Laser not firing, not water switch

[Stuart-1975 (Stuart)]

Good evening Brains Trust,

I’m having a small problem with my Red and Black X700 at the worst time of the year to have one.

The laser was cutting away merrily then the beam cut out. No ouput.

Test pulse did nothing, no laser coming from the tube.
Power and controller fine.

Followed the guide here:

Co2 Laser Power Problems and Trouble Shooting

To test if the power supply and tube was ok. Took out the plug in the photo below as in the video:

Pressed the test button on the power supply and the laser fired.

So not the power supply or the tube.

Went on to the water sensor test, shorting out WP and G. No luck, probably down to me.

Decided to cheat and cut the water sensor off and twisted the ends together (I have two new water sensors on the way and will replace in due course, I am using the alarm on my chiller until then).

Same problem.

I am now at a loss and hope someone here can help me find the fix.

Yours in Lasering,

Stuart

[Chuckphd (Chuck Terra)]

Sounds like you are doing all the right steps…
So, you were in the middle of a task and it stopped !

I am not familiar with your model, but…
From a trouble shooting POV I would offer:
Go to ALL of your wire screw downs and tighten them all.
I don’t expect this is a fix for your issues, but I know when I got my new laser
I found a number of the connections loose and over time would have failed.
I would also offer to put this on a yearly maint. list, as vibration and temp.
change can loosen these connections,
As a second task UNPLUG all of the green connectors and re-seat them,
this wipes the connection for better metal to metal connection, especially if your laser is in a shop that may have moisture from cold or like here in Florida, just humidity and these can oxidize and become a problem…

It does sound like a wire issue, maybe a loose wire on the High voltage to the Laser, even tho it did fire with the button press, could have been a fluke…

Last question: did the X/Y movement stop ? or just the laser Cutting ?
You can see where I am going, typical lockouts will also stop the movement.
typical indication of ‘any’ signal triggering the ‘stop cut’ function also stopping movement.

But if the X/Y did not stop moving, I would focus on the Laser Tube/ HV power supply / wiring and associated connectors… it’s a good start as you have seemed to have already started that process…

I am interested to see what you find…
Chuck
best of luck…

[Stuart-1975 (Stuart)]

Hi Chuck,

Thanks for the help. I’ll check the wires in the morning.

Without the second (controller) plug in the power supply, the laser fired fine several times over the two or three hours I was tinkering with it.

I suspect there is a safety feature somewhere that is stopping the laser for my safety.

[ednisley]

@Stuart-1975

a safety feature somewhere

Perhaps the lid interlock switch?

On the controller display, get to the Diagnoses display (I think by pressing Z/U to bring up the main menu), then verify the indicators light up (or not) as expected:

When you lift the lid, I think the Open Prot indicator should light up. If it’s stuck on, there’s the problem.

On my machine with a KT332N controller, the protection indicators light up when the input is “active” = “there is a problem”, but I am long past being surprised at how different machines are different.

[jkwilborn (Jack Wilborn)]

Most Ruida based lasers do not use the P terminal on the lps and it is wired directly to ground. This is the black jumper in your photo, from G → WP. So your water protect is being handled by the Ruida.

You should wire in your chiller as it adds a layer of protection from temperature and coolant flow. I think most of us have done that…

@ednisley

“active” = “there is a problem”

On mine and I’m sure on the photo you posted, Y Limit+ is active and X Limit- are active and mean the inputs are actively pulled down… When everything is working, it’s sensor is active, so if it’s illuminated it’s being actively pulled down, which is an operational mode.

On my Ruida, I lost the LWP1 (water protect) input. Shows correctly on the external led, but doesn’t show up on the Z/U → Diagnosis screen.

This is for the Y home switch and external led.

On this the Water protect and X home switch are active.

@Stuart-1975

laser was cutting away merrily then the beam cut out. No output

Did the mechanics stop working or just the laser?

If the Ruida senses a fault, such as door or coolant, it will pause the entire machine, including the laser.

It should also put up some type of error message. If the mechanics kept running and no laser, it’s likely between the controller (hardware) and the lps.

@Stuart-1975

Power and controller fine

How do you know this?

@Stuart-1975

Decided to cheat and cut the water sensor off and twisted the ends together

Don’t do hacks like this, I know it comes from desperation, but it only adds another layer of bugs to arrive and increases the threat to the machine. A volt meter or ohm meter is all you need to check these.

[Stuart-1975 (Stuart)]

Thankyou to all who have helped so far and here are some clarifications:

1. This is the job I was cutting when the laser cut out.

The job completed, but as you can see is that the laser just stopped while cutting.

2. Here is a photo of the sensor screen from the Ruidia, no water alert (or any other really).

Interesting note is the X limit error as my limit switched have not worked in years.

3. Here is a photo of the controller in the hope that something is obvious that I have missed.

4. I think the power supply and the tube are OK because when I disconnect the
   plug on the power supply here (this is the plug from the controller) and press the test button (red), the laser fires just fine.

Also, as you can see, the WP and G terminals are jumped, so I am told the problem is probably with the controller.

I hope someone knows what I should check next.

Thankyou all,

Stuart

[Stuart-1975 (Stuart)]

Got some help from over on FB, so I have checked more things, but still no idea. Hopefully this helps someone here recognize the problem.

I have checked the TL, IN and G connections between the controller and the power supply (I am told that TL fires the laser and IN tells it the power to fire at).

When running a file, the x and y move but the laser does not fire.

At the controller TL-G (GN5 plug 2 and 1) read voltage.
At the controller IN-G (GN5 plug 3 and 1) read voltage.
Checking the wires between the controller and the power supply, TL, IN and G read voltage and continuity.
Checking at the green plug on the power supply; IN-G shows voltage but IN-G does not.

Any ideas guys?

Still figuring it out,

Stuart

[jkwilborn (Jack Wilborn)]

@Stuart-1975

TL fires the laser and IN tells it the power

Yes, L input is laser enable and the IN input sets the lps current limit.

You should read a % of the 5V supply on the IN terminal… if set for 50% power, then expect 2.5V if 20% power would be 1V.

If you are just cutting continuously, then I’d expect the L input to be low, not reading a voltage, that enables the lps to cause it to lase at the IN set current limit.

I don’t know if you can switch over to laser 2. You’d have to move the L-On1 output to L-On2 along with the LPWM1 → LPWM2 and change the configuration within the Ruida.

The way these are built, you could just swap CN5 ↔ CN6, that would move all of your control signals from laser 1 to laser 2 on the Ruida.

I’ve never tried this, so it could end up messy… but a thought

@Stuart-1975

X limit error as my limit switched have not worked in years

The suffix of - indicates a home switch, + indicates a limit switch. I doubt you have limit switches on your machine, these are home switches. You’d have to have 6 switches to support limit switch operation on these. Although the Chinese label them a LmtX-, it’s really a home switch.

Once the machine boots it ignores the - (home) inputs and watches the + (limit) inputs as limits… these also have to be enabled within the Ruida. If this switch didn’t work, it couldn’t complete a home operation, which it apparently does.

---

I’d suggest you look at the L input as it should be low when the laser needs to lase. You didn’t mention what the machine was doing or what voltage you read when testing these. If you’re doing something the laser turns on/off, then the L input will be some voltage based on it’s average voltage. You really need a scope to see what it’s doing and you have to know what operation you’re performing when you read these control signals.

Unlike grbl or digital machines. the Ruida produces a continuous PWM output while it runs the whole layer, laser enabled or not.

Good luck

[Stuart-1975 (Stuart)]

Hi Jack,

Thanks for the insight.

While running an all cutting file.

The head moves as it should but the laser does not fire.

Reading the TL-G is 4.2V at both the controller end and the power supply end
Reading the IN-G is 0.23V at both the controller end and the power supply end

Given that the LPS will fire the laser when using the test button without the controller plugged in AND
The signal is getting from the controller to the LPS.

Is it fair to assume that the problem is somewhere in the LPS interpretation of the controllor signals inside the LPS?

Cheers,

Stuart

[jkwilborn (Jack Wilborn)]

@Stuart-1975

TL-G is 4.2V … IN-G is 0.23V

L to G should be zero (or very close to it) for the lps to lase.

The IN terminal should reflect what ever power percentage you’ve chosen in the layer…

Since you didn’t mention it, I don’t know what it should be, voltage wise, but I can say at 20% power you should have at least 1V there and you have much less. My machine won’t lase at that low of an IN value.

Neither of these values are what I’d expect. What layer value did you use for power when you did this?

[Stuart-1975 (Stuart)]

Hi Jack,

You are of course correct. I have my readings back to front.
Having double checked.

L to G is 0.23V and IN to G is 4.2V, spot on for the 85% I was running the laser at.

Sorry for the confusion.

Cheers,
Stuart

[Chuckphd (Chuck Terra)]

Stuart…

Not sure if you mentioned this, but have you done a simple task, as cutting a square or circle, just to see if it would complete?

Also I noticed the X- wire looks to be under tension, pulling from the spiral wrap, maybe a good idea to unwrap a few inches and cut it off, to take the tension off those couple wires,
Also where is the X- connected to? as Jack mentioned there must be a sensor associated with this input…

[jkwilborn (Jack Wilborn)]

I’d think lps, as it’s getting the correct signals to lase, but isn’t.

I don’t recommend trouble shooting with that much power. If it’s going to lase, it will lase at 50% power without risking anything.

[Stuart-1975 (Stuart)]

Hi everyone,

Thanks for all the support. I have ordered a new LPS and will update when I have it installed. Hopefully it arrives quickly given the time of year.

Cheers,

Stuart

[Chuckphd (Chuck Terra)]

Best of Luck… hope it works and makes for a Merry Christmas

[mdooher (Matthew Dooher)]

I had a very similar problem, The laser not firing was caused by a DC offset meaning the PWM signal was not being interpreted correctly by the laser power supply. The supply worked fine when pressing the test button. It took me a while to find (including me replacing the old power supply) and I needed to use an oscilloscope to see it.
The cause in my case was the cheap 5V supply for running the laser pointer in the beam combiner has an internal problem shorting +5v to the case which was attached to the machine chassis.
You probably don’t have this happening. But all the symptoms look like a DC offset on the PWM.

[mdooher (Matthew Dooher)]

DC offset obvious
The link above shows what a DC offset looks like on the control line, I forgot I had taken this video.

The little yellow triangle is the zero volt line, you can see that before firing the volage is below the zero volt . it should be on that line

[jkwilborn (Jack Wilborn)]

Not clear what I’m looking at, but interested. I can’t really read the scopes values or other settings. What did you use for a trigger?

On my Rigol, I can do a screenshot of the output… I’d suspect it’s possible on yours?

---

Using a Ruida, the pwm should be present the whole time you are executing a layer, lasing or not.

The lps shouldn’t respond to a negative voltage or have any effect that I can understand.

I believe you, I just don’t follow how a shorted 5V supply can cause this.

The Ruida runs off a separate 24V supply, so it’s 5V outputs, created from the separate 24V supplies are isolated from other supplies…

It’s also likely that maybe I’m misunderstanding you…

Thanks

[mdooher (Matthew Dooher)]

I found the PWM signal duty cycle varied exactly the way it should depending on the percentage power set.
This signal then goes through simple a low pass filter in the laser power supply which converts it to a 0-10V signal (if I remember correctly)
The PWM signal in the video should be switching between 0 and 10V, but it isn’t, it is actually switching between -2.5 and +6ish meaning the average voltage is too low
on the power supply you will se the laser LED at bottom left is not illuminating indicating that the tube is not firing.
In this condition if I increase the duty cycle to around 75% it will fire

The scope is DC coupled using the GND pin as the zero In this case not the same as the chassis ground (which it should be).

Sorry I fixed this a few months ago so some of the exact voltages might be incorrect
But if the laser power supply is not firing it is worth checking the input signal (you can use a DC voltage you don’t need a PWM signal)

[jkwilborn (Jack Wilborn)]

The swing voltage of a cnc motor controller is usually 0 to 10V, but if you look at a standard pwm for laser control it’s 0 to 5V designated as ttl compatible. You can’t run any ttl devices at 10V.

However it does change it to a 0 to 5V analog control voltage within the lps.

I know what’s going on with mine as I’ve been all over it and others. There is no negative voltage supply, so I wonder where that’s coming from. I use chassis ground interchangeable with ground on the Ruida or on the lps, without issues. They all appear to be wired together. The appearance of a negative voltage eludes me at this point. You still didn’t mention what you were triggering the scope on. I usually trigger on L-On1 or L/TL on the lps as that’s when it should lase.

Maybe you had some kind of grounding issue.

I also wonder why you have periods of no PWM, as the Ruida produces PWM continuously as the layer is executing. PWM is operating from the start of the layer to the end of the layer.

I’d like to zero in on what happened so I understand, that way I can suggest it to others, as you have done. I can’t do it, if I don’t understand what’s happening.