Losing USB connection ONLY when carving AL-Plastic-Al sandwich

I got X-Carve with X-Controller and DeWalt 611 spindle for about 1 month and I’m still learning.
Lately I came across a strange problem - got a 2mm thick aluminum-plastic-aluminum sandwich and the machine
losses usb connection at random while carving it. I can hear motors clicking like when initializing at first start,
and windows says usb connection to device lost.
Ths is happening only while carving this material - no problems with wood, acrylic or plain aluminum.
The same g-code runs flawlessly on other material or whit spindle running but with bit raized in the air and not touching the material…
Thought that this material could be acting as a capacitor so I grounded all axises with copper wires, also the spindle body and the both aluminum sides of the material - didn’t help.

Did you come across this problem? Can you give me an idea what esle dispite static charge can bug up the controller?

Thank you,

I would try to ground the aluminum to the chassis as well. I sounds like you are having an electrostatic discharge that is knocking out the USB. I encountered the same type of disconnect when I made a plasma table and mounted a plasma cutter with a pilot arc system. Every time the torch would ignite it would knock the USB connection out, to solve (never got it 100%) I got a longer USB cable and grounded everything. I got it where it would cut about 90% of the time but even then every once in a while it would still knock the USB offline. So make sure everything is grounded including the work.

Thank you Kenneth,
Yes, I grounded the work - both sides. The only thing that is not grounded is the bit, the shaft and the rotor of the spindle.
Maybe I try to ground them with some kind of brushes.
Next thing I’ll do is to wrap the spindle power cord with aluminum foil

I was wondering where you grounded them to? I grounded everything to a common ground at the receptacle. this of course is grounded to an earth ground.

It may help if you can find a heavier USB cable with ferrite beads molded into the insulation. The beads help cut down on interference.

FWIW I spent about a week getting mine isolated where it would quit knocking the USB offline. but again I was killing it with a High Frequency Igniter that would knock it offline if I started it in the general area and not even hooked on the gantry. We are talking extreme electromagnetic field. So I am saying it can be done but you will have to work to find what will isolate your system for your setup.

Everything to a common ground and to the ground of the outlet.
Thank you, Anton, I’ll try alos changing the usb cable.

Changed the stock USB cable with one with ferrite beads and everything is working now!
Thank you, guys

Awesome, glad to hear that helped.