LaserUser.com Forum (formerly RDWorksLab)

I have an 80 W CO2 laser tube that I recently purchased (along with a red/black Chinese laser).
I have a 5 gallon bucket circulating water. It has been fairly cool in my garage.
The tube doesn't have much time on it. I've cut a few projects ranging from 50% to 80% power.
Now if I set the power on the Ruida 6442 controller above 60%, the tube doesn't fire. Also,
the beam seems to swirl at the discharge end of the tube, creating a wider beam pattern.
I'm new to lasers so any help would be appreciated. Thanks.

Hi Mike- do you have a mA gauge on your machine? The % of power is different on every machine and often even with different components on the same machine- if you know the max current on your tube, that is what you should really use. If you don't know the brand of the tube [very common] there are table that will give a general max for a wattage of tube. I do not really understand what you mean by swirling of the tube output- do you mean the visible blueish light inside the tube? That will be erratic at low power before the beam really forms- the invisible light beam that does the work in a laser can be checked with a piece of acrylic or similar held between the tube and the 1st mirror [it will burn].
Not firing above 60%- it sounds like it was firing above that at one time? You can test fire it at [for instance] 55% or 57% to see where it stops firing- that may make it easier to trouble shoot. My first suspicion is the HiVoltage power supply or less likely the controller.

I'll second Gene's comments.

The power percentage shown on the display is a pure fantasy number, and good only as a reference to that particular combination of laser tube, laser PSU, and controller. I have changed controller and laser PSU, and have had to redo my power curve to display percentage measurements EVERY time. They have been within around 3% each time, but they DO change with component change.

Without an actual power measurement, you will never know at what percentage you hit your 80W. EXAMPLE: My tube is labeled at a work current of 24mA for 80W. Actual measurement puts the 80W threshold at 22.5mA. Bumping to the 'full 24mA' only gained me a hair over 1W. Guess what my new max working mA setting is?

Thanks for your response.
50% power - 14ma - works good
55% power - 16ma - works good
60% power - 18ma - works good
64% power - 19ma - when cutting a straight line, starts cutting for an inch or so, fades out to no cut, then fades back in cutting again.
65% power - 19ma - tube has the blue beam down the center, but no cutting or even etching
95% power - 30ma - same
100% power - 31ma - same