[degrafex]

Hello all,

I am new here but have used you all as a resource in the past when I built a momus CNC machine a couple years back... I have experience in CNC and 3D printing but now have ventured into laser cutting/engraving. I recently got a used Liaocheng Shenhui 60W laser cutter. The machine worked fine when it was picked up, and even had an extra new laser tube.

Here’s the deal:
The machine powers on, I can connect it to my laptop just fine and run sample code. (move the x and y) This x and y also work manually. However when I press the “laser” button nothing happens. There is no mA reading on the analog gauge above the display on the cutter, no noise, no light. I attached the wires on the laser with solder and silicon like the manual states.

I did examine the power supply a bit and after some research, seems to be okay. I’m getting 220 into the supply. The fan works, the appropriate lights are on. I ground off some additional paint around the ground wire to make sure it was a good connection. When I touch the laser wires after turning the machine off, I do get a light shock. Also, when I press the “test” button on the laser power supply I can hear a faint crack from the laser compartment sounding like it’s arcing to the chassis. I have changed to the other tube with the same results.

Does any of this sound familiar to any of you?

Thanks so much!
Lee

[gfacer2]

If you hear arcing, it probably is arcing. First, open the cover where the tube is so you can see things. Then inspect the tube within an inch of it's life and look around the compartment for any arc marks.

3 basic issues that can be at play that I know of. 1) the arc is from a broken tube (look for cracks, water in the outer tube etc) and the arc is inside the tube. 2) the connection is not insulated enough. Sheath the connection in some silicone tubing over everything else and then seal that too. I've had it arc though a lot of HV splicing tape before. 3) it might be in the case of the power supply. I had a really intermittent arc. No marks near the tube and not too loud. Eventually due to other issues, switched the power supply and saw the arcing on the bottom of the board to the case. I also might have had arcing once from the emergency stop to the frame - the switch melted once at any rate but no longer sure if due to an arc or something else.

If you have tried both tubes, my guess is either 2 or 3.

[gfacer2]

Also this is assuming you know it just isn't hitting a mirror at some point so not making it to the end?

[degrafex]

Thanks for the reply! I'll shield the connection a bit more tomorrow and see how that goes. I didn't hear any arcing when pressing the laser button on the control panel which I thought was weird. Could one of the E stops be stuck closed internally I wonder?

[degrafex]

Also this is assuming you know it just isn't hitting a mirror at some point so not making it to the end?

And yeah I had some cardboard in front of the first mirror to test for that as well

[gfacer2]

Thanks for the reply! I'll shield the connection a bit more tomorrow and see how that goes. I didn't hear any arcing when pressing the laser button on the control panel which I thought was weird. Could one of the E stops be stuck closed internally I wonder?

Yes. When my e-stop melted I changed the whole power supply before I figured it out (ie when the new power supply did nothing too).

You can also test the input from the control to the power supply. I believe one input is approx 5v (or whatever its getting from controller as a raw feed) and then the other varies as a percentage (100 is full voltage etc). So you can run a test with the laser power supply unpowered and just make sure the control signal is OK. Usually it is though I think. Anyhow - do a bit of research - I can't recall which input is what on the control to power supply part but I found the info easy enough when I needed to test it.

[degrafex]

Good to know, I'll bypass those e-stop switches just to test. I didn't know I could test the control inputs when the supply is off, great to know I did stumble on a wiring chart for those TH, TL and whatever else those ports were. I was testing and getting some numbers without having any idea what they meant. I think you just shined some light on that for me. It is a bit nerve racking getting under there, these things scare the hell out of me as a newbie

[gfacer2]

Yeah - I know about that - I have all the training that a political science degree provided for these things!

[degrafex]

Yes. When my e-stop melted I changed the whole power supply before I figured it out (ie when the new power supply did nothing too).

Half way there!!
So I burned cardboard this morning! The mirrors aren't aligned apparently but I burned from the first mirror! I bypassed the E-stops on the front panel and I am now able to fire the laser from the power supply. My next issue it that I cannot fire it from the lcd control panel. I'll take a multimeter to the PS later to see if I'm getting an input but I'm assuming that these control panels can go bad as well?
Thanks for the help!

[gfacer2]

I suppose they can. maybe more likely if you had actual arcing issues before. Does it come on and show things on the screen? You might check what the control's laser power level is as if it is too low the test will not fire. It generally overrides that setting when running a file but it is relevant to the test button.

[degrafex]

I suppose they can. maybe more likely if you had actual arcing issues before. Does it come on and show things on the screen? You might check what the control's laser power level is as if it is too low the test will not fire. It generally overrides that setting when running a file but it is relevant to the test button.

The laser is set at 60% on the control panel. And everything on the panel seems to work 100% visually. When I get a minute I'm going to try to see if there is a loose or bad connection coming off of the panel to the PS.

[degrafex]

SOLVED! I was playing around with the input wires going into the PSU and found one that had a bad connection. Tightened it up and I now have control from the panel!
Thanks for the advice!!
Lee