G.Weike LC1490 strange cutting problem

[Dave Sheldrake]

Hi Johan,

Methanol is a little harsh, try IPA (IsoPropanol) on a Q-Tip, also check your water flow by removing the hose from the input side of the laser and directing it into the chiller tank, the CW5000's have occasional pump problems so the water flow may not be what it's supposed to. All the symptoms suggest heat build up as the amps are rising (and it's measured on the negative side of the HT so the tube is passing the current ok).

cheers

Dave

[Johan Verbert]

Dave,

Thank you for your help

We will clean the tube lens tonight and check the CW5000's flow

Im not sure it is a heating problem though.
* The machine does not cut through anymore (even the first cut line after a day of being idle)
* Sometimes (it happened a few times on a night of testing) we see that during a cut, the power lowers even more.
It happens instantly (during the cutting of one line of a rectangle for example) and at the same time the ampere goes up to 40(ish)
But the next cut could be normal again (although still not through)

Weike contacted us. They suggested the tube could be the issue and asked us to cut acrylic at 100% power and see how thick we can cut.

regards,
J

[Bill George]

I don't see how dirty mirrors or lens can make the amp draw change. If its does not cut from a cold start, how can overheating be an issue? Been troubleshooting electrical controls since 1962. Sounds like an intermittent power supply or tube issue. But cleaning the optics can't hurt.

Here is a link to G.Weike website troubleshooting videos, it is so s l o w being its Chinas answer to You Tube
http://wklaser.com/video.aspx wait for the page to load, its the lower left corner for the tube and power supply.

They never stress turning the power off... BUT please turn off and/or un-plug the power before sticking your hands or other body parts into the high voltage areas.

[Dave Sheldrake]

don't see how dirty mirrors or lens can make the amp draw change.

Quite right, it doesn't but it can give some / all of the other symptoms that Johan is getting so better to rule them out (as it's free to do so anyways)

If its does not cut from a cold start, how can overheating be an issue?

When a resonator fires Bill the 100% mirror in the back is subject to heating very quickly (seconds) if too much heat builds up (again seconds) the resonated Photons scatter more so than usual, this "heats" (in effect, what it actually does is excites more of the gas molecules than normal) the gas fill lowering the resistance and increasing the pull on the PSU.

and at the same time the ampere goes up to 40(ish)

Not good, that's 25% above the tubes maximum rating for the 6 series.

Could well be the tube more so than the PSU, the HV PSU's on Chinese kit tend to work or not work with not much middle ground. The 40 mA will almost certainly damage the tube if it's run like that for any time.

A 6 series should handle 10mm acrylic at 5mm per second at 100% power.

cheers

Dave

[Bill George]

Dave you forced me to learn (a little) about CO2 laser tubes. I assumed they were like an ordinary vacuum tube. Wrong.

[Dave Sheldrake]

They are fun Bill but can get silly complicated quite quickly

cheers

Dave

[Rich Harman]

I once forgot to turn on the chiller and ran the laser at full power for 6 minutes before I noticed the error, it was cutting just fine. That was a long time ago and there has been no adverse effects as a result.

[Jerome Stanek]

I was fighting the same thing today. I checked the mirrors and the tube then the power supply. Nothing seemed to be the problem. I started with the mirrors again and they were set correct then the final mirror into the lens that is where my problem was the beam was bouncing off the side of the focus tube and hitting the center of the tube. I noticed that there was soot on the side of the tube so I left it off and did a test fire and the beam was way off center.

[Clark Pace]

Hello,

We have a Gweike laser and it's been nothing but trouble. We had a similar problem. We had to slow the cuts down and never go above 80 power. Our mirror also unalign at will. So part way through a cut the alignment will go office. No matter how many time I align and tighten the bolts. I feel your pain.

[Dave Sheldrake]

I once forgot to turn on the chiller and ran the laser at full power for 6 minutes before I noticed the error, it was cutting just fine. That was a long time ago and there has been no adverse effects as a result.

With a full mirror chamber it will Rich but if there is a bubble you get hot spots and warping of the total reflector.

cheers

Dave

[Johan Verbert]

Hello All

I was travelling last weeks and today we tried to resolve the problem with a fresh mind.
Unfortunately the tube seems to be dead at the moment. No cut, not even a mark on a piece of cardboard.

Could it be the power supply ?

• On the powersupply of the laser the red light goes on when we press "laser"
• On the control panel we put 40ms as time and 90% as power for the laser
• The AM meter goes only up to 4mA when we press laser and nothing happens for the rest. If we place a cardboard piece on the mirrors it does not even give a minor cut.

• We tested the power supply like in the youtube video (connect the resistance, disconnect the data cable, connect the other green fiche). If we then press the red button on the power supply, the MA meter goes up to 49mA

Based on these tests we are afraid the tube is broken.
But we see no visible damage on the tube.
What could be the cause?

As I mentioned before, the machine is brand new and the tube has only cut for about 5 hours in total spread over several weeks.
The first 4,5 hours were also without any problem.
The chiller works and there were no airbubbles trapped inside.