Suppose you want to establish tolerances for each element in a brake
assembly.

You also want to do the following:

Compare statistics from your
own estimates of tolerances and those calculated using this procedure

Limit the width of the gap by
entering upper and lower gap specifications

The tolerancing procedure has two parts. The first part, described in this
topic, uses
Calculate Gap
Pools.
The output from this command determines how you do the second part of the
procedure, which uses
Allocate Gap
Pools.
For the second part of this example, go to
Example of Allocate Gap Pools.

Choose
Six Sigma > Design for Manufacturability > Calculate Gap Pools.

In
Element names,
enter
Elements. In
Means,
enter
Means.

In
Directional vectors,
enter
'Dir Vectors'. In
Standard deviations,
enter
'St Dev'.

In
Long-term PPM,
enter
3.397673. This is the default value and corresponds
to having a long-term gap Z = 4.5.

Under
Gap Specifications,
in
Lower spec,
type
0.001. In
Upper spec,
type
0.251.

Click
Options.

In
Complexity,
enter
Cmplx.

In
Lower spec,
enter
Lowers. In
Upper spec,
enter
Uppers.

Click
OK
in each dialog box.

Interpret the results

The long-term Gap Z.Bench is 3.77. However, a value of 4.5 is required to
achieve the desired long-term PPM on the assembly gap.

The Gap Pool Statistics table shows the gap mean and variance pools. There
is no mean pool to allocate, because, in this case, the short-term gap mean is
equal to the midpoint between the gap specification limits. When this happens,
the mean pool is always equal to 0. The variance pool is −0.0002839, which
means that the long-term gap variance must be reduced by 0.0002839. To
accomplish this, you must perform the second stage of the analysis, the
allocation stage.

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