New Laser Tube Installation

On my recent "Laser Upgrade Weekend", I installed a new laser tube. It was pretty uneventful, but there were a couple of challenges to overcome.

I decided to install the new tube when I realized that, using the old tube, I could cut thin plywood as easily (and possibly even better) at 6 amps of current as I did at 18 amps. Clearly, my laser tube was not getting any benefit from the extra power available. That means the tube was only capable of about 33% of what it should be.

I ordered the tube from qiandingzhensatisfaction on eBay. Who would have a name like that? Consider that their previous name was lovehappyshopping, so I guess the current name is nothing surprising.

I ordered from them because of their reputation for quick delivery, great pricing, great service, and unbelievably safe packaging.

Shipping laser tubes half way around the world carries a high risk of breakage, but after seeing how the package was actually put together, I can understand why they have been so successful at it. Here is a short video that shows how they did it.
Before I could install the new tube, I had to remove the old one. That was a bit tricky; I wanted to remove the old tube in such a way that the new tube would go back in while minimizing the amount of realignment of the tube and mirrors.

I started by backing off the bottom positioning screw in each of the two tube mounts. I left the upper two screws of each mount alone; I wanted them as reference points for installing the new tube.

Water fittings not able to pass through the mount.

Unfortunately, the water fittings and power connection on the head (exit) end of of the tube would not fit through the tube mount.

The old tube was installed when I built the BuildLog.net Laser 2x machine and prior to the installation of the first mirror. That allowed me to mount it by passing the tail end through the mounts. It never occurred to me that the head (exit) end of the tube would not also fit.


I was able to move the tube back and offset it at the neck enough that I could use a rat-tail file to notch the tube mount where the water fitting needed to be. That allowed me to slip the tube through the mount very easily.

Notched tube mount and tube fitting through the modified mount.

Interestingly, the new tube fit just fine. I assume these tubes are all hand made in China, so no two will ever be exactly alike.
I closely inspected the old tube. I had, for several months, unknowingly been over powering the tube, so I was not surprised to find that the metal ring at the exit end of the tube was badly burnt, showing the effects of the abuse.


Seeing the two tubes side by side made it even more obvious. The lesson here is that there are maximum current rating on these tubes, and you really need a mA meter on your system to ensure that your current does not exceed the recommendations.

Rather than trying to reuse the tubing for the water connections, I cut short pieces of some latex tubing I had that was the right size. Getting the tubing of the barbs on the water connections was a snap. I just put the tubing pieces in hot water for a couple of minutes. That made the tube super stretchy. They slipped on quite easily and when cooled, they provided a nice tight fit.

Putting the new tube back in was a snap. Slip it in, snug up the lower positioning screw on each mount, wire it up and test. Ta-Da! Not only did I NOT have to realign anything, it was actually better than the original. (Tubes are never exactly the same diameter either, apparently.) Needless to say, I was pretty happy about the whole experience.

The new tube has proven to be a great change. Even at safe power levels, it cuts plywood and acrylic at 4 times the speed I got with the old tube. I still need to do some testing to update my database on settings for different materials, but I am really happy with having the new tube installed.