Cuts better at 50% power than at 100%, what is the problem?

[Linda Smith Alabama]

Chinese 60w laser cuts better at 50% power than at 100%. It barely fires at 100% power so we use it at 50%, and seems like it's getting worse. What do you think the problem is... laser tube, power supply, or optics?

[Harper Abbot]

sure doesn't sound like optics.

Does the power degrade over the course of the cut - does it drop power as the cut continues? It could be an overheat issue - like a component loses power as it is heating up. Not driving it so hard would keep it cooler, thus not overheating, and retaining power.

Since it's a chinese machine maybe you should just buy both components? Spares are good.

[Linda Smith Alabama]

It doesn't degrade over the length of the cut, it simply cuts better with a power setting of 50% than it does at 100%. Around 50% seems to be the peak, with the power getting lower as it increases or decreases from there.

[Dan Hintz]

Assuming this is one of those systems that uses a potentiometer to set the tube current... check the resistance over the pot's entire range of travel to make sur eit is increasing/decreasing appropriately.

[Linda Smith Alabama]

No.. this doesn't use a potentiometer. The power, I assume, is controlled by the computer and software. I wish there were a way to check the output power of the power supply to determine if the output was bad or if the tube can't convert the voltage to light. I just need a better way to determine if a new power supply of a new tube is whats needed.

[Viktor Voroncov]

Do you have possibility set power from laser panel? Or only from software?

[Linda Smith Alabama]

Only from the software; won't do anything without the software running. It uses a Leetro MPC03 PCI controller card and Lasercut software.

[Viktor Voroncov]

Sorry, in this case my possible advice will not work

[Kim Vellore]

I am guessing it would be the power supply. At 50% it is able to supply the current to keep it running and at 100% the power supply is not able to keep up and the laser is not firing properly. If the laser power is ok from low to some point higher then it starts failing I would start with checking the Power supply. Not sure how these are made if it has a DC power supply or a HV supply for the tube...
Kim

[Linda Smith Alabama]

Well, it looks like it is putting out the power, but whether it's getting to the tube or not I don't know. I hooked up a simple electricity meter to see if there is more power at higher power settings. Here are the results:

2.2 amps doing nothing (this includes the water pump & fans)
3.0 amps cutting at 5% power
3.4 amps cutting at 10% power
3.7 amps cutting at 20% power
3.8 amps cutting at 30% power
4.1 amps cutting at 40% power (best cut)
4.2 amps cutting at 50% power
4.3 amps cutting at 60% power
4.5 amps cutting at 70% power
4.6 amps cutting at 80% power
4.7 amps cutting at 90% power
4.8 amps cutting at 100% power (barely any output)

The power increases consistently but I don't know if that means anything. The best cut was at 40%, as power increased output decreased. Any ideas?

[Norberto Coutinho]

If yes, try with a new set. After with a new lens if you have a spare too. Or first with the lens and after with mirros.

[Dan Hintz]

I'm not sure I like that power curve very much... it tends to taper off in the wrong direction...

[John Frazee]

When I first had my chinese laser set up, the tech was doing something and switched some things around that made mine do similar. When I set it to engrave at 10% it powered up at 90%. When I set it at 90%, it barely fired. Everything was flipflopped. He corrected it.

[Chuck Stone]

.. on the bright side, consider the savings on your electric bill..

It sounds like something in the software isn't kosher, but I don't know.
It seems like if it were a tube problem it might not be so consistent.. but
I'd still check the connections, look for dry caps.. things like that.
(I have no idea about the machine)

[Linda Smith Alabama]

I got some advice on how to check input voltage from the computer at the power supply and that checks out OK. Try this on for size... visibly looking at the laser tube with power at 10% the purple light is barely visible and will not burn thru a tissue at the end of the tube. At 30% the light is brighter and will burn a hole through a tissue at the end of the tube. At 90% the purple light is VERY bright but will not burn a hole through a tissue at the end of the tube (my silly husband put his FINGER at the end of it and didn't feel any heat!)

I'm at a total loss!!! How can the light be so bright with almost no output?