80w seems to be rapidly losing power

[MitchL]

So, my 80W DIY laser is at the point where I can run jobs on the DSP. I've got good mirror alignment, and I think I've got good focus. I've scored some lines in wood (about 0.3mm), done a quick engraving job. (it's pretty cool that one can build a tool that one does not know how to use ).

I'm having a really hard time cutting through 3mm acrylic. In fact, I may be having a _progressively_ hard time (I can't prove it, but I think the laser is getting weaker). I cant punch through 3mm acrylic even at 100% power and 5mm/sec , so I think there's got to be something wrong. In LaserCAD, I'm setting both Power1 min/max and Power2 min/max to the level I want. PWM is set to 20000.

I have the LO 80W power supply and a Reci 80W tube, pro mirrors, lenses, and head. I haven't changed any of the adjustment pots on the power supply, I figured I wouldn't need to since they're both 80W.

I would think that 3mm acrylic would pose no problem to an 80W laser.

The cooling system is a Koolance EXC-800 chiller, fittings, and coolant. Flow rate is at least 5LPM, I can make it faster. I have the temperature set to 20C. I don't think I've ever seen the temperature increase.

I have only 30 minutes of "on" time on the tube, mostly small rectangles, circles, and other shapes. The longest job I've run is about 2 minutes for engraving, most jobs are under 15 seconds.

Even when I put a tape target in the path of the laser (say, at the #1 or #2 mirror) and hit the laser button, I don't get quite the fireball I used to get. The laser tube used to glow more brightly than it does now.

I don't have an ammeter on my laser - I was tempted to order one to see if maybe the current is way off.

Any chance my laser tube could have gone bad? It did sit in its box for about 9 months before I used it.

Could I have killed it that quickly if the current is too high?

Anything particular I should be trying to figure out what's happening?

/Mitch.

[Tech_Marco]

Mitch

Without knowing the tube current, there is no way I can tell you whether is it a bad tube or a bad power supply. You better to have an ammeter installed to protect the laser tube. If driven by over current, the tube won't last very long. A 80W PSU can output as much as 32mA.

There is a batch of dual input PSU 110V/220V got a bad switch issue. The selection switch is defective. If you set it to AC110V, and from time to time the switch contact burned out and causing open circuit. The PSU became AC220V. So, when you input AC110V, it will output up to 9mA only and in that low current, it is hard to do cutting.

FYI, a good Reci 80W can cut through 5mm acrylic with speed set to 12~15mm/s.



Marco

[MitchL]

Thanks Marco!

Without knowing the tube current, there is no way I can tell you whether is it a bad tube or a bad power supply. You better to have an ammeter installed to protect the laser tube. If driven by over current, the tube won't last very long. A 80W PSU can output as much as 32mA.

I'll order an ammeter (from you) today. My trusty Fluke 16 only has a uA range, not mA, otherwise I'd have just used that.

From your catalog, it looks like this is the ammeter for the job:

http://www.lightobject.com/3-digit-Mini ... -P457.aspx

or:

http://www.lightobject.com/DC-0-100mA-A ... -P242.aspx

The analog one has the advantage that it does not need its own power supply. Got a preference?

Meanwhile, I'll run to Fry's tonight to see if they have a DMM with a better ammeter range. Sounds like a great excuse for more test equipment.

I assume the 'laser' button runs the laser at 100%.

There is a batch of dual input PSU 110V/220V got a bad switch issue. The selection switch is defective. If you set it to AC110V, and from time to time the switch contact burned out and causing open circuit. The PSU became AC220V. So, when you input AC110V, it will output up to 9mA only and in that low current, it is hard to do cutting.

Fascinating. I wonder how I could tell if that's the issue (besides seeing 9ma on the tube, which might still be a tube problem). I assume the 5V output would still be 5V in either case. The PSU's fan doesn't seem like it's running slowly (it's pretty noisy), but that may not be affected by a bad switch.

FYI, a good Reci 80W can cut through 5mm acrylic with speed set to 12~15mm/s.

Yeah, that's kind of why I wanted the 80W one. 3mm and 5mm acrylic are what I plan to cut.

Support here has been fantastic -- thanks Marco!

/Mitch.

[MitchL]

OK, I picked up a DMM that can read in the mA range tonight and took a measurement.

When I press the LASER button on the AWC608, the laser draws 5.5ma, so that's definitely on the low side.

5.5 is way less than 9ma (and way, way less than 30ma) - should I be looking at the PSU or did I somehow kill the tube?

/Mitch.

[Tech_Marco]

It is not the way to test the PSU. Test button only output certain % but not in full
What you need to do is to connect +5V to the IN, ground the WP. Then, get a momentary switch or a wire to bridge the "TL" to the GND (ground) and the PSU will fire full power.

You need to download the PSU working instruction from the forum "Manual Download" section. I know you don't like read manual but if you do, it save you a lot of headache


Marco

[MitchL]

You need to download the PSU working instruction from the forum "Manual Download" section. I know you don't like read manual but if you do, it save you a lot of headache

Not sure I'd 100% agree with you on my desire or ability or desire to read manuals, but thanks for the info! (answer: I do). I'll wire up a test switch and report back.

This is a hobby project. to me, the adventure of getting it working is part of the fun, including solving problems like this.

/Mitch.

[MitchL]

OK, I had enough time this morning to make the test button fixture.


As you indicated, test fixture as follows:

- WP to GND
- TL through a momentary contact switch to GND
- IN to +5V (using the +5V header on the laser). The +5V terminal reads 5V on the meter.

I am seeing a little over 5.6ma to the laser, sometimes peaking at 6ma.

I also checked the HV and GND connections at the laser tube, they seem solid, no corrosion, frayed wires, or anything.

/Mitch.

[Tech_Marco]

Be honest to you, I don't like to read manual

5.6mA seems very low output
Are you running AC110V or 220V for the input?

Is there a switch installed for the input selection?
Is so and if you're running AC110V, we will be ready to go phase II exploration.


Marco

[MitchL]

Hi Marco,

There is a switch installed, and it is set for 110 V. I have tried flipping the switch back-and-forth to be sure that moves solidly ( it is not loose) it is in the correct position.

I have also verified solid connections to 110 V input to the power supply.

I can remove the power supply, and check the contacts of the switch. To do that, I would have to open up the power supply.

I don't recall any markings on the supply (bought from lightobject about 9 months ago). The cardboard box it came in was labelled 80W. Is there any way to make sure it's the right unit?

I am happy to do any experiments you suggest.

Thanks!

/Mitch.

[Tech_Marco]

Open he case and you will see two wires attached to the AC110V/220V switch. Simply cut it off and tap this wires together and that will run at 110V.If you removed the plug, it will become AC220V

Give it a try. Be careful when power ut up. Stay away from the HV cable


Marco

[MitchL]

Open he case and you will see two wires attached to the AC110V/220V switch. Simply cut it off and tap this wires together and that will run at 110V.If you removed the plug, it will become AC220V

OK, I'll also examine the switch to see if there's any sign of damage, ohm it out, etc.

Give it a try. Be careful when power ut up. Stay away from the HV cable

Will do -- I will definitely close it up again before applying power, and it'll have been off and unplugged for about 12 hours before I open it (so hopefully no residual charge in the capacitors). I'll try to get this experiment done this evening.

/Mitch.

[Tech_Marco]

Just press the Test button an it will discharge 90%
The remaining will give you a small shock and No harm
You can diachage it by using a resistor

No need to wait for 12hrs


Marco

[MitchL]

No need to wait for 12hrs

Unfortunately, I do have to wait. My day job gets in the way of super fun hobby time

/Mitch.

[MitchL]

Hi Marco,

I'll find out shortly, but I think your suspicion was correct: The 110V/220V switch looks like it's faulty. It's definitely open, and when I wiggle the switch sometimes there is contact. It's definitely a problem, hopefully _the_ problem.

I'll jumper the pins together, reassemble and reinstall the supply, and let you know.

I definitely should not have put the nuts for holding the PSU in place on the _bottom_ of my machine.

/Mitch.

Bingo!

[MitchL]

The 110/220 switch was the problem, Marco! Thanks for the heads-up.

I cut the switch off, jumpered the wires together, and put the supply back into the laser.

Now I get 26ma using the test button fixture (and also with the Laser button on the AWC).

For my tests, I put a scrap piece of material on the bottom of the laser, about 8" from the tip of the head. Even the unfocused beam has lots of power. I'll run a real cutting job tomorrow, tonight I need to CNC some stuff.

But, here's something interesting, I wonder if anyone has an explanation for it:

If I turn the red dot on, it projects the dot on the bottom of my machine, as it should.
When I press the Laser button, the red dot slowly *moves*, diagonally towards the rear-right, about 8mm away from where it started. If I let go of the laser button, the red dot jumps back to where it was.

You can see the dot moving slightly on the #2(gantry) mirror. I think #1 is too close to observe.

My conjecture is that the beam combiner's mirror is heating up slightly as the CO2 laser passes through it, possibly changing its shape or reflective characteristics.

The CO2 burn mark does not move. It's always in the same place.

(this is just an observation, nothing more, something fun to think about. I'll see if the combiner gets warm after a long job using an IR temp gun).

I took a video, if it came out well enough to show I'll upload it.

anyway: Thanks for the tip on the 110/220 switch, Marco! Now it's really a scary laser!

/Mitch.