View Full Version : Laser Machine Grounding/Earthing

15-05-2014, 11:45 AM
My machine has the earth linked out to a connector on the panel.
The manual and video make a big fuss about grounding .
Basically thay want you to make your own earth point with a metal stake into the ground and use it to ground the machine.

1st of all, I'm asking "WHY?"

some thoughts also... it is looped to the mains wiring earth, so the new earth point will effectively be grounding the whole workshop and house wiring !

Could this cause any problems elsewhere on the ring supply ?

I haven't connected mine up yet.

For those old enough to remember .. it reminds me of going outside to pour a bucket of water on the earth stake, when the ground got dry, and the tv picture got smaller ! lol

15-05-2014, 02:22 PM
Found this Laser Machine Maintenance (http://www.morntechusa.com/laser-machine-maintenance.html)Laser power and the machine body must have good grounded power connection. The earth wire should be connected between the power transformer and the machine grounding connection.
A good grounded connection is great for the following reasons:
A good grounded connection will assure the laser power to work normally
A good grounded connection can extend the life of laser tube
A good grounded connection will prevent any other electrical interference which can impact the outcome.
A good grounded connection will prevent any electrical damage to the machine.
Please make sure to ground the machine properly!

Also I would think that a large amount of static would build up when cutting plastics if the laser was not grounded. Watering the earth stake that's something I've never heard of, besides most household earths have been on PME for the last 30 + years.

15-05-2014, 02:33 PM
The machine IS earthed at the plug socket.

Would it be ok to earth it/the workshop locally too ?

From my audio/on stage days, earth loops can cause lots of problems too !

15-05-2014, 02:58 PM
link here => Untitled (http://www.tlc-direct.co.uk/Book/5.6.4.htm)

it seems it isn't straight forward, so I will do some more research !

I will make an earth point at the work shop and see if there is a PD between the supplied earth, and my local earth.
Obviously, if there is a PD, then a current will flow !

20yrs ago, when I bought my 1st house, the bathroom, when damp, (after a shower etc.) whould have an earthing problem. if you stood at the sink, and touched the tap, you would get a tingling feeling.. I measured the tap voltage at 50v with the damp floor. I contacted the leccy board who told me earthing was the housholders responsibly ! ... so I bonded the pipes and made a ground earth and all was good :)

My current house is 200 yrs old, and TBH I haven't considered the earthing untill now !
It definately hasn't been re-wires for a long time.
I'd have done it myself by now, but 'we' aren't allowed to any more :(
(yes, I'd have read the current regs and done it properly )

Web Goblin
16-05-2014, 07:14 AM
You can do you own wiring if your considered to be competent but you cant do it for anyone else. Although the exact explanation of competent is a bit vague.
As for your workshop wiring this can require a bit of "expert knowledge" shall we say. Is the workshop part of the house or attached to it or is it seperate from it? Do you know what type of earthing arrangement your house supply has? Most of the time the recommendation is for your workshop to have its own earth, ie make the workshop a TT type arrangement which is the earth rod in the ground.

16-05-2014, 09:03 AM
At the moment I have TN-S into the house.
Armoured cable off it's own box from the house to the workshop.
Workshop is about 50m from the house.
Workshop takes the Earth from the house cable. (like TN-S)

To make the work shop TT, I would lift the incoming earth and replace with an earth rod .
Is that what you are suggesting ?

Still, the question is .. does the machine need it's ground connector wiring up, if it has ground/earth through the plug socket (which is linked to the ground connector on the machine panel) To me, it seems redundant ?

I can only assume, that the Laser Machine manufacturers are covering themselves for installations that don't have an earth circuit / system, either because of country or location ?

Web Goblin
16-05-2014, 09:35 AM
Yes you can install an earth rod for your workshop distribution board. Keep your wire armour but remove its earth connection at your workshop distribution board end only. This way your workshop now has a TT instal and your cable feeding it still has earth fault protection from its supply end at the house.
As for the ground connection for the laser then I would go by the manufacturers instructions.

16-05-2014, 09:39 AM
Thanks WG

And as this is "The Internet" so it must be true :) , can I ask your experience with electrics ?

Always best to check !

Ta ;)

16-05-2014, 09:42 AM
Thanks WG

And as this is "The Internet" so it must be true :) , can I ask your experience with electrics ?

Always best to check !

EDIT ! :> Just checked your profile :) .. as you were !

BTW.. what style Karate do you do ? Grade ?
I got to 1st dan Shotokan before my back/joints stopped me doing more :(

Ta ;)

16-05-2014, 09:51 AM
Always clearer with pictures :)

the panel
http://i121.photobucket.com/albums/o238/RichAAC-UK/IMG_20140516_094910.jpg (http://s121.photobucket.com/user/RichAAC-UK/media/IMG_20140516_094910.jpg.html)

the wiring behind it
http://i121.photobucket.com/albums/o238/RichAAC-UK/IMG_20140516_095110.jpg (http://s121.photobucket.com/user/RichAAC-UK/media/IMG_20140516_095110.jpg.html)

you can see why I think it's redundant !

Web Goblin
16-05-2014, 09:58 AM
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://electrical.theiet.org/wiring-matters/16/elect-inst-outdoors.cfm%3Ftype%3Dpdf&sa=U&ei=XNJ1U6qMMM-XOpa_gDA&ved=0CCAQFjAA&usg=AFQjCNF0OKPYpryeAc3aml4BrZ8984jbww

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
16-05-2014, 10:00 AM
Odd connection type. Is it a banana plug/crimp type connector?

16-05-2014, 10:08 AM
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 ?

http://i121.photobucket.com/albums/o238/RichAAC-UK/IMG_20140516_100738.jpg (http://s121.photobucket.com/user/RichAAC-UK/media/IMG_20140516_100738.jpg.html)

Web Goblin
16-05-2014, 10:15 AM
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
16-05-2014, 10:22 AM
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

16-05-2014, 10:24 AM
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 .

16-05-2014, 10:42 AM
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
http://i121.photobucket.com/albums/o238/RichAAC-UK/manpic1.png (http://s121.photobucket.com/user/RichAAC-UK/media/manpic1.png.html)
http://i121.photobucket.com/albums/o238/RichAAC-UK/manpic2.png (http://s121.photobucket.com/user/RichAAC-UK/media/manpic2.png.html)
Userís 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 wonít assume any responsibility and obligation to the fault and the
accident caused by bad grounding!!!

16-05-2014, 10:53 AM
That earth connector looks insulated from the case on both sides. Is it?

16-05-2014, 11:03 AM
multimeter says the case and the ground connector are earthed somewhere :)

Web Goblin
16-05-2014, 11:07 AM
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?

16-05-2014, 11:11 AM

"Combining both of them wouldnt be a good idea."

That's why I started this thread ! .. I didn't think it would be a good idea !

I think Robin may have suggested to 'un'earth your cooker to make it safer ! lol :P

Robin Hewitt
16-05-2014, 11:24 AM
Robin, what part of this "rant" would cause someone to be killed due to electrocution?

I like to add a disclaimer before I start to rant. If I guarantee death will follow my opinion I can hardly be blamed if proven correct.

Robin Hewitt
16-05-2014, 11:36 AM
"Combining both of them wouldnt be a good idea."

Interesting question. Theoretically your generator has 3 phases all off earth. The three phases are divided up between the houses at your substation to try and equalise the load. Your single phase earth connection comes with your mains supply and you back it up by connecting it to a water pipe. The local ground is probably thus already in place, no spike required.
The earth resistance is noted on the house certificate, usually calculated by distance and square mm rather than by measurement. The distance is measured back to the 25mA breaker which is why you see a lot of fat naked copper heading for the fuse box. Overkill makes the sums easy.

16-05-2014, 11:44 AM
unless you have a plastic water supply pipe :)
We don't... old house.. but I still have 50m of reltively small cross section cable from the house to the shop.
There will be, I would think, significant resistance in the earth wire.
The cable armour is not connected to earth AFAIK (was installed before I moved here) It's 3 core, and the earth wire is my shop earth

Web Goblin
16-05-2014, 12:05 PM
Robin, Ok I see what you mean now. RCDs are normally 30mA.
Want2build1, the steel wire of the armour should have been connected at the supply end of the cable. This way the circuit protection would operate if someone drives say a pick or something through the cable and protect said person.
If you are going to change the earth then you would need to connect the armour at the supply end only.

16-05-2014, 12:06 PM
I shall check the cable armour at the house box, when I get a chance :) Thinking about it, it should be earthed !

16-05-2014, 12:08 PM
typed at the same time !

19-07-2014, 07:43 AM
To add to this ...

Recently my Laser PSU died.
So, I've had to read up on PSU wiring, inputs and outputs ...

The return wire from the tube is connected to the case/chassis !

so, if you get a bad earth connection in the mains supply or plug - either end- then the chassis is potentially at 25Kv .

Unlikely , you might think but ! ...

I just bought a K40 laser machine as a backup. This arrived with a dud tube. The fault was a cooling water leak INSIDE the tube ! which effectively shorted the 25Kv HT to the chassis !

Sooo .. I think the warning for the extra earth connection direct from machine to ground, is sort of a make do safety precaution, to cover this bad design 'feature' .

When I realised this, I had to wonder how the RCD didn't trip, with a constant 20mA or so leaking to earth. I came to the conclution that the flyback transformer produces an isolated current, so the RCD wont protect you.

It's kind of unbelievable that this is a designed situation, not a fault situation.

So .. check your earth connections everyone !


19-07-2014, 12:56 PM
and more to add ..

Watching a blog vid of someone reviewing a laser in the USA, He stated he had to install the ground wire, as his house didn't have ground wiring !

That was one of my 1st thoughts.. although I assumed the contries like the US would have ground wiring in their houses by now ?

03-02-2015, 09:50 PM
If you bought the machine from China I would earth it using the spike. It could be that parts of the machine are electrically isolated from each other. In which case, knowing how they connect the laser tubes, I wouldn't fancy 25 volts bouncing around the frame. :) Basically as he above said. :)

Clive S
08-02-2015, 10:13 AM
If you bought the machine from China I would earth it using the spike. It could be that parts of the machine are electrically isolated from each other. In which case, knowing how they connect the laser tubes, I wouldn't fancy 25 volts bouncing around the frame. :) Basically as he above said. :) 25V won't hurt anyone but 25Kv will. It is true that it seems in these lasers the current meter is connected to the ground side of the 25KV and if one side of the meter becomes disconnected it could be a bit hairy ..Clive

09-02-2015, 09:18 PM
If you bought the machine from China I would earth it using the spike. It could be that parts of the machine are electrically isolated from each other. In which case, knowing how they connect the laser tubes, I wouldn't fancy 25 volts bouncing around the frame. :) Basically as he above said. :)

you have to consider it in more detail than that !
It depends on your current earth setup.
If my earth is from the elec provider .. and I install a spike .. there could be considerable difference in potential from one earth to the other .. this would cause a large current to flow in the earth wiring.

If I was to add a spike in the workshop, it would be best to use that earth for the whole workshop, and "lift" the incoming earth from the supply