The Challenge

• As this application was for naval electronics, the case (and its performance) had to be compliant with military specifications, including MIL-STD-648 and MIL-STD-810. Corrosion resistance of the case and all case hardware was also imperative.

• The chassis housing the customer’s electronics had to be EMI / RFI shielded.

• Shock and vibration attenuation was of key importance for the customer’s mission critical electronics.

• In addition to the mandatory performance criteria, the case had to perform within strict dimensional and weight constraints.

• A rapid turn around time (from design concept to prototype manufacture) was required.

The case design consisted of an inner chassis which was suspended on eight elastomer inserts for shock and vibration attenuation. A series of stainless steel threaded posts were installed in the base of the chassis to facilitate installation of the customer’s electronics. In order to prevent inter-granular corrosion (“galvanic action”) between the aluminum and stainless steel, the aluminum chassis was treated using the chromate conversion (also known as “iridine” or “alodine”) process. The customer machined their own top cover plate for the chassis (not shown in photo), however the chassis as a whole needed to have EMI / RFI shielding when closed. Impact provided the “open” chassis with a custom EMI / RFI shielded gasket mounted to the mating flange. Both the inner chassis and outer case were fitted with automatic pressure equalization valves. The outer case hardware and all fasteners were made of 300 series stainless steel to resist corrosion in marine environments. Ribs were added to the cases shell to prevent latches and handles from shearing forces.