The dreaded bubbles. (Sorted)

[CNCBob]

Hi all

I have just bought a 6840, I think it a nicely made machine run by a clunky bit of software, so I draw my CAD
In Vectric Aspire which I use for my CNC router and then export the DXF to Lasercut.

My Big problem is bubbles in the tube, I managed to cut a few small engraving jobs, all was fine, over Christmas
I tried to do some trial cuts, I checked the laser tube first but it was full of bubbles, whatever I did they came back.

Squeezed the feed tubes ( I now have a proficiency cert for milking a laser )

De-ionizer water
Mains water
Mains feed
Leaving the pump running 24 hours
Reduced the feed on the water pump to cutout any cavitation
Tried a higher feed pump
Raised one end of the machine thinking that a bit of gravity might help
I did try to blow out the water by mouth but there was extreme resistance, either there is a blockage
or some sort of valve that is restricting the flow.


So far it is an expensive door stop, can anyone help as the guys at HPC are still on holiday, I do not want
to chance it in case I might damage the tube

Regards

Bob

[Daven]

Hi Bob,

I think there would be a flow control valve on the 6840 but if that was restricted it would stop the tube from working. It may be worth checking it is clean and letting enough water through.

Bubbles near the mirrors are the ones to worry about but I would try draining the system and slowly filling with de-ironised water. Mains would have a lot of oxygen where as de-ironised that has been standing a bit longer won't.

I use two pumps - one for the chiller and one for the laser, I suspect that this helps as the water has not been agitated by the chiller directly before the tube and any bubbles can escape into the tank.

Best

Dave

[Spooky]

Hi Bob,

Is the exit end of the tube under water on it's return back to the tank?

Ideally it should be below the level of the outlet from the machine.

Failing that are all the hoses tight? it sounds like a bleed in of air on the inbound side as cavitation bubbles tend to be very small.

Orientation of the tube is also important to minimise bubbles forming in the mirror chamber, small pin bubbles in the tube aren't at all unusual and "usually" won't do any harm but as Dave said the mirror chamber is critical. That gets too hot and ping, new tube time.

best wishes

Dave

[ncamacho2000]

Hi Bob

I have a 6040 and have recently have problems with bubbles damaging the tube, the end of the laser tube fell off after the mirror. Luckily i was able to glue it back on and it has worked. I tried a few things that now help.

Use di ionised water only
Ensure the pump is completely submerged under the water
Run the pump for 10 mins before use
Check your tubes are tight around the ends
Keep the pressure up on the pump
Use a drop of milton to get rid of the tiny bubbles
Give the tubes a squeeze, especially the last two that run to the end before laser is used


Im not sure if there is a valve on the laser but would be interested to know if there is, i always find small bubbles in my tube but the longer i run the machine and keep the pressure in the tube the more they disappear. I have also heard that running the pump all the time will keep it clear, however, im too tight to use the electricity and i think the pump warms up the water.

Finally its the big bubbles that don't move you need to worry about, these stop water getting to that area of the tube and it gets over heated.

Hope this helps

Nige

[CNCBob]

Hi Bob,

I think there would be a flow control valve on the 6840 but if that was restricted it would stop the tube from working. It may be worth checking it is clean and letting enough water through.

Bubbles near the mirrors are the ones to worry about but I would try draining the system and slowly filling with de-ironised water. Mains would have a lot of oxygen where as de-ironised that has been standing a bit longer won't.

Dave

There is a valve, I checked that for blockage and sticking, but it was OK.

Hi Bob,

Is the exit end of the tube under water on it's return back to the tank?

Ideally it should be below the level of the outlet from the machine.

Failing that are all the hoses tight? it sounds like a bleed in of air on the inbound side as cavitation bubbles

best wishes

Dave

The return tube is under water and at floor level, all the hoses look tight enough, my worry is all those small bubbles making a large bubble. My thought was cavitation bubbles, I did reduce the pump flow , but it had no effect, the only
Other place is the non-return valve, but I have no way of testing that.

Hi Bob


Use di ionised water only
Ensure the pump is completely submerged under the water
Run the pump for 10 mins before use
Check your tubes are tight around the ends
Keep the pressure up on the pump
Use a drop of milton to get rid of the tiny bubbles
Give the tubes a squeeze, especially the last two that run to the end before laser

Nige

I have filled it with de-ionizer water from day one , on the second day I added Milton. The pump is submerged and running 24 hours a day to see if it clears but I still have what I think is too many small bubbles, squeezing the end tubes helps but they are still all along the tube.

Thanks for all your suggestions, I will go over everything again till HPC open in the New Year.


Many thanks

Bob

[PhillyDee]

I would flush it through, and use pure deionised, just in case its the milton.

The exit part of the tube is flow restrictive.

[CNCBob]

I would flush it through, and use pure deionised, just in case its the milton.

The exit part of the tube is flow restrictive.

I will give it a try

[Spooky]

Hiya Bob,

Tiny bubbles are quite normal in the main body of the tube, cavitation is a problem in the marine industry that has yet to be solved so it's affect on lasers is likely a few years off of being sorted

It's all about the mirror chamber and lens cooler, if they get a large bubble (6mm upwards) it's going to kill the tube pretty quick. Good tube orientation will sort most of the problem, just ensure there is no "captive pocket" in the top of the mirror chamber..

best wishes

Dave

[avalonman]

I had a bubble problem that sounds the same.

I solved mine by lifting the machine about 2 degrees on the side where the water exits the tube, it might help

[CNCBob]

I had a bubble problem that sounds the same.

I solved mine by lifting the machine about 2 degrees on the side where the water exits the tube, it might help

Thank you, but I have done that.