Laser Machine Grounding/Earthing

[Web Goblin]

Im an electrician. Electrical technician and although I dont really do much installation work these days I do try to keep up with things. Im in maintenance now and spend most of my time on cnc profiling machines or robotic welders.
Have a look at this for your workshop supply: https://www.google.co.uk/url?q=http:...ml4BrZ8984jbww

I do Shotokan with Shoshin Karate Centre Falkirk, part of JKS. I should be going for my 1st Dan end of next month.

[Web Goblin]

Odd connection type. Is it a banana plug/crimp type connector?

[Want2build1]

Not Banana, no .. no hole.. more like a power supply terminal.

Either ring type crimp, or wrap wire and tighten up screw.
I usually make a loop in the wire and solder the end before connecting it up (if that makes sense ?)

Good luck with your grading .. I came out of mine with a broken rib ! lol .. we go a bit carried away :)
Still .. no blood .. do no disqualification :D
Which Kata have you chosen ?

[Web Goblin]

Not an earthing connector then. I wonder if its for a grounding wrist strap if your working on the machine.

My katas will be Bassai Dai and Junro Shodan. If I get through ok with them and the basics and Kumite then the grading instructors will pick one of the five Heian katas for me to do.

[Robin Hewitt]

Anyone who believes a word of this rant will be in immediate risk of death through electrocution. You have been warned.
You are up against the Elf'n'Safety fruitcakes here. Originally there were no regulations and working people accidentally sawing through cables electrocuted themselves. Then industry was compelled to put every live conductor either out of reach or inside a steel conduit. Then they decided there should be domestic regulation and they hit a big snag, steel conduit was not credible.
If you compel someone to earth their electric cooker you might simply be providing a return path for the electricity thus completing the circuit and killing someone. A poor ground connection can save your life. So they floundered about then settled for the 25mA residual current breaker (RCB). You really want one of these in the circuit so let's not start sinking earth spikes.
The RCB is a sort of transformer, there are a couple of windings to take the current out to the cooker, a couple of windings to bring it back. These two windings go in opposite directions so they should cancel each other out. If they don't cancel each other out it is assumed that some of the current is leaking to ground, possibly through you, and the breaker opens the circuit to save your life. Test showed it took more than 25mA to off you hence the leakage limit.
Let's now consider the poor unfortunate making the laser who has to try and be CE compliant. ie: it mustn't interfere with your telly. You might think that putting it close to the telly would reveal all, but of course the standard is for telly's of yesteryear which used to be analogue. When things get CE tested for emissions they usually fail because testing is expensive and the tester can make more money if you flunk. So what they do is bung on the CE sticker, add the occasional ferrite to the power lines and waffle on about earth connections in the manual.
This is what you are reading and getting worried about. What you really need is a bit of info about Faraday cages, earth loops and how to get data lines into/out of a cage. Anywhere the 25000V laser PSU might leak wants to be within 1" of the earthed case and your fingers must not be closer than that when it is switched on. /rant

[Want2build1]

Ah, we did the Two for the grade, and then pick a fav from previous gradings and perfect it.

The ground ... they show pictures of a big metal rod to be driven into the ground and connected up ! so definately an earth connection point.

As I said, as these are sold worldwide, I assumed it was for counties or area where the supply had no PE system ?

With a TN-S system in the workshop, I didn't want to add a local earth to the machine due to the resistance in the earth from the house/supply to the shop.
If I change to TT, then it's not a problem to double up, even if it doesn't seem necessary .

[Want2build1]

Robin .. everything is earthed (by law AFAIK) apart from double insulated . All we are discussing is changing from supplied earth, to a local earth.
I know the theory of 'floating'potential' , but we just don't have it here in the UK ,unless you disconnect the earth at the main consumer board where the supply comes into the house (again illegal)

Yes, I have RCD from the house to the shop, and again at the shop dist' box.





From the manual.... it's the failure rate of the machine I don't wan't to happen ! I can't see how, but it says , so I'm asking !


5. Safety Grounding
Morn laser engraver uses fourth type of laser tube. The type of drive is
high-voltage-driven, so during users use the machine, they must comply with the
"Safety Note ". On the other hand, it asks stringent requirement about the safety
grounding to the users. The safe Line-to-Ground Resistance should be less than 5Ω.
Specific connection method are shown in Fig.F2-12, F2-13
F2-12

F2-13

10
User’s Manual of Laser Engraving / Cutting software
Attention please, bad grounding can cause high failure rate of equipment and at
the same time may cause other safety incidents! ! !
The company won’t assume any responsibility and obligation to the fault and the
accident caused by bad grounding!!!

[Isaac]

That earth connector looks insulated from the case on both sides. Is it?

[Want2build1]

multimeter says the case and the ground connector are earthed somewhere :)

[Web Goblin]

The drawing makes a difference. Definately and additional earth connection then. I would follow their recommendation and install it as drawn.
If you do go down the TT route then make sure that you do disconnect the armour earth and any other earth connection you have coming from the house supply. Combining both of them wouldnt be a good idea.
Robin, what part of this "rant" would cause someone to be killed due to electrocution?