Structure, function, and failure analysis

Levels on the canvas

The canvas is divided into one column per level, and components get smaller as you move to the right. In a three-level analysis like this one, Level 2 in the middle is the focus element, the center of the analysis. Level 1 is the next higher level, where failure effects are defined, and Level 3 is the next lower level.

Level 1 is not always your own product. When you analyze a component, Level 1 is often the customer system it goes into, even if that system is outside your design responsibility.

Step 2: structure analysis

1. 1On the empty canvas, click Add First Structure Element.
2. 2With an element selected, press Enter to type its name, for example Windshield Wiper System.
3. 3Press Shift + Right arrow to create a lower-level element. It appears on the next level, already connected.

The toolbar on the right does the same with buttons: Add Sibling creates an element on the same level, Add Higher Level on the level above, and Add Lower Level on the level below. Hover over a button to see its keyboard shortcut. The top buttons zoom and fit the view, and the bottom button deletes the selected element.

Step 3: function analysis

Describe what each structure element does. Right-click a structure element, choose Add Function, and type the function.

• Select a function and press Shift + Right arrow (or click Add Lower Level) to create a function on a lower-level element.
• If there are several lower-level elements, a dialog asks which one should get the function. With only one, it is created right away.
• Green lines link higher and lower functions. Failure chains later follow these paths.

Step 4: failure analysis

Describe how each function can fail. A failure of the top-level function is a failure effect. Right-click the function and choose Add Failure.

1. 1Select the failure effect and press Shift + Right arrow.
2. 2Choose the lower-level function that holds the failure mode. The failure mode is created under it.
3. 3Press Shift + Right arrow on the failure mode to create the failure cause below it.

A failure effect, failure mode, and failure cause linked like this form a failure chain, shown with orange lines. Build further chains the same way from the same failure effect.

The red S box inside a failure effect is its severity. It starts out empty and is rated in step 5, risk analysis.