In the base, non-normalized allocation method, you enter the desired failure rate for a particular assembly as either a failure rate or MTBF goal. You then assign a weight factor of any value to each child item (subassembly or part). The failure rate allocation is:

Where:

wi = The weight factor for the subassembly or part.

λs = The maximum allowed failure rate of the assembly.

In the previous expression, wi is a normalized weighting factor. Therefore:

Normalized weight factors need not be specified. If Wi is the non-normalized weight factor of assembly i, then the normalized weight factor is computed using the following equation:

The equation for calculating the allocated failure rate for a subassembly or part is:

An assembly has an allocated failure rate of 100. This assembly has four parts (Part 1 through 4) with weight factors 1, 2, 3, and 4, respectively.

You enter the desired failure rate of the assembly as the failure rate goal in the assembly’s Allocation pane. For more information, see Base Allocation Method. For each part, you then assign a weight factor in its Allocation pane. For more information, see Allocation Pane (Part).

The allocated failure rate for Part 1 is:

The allocated failure rates for Parts 2, 3, and 4 are 20, 30, and 40 respectively.

If other parts in the assembly have calculated or specified failure rates (non-allocated), these failure rates are subtracted from the total. Using the above example, if other parts in the assembly have a total failure rate of 50, then the allocated failure rate of Part 1 is:

The allocated failure rates for Parts 2, 3, and 4 would then be 10, 15, and 20 respectively.