[scrappyjedi]

Hi, all! I've just spent a couple of hours reading through some very informative posts relating to a problem I'm having with my laser cutter, and I want to start by thanking you all for the wealth of information that is here!

I found lots of posts that might relate to my situation, but I wanted to post and see if anyone had any further insight.

I have a home-built (Buildlog 2.0) laser cutter that I've been using in production for over a year. I'm very used to how it normally operates, so when things started going awry last week, I immediately checked all the usual suspects.

Some specs that might help:

- 40w tube (we buy from Light Object)
- Water chiller inline (it's a lab-grade chiller, and water is kept just under 60 degrees F)
- No protection switches for water flow or door closure (I do have an indicator that shows if water is running or not and check it very, very often, as well as continually monitoring water temperature while working)
- The cutter is run anywhere from 5 to 18 hours in a day and has done this for over a year
- Mostly cut 1/16" cork and wood, sometimes 1/8" acrylic

I started having two concurrent problems, and I'll start with the most troubling one- power loss during a cut. I've seen this happen a few times before- we got into a couple of bad tubes last fall, so I know all the signs of a failing one. Cuts would start out great, and by the bottom of the sheet (anywhere from 12 to 25 minutes later), the beam would no longer cut through the material. The tube was rather new- just installed September 1st and had a few hundred hours on it (we run hard here!)- so I was surprised that it would start to fail so quickly. We did investigate and replace the high-voltage power supply, but it didn't make a difference. After verifying alignment (again- so many times since last week!) we pulled the tube and replaced it with a new one that we just got in about 6 weeks ago (we always keep a spare on the shelf). Imagine my surprise when the issue continued!

At this point, with a new tube and new power supply in place, we wondered if the controller (an AWC-608) was having trouble, so we swapped in our spare of it (yes, we keep gobs of spares here). Still no fix. Not only that, but I discovered that now the laser would sometimes emit a high-pitched whine/squeal when first trying to cut at full power, especially if I'd been running at PPI for a while. I actually managed to catch that failure on video and uploaded it to YouTube.



Since discovering that, I've put the original HVPS power supply back in, and the whine/squeal is still happening. I don't see any arcing around any of the connections or wiring when running with the lights out. I did redo all of the high-voltage connections just this afternoon for good measure.

At this point, I'm wondering if I either a) have had two bad tubes in a row (it has happened before) or b) have had two bad high-voltage power supplies in a row. Or is there an option c) that I haven't thought of yet? At this point we've replaced every major component in the cutter with the exception of the low-voltage supply. I do have an extra one of those, but it just seems so unlikely that it's the culprit.

Any help or ideas would be greatly appreciated!

[scrappyjedi]

I neglected to mention- my power supply does have a Test button, but when I press it, most of the time nothing happens. Every once in a while it will cause the tube to fire with a very weak beam. If I use the Laser button on my AWC-608 controller panel, the laser fires reliably, though sometimes with the same squealy-ness.

[scrappyjedi]

After a couple of days of more testing, I've found that if I cut at full power (no PPI), the squealing goes away. When I go back to PPI OR if I drop the power below about 40% in software (meter shows 6-7 mA at that level), the squealing and odd beam profile starts again.

[stratop80]

Hello!

Did you find any solution to your issue? I'm having a similar problem. It's a RECI 100w, installed in February, running in a RDC633XG machine.

It started a few days ago: power loss during a cut,

My laser starts just like it usually does, behaving as expected and programmed, but some 30 seconds later it will start dropping power, the beam going weaker evenly until no beam touches the material. That happens when using low power settings (about 20, 25%) to make some vector drawing, Amp meter then reads 6-8 mA. With the same readings, it fires ok in the first seconds/minute...

On higher power, beam will still be there, but it wont cut through any material, and you may see how depth of cut is not complete, I guess that should I leave the work progress I would see the beam dissapear too. I try to -and get it- runinng at (not more than) 26mA in that setup.

Tested the HY-DY13 power source succesfully...
I use a CW5000 chiller set at 22C degrees, no prob in that, I think.
No vibrations, no misalignments, enough grounding, afaik, etc..

I'm quite lost at the moment, Any help would be much more than highly appreciated.


(please excuse my english)

Best regards,
Javier.

[davoque]

Did you solve your problem, I am getting the same thing.

[scrappyjedi]

We were cutting using PPI, and for some reason these tubes just do not like to run in that mode. We've stopped running in PPI, and the tubes are fine now.

[electronrancher]

I have heard that squeal at low current. When I looked at the current through the LV side of the tube with an oscilloscope + sense resistor, I saw that it was varying wildly. I chalked it up to oscillation in the power supply, although I can say for certain that it was much worse at the end of an old tube's lifetime than at the beginning of a new one. But I'm very interested in getting to the bottom of this squeal, because I also don't know if it's the tube or supply. Like you, I changed all sorts of components in trying to debug it.

I don't have the PPI option yet, my laser power is controlled via a PWM setting on the front panel. By raising and lowering the power percentage on the front panel, the duty cycle of a ~20kHz square wave is increased and decreased. This PWM signal is fed to the laser PSU's PWM input to control the current.

Here's what I'm interested in:
1) Does anyone with the very simple "knob" type power setting still get this squeal? If anyone out there has this style laser, please turn the power down and do some cutting with a continuous beam. Turn the power down until the beam goes out, then raise until it's just barely on. Do you hear a squeal or hiss from the power supply as the beam starts a cut?

2) For the AWC crowd: I believe you can change the PWM frequency, right? Try raising it to 30kHz or higher, and do the same low power test with continuous cuts. Does it make the squealing better? Worse?

I just got an AWC708 but have yet to install it. I will try these tests myself at some point, but for now any data is helpful.



And PS - scrappyjedi... Are you saying that this his causes the tube to degrade? I don't know, but I'm wondering.