A number of you have talked about orientation of water inlet and outlet on the laser tube. My Omtech 60W/50W came from Omtech with both sideways. I have never changed or attempted to change.
I have little problem with bubbles after I have run the machine 1 or 2 days without draining the water. Have always had one tiny bubble at outlet end and have never been able to get rid of it.
Hesitated to loosen clamps and turn it the 1/4 turn it would need to have them on top. I am comfortable with alignment of the beam. Jack has said numerous times to folks that it should be on top. Other than it having that one bubble will that add to deterioration of the tube?
I have always been very nervous about air bubbles in cooling systems. Even though my inlet and outlet of the cooling hoses are positioned correctly, I also have a small bubble at the outlet when I haven’t used the machine for a day or more. I always squeeze the hose 3-4 times until the air bubble is gone.
Why am I afraid of a small air bubble? A few years ago I worked with large engines in a power plant, they ran on natural gas. During routine inspections, we recorded tiny pittings in the cylinders themselves. It was found that shaping the cylinder heads caused gas pockets, these bubbles exploded due to pressure and temperature. In the end we had all the pistons and cylinder and cylinder heads replaced, 2X12 pcs.
Cavitation on one of the cylinders, that is the “outer side” or the side that is in contact with coolant.
Here the damned air bubbles could accumulate and explode.
Our air bubbles in the laser tube probably won’t explode 
but who knows if they won’t get heated anyway, and I avoid this risk by always checking and squeezing the water hose for air.
I have a spreadsheet with the power versus mA, from day 1.
At regular intervals I write down instantaneous values, so I catch in good time when the tube starts to weaken.
When I had the other coolant in mine, it pumped tiny bubbles all the time…
I’ve gone with the OMTech coolant to see how it works out…
The problem with bubbles is you don’t want them to ‘stick’ to the wall next to the lasing gasses. If they are sticking, they will allow the glass to collect heat that should have been picked up by the coolant. This can cause the tube to break as a small spot gets too hot…
When I changed out the coolant, I removed my tube and tilted it to clean out the previous coolant…
I checked the alignment and it’s still on… so moving the tube around didn’t disrupt the alignment…
I have a tube holder by Russ Sadler…
@ferg don’t be afraid of rotating your tube… Alignments should not be a real issue…
Good luck
That Omtech coolant should work, I seen their price for it plus shipping. Wonder how close it is to engine coolant, no I am not going to try that. lol
I will give the tube that quarter turn and see what happens…
gurgle—gurgle!
Merry Christmas to you and your family Jack!
There is a major difference between standard engine antifreeze and one designed as a coolant for tubes and motors.
The biggest problem with normal antifreeze is that it conducts. There is multiple reports of a hv discharging via the coolant from the anode. This makes everything conductive ‘touching’ the coolant at the hv potential… not a good thing…
I ran distilled water with Propylene Glycol at 50% and that’s supposed to be good to 15F… It’s thick and slowed the coolant flow rate by 50%… Ran with that for over a year…
Propylene Glycol mixture also generated bubbles, fine bubbles, but bubbles… here’s a video I took since I was concerned…
Thought I’d try OMTech coolant, although I don’t like using toxic chemistry, Ethylene Glycol, if I can help it…
I’d buy this if it was reasonably priced here in the US…
Although based on Ethylene Glycol, Laserscript CoolFlow has been tested and classified as Non Toxic by an EPA certified laboratory. Previously Propylene Glycol was the only non toxic glycol available, that is no longer the case. The DeTox® additive. DeTox® prevents Ethylene Glycol from being metabolised (during digestion) into toxic by-products, which cause kidney failure, blindness and death. Tests carried out on CoolFlow confirmed the toxicity was “so low that it was impossible to determine an LD50 value”.
Most people don’t know what ‘rating’ the LD50 represents… It’s the “Lethal Dose at 50%” or 1/2 the lethal dose. It usually results in severe organ damage and other not good health problems …
Take care…
Hope you and yours have a wonderful Christmas …