How to properly ground hotend?

Arminas

Hello, I have 4 printers that makes a spark once I touch them by hand or if I touch the nozzle with tweezers. I guess it is not okay, so I am thinking where is the issue? All printers have grounded beds.

droftarts

@Arminas Run a wire from the hot end metal parts (hopefully there's a mounting screw you can use) and/or extruder stepper motor (usually one of the mounting screws should work) to the PSU negative (NOT the PSU mains ground/earth). This can be the VIN negative screw clamp on the Duet mainboard or toolboard, or a frame screw if the frame is grounded.

Ian

EasyTarget

@Arminas
You definitely should ground the hotend on a 3d printer, the effect of pushing plastic through tubes and nozzles will cause static buildup and possibly sparks.

But do not ground it directly, instead use a high value resistor (100K / 1M) to bond it. This will safely deal with the static, but helps to protect the printer against accidental shorts (frayed wires and case defects) between thermistor or heater leads and the hotend.

I'm sure I saw this advised here long ago, but couldn't dig up a reference.

droftarts

@EasyTarget Yes, it's how @dc42 has been recommending doing it for a while.
https://forum.duet3d.com/search?in=posts&term=100k+resistor+ground&matchWords=all&by[]=dc42&sortBy=timestamp

Ian

Arminas

@droftarts @EasyTarget so which option is better - hotend or extruder stepper?

Would it additionally help if I would print hotend parts in ABS ESD?

droftarts

@Arminas said in How to properly ground hotend?:

so which option is better - hotend or extruder stepper?

It depends. Ideally, both if there's no conductivity between the motor and the hot end. If you have something like a E3D Hemera, where all the metal parts touch both the hot end and motor, you can probably ground just one. At worst, ground the hot end, as it's ESD building up in the metal parts of the hot end, then sparking between that and the temperature sensor wiring that is a particular problem for the controller board. Less so if the ESD short to the heater wiring, I would have thought.

Would it additionally help if I would print hotend parts in ABS ESD?

Possibly, I don't have any experience with that. If it doesn't have a high capacitance, has low resistance, and makes good contact with the hot end and/or motor, I'd guess it might help. But unless it has a good connection to ground (perhaps through the mounting and frame), it probably still needs a grounding wire.

Ian