors, you have to activate the list accordingly by clicking on its title bar.

When another list control gets activated, now independent controls loose their first column while dependent controls will show the column for the relation value.

The arrows change their direction and color accordingly.

Setting Relations for Signal Factors

After clicking the title of the Signal Factors, the layout of the form has changed:

Now the arrows lead from the Signal Factors to the CTQs, Verification Tests, and Failure Modes.

  • If you are working with an activated Noise Factors list, selecting a noise factor from another list will activate this list automatically. In this case you do not need to click on the title bar.

Setting Relations for CTQs

With activated CTQS, the form looks like this:

With a selected CTQ, relations can be edited for the 5 types of noise factors, for signal factors, and for product characteristics.

  • Only Noise Factors, Signal Factors, CTQs, and Characteristics can be activated. In all scenarios Verification Tests and Failure Modes will be dependent or not active.

Need more information? Open questions? Please let us know.

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