2 inch arc from laser tube to the chassis
Hi,
I just received cheap Chinese 40W CO2 laser (Shenhui Laser). It did came in perfect condition, but it's not working. Problem is this:
Few pictures of the laser tube:
http://lauri.jamsa.me/pic/laser/2011...2012.53.58.jpg
http://lauri.jamsa.me/pic/laser/2011...2012.53.50.jpg
http://lauri.jamsa.me/pic/laser/2011...2012.54.07.jpg
There is no loose wires on anything like that. The isolation of the high voltage wire seems to be also ok (according the pictures). Still the arc flows to the chassis. Why? And how I can fix this? Of course I have contacted the seller, but I don't want to send the machine back to China - I need to cut stuff!
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Ha ha, looks exciting! I am not sure it would change things but it doesn't look like you have the water cooling in place??? It could be a bad tube. If the gas micture is wrong or missing (vacuum) then you will not get emission. I'd try it with water cooling but it seems there is a problem with the tube, I have no experience with these tubes so I could be completely wrong, just my $0.02.
Matt
Water cooling is in placeOriginally Posted by keebler303
The water is only in the outside of the tube, not the inside, correct? The ground wire at the other end of the tube is connected to where it should be?Water cooling is in place
Matt
I'm not sure about this. I just connected the water inlet pipe to the pump and noticed that the water is circulating properly and no leaks present. Blue wire from the other end of the tube goes to the huge resistor (10 x 2 cm), so yes, I think.
Laser tube gone bad?
Like I said I've no experience with glass laser tubes, though I have experience with lasers and high voltage. I would think that the tube may be bad because the current should travel through the tube, which would present less resistance than jumping a 2 inch gap to the chassis.
Have you talked to the manufacturer? I would think others may have had similar experiences.
Matt
My bad idea.
Last edited by Curley; 10-19-2011 at 04:18 PM.
Malagant,
Remove the foam rubber from your machine - I think it causes your problem...
-Hannu
I removed it before powering up the device. Device is new, so it might be that the problem is gas leak on the laser tube or something like that. Let's see what the seller says about that. I'll keep you posted.
Double check the isolation of your wiring and add some more (for test). You could also try to clean the surface of the tube to remove any possible conductive stuff from it...
Hope you get your problem solved
-Hannu
Tubes dead, and shortly to follow will be your power supply if you allow it to arc like that.
That arc is 22,000 volts, if the loop is across your heart on way to ground it will kill you.
Most laser tubes when they eventually die act this way.
best wishes
Dave
As has already been said - Unfortunately, that is often what happens when the tube is dead. You need a replacement tube.I just received cheap Chinese 40W CO2 laser (Shenhui Laser). It did came in perfect condition, but it's not working. Problem is this:
Tweakie.
CNC is only limited by our imagination.
Thanks. This is what I needed to know. I'll ask for the replacement tube.
Get a spare laser tube Power supply while you at it , order 2 tubes , then you have one working and one spare. PS should be around $100-120 , 60w tubes around $150 a pop.
You better check Anode (red wire) isolation.
Even if the laser was dead there CAN NOT BE arcs like that. NEVER
Put some plastic between anode and machine body and check again.
Dead lasers are dead. They do not makes the air more transmitting for elecricity.
As I see on the picture ther are two dark points on the plastic anode hood.
This looks to be arc sign.
Remove - very gently - this plastic and make new isolation using special self-vulcanizing rubber tape. DO NOT USE ORDINARY plastic tape.
Isolation should be thick all around anode (small metal rod coming out of glass) and red wire.
I think you propably tried to start machine just when she came and there was some wet from the air.
Last edited by cinematic2; 10-20-2011 at 02:37 PM.
CNC lasers, constructions, service
Why is this? If the voltage goes up to >30kV, there will be arc through air if the laser itself isn't conductive at all.
However, I did add more isolation on the top of the anode. There wasn't so much silicone on it. It didn't help at all. When I set the current to the minimum or little more and press test button, there is just this "iinnnnn..." sound. When I set little more current, the arc flashes instantly after I press the test button.
I took two pictures of the cathode's connection. Could someone comment something about them? Good enough?
http://lauri.jamsa.me/pic/laser/cathode_connection1.jpg
http://lauri.jamsa.me/pic/laser/cathode_connection2.jpg
Nope. Pictures were taken before I tried to power on the machine.
No I didn't. I powered it on next day after the delivery.
This is what isolation is for. To prevent from arcs through the air.
No matter 1000V or 30 000V. There cant be arcs.
Even if laser is dead.
The end of the story.
CNC lasers, constructions, service
We could probably debate this for all time but...
From experience with these machines, the anode usually arcs to the chassis when the tube is dead.
Tweakie.
CNC is only limited by our imagination.
If it arcs to the chassis , it means the isolation medium is not isolating, the spark should not jump anywhere .. like a sparkplug wire , if its good , even if the plug is dead , it doesnt "arc" to anywhere. If there is an arc from the tube to chassis , then its likely that the tube is somewhat compromised or cracked.
Cinematic, I've seen this numerous times.The machines are DESIGNED to arc to the chassis in the event of no path for the current via the tube as the chassis is earthed.
If that arc is insulated so it can go nowhere ,what do you think is going to happen to all that power??
I'd be avoiding lasers if I were you, advice like that can get people killed.
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