How Do I find why my machine has stopped cutting

I have a k40 and it has been cutting 3mm ply with no trouble for 2 months. It now will not cut through 3mm ply at any power. I have chenged lens changed laser tube aligned and cleaned mirrors. What can I do next please

What is the water temperature you are running through the laser tube?

you’ll probably be asked for showing pictures of your system( power supply, controller, and control panel ) which helps us understand what kind of K40 we’re talking about.

It was 18 degrees. New tube new lens still won’t cut. Do you think I should change the power pack

Have you tried pushing the ‘fire’/‘test’ button that is way down on the laser power supply near the connectors? I pretty sure that button will fire the laser at full power regardless of the POT setting or the digital display if you have that kind of machine. BTW, you don’t want to run the K40 laser at full power. It’s all explained in the FAQ at the top of this page and I hope you have read all the way through it.

K40’s come with cheap tubes and cheap digital controls so anything over 18ma through the tube will wear it out quickly. Digital setting are worthless and almost always greatly out of spec with reality. ie 40% power is often greater than 100% power. You need an analog meter as spelled out in the FAQ.

But that fire button on the laser power supply will let you know if your power supply is the problem since you said you have a new tube and properly setup mirrors and lens.

Please post a video of the tube firing showing the plasma.
Please post a picture of what your beam looks like at the 1st mirror burned on a piece of paper

Definitely follow Don’s requests but I’d like to add to what I’d said since you mentioned you replaced your lens too. Make sure the lens is installed correctly, there is a top and a bottom. And of course you need to do a Ramp Test again just to be sure you have your focus correct with this new lens.

Thanks new power pack and all is good

By power pack I assume you mean the laser power supply?

As the saying goes, the last thing you replace is usually it.

Sounds like you probably have a good number of spare parts to pick from when the next problem hits.