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EQUIPMENT Vacuum Makes Honeycosnbs N e w vacuum process speeds up b r a z i n g of honeycomb panels for missile structure, gives better bonds
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A I H C H A F T and missile metal honeycomb panels can be brazed quickly and easily now, according to F. J. Stokes Corp., Philadelphia, Pa., developers of a new brazing process. The company uses a vacuum instead of an inert gas atmosphere to reduce oxide formation at brazing temperatures of stainless steel components. And Grumman Aircraft plans to use the Stokes equipment to fabricate structures for the Navy's Eagle air-to-air missile. • Old Way. Conventional method for fabricating these assemblies calls for expensive, welded metal "envelopes" to hold core and skin in position to b e welded. The envelopes are filled with argon or some other inert gas. Then the entire package is sealed and heated in a press to welding temperature. Stokes points out that not only is inert gas expensive—argon cost at one brazing installation now in operation on honeycomb panels exceeds $50,000 per month—but the grade used is said to contain enough contaminants to produce some oxide film.
'• New Way. A vsacuurn, on the other hand, is a truly inert atmosphere, according to Stokes. M o r e over, at processing temperatures, it can evaporate any troublesome residual surface contamination^ can. gi^'e a better bond witli the sterling silver brazing alloy. Stokes equipment cUoes a.way with making, filling, reL"novii~ag, a n d recovering the individual imitai envelopes. It consists of a h e a t e d press, having airtight platens sealed w i t h r u b b e r O-ring gaskets £or evacuationA tacked-together ( spot-^veldecl ) honeycomb sandwich is hicM on t h e h e a t e d graphite reference bast3 atop a heating tray. On top of the panel a metal coversheet forms a vacuum-tight seal with the upper gasket. A similar sheet and O-ring directly bet îeiith the g r a p h ite base complete the ν iicuum chamber. T h e upper heairing d a m e is pressed hydraulically onto the top cover sheet and a high vacuum ( iibout 1 0 s mm. of mercury in the hon
