G.Weike LC1490 strange cutting problem

[Johan Verbert]

Hello all,

We have a Chinese G.Weike LC1490 with
- a Z6 RECI lasertube
- a CW5000 chiller system
- a 150W power supply


We have been using it since February of 2014 (it is a new system).
Mostly cutting MDF of 3mm and it worked flawlessly (at speed 30 and power 60)


However since two weeks we are unable to cut anything reliably.


Symptoms:


1. It just doesn't cut through anymore.
Speeding down does not help, increasing power does not help.
Also when pressing 'laser' I have the feeling that it is less powerful than before.


2. The strange thing is that if we use the 'cut contour' option on the control pad, most of the time it cuts the square perfectly. With this info we found out that if we put the power at 30, that we can get a somewhat clean cut. If we go to 35 or over, it doesn't work anymore.


3. Also the power of the cut varies during a cut (sometimes)
As you see in the image, it started cutting at a certain power, but when it reached the location of the cursor the power of the cut decreased drastically (and the ampere output meter on the machine went up at the same time). This behavior never happens when we use the 'cut contour' option on the control pad.
285755




The steps we took in order to correct it:
* checked the tube for cracks
* checked the connections of the tube for bad contacts
* checked and realigned the mirrors
* used a higher pressure air blower
* changed the focusing lens (tried cutting at different offsets)
* tested the chiller (the alarm goes of if the flow is interrupted)
* tested the power supply (disconnect the data cable and press the button / we haven't tested it yet with the supplied resistance)
* used the same sheet of material we could cut before


We contacted Weike but so far no response.
We have a spare tube we could install, but i would not like to blow the new tube if it is a problem in another system (power supply ?).


Does anybody have any ideas on how to resolve this issue ?
Is it just the tube ?

Any suggestions would be most welcome.

[Bill George]

You might head over to CNC Zone they have a G.Weike rep online most of the time in the laser Forum, maybe she can help with the contact info.

[Travis Wizniuk]

I have a very similar laser from G. Weike and have experienced some similar result. Here are my suggestions.

1. Your table is no longer level to the laser head. This is why the laser seems to work in one area and not another (it goes out of focus). You need to level the table to the laser head. Move the laser head to the 4 corners of the table and measure the distance. If its unlevel side to side or fore to aft, you can level it by turning the jack screw with the power OFF. If its unlevel diagonally, then its much tougher.

2. Clean your lens. It might be dirty if you have been cutting without air assist or blower fan.

3. Re-align your mirrors.


My guess.. You will find your table out of level...

[Johan Verbert]

Thank you for the suggestions.


We already cleaned the lenses (we even switched the lens to be sure) and tried cutting at different heights to see if our focus distance was wrong.
We leveled the table making sure that the distance between nozzle and table was equal at all 4 corners.


It is not really a question of the laser cutting wel in one corner and bad in another.
It doesn't cut anywhere anymore.


We are thinking it is a power supply problem or a laser tube problem

[Kev Williams]

Ok, since your manual "cut contour" works, and what you send to the machine from your computer doesn't, that leads me to believe you have a data transfer or software issue. Check or change your connector cable. And, have you checked your settings in your software? Your software may be sending conflicting data to the machine...

I was sent 2 versions of engraving software with my Triumph, and I have to use the older version because the newer version has a mind of it's own. After spending a day setting backlash settings for different speeds, the next time I loaded the software I ran a test job (thankfully) on some wood, and the lettering engraved on the left-right sweep was almost 3/4" apart from the lettering on the right-left sweep. I checked the backlash settings and all my entries were replaced with 12-digit exponential numbers only Sheldrake would understand! ;)

Another thing to check, parts of graphics outside the defined working area... My Triumph did this weird thing once where it was obvious the stepper motors were fighting themselves in certain places, causing erratic engraving and re-positioning of the coordinates. The problem turned out to be a phantom point (a control point or node that's there, but for some reason you many not see it) that was outside the perimeter of the working area. Any graphic that was placed where that point was within it's vertical boundaries, when it tried to engrave that's when the funny stuff started. I thought the machine was messed up, but I've had this happen before so I zoomed way out on the software and drew a grouping box, and the box grouped something way off to the left of the zero-left boundary. Couldn't see it, but something was there. Yet the program wouldn't group or delete it. I found the point in the Corel job I sent to the engraving program. I WAS able to delete it there, re-sent the job to the engraving program and all was well...

[Bill George]

Thank you for the suggestions.


We already cleaned the lenses (we even switched the lens to be sure) and tried cutting at different heights to see if our focus distance was wrong.
We leveled the table making sure that the distance between nozzle and table was equal at all 4 corners.


It is not really a question of the laser cutting wel in one corner and bad in another.
It doesn't cut anywhere anymore.


We are thinking it is a power supply problem or a laser tube problem

IF it won't cut over 30 amps like you said in your first post you are on track with either the HVPS for the tube or the tube its self. Did you check the low voltage in this case either 120 or 240 volts to your PS and of course the PWM control connections to the same PS? Tina over on the CNC Zone like I suggested works for the company.

[Dave Sheldrake]

As you see in the image, it started cutting at a certain power, but when it reached the location of the cursor the power of the cut decreased drastically (and the ampere output meter on the machine went up at the same time).

Temperature, as the tube gas heats up the resistance drops increasing the amperage but making the beam unstable. The chiller flow sensor and temperature monitor won't help as that measures mean temps and not mirror temps and flow not presence of bubbles, I'd guess you have a bubble in the positive end of the tube leading to mirror heating and distortion.
When a mirror heats up (internal 100% reflector) the beam will increase in size but will no longer resonate evenly inside the tube (the mirror basically warps).

I'd check the tube for bubbles in the ends.

Failing that it may well be the settle of the tube, 30 speed 60 power is quite quick for a Z6 tube (they are 130 watt with a peak of 150) on a true 150 (Z8 or ZX180 EFR) you would expect 40mm p second at 75 to 85 power after they have settled.


cheers

Dave

[Johan Verbert]

Ok, since your manual "cut contour" works, and what you send to the machine from your computer doesn't, that leads me to believe you have a data transfer or software issue. Check or change your connector cable. And, have you checked your settings in your software? Your software may be sending conflicting data to the machine...


Unfortunately the manual 'cut contour' no longer works better than what we send from the computer.
We installed the original software again but this did not improve the results.
At the moment we are just trying to cut a small rectangle, so no intricate details.

[Johan Verbert]

IF it won't cut over 30 amps like you said in your first post you are on track with either the HVPS for the tube or the tube its self. Did you check the low voltage in this case either 120 or 240 volts to your PS and of course the PWM control connections to the same PS? Tina over on the CNC Zone like I suggested works for the company.

We still need to check the 240 volts.
Thanks for the hint. I posted the same question on CNC Zone. When we solve the problem I will post the solution on both forums.

[Johan Verbert]

Temperature, as the tube gas heats up the resistance drops increasing the amperage but making the beam unstable. The chiller flow sensor and temperature monitor won't help as that measures mean temps and not mirror temps and flow not presence of bubbles, I'd guess you have a bubble in the positive end of the tube leading to mirror heating and distortion.
When a mirror heats up (internal 100% reflector) the beam will increase in size but will no longer resonate evenly inside the tube (the mirror basically warps).

I'd check the tube for bubbles in the ends.

Failing that it may well be the settle of the tube, 30 speed 60 power is quite quick for a Z6 tube (they are 130 watt with a peak of 150) on a true 150 (Z8 or ZX180 EFR) you would expect 40mm p second at 75 to 85 power after they have settled.


cheers

Dave
We cannot find any bubbles in the tube.
And at the moment we are only trying to cut small rectangles (3cm x 5 cm), one at a time so overheating should not normally be a problem ?

Even at low speeds and higher powers (25mm/70% or higher) we are unable to do basicly more than engraving the wood.

[Dave Sheldrake]

Hi Johan,

Internal mirror temperatures can shoot up in seconds in the event of a bubble, that said have you checked the output coupler? (the lens end of the tube) to make sure it is clean?

cheers

Dave

[Travis Wizniuk]

We cannot find any bubbles in the tube.
And at the moment we are only trying to cut small rectangles (3cm x 5 cm), one at a time so overheating should not normally be a problem ?

Even at low speeds and higher powers (25mm/70% or higher) we are unable to do basicly more than engraving the wood.

Hhmm try this... Focus the laser closer.. Maybe %40 closer (not quite half).. Does it cut better when you do that?

I'm thinking you might have installed the lens backwards when you took it out and cleaned it. I'm just guessing though..

[Larry Robinson]

I would make sure you put the mirror back in correctly. The concave side should be toward the work table.

[Johan Verbert]

Hi Johan,

Internal mirror temperatures can shoot up in seconds in the event of a bubble, that said have you checked the output coupler? (the lens end of the tube) to make sure it is clean?

cheers

Dave
Hello Dave,

When we installed the tube we really made sure that there were no bubbles.

We checked the output coupler visually and saw no dirt/soot.
I am a bit apprehensive to clean it.
But methanol and a Qtip should do the trick, no ?

[Johan Verbert]

Tonight we will check the lens again. But we were really careful to mount it curved side towards the laser.

We tried different distances and really found the location where the laserline is the thinnest.

[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.