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. (  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:


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