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.
GLAST-LAT Performance and Safety Assurance