How is the Prusa Original Enclosure grounded?
Folks, I don't see where the "tin can" is grounded. Looks as if the grounding is isolated to the printer if there are no addons. If you look at the Auxiliary PSU, it appears to attempt to ground via the two star washers. Does anyone more knowledgeable than I, explain if or how it grounded. Seems like a safety issue to me --- potential for a large capacitor waiting to discharge.
Please enlighten
St George
RE:
Good question . Appliance chassis are typically grounded to prevent a "live" chassis - one inadvertently connected to the "live" wire of the power outlet.
The typical scenario would be a loose screw-down terminal allowing one of the conductors from the wall to touch the chassis. In this case, if the chassis is connected to (true) ground, electricity would take this instead of through a human.This is more of a concern where the appliance uses high-voltage (not just at the plug) like a washing machine with a giant motor (or 3D printer with heated bed).
In systems where there is no ground wire on the plug, I believe the solution is double insulation. High voltage systems (e.g. screw-down terminals) would be insulated or covered somehow, and the chassis would also be electrically isolated from these systems (plastic standoffs, plastic brackets, plastic covers, etc). AFAIK, "high voltage" only applies to devices operating over some voltage/current/power threshold (like >12V, >1A, or >25W).
I believe some certifications actually require grounded enclosures AND double insulation, because in a worst-case situation, you could have two problems: a "live" chassis and a break in the connection to ground. In this case, double insulation would be the only thing preventing electrocution.
I just ordered MK4 and enclosure, so I can't comment on this configuration.
RE: How is the Prusa Original Enclosure grounded?
I've seen several threads where people are adamant that no additional grounding is necessary. I have also seen my display blank, and my system reboot after a static shock. Also have you noticed that whenever you move any of your motors the LCD lights up. Is this due to a current generated by the motors suddenly working like a generator? Both leave me slightly concerned about whether the system is grounded properly. Also when discussing it, remember there is a difference between an earth ground and the neutral wire. The neutral wire completes the circuit. The ground wire is a safety component that gives a safe path ( or at least safer than through you ) to ground for any current applied to an unexpected location. Also please remember there is a difference between AC current and DC current. The AC from our walls is converted to DC in the printer. I believe it is safe to say that no item outside of a planned circuit should ever touch the wiring in a circuit. So I would not ever consider grounding anything to the neutral of a circuit. I do believe there is a case to be made for having the printer and the enclosure properly grounded to an earth ground, I believe a static charge may have taken out the ethernet port on my MK4 earlier today.