This is copied from my Facebook business page. Thought I would share it here too.
The term "Rat's Nest" in the context of a control panel, typically refers to the state of the wires inside, and how they are routed. A "Rat's Nest" is the same thing as a "Spaghetti Bowl;" a panel where wires are just all over the place, in bundles and knots. Less commonly, it can refer to a literal Rat's nest inside a control panel.
Strantor received a call today about a CNC mill with a spindle drive that was experiencing intermittent failure. Upon arrival, the pictured rodent squatter situation was discovered. The rat(s) who built this cozy mattress opted to use invaluable system drawings and other important documentation which are no longer available from the manufacturer. Dried evidence of fluid waste was found in places that could have contributed to the problem. Luckily, no wires (that we know of) were harmed in the process.
This post is a PSA about panel sealing. Panels should be reasonably well sealed to keep out dust and debris. Openings large enough for rats to enter, lead to premature failure. Conductive dust, especially in a machine shop environment, gets into electronics and shorts out components. Some components on circuit boards have static or magnetic fields which attract metallic dust. See the bottom of that panel? It's supposed to be white. If that much particulate has settled on the floor of the cabinet, imagine how much is caked on the control boards! Also it is impossible to control humidity (another enemy of electronics) inside a panel with gaping openings.
Conductive dust is bad. Humidity is bad. Rats are bad (they chew ANYTHING, including wires). Not to mention the biohazard for anyone who has to work in that panel (some things were "sticky"). Keep your panel gaskets in good order. Keep your fan filters and panels clean. Keep your knockout holes plugged. Your machines will last longer, I promise!