I managed to catch this on video, the tube seems fine, cuts and engraves, this happens more when engraving though.
Every so often I hear a crack, and figured something was going on, so I opened the end of the gantry and saw this happening. Usually just after starting a job and maybe again in 30 mins if running a long job.
Been doing it for few weeks, sometimes not doing it for few days then doing it more.
Tube problem? Is only 3 years old and like I say cus fine.
From an electronics point of view, you have an insulation breakdown or high humidity (or condensation on the glass tube). Do not allow this condition to persist, even if it does not seem to hurt operation.
Can you tell us where it originates and terminates? It it originating under the red end cap?
This sounds almost like an insulation failure, but usually once the hole is there, hv doesn’t have much trouble finding it.
I assume it’s outside the tube?
Generally when we see this, the tube has failed. The lps keeps increasing voltage until it reaches trigger voltage and the tube starts to conduct. If the tube doesn’t conduct, then the lps keeps increasing voltage and it can punch through the hv insulation. I’ve never seen a tube that would work then fail then work.. Doesn’t mean they don’t exist, I’ve never seen one.
The silicon sleeve is there to protect you from this. Might have a look in there and see if anything telling.
Turn the laser power supply off a couple hours before you work on this. The anode end (high voltage) has a very high impedance and can act like a capacitor and takes time to bleed off.
Visually check it. These run such a high voltage that you can’t really check much to help diagnose an issue. I’d target where it’s arcing and see if that fixes it.
I do have the HV connected with a circle spade connector, could this cause the issue do you think, maybe I should remove this and just put the wire under the screw
That looks pretty secure. I wouldn’t rule it out though. That’s 2 connections VS 1. You could always give it a try if you have enough wire. How do the other connections look.
The ring lug puts a sharp metal edge half an inch away from the metal cap and creates an air gap under the silicone HV insulating cap. As a result, the silicone cap isn’t doing much: the arc travels through the air along the wire, latches onto the conductive dust coating the tube surface, and proceeds to the nearest part of the frame.
To do:
Cut off the ring lug
Wash the tube with water + detergent
Wipe the tube with 90% (-ish) isopropyl, not fancy rubbing alcohol with skin-softening lotion
Wash & wipe the cap inside & out
Wipe the wire with alcohol
Attach the wire directly to the screw
Install the silicone cap
Inspect the inside of the cap. If it’s charred from the arc, replace it. The charred residue forms a low-resistance path between the glass tube and the cap.
Ordinary RTV silicone adhesive / caulk is not rated for high voltage applications. The curing process releases acetic acid which provides a relatively low-resistance path for high voltages.
If that arc reaches any wiring inside the machine, it will instantly kill the controller.
