No laser beam?

[moos]

Hi all,
First I want to apoligize for starting a new thread because I have no idea what keywords to use for searching this forum.
The problem is that unfortunatly our laser cutter/engraving machine stopped cutting in a proces.
We checked the tube for dark/burned places and or cracks but all seems to be fine!
We contacted the manufacturer and we both did several tests with no results.
At last I decided to replace the tube.
Did a manual laser beam test by pressing the test button on the control panel.
Viola!, ...it works!!

Now back to the PC to run a cutting proces. What happens is that the head is moving but without cutting!
So the machine is now only cutting with the toggle switch in MANUAL mode!
AUTO mode to control the power by software isn't cutting....

We also had another PC running the software with no results.

Anyone any idea about this problem?
Would be great,

Moos.

[zax15uk]

If your machine has interlocks (safety switches), make sure these are all engaged. On some systems the manual fire overrides these.

Zax.

[moos]

Hi Zax,

As far as I can see there are no other visible switches on the outside of the machine CP for usage. We also did not change any other (dip)switches on the machine PCB's. Same for the cutting software values.

Only thing we changed/replaced is the laser tube.

If these interlockes may have changed in a sudden way, do I have to look for hardware or software switches?

Thanks,
Moos.

[zax15uk]

There is probably a switch on the enclosure where the laser tube is located, if this is not making contact it could be the problem.

The switches in question are hardware.

On my machine it is possible for the cover to be closed but the switch still doesn't make connection until the lock/latch is engaged.

Zax.

[moos]

There are no switches found on the cabin and laser cover.
Could this be a problem of the power supply itself that feeds the tube or the controller card?
Moos

[zax15uk]

It could be the controller or software, and possibly a wire from the control card to the laser PSU (if it has a parallel wire for the test function).

Zax.

[moos]

Thnx Zax,

So this could be very tricky to trace the fault...

Moos

[zax15uk]

It's possible, but I expect it's something simple and obvious. The machine was working before you opened it up, so I don't think much is wrong.

Unfortunately some things are difficult to diagnose over the forum, but with some basic fault finding skills it should be easy.

I would start by locating the laser output signal from the controller (low voltage input to the laser PSU) and checking it. If that isn't working then it is most likely a software or configuration issue.

Zax.

[moos]

Okay, we checked the output values from the CC.
As our CC is the MPC03 we checked the pins 14, 15, 17 and 18 according to scheme.

14GND 15 Laser output results in 3.3Volts by pressing the Test button on the CP of the machine and toggle is in manual and auto mode. So..
Manual>Laser fires up (3.3Volts)
Auto> No laser output (3.3Volts)

17 and 18 Laser Regulation (in auto mode - software)>
NO laser output at values below.
pwr 90> 0.1Volts
pwr 65>1.17Volts
pwr 20>2.9Volts
pwr 0 >3.3Volts

Have to mention, when stopping the cutting proces the output shows 3.5Volts for all power settings. When running again it shows the above results till it finishes.

So I think there might be an electric circuit (malfunction) between TP of the centronics on the machine PCB and PSU when controlled by software?
As you said earlier it overides these when in Manual mode.

Moos

[blinton]

SOUNDS LIKE THE SHUTTER NOT OPENING. COULD YOU POSSIBLY HAVE MOISTURE IN YOUR AIRLINE THIS CAUSES THE SHUTTER NOT TO OPEN IN AUTO MODE.

[moos]

Hmzzz...
Do you mean this shutter thing is a mechanical part in line with the airline to the nozzle?
I can't find any specific part, because the airhose is 1 straight tube from the aircompressor to the nozzle.

Moos

[blinton]

the shutter atleast on our machines, opens to let the beam thru. on our machine if you have moisture from the aircompresser the machine senses mouisture and will not allow the shutter to open. the shutter kind of works like a camera. i do not know much about engraving machines but im sure its the same concept. what kind of laser is it?