Grounding

Should a 3D printer have the ground lug of the AC power cord connected to the printer frame i.e. have the printer frame tied to building / earth ground?

Should the "negative" wire coming from the 24V power supply, also be tied to the same "frame ground / earth", or left separate?

What other points of the printer should be "grounded", for example should an aluminum moving heatbed that rolls on POM wheels, which is otherwise isolated from the printer frame, also be grounded? Doing so will require a dedicated grounding wire, and I don't see such a wire on most printers....

Edited 1 time(s). Last edit at 06/28/2024 05:51PM by PCLoadPLA.

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PCLoadPLA
Should a 3D printer have the ground lug of the AC power cord connected to the printer frame i.e. have the printer frame tied to building / earth ground?

Yes, for safety.

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PCLoadPLA
Should the "negative" wire coming from the 24V power supply, also be tied to the same "frame ground / earth", or left separate?

My advice is generally yes. However, if you connect the printer to a PC via USB then you risk creating a ground loop. See [docs.duet3d.com] for how to mitigate this.

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PCLoadPLA
What other points of the printer should be "grounded", for example should an aluminum moving heatbed that rolls on POM wheels, which is otherwise isolated from the printer frame, also be grounded? Doing so will require a dedicated grounding wire, and I don't see such a wire on most printers....

If the bed uses an AC mains voltage bed heater then it is essential to ground it for safety reasons. If it uses a low voltage DC bed heater then grounding it is not necessary.

The hot end metalwork should be also be grounded, either directly or through a resistor to ground or DC negative. Extruding plastic generates static charge and if this has nowhere to go then it can arc across to the heater, thermistor or stepper motor wires, which sometimes causes damage.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

More about AC heatbed grounding:

I'm running a dedicated 22ga grounding wire to be bonded to the metal heatbed. However the grounding wire only functions correctly if it the main AC conductors are fused. Otherwise, a short to the heatbed is just going to cause a short in the wires and heat them up until a wire melts and starts a fire. Crazy enough, the printer didn't have any fuse on the AC heatbed from the factory, but it DOES have a fuse on the main A/C receptable. Is that sufficient?

So I'm going to add a 10A inline fuse which I think should be good for a 750W bed heater, but the question is where do I put the fuse. Do I put it on the AC "phase" conductor? On the AC "neutral" conductor? Both?

I believe the AC "neutral" conductor is not supposed to be connected to "earth" inside of devices. That makes me think the AC neutral conductor should have a fuse on it as well. But I'm not an electrician.

10 Amp is far too big for your 750W heater, particularly as it will use very much less than that once it is up to temperature. Assuming a 240 V supply, the current will be a little over 3A. A 5A slow-blow fuse should be O.K.



Put the fuse in the live wire.

I would also go for a bit more than 24 gauge wire, possibly 20 SWG.

Mike