I'm doing the final machine work to the front panels now (integrators panels only), but before I can complete the job and start assembling the individual 19" cases I have to figure out a convenient way to electrically connect (when mounted in the rack) each front panel to the other.
Back in the good old days analog computers were made with big, heavy power supplies with heavy, low impedance bus bars for the ground distribution as powering racks of various analog modules from common rails inevitably meant that the signal ground and power ground return was essentially one. Big heavy bus bars for the ground with low resistance were therefore mandatory to keep interference/interaction between the modules to a minimum.
I've worked around this problem by instead incorporating a separate power supply into each rack case, to power the (standardised ten) analog modules in that same case only.
Each front panel will have a single star grounding point to which all the module grounds and the PSU ground terminate. Power supply ground return currents are therefore kept inside the case and no power supply ground return currents share the signal ground termination between rack cases. This means that the entire front (patch) panel acts as a low impedance signal ground plane (and to a lesser extent the equipment cases and the actual relay rack(s) itself.
However I don't think that I can rely upon the mounting hardware holding each chassis into the relay rack to behave as a solid earth connection between the panel and the rack itself, thus ensuring that all (grounded) chassis panels are electrically connected together. After all the panels are painted, as is the rack, and the mounting bolts screw into (otherwise loosely fitted) cage nuts.
At the moment I am considering fitting a 4mm nutsert (press fitted captive nuts) into each of the four corners of each panel, so that each chassis panel (after fitting to the rack) can be linked to the ones directly above and below it with a total of four short (a couple of cm) earth braids having a lug at each end.
That will work but its probably not the most elegant solution. I am open to alternative suggestions. The design also needs to remain modular and not all chassis panels will be 3U.