Earthing...

[YaaJ]

First of all, I'm not a safety nazi, and played with mains since the age of 10 or so...

But not a professional. But made a large part of my house and metalworking worshop, including the machine tools power and commands enclosures ; had to read a lot, but still not a professionnal !

Just for the sake of curiosity, I measured the resistance between different screws and nuts, including roll nuts, on the frame of my 2.4.

Surprise ! Sub ohm !

The extrusions, by Misumi, are powder coated, but ensure a good electrical contact between
- two extrusions (screws and bolts !)
- a roll nut, or a T-nut, and the extrusion

It was a surprise because I recently had problems earthing a power amp, where there was no eletrical continuity anywhere. Had to remove the anodization in some places, in order to get both earthing and shielding (NaOH was my friend)

In the Voron manuals, we can read some generic instructions, as regulations can vary...

No idea how extrusions have to be earthed. Something must exist, as extrusions are used on a very large scale in the industry. Googled "Misumi earthing". And found this (second surprise)

[EDIT] on the LDO kit, the DIN rails being earthed, and bolted to the bed extrusions, that are in turn bolted to the frame, the whole structure is earthed (most likely).

I'd love to read about some measurements using a simple ohmmeter

Super simple. A roll nut, a grub screw, a washer and a nut. These extrusions are designed for earthing.

Also had a look to the regulations where I live. Regulations are based on common sense, and probably very similar all around the world.

Where I live, it is pretty simple : just one thing is missing on this accessory : a lock washer. Found no mention of the material ; we see copper on the picture, the regulation just says it has to be some stainless material, and some very basic and common sense other things.

Nowhere I read about earthing and 3D printers, except about the lack of safety of some mains powered, non strain relieved beds (Tevo Tornado for example).

Nowhere in the LDO kit documentation I see instrutions for the frame earthing.

It is so easy ! Why ?

Drop a roll nut, tighten a "sharp" grub screw, made of stainless steel (don't know the name for sharp grubscrews in english); this will create two good contacts. The grub screw biting the extrusion, and the roll nut on the opposite side. Then a large stainless washer (automotive, bodywork, or shipchandler), then a ring type lug, then a lock washer, then a nut. End of story.

Searched the remaining parts, then the LDO BOM. Nothing. But could be wrong ?

LDO only mentions the DIN rails earthing. Where I live, every metallic part that could be accidentally touched by a live wire has to be earthed. Also, it has to be impossible to insert something larger than 25mm in a mains powered device (it's more restrictive for bathrooms and kitchens). Believe it or not, even metallic window frames have to be earthed (new buildings) ! The mains wires from the IEC socket being close to the frame, the frame should be earthed. And all earthing wires should converge to one point (star wiring).

Did you earth your frames ?

Edited January 8 by YaaJ

[YaaJ]

My edit was lost...

On the LDO kit, the DIN rails are earthed, bolted to the bed extrusions, that in turn are bolted to the frame. The entire frame is earthed (most likely)

Would love to see some readings, using a simple DMM.

(My build doesn't make use of the DIN rails, the electrical compartment is very different)

[virtexultra]

I have connected my frame to earth by removing the anodizing of the frame with sandpaper and using a normal t nut and a ring cable lug. I measure about 0.35 Ohm between the furthest part of the frame and the wall plug. (<1.4V measurment voltage). The DGUV v3 (Germany) says something about < 0.3 Ohm at a measurment current of > 10A. Don't have the right equipement for this measurment.

I would not use a classic lock washer. At least not that thing that is defined in DIN 127 A or DIN 6797. Most people agree that they lose their spring tension over time or at least have no positive effect on holding the nut. If you want, use something like DIN 25201.

I additional used some contact grease like Wago 249-130, to prevent the aluminum from oxidizing again.

Between the frame parts I havent done anything special, the mesurments are good enough in my opinion. Its a frame with blind joints.

 

[YaaJ]

DIN127 is for mechanical use, and not reusable (in theory...) ; most of those sold in DIY stores are pure crap, and don't have the shape that makes them bite into the metal ! I even broke some under the pressure while torquing bolts ! Seems to me that in France they are prohibited for earthing.

DIN6797 is the most commonly used in electrical equipments, and what I am about to use, because I have lots of them. Very rarely encountered DIN 25201 (maybe one time only, on very high end equipment, and didn't understand why - thanks for the information)

Was wondering one thing... For the bed, we have 3 wires : L, N, and PE. PE is bolted to the bed, and the wire goes to the common PE connector. L and N have Wagos under the bed. Not PE. Common sense tells that this connection should be direct. In Germany, would a PE Wago be allowed in the path ? (of course a Wago, not a knockoff)

French regulations tell that the connection on the alu plate must be threaded at least half the screw diameter (it is), and self threading screws are prohibited (many in chinese equipments !). Also, the earth connection must be dedicated to PE, usage of a structural screw or bolt is prohibited (for example a transformer bracket) ; same in australia, Dave Jones (EEV  Blogs) has been ranting against this during tear downs. But didn't find anything about terminals or Wagos in the path of a PE conductor. Only thing I found is that the earth connections have to be secured so they cannot be disconnected without an intentional operation (for example using a tool).

I'd like the bed to be easily removable. Chinese printer manufacturers have been using and most likely are still using cheap GX "aviation" connectors that are not even rated for the voltage they carry. Even worse, the male pins are exposed on the controller side ! GX at best are rated 300V (IIRC), while the wires have to be double insulated and 1000V (AFAIK) ! A IEC 3 point connector is not suitable. Too bulky and dangerous : imagine someone in the future taking the printer apart, and pluging the bed in a wall power outlet using a standard cable. There's a thermal fuse, but it wouldn't be a good thing !

What could be used for a detachable bed ? Are Wagos allowed in your country ? (most european and french regulations being inspired by german ones)

Another concern : the IEC socket. How do you wire the PE terminal ? Until now, I've always been using a Faston connector. Faston connectors are secure... to a certain point. In Germany, are Faston's allowed, or has the PE wire to be soldered ? In equipments I took apart, they are generally soldered, but it could be for economical considerations only !

Edited January 8 by YaaJ

[SuperBoppy]

It's important to insure all metal parts of the printer are grounded. Not only for safety, but for the electronics as well. Any differences in ground could affect the performance of the electronics and could even damage them. A simple ohm meter will easily check for this. Use bolts or self-tapping screws, if necessary, and proper ground wires to insure all metal parts are grounded and at the same potential. 

 

Edited January 8 by SuperBoppy

[YaaJ]

You will laugh ! When I built my bed slinger from a Tevo Tornado, I made a mistake. The bed heater is driven by a SSR (of course), but was thinking MOSFET while wiring... As a result, the SSR is on neutral, not the live wire ; it makes no sense, there's no polarity... Was using a single sided mag bed. Discovered the mistake touching the spring sheet with my arms (some tiny zap). The bed is from a Tornado (borosilicate, excellent insulator). But the capacitive coupling is so strong that the DMM was showing 200+ volts between the spring sheet and earth ! Not dangerous (no real current can flow), but took some time before I understand ; had to look at the schematics I drawed myself, and : . Surprisingly, the BLTouch doesn't care... (fixing the issue is in the todo list ; it's been for 1+ year ; definitely not a safety nazi - this bed is always fully live, not only by the SSR leakage current...)

Just found a suitable nut, DIN 25201-like, from an electrical equipment ; the ring lug is a genuine Scotchlock, and exactly fits the washer and flanged nut. Lucky...
Have loads of grub screws, from M3 to M12, all phosphated ; only one M5, also phosphated ; the wrong kind. Unlucky... Will have to order some. But will do it for now, measured 0.1 to 0.3 ohm (after zeroing the DMM, and using super sharp probes). A good DMM, with EEVBlog on it (Brymen BM786). But not a earthmeter...

BTW, stainless on alu is not great, at least when in humidity. The directives also ask for taking into account the risks of corrosion when various metals are used.

Reason for the contact greases. Until now, I thought they were used only when using large alu mains wires (copper only in the house, and have nothing larger than 16mm² = AWG6) ; now understand why I found some old electrical equipment I took apart somewhat greasy (medical devices)...

Learning every day is the best thing in life.

 

Edited January 8 by YaaJ

[kingstar]

I just built an LDO 250 Trident Rev A this past week and it has you connect a wire to the frame (see attached image from LDO wiring guide). It doesn't have you scrape any of the anodizing away. I did the inverted electronics, so at the moment, only the DIN rail under the SSR is grounded as it gets its ground through the SSR mount. I did check all around the frame with the multimeter in beep mode and verified everything was connected. Didn't look at the actual measurements, but everything beeped.

[YaaJ]

Great ! Good to know.
No such precrimped cable with the 2.4 kit. Just verified, the cable kit being untouched. But could have lost some part...
Currently rewiring power, earthing being now similar to yours...

My LDO kit is not anodized, it is powder coated. (worse from an electrical POV)

Edited January 8 by YaaJ

[YaaJ]

I did this : didn't want to order stuff, made my own grubscrew, with a power drill used as a lathe spindle, a benchtop grinder as a precision rotary grinder, a handsaw. From a zinc plated screw. Yes I know, the slot is not properly centered... The nut is the DIN 25201-like salvaged flanged nut.

Results : at best 0.3 Ohm, at worst 1.5 Ohm, from the power cord  earth to the frame screws. After zeroing the DMM of course.

Impressed !