Need clarification ref grounding print head and tool board
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I'm slightly confused (not hard for me these days)
. Reading the documentation for tool boards I came across this........."We recommend connecting the hot end metalwork to ground on the toolboard via a resistor (10k to 1M Ohm), if it is not grounded through its mounting system". Does that mean if the tool board isn't otherwise grounded or if the hot end metal work isn't grounded?Also, out of curiosity, why the resistor and what bad things might happen if it was omitted?
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@deckingman if the hotend metal work is not otherwise grounded. The toolboard is connected to the power supply ground when its plugged in.
On newer tool boards we have connected the mounting holes on the tool boards to ground via a resistor, so if the toolboard is screwed into the extruder (e.g. Hemera) via metal screws then this ground the extruder via the toolboard ground. If the toolboard is mounted separately and the extruder is not otherwise grounded then a short wire to the mounting hole screw from the extruder metal work would do the job on a newer toolboard.
The resistor is there to separate the chassis/extruder ground from the ground on the toolboard, while still allowing electrostatic build up to bleed away to ground. If omitted you may see a bit more noise on toolboard ground and in theory an ESD discharge to the extruder would have a path to ground without resistance so could damage something on the tool board.
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@T3P3Tony Thanks Tony - I think I've got it. So to be clear, I can ground all the metal work as normal. In my case that means connecting all the PSU gnds together and connecting these to mains earth, and also connecting the frame and any hot end metal work to the same mains earth. Then I can mount the tool board to the print head metal work using brass screws and it'll be earthed via the inbuilt resistors. Yes?
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@deckingman yep ground all the metal work as usual, by your description the hotend will then be grounded already so you do not need to use the latest tool board that also grounds the mounting holes, because the hotend is already grounded. Also brass screws are unnecessary, steel ones work fine in this application.
