In an effort to improve
delivery efficiency and minimize material handling, SLAC LAT QA performed a
final receiving inspection on aluminum honeycomb cores at the manufacturer's
facility (Plascore, Zeeland, MI) on 28 January 2004. Following this inspection, the final parts were shipped air
freight directly to Pisa. Enclosed with
the parts are the certificate of conformance provided by Plascore and final
receiving inspection reports completed by SLAC LAT QA.
Two items regarding the
final condition of the finished cores are discussed below to provide some
detailed information and technical reasoning for SLAC LAT QA final acceptance
of the finished cores.
1. Aluminum honeycomb cores PAMG-XR1-1.0-0.375-P-5056 (310 pieces
meeting Plascore's Visual Grade material specification) are fabricated from
.0007" thick foil. Plascore
typically cuts cores from a sheet of expanded honeycomb using a die stamp
matching the final part length and width dimensions. However these lighter density (1.0 lb/cu.-ft) cores could not be
cut using the die stamp because the edge cells would crush before cutting. Instead Plascore had to saw cut these pieces
to final dimensions. This resulted in
some variation in cell run-out on the edges, i.e., edge cuts that are slightly
non-orthogonal to the cell pattern.
This was an issue that was written up before by Plyform, but of the
panels inspected for this at Plascore, none showed the extreme cell run-out of
the one panel that was written up in the INFN discrepancy report 10/23/03. However there is no requirement in
MIL-C-7438G or in Plascore's Visual Grade material specification that defines
how orthogonal the
cuts must be relative to the
cell orientation; this would be a specification for the finished part, and the
maximum allowable non-orthogonal tolerances for these edge cuts was not
specified. Therefore this condition was not cause for rejection.
2. All cores showed some aluminum trimmings loosely held to the cut
sides of the cores. The sawed cores
showed larger and more numerous examples of this than the higher density cores
(PAMG-XR1-3.0-0.375-P-5056, 3.0 lb/cu-ft, 112 pieces). Both Plascore's Visual Grade and MIL-C-7438G
are specs for the honeycomb material itself, not finished parts. The first cores delivered to Plyform last
year showed this same condition since those finished cores were manufactured
the same way as the cores most recently purchased. It appears that any aluminum trimmings loosely held to the cut
edges can be easily trimmed off as required during panel manufacture. Also the core edges will be covered and
contained by the close-outs and the face sheets in the final tray
assembly. Loosely held trimmings were
not an issue voiced by Plyform in the past and because our final part
specifications did not call out a requirement for cut edge condition, I did not
reject any cores for this condition.
The finished cores have been
packaged in custom-sized cardboard boxes with kraft paper separating each
core. Approximately 15 cores are
stacked in each cardboard box, and each box has a label identifying the size
and density of cores inside. Additional cardboard sheets are laid on top of the
stack to fill the space between the stack and the top of the box. The cardboard
boxes were then packed in custom-sized wooden crates (total of 4 crates) for
shipment to Pisa.
Care must be observed when
unpackaging the cores. There is enough
space between the cores and the cardboard box walls to allow careful removal of
cores one at a time by hand from the cardboard boxes. The boxes should be
opened carefully at the top to facilitate removal of the cores; do not attempt
to cut the boxes open lengthwise with razor knives, or the cores could be
damaged.
Please respond with any
questions or need for additional information.
Also, please indicate if a
receiving/incoming inspection of these cores will be performed at INFN or at
Plyform.
Regards,
Joe Cullinan
GLAST-LAT Performance and
Safety Assurance
(650) 926-5034