HPC CO2 Laser intermittently making strange noises when firing, power curve weird

[robotarmy]

Hey all,

We've got a HPC laser cutter here at rlab, and it's making strange noises on firing sometimes.

I've got a video of it. I thought it might be a discharge somewhere but I can't see anything:

http://www.youtube.com/watch?v=YKxe0sS-ZMg

Also, the peak power seems to be at a tube current of ~ 13 mA, and although there's never been good data about it, I'm quite sure that it peaked at a higher current than that previously.

We've ordered a spare tube, as we're running a workshop on the beast this weekend, but I'm a bit perplexed about what could cause this behaviour...any ideas anyone?

Thanky!
ryan@rlab.org.uk

[macona]

That is from the power supply. You are hearing the power control. If anything I would have a spare power supply. They are only made so-so.

Do not keep spare tubes on hand. They have a limited shelf life. I have a 40 war tube and sitting on the shelf for a year it was down to 27 watts. My guess is helium migration through the soft seals.