Never leave unattended!


(Wayne Smith) #1

This has been said many times on various forums and groups, but I feel it can’t be said enough. I have always followed this advice and never leave my laser when in use. And this is the only thing that allowed me to avoid catastrophe. While engraving a stamp I heard what sounded like electrical arcing so I immediately hit the red button, unplugged everything and found this


(Anthony Bolgar) #2

Yup, you could have had a major problem if you were not there to react as quickly as you did.


(Chris Wright) #3

I had a similar problem. Whoever came up with the idea of wrapping wire around a smooth steel post with a big gob of silicone smoo as insulation and thought that was a good idea, seriously needs to have their head examined. I understand cutting costs, but a threaded post couldn’t add cost that much.


(loather) #4

The problem is that the HV electrodes are sintered tungsten and don’t thread well. They’re brittle. They’re difficult, if not impossible, to solder to and not have a cold connection (getting it hot enough to properly solder would likely crack the tube at the glass junction). Sadly, the wrapped wire with silicone insulation is really the best reliable mechanical connection here, unless you can come up with something spring-loaded to clamp onto the electrode (then cover with insulation). A lot of folks use alligator clips, but I think that’s asking for trouble.


(Wayne Smith) #5

I wrapped the wires around the electrodes and soldered them on securely. After that I covered them in heat shrink. I had to bring the soldering iron up to 380c to get adhesion.


(loather) #6

Heat shrink isnt a good enough insulator to withstand the 22kV needed to excite the tube (an arc will go right through it as though it wasn’t even there). You should still grab a tube of silicone and cover the electrode completely, to be safe.


(Wayne Smith) #7

You’re right. I submitted my response too quickly and left out a step. Before the heat shrink, I wrapped the connections with a few layers of silicone self fusing electrical tape which is rated for up to 35kV.


(Julian Ashcroft) #8

When I fitted a new tube to my laser about three years ago, I used a brass terminal block to connect the wiring to the tubes pins, they give an excellent connection with no issues since.


(loather) #9

screw terminals then cover it with silicone? Clever. I actually really like that idea.


(Ray Kholodovsky) #10

Crimpy Crimpy! :slight_smile:


(Willy Ivy) #11

Just a reminder if you do decide to walk away for a few minutes. A few more minutes and I would have no shop to return to.


(Wayne Smith) #12

Glad it wasn’t any worse than that. Do you know what caused it to burn?


(Willy Ivy) #13

I can’t be sure with absolute certainty but looking at the aftermath (still in the back corner of my shop), I would have to say that the 1/4" acrylic backing paper probably started the burn and slowly festered from there. The wood cutting bed was burnt pretty bad but I think it was from the acrylic burning and dripping on to it. I was cutting from TL as home position so the draft would have continually been flowing across the fire during the whole process. The cut finished and when the laser head returned to home it would have fed the fire even more with the air blowing from the nozzle. I do think that I remember (before the days of Russ RDWorks learning lab) that I was running the tube at pretty close to 100% because I didn’t know any better. I also do not recall but I may have had the lid open the night before instead of closed as I watched the cuts.
Either way, I only run it at max 67% power now and NO WOOD FOR THE CUTTING BED. If I must walk more than 20 feet from the laser, I pause it and I keep a fire extinguisher next to the door as well as beside the laser.
BTW, ironically I was cutting all the pieces to change from a 50w to 60w tube. When I got the second laser I installed the new 60w tube before I ever turned it on figuring that if I had to learn another new machine, I might as well learn it with a hotter tube.


(Doug Fisher) #14

A wood cutting bed?!!! No way. Wow. That is the ultimate shortcut I have seen by a Chinese laser maker!


(Willy Ivy) #15

Actually the wood cutting bed was my fault. This was back before so many people had these Chinese lasers and guys like me experimenting with better cutting beds. It was heavy duty with 2 1/2" finish nails for the material to rest on and worked great with hundreds of hours laser time with no issues. Also keep in mind that is was before any laser forums and very few youtube videos with guys like me telling you to be careful and don’t do it, from hard learned experience.