The following checklist should be used in the development of a management plan for implementing ESS in each phase of the acquisition process:
DEMONSTRATION & VALIDATION
- Establish adequate ESS funding. To facilitate this,
a cost/benefit analysis should be conducted to justify funding. The basis of
this analysis could be the development of a historical data base on costs to
implement various screens versus return on investment (cost avoidance).
- Assess the training needs of ESS personnel and
develop a plan to correct any identified training and/or qualification
deficiencies.
- Determine equipment availability, adequacy,
capacity, etc., toperform the intended screens.
- Identify special long lead equipment requirements
(e.g., fixtures, racks, etc.).
- Determine appropriate initial profile.
- Establish a FRACAS to report and analyze faults that are precipitated out during screening.
ENGINEERING & MANUFACTURING DEVELOPMENT
- Continue to tailor, refine, and evaluate the
adequacy of the ESS profile, striving for an optimum screen. The absence of
fault precipitation during initial production or reprocurement may be an
indication of a weak screen that needs further optimization.
- Establish or continue a closed-loop FRACAS to
report and analyze faults that are precipitated out during screening.
- If a test-analyze-fix (TAAF) program is being
implemented, apply ESS just prior to the start of the TAAF program, while
continuing to strive for an optimum screen.
- Document ESS requirements and appropriate details
such as profiles, screening equipment and fixtures as part of the product
technical data package (TDP). The requirements shall be referenced on the
appropriate part/assembly drawings or parts list. Include in the TDP the
statement: "To the extent that the profiles are equipment and/or
manufacturer unique, they may have to be modified due to changes in material
or production processes."
- Finalize the ESS profile before the system enters into production. The following guidelines are provided to assist program managers in determining whether or not a reasonable screening profile has been developed. One or more of the following techniques may be required.
- Verify that the more severe temperature screening
profiles are used at the lower assembly levels (e.g., printed wiring assembly,
module, subsystem, etc.). A good ESS program should drive out most faults at
the lower levels where faults are more easily corrected and less costly to
repair. - Verify that the proposed screening profiles meet or exceed the
Tri-Service baseline presented in Tables 3-3 and 3-4
. When the profiles do not meet or exceed the baseline, verify that rationale for this deviation is acceptable.
- Verify that the proposed screening profile is not so severe that it is damaging to the item being stressed. By reviewing failure analyses a determination can be made whether or not a failed component has been overstressed. If the results of this review indicate that the item is being overstressed, the screening profile should be adjusted until failure analyses indicate no failures are due to overstressing. In some cases a minor design change, such as additional support for a resonant component, would be a more logical and cost effective solution.
- Verification may be made that a screening profile is adequate by seeding known faults into an item and then determining if the proposed screening profile is adequate to precipitate them to hard failure.
The profiles should not change unless the manufacturing processes are changed, the system is redesigned, parts are changed, or a different type of screen is found to be more effective.
PRODUCTION AND DEPLOYMENT
- Establish or continue a closed-loop FRACAS to
report and analyze faults that are precipitated out during screening.
- Establish procedures to correct/monitor any
workmanship/parts problems identified during screening. Screens help to
identify processes (both in-house and vendor processes) that are "out of
control."
- Provide parts failure information to parts
manufacturers and require continuous improvements to reduce these
deficiencies.
- Establish procedures to track fielded systems and
evaluate field failure information against the effectiveness of the current
screens wherever possible.
- Establish criteria acceptable to the Government on when and under what conditions 100% screening should be reduced to sampling. See continuous sampling plans in MIL-STD-1235 (Reference B.1-12).
REPROCUREMENT AND DEPOT LEVEL OVERHAUL
- Derive the same benefits of ESS in reprocurement
items and depot overhauled items as initial production environments. Though
the frequency of failure may be lower for depot overhaul items (infant
mortality/design updates are already in place through field use), poor
workmanship and bad replacement parts are still a problem in the depot
overhaul environment.
Note: Numerous applications of ESS may be harmful to equipment. Depending on the particular equipment, the ESS program and the frequency of overhaul, some useful life of the equipment may be consumed.
- Require that all equipment that are reprocurements
be screened if ESS was required on the original procurement contract. System
level equipment should be screened at the originally developed screen or at
a government approved equivalent screen. Where original screens were not
developed for replacement modules, a determination based on criticality and
cost should be made to determine whether or not to develop an appropriate
screen.
- Establish a FRACAS whenever there is a screening
effort.
