Perhaps it's better not to know.

tweakie · Post by **tweakie** » Mon Oct 03, 2011 12:26 pm

Hi Guys,

Many times the mention of PAT testing has cropped up on this forum. The basis of Portable Appliance Testing (which incidentally is now, in most cases, including portable and semi-portable) is that a piece of equipment is electrically safe for us to use. Our lasers are in the Class 1 category (metal casing with earth connection) which is considered to be the most dangerous of all the equipment types and guess what – on most of our machines the basic PAT test can fail.

The problem is with the earth bond continuity test where all accessible metal parts of the machine must be within 0.1 Ohms of each other when under test.
The 3 or more opening panels are not electrically bonded, they rely on the hinge pins (which are coated in paint) to make the earth connection and this is just not good enough to always / under all circumstances pass the test. Wobble the panel about, repeat the test and it may then pass.
Just suppose, for a moment, that the rear opening panel was not bonded to earth correctly and the 18,000 volt lead shorted to this panel and then you touched the panel. Could this happen ?? I doubt it but it is worthy of thought.

In my opinion, all the opening panels should be fitted with a braided earth link which is securely bolted to the exposed metal of both the machine frame and the panel itself. This would then ensure an ‘always pass’ on the earth bonding test and not leave it to chance.
A machine could pass 99 times out of 100 but when it comes to an accident, Murphy’s Law always seems to single out that 1%.

In the photo below the first test passed OK, I moved the panel slightly and the second test failed so I took the shot.

Tweakie.

Spooky · Post by **Spooky** » Mon Oct 03, 2011 1:06 pm

Great info Tweaks

On the 1290 there are earth *straps* between the moving pannels and the main body of the machine.

best wishes

Dave

Post by **Daven** » Mon Oct 03, 2011 1:12 pm

Could we add them ourselves? Dont' fancy an afro for Christmas

Dave

Spooky · Post by **Spooky** » Mon Oct 03, 2011 7:06 pm

From experience it does indeed track direct to the nearest point,on the 68 series thats either the tube extension or the mainframe of the machine.
Scary as hell (clean trousers time) but didnt do me any harm

I don't understand either the law on electronics or any of the statutes but I do know the machines have passed CE compliance,

Wanna see a real horror story? check out some of the direct Chinese imports!! no door switch, twin core 2 pin plugs....even with my very limited understanding they are unsafe

best wishes

Dave

PhillyDee · Post by **PhillyDee** » Tue Oct 04, 2011 12:23 am

I actually had a similar thought when looking at the front of the ls3020. There are 2 little rubber stops at the front door, obviously to act as softstops to stop it banging. However, it creates a small 2-3m. Gap through which the laser could potentially reflect through. Needless to say, I will be adding a small lip to the door. Just in case. Is it permitted to add earth bonding to the doors? I will go this myself, and have had the same thought myself!

Spooky · Post by **Spooky** » Tue Oct 04, 2011 12:39 am

I'd guess Chris wouldn't have a problem with bettering safety. That's just opinion though until I ask him but its a mod I'd happily support.

The 1290 does indeed have them already (mine does) but from memory I don't recall seeing them on the 6840 (mite well be wrong) mine was the slightly earlier model, I still had the seperate slats as a bed not like the latest one piece bed so may well be on that model now.

Maybe Tweaks could post some suggestions? pictures to help maybe of the mod if Chris is ok about it?

To those that haven't looked at Tweakies site please check it out.This guy isn't the "average bear" as they said about Yogi,A LOT of information and ideas to study

best wishes

Dave

Post by **Daven** » Tue Oct 04, 2011 9:30 am

Just had a look at my bandsaw - the doors are removable and they have no earth strap either. It's made by a US manufacturer so you would think they would make sure they have it right! May just have to do a bit of Googling a bit later

Dave

Spooky · Post by **Spooky** » Tue Oct 04, 2011 1:58 pm

Asked the question

The addition of earth straps should you feel them to be required is fine

it WON'T affect your warranty

If Tweaks would like to post a how-to that's fine

best wishes

Dave

PhillyDee · Post by **PhillyDee** » Tue Oct 04, 2011 2:21 pm

Spooky wrote:Asked the question

The addition of earth straps should you feel them to be required is fine it WON'T affect your warranty

If Tweaks would like to post a how-to that's fine

best wishes

Dave

Excellent. I will get around to doing on mine at some point! What thickness earth wire would be recommended? Just some standard stranded stuff?

Spooky · Post by **Spooky** » Tue Oct 04, 2011 2:44 pm

I can't help Phil, I don't know anything about that subject. Tweaks or somebody with electrical experience should be able to answer?

best wishes

Dave

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