Bad Laser Tube?

So this morning I made a few material test cards (involving cutting and engraving) and had great success cutting 0.125" material at 7mm/s @ 12 mA. I then started on a template for holding some bottle openers. Working on the sizing I noticed that the laser was not cutting though the same material so I cleaned the mirrors and lens, which were not very dirty at all. I tried a few more cuts and had no more success and noticed that the cut seemed wider that before - like it was out of focus. I verified that focus and still had problems. So then I began testing the beam to be sure it wasn’t missing/hitting anything on the machine and it wasn’t, but I did notice that the beam at mirror #2 was in two small dots and at mirror #3 it was three larger dots.

It’s only been about two months since I got it up and running. Is my tube bad already?

That looks like it has shifted to TEM02.

Do you have an analog ammeter?

Can you describe how you cool your tube?

Wow, that math is WAY above my grade.

Yes, I was running it at 12mA for the material cards and did bump it up to about 15mA, but there were no changes.

I use an aquarium pump in about 4 gallons of distilled water. It came with a temperature gauge installed - it’s taped to the inlet side of the tube’s water supply. I generally target 20 degrees C and use frozen gallons of water to cool if necessary.

I’m not a physicist nor do I play one on TV; I’m just going by the pictures. :slight_smile:

15mA should be about 30W, so within what’s reasonable for the K40, and what you describe for cooling should work. Sounds like bad luck with the tube.

There are plenty of pictures that looks like TEM01 posted here on the forum; I can’t recall seeing the X pattern of TEM02. Kind of like what you don’t want the doctor to say while examining you: “Oh, interesting!”

@NedMan have you seen TEM02 posted here before? Would you agree this looks like the tube has shifted mode?

What did it look like at the first mirror and at the tubes end?

Yeah definitely looks like a mode shift.

image

Unfortunately it looks like you got a marginal tube.

I’ve seen splitting occur from a cracked mirror before so you could carefully check for that.

Here’s the first two mirrors.

Will do, thanks.

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Hard to see but ya that looks like a mode shift … sorry!

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Thanks for all the help, guys! I contacted the seller and also ordered a new tube from Amazon. If the seller replaces, I’ll have one in stock I guess.

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