Intermittent "squeal" from somewhere in the cutter

[scrappyjedi]

Hi, all!

I had a very frustrating weekend with my laser cutter- a Buildlog 2.0 machine with a 40w tube and using an AWC608 controller. It started out of a loss of cutting power after several sheets (3-5) of 8x12 1/16" cork or wood. We replaced several parts including the high-voltage laser supply, the controller (swapped in another AWC608 that we keep as a spare on the shelf) and finally a new tube. After each part we tested and found that the same results were occurring. Cooling temp is a steady 59 degrees F, which is what I have cut at for over a year with great success.

The problem is largely the same after all those replacement parts, but has added a new trick- a high-pitched whine that accompanies a change in beam quality inside the tube and a loss of power in both the cutting beam and on the amp meter (that's a little harder to see since it's also adjusting for cornering and also between cuts). I should probably back up a bit and explain- I cut cork sheets at 600ppi and wood at no PPI. I have been cutting (or trying to cut) cork at 600PPI all weekend (I have done this for months with no issue) and finally decided to test at no PPI. That's when I noticed the squealing, which does settle out after a few seconds. The video was taken after I'd already witnessed one long string of whiny cutting at no PPI in which it barely marked the material (attaching a photo of those cuts).

Here's the video- https://www.youtube.com/watch?v=FqFYn8R ... e=youtu.be

With these results, I would suspect the high-voltage supply, especially given a brand new tube (the tube we pulled out, by the way, had only been in since September 1. The tube before that lasted more than a year under the exact same cutting conditions under which we are now having failures, and we can run 16 hour days here sometimes). The thing is, the HVPS is one of the parts we replaced. Could we have two bad supplies? We've checked the wiring while running and did not notice any arcing.

We are also having a separate problem where the x-axis is either losing steps or simply drifting (attaching a photo of this as well- shown by cutting not lining up with engraving), and the laser drifts off of origin on the x-axis when returning to home, as well. We've been assuming that the x-axis stepper driver needed to be replaced (we just had to replace a failed X stepper a few weeks ago), but could the two be related?

Can anyone help?

Thanks so much!
Melissa

[scrappyjedi]

Just an update- swapped back in the old HVPS last night, and having the same issue. The tube, HVPS, controller, and a host of other parts were purchased from LightObject (under my husband's account- I can provide order numbers if needed), so I was hoping that there might be some ideas as to what the issue is.

[Tech_Marco]

How fast you ran the machine? What mico stepping is using?
It look like you have two issues here
1) Backslash
2) Beam alignment

All our laser tune tested before shipped. So chance of a defective tube seems is unlikely
You may want to test your alignment by drawing a square on each corner and check the outcome.
Also, make one in the center as well. That way it can tell more about your case

Cleqn tje lens as well

Marco

[scrappyjedi]

Marco,

We have done all of that, including cleaning the mirrors and lenses, multiple times. Alignment is spot-on. Running at 1/16th microstep, using the same settings and speeds (500mm/s engraving, 23-30mm/s cuttting depending on material) successfully for over a year.

I also do not think it is a defective tube. After more testing, it could be wiring. When I press the test button on the HVPS, sometimes nothing happens, sometimes the laser will fire with that squeal, and sometimes it fires without the noise, but the meter maxes around 9-10 mA.

[Tech_Marco]

Can you set current higher like 15mA and give it a try.
If it work out good,chance is that the power supply is the trouble maker


Marco

[scrappyjedi]

I am running that now and will report back!

I really, really *don't* think it's the tube and am inclined to suspect the power supply, as well. During the short intervals when everything has run correctly, the new tube is a BEAST (in a good way!). It cuts so much better than my previous 40W (which was the style you carried previous to what you have in stock now), even when that one was brand new.

[scrappyjedi]

Boosted the power to 60% in software, which only yielded about 11.5mA to the tube. I used to run this same power supply at 40% and get 13mA. Cut fine at 600PPI for three 8x12 cork sheets, and then I tried a test cut at full power. Got the whining/squealing again and a very low power beam that barely etched the material. Let it sit for a few minutes and tried full power cut again, no odd noises this time and a cut that maxed power at 11.5mA. Went back to try another production run at 600PPI at 60% power and had extremely degraded cut quality. It's almost like something is heating up after running for a while and starting to fail.

[scrappyjedi]

Tried another sheet of cuts (~6 minutes of cutting) @65% power @600PPI (max power on the meter was about 5.5mA during the cut). Started out cutting reasonably well, but by the end of the run was failing to cut through the material.

I've ordered another high voltage supply from LO in case we somehow have two bad ones here, but honestly we have similar results with either of the supplies that we already have hooked in.

The tube cuts very well when everything is working, and we swapped it in for the previous tube when these same issues were happening late last week. If it's that tube, that would mean that we also have two bad tubes, which seems unlikely. (Same for the controller- we have a spare of those and have tried both on the system with the same results.)

I checked and then re-wired the high voltage connection for good measure. At this point the only part that hasn't been replaced is the low voltage supply.

[scrappyjedi]

Marco- quick question- how do you test the tubes before sending them out? Is it a sustained test for any length of time, or is it a quick power-up to check alignment within the tube and for beam quality?

[Craig_Johnson]

Just for fun, try a lower PPI setting. The laser is being pulsed on and off with the PPI setting, there is little documentation for it. I like the 200 PPI setting, but it is noticeable. My guess is that a change in PPI setting would have a direct effect on the tube? Maybe 600PPI is freaking it out? indicating an issue with the tube? Just guessing....

[Tech_Marco]

Marco- quick question- how do you test the tubes before sending them out? Is it a sustained test for any length of time, or is it a quick power-up to check alignment within the tube and for beam quality?

We power up a laser tube for and run for about 2~5 min, starting from low current to the max and observed the burning spot on a piece of cardboard (beam spot testing) and to a concrete block to check the power. Inspect any missed fire possible happen and leaking. Then, turn On/Off frequency on the tube see the response from the tube. This is a preliminary test the much we can do. We're not the manufacturer so we can't test divergence or power testing. But from our test, we know the tube work and in good power based on our observation.

Marco

[Tech_Marco]

Melissa,

Observe the LCD see if it fade out a little when you fire up the laser. If it does, it mean that there is grounding issue. Also, if the max current output is 11 or 12mA, it is NOT ok. It is easy to output 20~21mA from a 40W power supply. Make sure you ground the power supply well to discharge "static" caused by the electromagnetic fields. Also, check the light route on the laser part; intake hole to the focus lens. Make sure it is straight. You can raise up the laser head up and down and check the spot. If it hit to the same spot then it is good. But if it is off, that mean the focus isn't right (beside focus point)

Don't worry, we're here. You will get the problem fixed. There is so called "no pain, no gain". You will learn a lot. Things make you feel better is that we charge customer $100/hr for onsite repair. You taught yourself and you don't need to pay me or someone to go to your site for services. and you can do it yourself. Isn't it sounds great? So, just be patience, you will get down there.


Marco

[scrappyjedi]

Marco- thanks so much for the reassurance. I actually look forward to figuring out what's causing this. Every time the machine breaks, I learn something new.

I did not see the LCD flicker or fade when firing the laser, and I rewired the ground on the PSU just to be sure. I also use a Post-It note to check that the beam was centered on the inlet of the cutting nozzle, and it was perfectly centered.

I do have a new data point to throw into the mix. Based on Craig's suggestion, I tried cutting cork at 200PPI and was still able to induce a failure when I went back to cutting without PPI. I then decided to see if it would remain stable at full power (the squealing usually lasts for a short time after switching back to non-PPI mode, and then things settle down). I cut wood at 29mm/s, 49% power for 3 hours straight without any trouble at all. I then decided to see if I could cut cork at a lower power with no PPI. I found, though, that when I dropped the power level in the software below 40% (again, no PPI!), the squealing and unstable beam in the tube would start again! So it looks like this is a low-power issue and not specifically PPI related?

At 49%, with this power supply I would normally see the meter read 12-13mA, and right now it reads 9-10mA. Things seem to start to get really screwy in the 6-7mA range.

[scrappyjedi]

My new PSU arrived today. Marco, your team got it out the door less than an hour after I ordered it!

Installed it and did a couple of small test pieces at high and low power, with and without PPI. It *seems* to have fixed the issue! I want to run for a while before I claim victory, but I think that it's done the trick.

[Tech_Marco]

Can't wait to see the glory!

Marco