Help! Static electricity buildup keeps killing my prints!

Yep, you read that right. Static.

Seems that when my printer is connected up to my PC, and the external power supply, any time I go near the thing I get a USB disconnect from the PC due to static. Actually, if it's been printing for awhile, and I touch any part of the printer, I get a nice little "zap!" and the thing disconnects.. heck it doesn't even need to be printing. Some days it's worse than others, but it's a constant thing.

I thought originally that it was just that it's winter time here in the Chicago metro area, and the air is dry, and that well.. I need to be more careful.. but I don't get static buildup anywhere else in the house. Only right near that printer. Additionally, I've tried a humidifier and that hasn't helped any either.

I *suspect* that I've got something here that's causing a problem. Here's my setup;

Standard Prusa I2 model, with a few tweaks in parts (low-profile X carriage, captured nut style X-end's, SCS8UU pillow-block style bearings for the Y-carriage build plate)
Azteeg X3 Controller, Repeiter v091 (with tweaks to support some addtitional M codes like cold-extrusion, making the PID tuning code follow what's on the Wiki, tweaks to fans)
5x "StepStick" stepper drivers (cheap ones, picked up on eBay though from a domestic source, not foreign.. not that that means anything really..) - 1ea for X, Y, E and two for Z (I "mirror" the step signals to Z, and E1 on the X3 through repeiter)
Bulldog XL Extruder
E3D Hotend (Direct Drive) / 12V heater cartridge
Corsair 600W ATX power supply, slightly modified:
1: Each "Rail" was identified, and all wires gathered up and trimmed down to two pairs (+ and GND) for each rail (this particular supply has 3 12V rails, and 2 5V ones - so I have 5 sets of wires coming out: 12V Rail #1: Two wires for +12V soldered together at the ends, Two for GND, 12V Rail #2: Two wires for +12V soldered together at the ends, same for GND.. 12V Rail #3.. etc, etc.) I also permanetly connected the ATX power-on/gnd pins.
Basic USB connection back to my desktop, which sits about 3 feet away..
MK2 heated bed, aluminum build plate

Both the PC and the printer/power supply are plugged into the same 3-prong surge suppressor and (and thus, connected to the same outlet)

I'm wondering if:
A) I somehow screwed something up when I re-wired the PC power supply.. I've got 12V Rail ground #1 connected to 12V Rail #2...though it SHOULD NOT make a difference.. Ground is Ground in a PC power supply (post rectification/regulation).. or should be.
Those extra "rails" that are not in use.. they're wrapped in electrical tape, and maybe they're just too close.. so for example - Rail #2 has 2 +12V wires soldered together, and two GND wires soldered. Those soldered ends are wrapped in electrical tape (seperately) as insulators, and then bundled together.. somehow those are acting as a capacitor after the thing's been running for awhile and I'm getting a little zap that way..
C) Somehow, there's a difference in potential between the desktop PC and the 5V USB rail, and the external power supply's 12V rail/Ground.. (The +5V and +12V lines should never come into contact on the X3.. it wouldn't work otherwise). I don't know if the X3's USB/GND and EXT-VCC/GND are connected anywhere (they *should* be, I'd have to disconnect and look)

For what it's worth, the X3's "top plate" had a defect when I received it. One of the SMD pin headers stayed in the socket when I separated the shield from the lower board. I dug it out and re-soldered w/o issue. Since I'm not using anything on the upper shield at the moment, it shouldn't have been an issue, but.. well.. you never know...

Anyone have any suggestions here? What might I be missing? Is there a test I can perform to locate the source of the static? Is there a grounding recommendation floating around out there that I don't know about? Anyone else experience this? As I said, I'd chalk it up to a dry winter, but the printer is not in a "dry" area of the house, and I've run a humidifier in the same room as the printer and that hasn't helped at all.

It's really, really disheartening to come home from work to see that you've got an hour left on that 20 hour print job, brush the desk the printer is on with your hand as you walk by, and *poof*.

I've got a "meanwell" style switching supply I'm going to pull from another project and see if that makes the issue go away, but i'd really rather just discover that the X3 has a design flaw and a simple jumper from the USB connector shield, to the GND on the 12V input will fix the problem.

Thanks,
-Jeff

I have the same problem with my i2. If I touch just the wrong part of the frame on a cold day, it resets my Sanguinololu. I still haven't done anything to fix it.

In electronic design, ESD effects are reduced through careful grounding of the chassis and ports, and putting suppression circuits on signals going in and out of a chassis. The goal is to get the shock to dissipate safely away from the sensitive circuitry.

The i2 is problematic since the electronics are out in the open, the frame is often dangerously close to the controller and wires that connect to the controller (endstops, HBP, motors), and all of the frame metal components are electrically isolated from each other (and ground) by the printed connectors.

The easiest thing to reduce this is to earth parts of the frame that you frequently come in contact with. Wrap wire between threaded rods at the frame vertices so that they share a common ground. Run the ground separately to the power supply frame and not the controller, since at a few kV the ground connection between the Azteeg and the supply is no longer negligible.

Ive actually had that happen once before. I touched one of my motors and zap! Everything disconnected. You could always buy an anti static bracelet or earth ground your stuff. When I worked on computers back in the day we would touch the case frame before touching anything else. That way if we did have built up static then it would discharge at that point.

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put a faraday cage around your electronics, ground the shield of the USB on the cage - that way if you do shock/short circuit, it won't interrupt anything.