| Often production
complains about the datum features selected. In general, datum
features should be selected based on function-not on how the
part will be produced. Two datum reference frames are used on
the part shown below. The datum reference frame established by
datum features A, B and C was selected because these are the
features that locate and orient the bracket. From this datum
reference frame the features used to locate and orient the
module are located. The auxiliary datum reference frame D, E,
A could then be established to position the four mounting
holes. This approach to selecting datum features is functional
and will usually result in the least variation in the assembly
at the lowest cost. It is then up to production to use their
skill, knowledge and expertise to produce an in-spec part.
Besides, most Production folks will tell you they really don't
want the Design folks telling them how to make
parts.
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