The reliability of a well-designed product is usually degraded to some extent in manufacturing it. A low but finite number of defects in both parts and workmanship is generally considered "normal" in manufacturing processes involving people and machines. To sustain the level of reliability inherent in the design, however, these defects must be discovered and corrected before the product leaves the factory. Otherwise, they will show up as product failures in service use with possibly serious military consequences and always with undesirable cost impact. Further, the discovery and correction of defects in the factory contributes significantly to the manufacturer's production costs, as do field returns for correction of defects under contract requirements and warranties. Both the Navy and its suppliers, therefore, have a vital interest in the most efficient and effective means for the earliest elimination of defects.
Most Navy programs acquiring electronic devices and systems traditionally have depended on the final acceptance test to catch manufacturing defects. They have relied on this screen as a sufficient incentive to the manufacturer for the inclusion of additional pre-acceptance test screens of many different forms in his production operation. Some contracts have called out specific pre-acceptance tests (e.g., burn-in) for the primary or ancillary purpose of defect detection. For a variety of reasons, both technical and contractual, the vast majority of electronic devices and systems delivered to the Navy continue to contain manufacturing defects in parts and workmanship which could have and should have been discovered and eliminated in the factory.
This publication provides guidance concerning the use
of temperature cycling and random vibration as manufacturing screens for
defects in both parts and workmanship. The requirements for such screens are
called out in Navy instructions and reflected in contract requirements. Section 2.0 on temperature
cycling is derived from a Martin Marietta report for the National Aeronautics
and Space Administration on industry experience in assuring long-life
hardware. Section 3.0 on random
vibration has been prepared by the Grumman Aerospace Corporation under the
direction of the Naval Electronic Systems Command. It summarizes the
experience of Grumman and others supporting the NASA manned space program.
Grumman recently has devised a technique to simulate random vibration at low
cost without a sacrifice in effectiveness as a manufacturing defect screen.
This technique is included as an appendix to this publication. Section 4.0
contains the minimum recommended thermal cycling and random vibration manufacturing screens to be used in the production of Navy equipment.