[fishface]

I have a cheap 40W CO2 laser engraver that has been working fine until today.

On full power, the ammeter which is in series with the tube, used to show about 15mA when the laser was firing. Now it only shows about 3mA on full power, and the power of the beam produced is in keeping with 3mA.

Immediately before this, I had a little mishap. I was trying to cut some plywood on full power, but I messed up the origins for the work, so the cut actually went off the edge of the plywood. The beam therefore struck the dirty aluminium table that lies about 18mm below the surface of the plywood. Being aluminium, it could quiet possibly have reflected the laser back up through the lenses/mirrors and into the tube.
So I have some questions:
a) Is this possible? Wouldn't the beam passing back the wrong way through the focusing lens, defocus the beam somewhat, so the energy would be dispersed.
b) If this did happen, could it have damaged the tube at all, and if so, how?
b) Are the symptoms of a faulty tube that it no longer draws much current from the PSU?

Any help or advice welcomed!

[Melody-gweike]

It seems the tube is broken.

[Exsecratio]

The chances of getting a beam back scatter all the way to the tube is next to nothing. Beams scatter quite a bit so by the time it gets back to the tube it would have next to no power density left. Aluminium also makes a terrible mirror (dirty aluminium makes a non existent mirror)

The beds of the pin tables I make are aluminium, that doesn't cause any problems

Laser lens focus is both directions (you *can* fit them either way up) so it won't "de-focus" the beam.

It does sound like the tube is on it's way out but *could* also be a faulty power supply.

best wishes

Dave

[epilotdk]

My HV PSU blew when I recently fired the laser at full power during an alignment check. I normally cut at 85% power. Possibly the increase in output was too much for the PSU.

[EXLASer]

Hi ,
Passing back the way through laser tube won't make it broken . As there is a lens on negative /cathod on laser tube , the laser beam will reflect back again even if the beam hit the surface of diffuse reflection objects ,and has little relationship with power from laser tube . But it doesn't means that your laser tube is Well .By the way ,checking the laser beam is as much as what you got before this operation ? any crack inside ...I'm quite agree with Exsecratio on floor 3 ,that psu might got problems . Try to install ammeter in series again , while see it's output current when 100% firing . Normally current value of 40W laser tube should between 15-16mA . Hope you find the point as soon as possible ~ and share the results together !

Best regards,
XYZ Machinery

[fishface]

Thanks everyone for your replies.
It turns out after much investigation, that it was a problem with the power supply. Specifically, one of the wires to the safety interlock connector was not properly connected and the vibration of caused by the laser moving must have been rattling the connector on and off. I fitted a new crimp connector and all is well again. :-)

[EXLASer]

Hi,fishface :

I'm glad to hear that your find the point ! Thanks for the sharing together !:cheers:

XYZ Machinery