Laser power output problem(unstable)!!!

[khasabog]

Hi everybody.

I have a BIG question concerning my laser cutter. I got my 50wt laser tube and matching power supply from Steve Luo:
http://www.made-in-china.com/showroom/steveluo66

Now I have a big problem with the system. It seems that laser output power varies on time.
It is best noticeable during engraving. When you just turn the machine on and set output power for engraving, the first sheet comes out nice. When you start the second one you notice that previous power settings it not enough to fire the laser. You increase the power a little bit, and the engraving lines are different intensity. Some are really strong and dark (almost cut balsa through) others are much lighter (some are even absent).

I thought that low cost potentiometer which regulates laser power output is the problem. When I open the power supply, I found long unshielded wires going from the resistor to the board all around the board and along with wires from on/off switch (110V AC). I changed the potentiometer on multi-turn precise potentiometer and shortened and shield wires. All those efforts did not help.

Unfortunately I do not have second laser tube/power supply to test what’s wrong.

Any suggestions/thoughts would be greatly appreciated.

George.

[khasabog]

Just to clarify.

My laser system exactly the same Emission Technologies sells. 50wt laser tube and matching power supply. Does anybody have any experience with it?

[zoltan]

Hi,

May I ask what was the price from Steve Luo?

Thank you.

Zoltan

[CJL5585]

Originally Posted by khasabog Hi everybody. INow I have a big problem with the system. It seems that laser output power varies on time. It is best noticeable during engraving. When you just turn the machine on and set output power for engraving, the first sheet comes out nice. When you start the second one you notice that previous power settings it not enough to fire the laser. You increase the power a little bit, and the engraving lines are different intensity. Some are really strong and dark (almost cut balsa through) others are much lighter (some are even absent). Any suggestions/thoughts would be greatly appreciated. George.

It sounds like the high voltage to the laser tube is fluctuating. If the high voltage drops it will have this problem. Also, the current will vary somewhat with a fluctuation in voltage. One might not be able to see the current fluctuation difference on the panel meter, but then again, there is the possibility that you can by looking VERY closely to the reading.

As the laser tube ages, the output power will slowly decrease. If the laser tube has 2,000 or more hours of operation, it would also be suspect.

Jerry

[khasabog]

Originally Posted by zoltan Hi, May I ask what was the price from Steve Luo? Thank you. Zoltan

We paid $1106.00

[khasabog]

Originally Posted by CJL5585 It sounds like the high voltage to the laser tube is fluctuating. If the high voltage drops it will have this problem. As the laser tube ages, the output power will slowly decrease. If the laser tube has 2,000 or more hours of operation, it would also be suspect. Jerry

We think laser tube itself was a brand new (at least it was look like it). The power supply, however, looked old. It had scratches all over the body. Fans were full of dust and it was a lot of dust inside. When I complained to Steve about it, he just ignored my e-mail. When I then complained about instability, Steve told me that laser is stable with 10mA current and higher. This can not be truth. I cut birch ply with 9mA. Engraving goes with about 3mA.

Unfortunately I don't have schematic for the power supply. Steve Luo told me that there was documentation for it (two pages manual) and refuse to give more information.

Don't you think my only choice is to buy another laser and power supply and try them? May be somebody has a schematic for this power supply?

Thanks,

George

[hkxy]

My God!
$1106????
Whether PWM energy control,The outlook cannot affirm,The voltage undulation and the manufacture precision influence is stable.

Suggested uses the software control energy,Do not use the potentiometer,That is in China,Is eliminated.I use the color to control the energy and the order,Adjusts between 0-100.

[khasabog]

Originally Posted by hkxy My God! $1106???? Whether PWM energy control,The outlook cannot affirm,The voltage undulation and the manufacture precision influence is stable. Suggested uses the software control energy,Do not use the potentiometer,That is in China,Is eliminated.I use the color to control the energy and the order,Adjusts between 0-100.

We actually using software energy control. We replaced low cost potentiometer with multi-turn precise potentiometer and use Z to regulate laser output.

May be I did not explane clear enough what problem do I have? I do not change potentiometer settings during engraving. I just turn laser on and off using TTL signal. That's where I can see that engraving comes out with different intensity. From cutting through to nothing at all.

Any ideas how to test what's causing this instability - laser tube or power supply! I do not have money right now to buy another laser set!!!

[coleong]

From what i have gather from the above postings are the first piece cut was good then on the second piece the power start to drop.

Is it possible that the cooling of the laser tube has a problem, you need a constant flow of water at low tempreture. If the tube heats up the power will drop.- check the water pump and of course avoid air bubbles in the water flow to the laser tube.

Lastly check there is no arcing - its a bit diffcult but is easily done, just off the lights in your room when the laser is on.

Maybe you can take a picture of you layout for further comments.

coleong

[hkxy]

Uses the STEP accuracy control potentiometer?
I always do not use the potentiometer,
I use the software to control.
Light intensity.Eliminates the potentiometer,
Moreover the glass + power source is $***,
Is not $1106

[khasabog]

Here is my basic setup:

24"x48", vacuum table, Air assist.

Water flow is good with no bubbles.Water pump was purchased with requred waterflow for the tube. No arcing, I checked it. High voltage wire was puchased on McMaster with 40KV limit. On the second picture you can see water cooler. Water is always stays at a room temperature even if tube works for a long time on high power.
Now instability appears immediately. I ran many tests and engraving instable right from the begining.

To hkxy:

$1106 was laser tube and power supply shipped. Optics I purchased separately.

[coleong]

Hi Khasabog

If the water temp and flow is as specified, then this area is okay.

Other possibilities are:-
1. Check the mains 110vac power to the laser module - why not connect direct to the mains connector, i seen internal arcing troubles with multi connectors before.
2. Check the resistance of the HV cable just in case it is broken internally - make sure no high voltage is present.
3. check no dry joint present on the laser tube and laser power supply.
4. Instead of the laser beam moves(flying Optics), move the work piece - just to confirm that the no vibration present on the deflection mirror.

If all the above is okay, i afraid it bad news. Swapping to check is the easiest way out.

One last opinion - If you can loan a laser power meter, thats the best way to check the output laser power.- use safety goggles when doing laser power measurement.

coleong