From:
Marsh, Darren S. [marsh@SLAC.Stanford.EDU]
Sent:
Monday, April 21, 2003 9:57 AM
Subject:
Summary of Tracker Tray Assembly Production Readiness Review
A
Tracker Tray Assembly Production Readiness Review (PRR) was held on April
14-15, 2003 at Plyform S.r.l. (www.plyform.it). The purpose of the PRR was to show that the Tracker tray
production will meet the final performance and design specifications.
The
following individuals were participants in the PRR.
Darren
Marsh - LAT Mission Assurance - Committee Chair
Tom
Borden, LAT Tracker System Engineer
Alessandro
Brez, INFN Development Engineer
Riccardo
Bagagli, INFN Aerospace Engineer
Luisella
Vigiani, Plyform Aerospace Engineer
Fulvia
Caria, Plyform Staff
Completion
of the PRR and resolution of all resulting action items constitutes readiness
for production.
The
tracker tray production is for product manufactured at Plyform S.r.l. in
Varallo Pombia, Italy. A total of 362
flight trays will be assembled. Of this
total, 208 are middle trays, 38 are light trays, 76 are heavy trays, 20 are top
trays and 20 are bottom trays.
SLAC
tray assembly drawings and the Tray Assembly Procedure, LAT-PS-01584, can be
obtained at:
http://www-glast.slac.stanford.edu/Tracker-Hardware/latdocs.html
The following
issues were addressed as part of the tray PRR and action items are noted.
1. Discussion occurred on mini-tower and EM
tray assembly activities. 18 EM trays
and 5 mini-tower trays have been assembled at Plyform and delivered to INFN for
evaluation (travelers were not used for EM and mini-tower tray assembly
activities). Of these 23 trays, 1 tray
had inadequate adhesion of the facesheet to the honeycomb and 2 trays had an
external dimensional problem (mini-tower trays). The tray with the adhesion problem verified the capability of the
NDI test to detect problems with tray assembly. The cause of the bonding problem was associated with a deviation
from the vacuum-pressure specification requirement. A review was performed to ensure this critical process parameter
is adequately controlled. The
dimensional problem was an outcome of process development activities associated
with the alignment of the trays in the applicable assembly fixturing tool and
was isolated to two of the first mini-tower trays.
2. As specified in L. Klaisner's e-mail dated
4/11/03, tracker tray flight production cannot start until the issues with
loose carbon particles and with grounding of the aluminum honeycomb are
resolved. Proposed design solutions
will be submitted to LAT IPO for approval prior to implementation into
production activities.
3. A review was conducted of the LAT Tracker
Tray Panel Assembly Procedure, LAT-PS-01584, and affected tray assembly
drawings listed on page 5 and 6 of the procedure. This review took place both at the formal PRR at Plyform and
prior to the formal PRR with IPO personnel.
Comments and recommendations on the specification and associated
drawings were provided to Tom Borden for incorporation in the
documentation. The procedure and
drawings are to be updated and formally approved prior to flight production.
Specific
comments provided include:
a. The nondestructive holographic
interferometry (ESPI - Electronic Speckly Pattern Interfereometry) test
requirement performed at INFN needs to be included in the assembly
procedure. In addition, a procedure
must be developed for this activity by INFN (which is planned for). The NDI inspection results retention plan
will be referenced in the procedure.
The Plyform traveler needs to be revised to include the delivery of the
tray to INFN for this test.
b. There is no specific cleaning process
identified for tray assembly cleaning activities on tray drawings. However, the cleaning process is well
defined by an internal Plyform procedure (I.L. 02-1118) and documented on all
tray assembly travelers. INFN personnel
were reminded that subsequent tray cleaning and processing activities not
performed at Plyform need to be clearly defined.
c. The mass requirements listed on tray
drawings need to be stated as a requirement and the procedure updated to
reflect the requirement.
d. All drawings need to explicitly state
identification marking requirement.
e. Tray assembly drawings should not reference
supplemental drawing revision numbers due to the effort to keep this
information updated.
4. The draft Plyform Quality Plan for Tracker
tray assembly was reviewed and discussed.
The plan was complete and concise with the exception of the SLAC
generated tray assembly drawing revision list.
The Quality Plan needs to be released prior to production. Also, the plan needs to incorporate
reference to the Tray Panel Assembly Procedure, LAT-PS-01584. Configuration control
of SLAC generated tray drawings needs to be disciplined and appropriate documentation
must be maintained to ensure Plyform/INFN are working to current
revisions. It was recommended for the
Tracker Engineer to maintain a master control document list for tray activities
that lists current revision level.
5. Request for Actions (RFAs) generated at
the Tracker Critical Design Review (CDR) relating to tray assembly activities
need to be completed and accepted prior to start of tray production.
6. The requirement to meet the GSFC Fastener
Integrity Requirements document was flowed down to INFN/Plyform personnel. It was communicated applicable documentation
(certifications, inspection data sheet) must be retained. A copy of the document was provided to L.
Vigiani, Plyform Aerospace Engineer. An
electronic copy of the document will be provided to INFN personnel.
7. Contamination control and material
requirements were discussed. The
assembly procedure will be revised to reflect contamination control
requirements at Plyform. The requirement
for a vacuum bakeout of the trays was agreed upon and will be perform by
INFN. The bakeout will be performed
prior to delivery of the trays to G&A Engineering for ladder
integration. This process needs to be
added to the LAT Materials and Processes List and bakeout parameters need to be
established and reviewed with the LAT IPO/GSFC personnel. In addition, the face sheet lay-up curing
process needs to be added to the LAT Materials & Processes List.
8. A thorough review and discussion of the
Plyform tray assembly travelers occurred at Plyform. The travelers appeared to be concise and complete. It was recommended SLAC drawing revision
numbers be added to the travelers.
9. The inspection sheet for the inspection of
the assembly of the face sheet/honeycomb and closeouts should reference
acceptance/rejection criteria.
Inspection forms will be established for all inspection activities and
will include acceptance/rejection information.
Also, inspection forms should have form numbers assigned to them.
10. The following test coupons and cure samples
are being fabricated on a glue batch basis per Plyform internal procedures.
a. Insert bonding test coupon performed in
accordance with ASTM 100299
b. Sandwich gluing test performed in
accordance with ASTM 100299
c. Closeout assembly test performed in
accordance with ASTM 100299
d. Tungsten gluing test performed in
accordance with Plyform internal procedures
e. Kapton adhesive test performed in accordance
with Plyform internal procedures
Paragraphs
10.6.1, Tungsten Gluing Test, and 10.7.1, Kapton Adhesive Test, in the assembly
procedure will be revised to reflect the actual purpose of the tests.
11. A database is planned to capture pertinent
inspection and fabrication data. The
database will be developed by INFN personnel prior to flight production of the
trays. The database will be web
accessible and maintained through the life of the program.
General
comments.
1. Tracker Bottom tray design efforts have
been completed with final drawings being developed. Two EM bottom trays will be assembled and tested to verify the
design and the bottom tray assembly process.
The results from the completion of the bottom tray EM effort will be
review and approved by the IPO prior to flight production.
2. It is recommended metrics be reported weekly
to the LAT IPO (through Tracker subsystem management) on production
statistics. These metrics should
include production and quality measures such as completion quantity and
pass/fail test results.
3. Raw material and part procurements are
delegated between both INFN and SLAC and Plyform. Examples include:
a. "heavy" tungsten purchased by
SLAC
b. "light" tungsten purchased by
INFN
c. bias circuits purchased by SLAC
d. inserts purchased by Plyform
Assignment
of receiving inspection responsibility must be clearly assigned and understood
for all raw material and piece part procurements.
4. A thermal-cycle test was performed on the
original prototype trays. There were no
problems with this test on these trays.
Additional thermal-cycle tests are planned for EM trays. Thermal-cycle tests are planned to be
performed at Peruga site of INFN at Terni (near Rome).
5. All test coupons generated at Plyform will
be shipped to SLAC upon completion of all tray assembly work.
The
comments and action item identified were discussed with the PRR participants
and agreed upon by all. Verification of
closure on the above mentioned activities will be performed prior flight tray
production. Upon formal approval to
proceed, a source inspection will be conducted by LAT Quality Assurance on the
first ten trays manufactured at Plyform.
The source inspection will be planned to include activities associated
with INFN test activities.
Darren
S. Marsh
GLAST
Large Area Telescope Project
Stanford
Linear Accelerator Center
2575
Sand Hill Road, M/S 43A
Menlo
Park, CA 94025
(650)
926-4577