I use to get USB Disconnects a lot (Fall of 2015), and Carbide3D sent me a new GRBL board (2.4) and that solved 99.9% of my problems. I NEVER get a disconnect cutting metal, but I wood (pun) get them once in a while when I cut wood, but I was never able to pinpoint the exact cause…until yesterday. The humidity in my shop was 12% and I went from almost never getting a disconnect to getting one almost every few SECONDS.
I raised the humidity to 50% and then ran 500,000 lines of code without a single disconnect.
I then took a spray bottle and lightly sprayed the inside on my enclosure to increase the humidity locally (inside the enclosure) and this also worked as well (as increasing the humidity in my workshop)
So, in short, the next time you are plagued with USB disconnects, the fix might be as simple as a few sprays of water. (or adding a humidifier to your shop)
Hope this helps!
PS I have sent this information to @Jorge so that a fix can be found
PS2 I had several additional ground straps but since the wood (Black Walnut) was also very dry, the ground straps were useless. Perhaps the static was being generated between the 1.0 face mill and the router…like a Van de Graaff generator…