"micro" air bubbles in laser tube

[Mark Malley]

Hi All

First newbie question (probably the first of many)

I have just got a little K40 laser and I am just setting up

I have little "micro" bubbles of air in my tube (like fizzy pop) do these matter and if so how do I get rid of them

I have got rid of all big bubbles By the following.

1. making sure the water inlet and outlet are at the highest part of the tube,
2. lifting one end of the machine
3. pinching the inlet tube

(All with the machine disconnected of course apart from the water pump)

But I cannot seem to get rid of these micro bubbles any ideas anyone

Best Regards Mark

[Gene Uselman]

No worries- the will slowly disappear [or you won't notice them].

[Dave Vigness]

I've been told that the bubbles are mainly a concern if you're not using distilled water. The gasses let the water break down in the heat / light of the tube causing scaling. Not a major concern, one of the tube manufacturers even has the instructions on their web site for removing it if you're not using distilled. Just run a 20% hydrochloric solution though to clean it. Like using white vinegar to clean your shower head.

I've gotten that second hand, so take it with a few grains of salt. I used RV Anti-Freeze in mine until I got a tank heater / pump setup in place, then switched to distilled.

My current setup keeps the water and tube at a nice toasty 65 degrees most of the time. We had a night that got down to -10 the other night and the tank temp dropped to 40 but the tube return was 48. Have a feeling my probe is on the bottom and the tank un-insulated. Just one of those little things I didn't do with all my upgrades / mods.

[Tim Mellor]

Some of it will be down to dissolved Oxygen in the Water which is what Dave V alluded to. Water tends ALWAYS toward a less than pure state which includes taking in suspended Oxygen to a greater or lesser degree depending on other factors. In the case of the Laser the water is only a cooling medium and it just doesn't matter providing the inner tube that generates the heat is surrounded by water that has continual flow over it to remove the energy (heated water) elsewhere.

The reasons to use Demineralised or Distilled water is to reduce bug/algae growth no more and no less. Internal slime on the tube will reduce cooling efficiency and obviously it can't be scrubbed mechanically so it will be hard to remove. Adding any other chemicals should be considered as algae treatments or in the case of you frozen mob Glycol type of options to stop the tube freezing and shattering due to expansion.

Get rid of as many larger air voids as you can by by lifting one end of the K40 (don't try this with 300kg of laser ) and running the pump only and over time the remaining bubbles will settle down to a natural more steady state in use.

[Dave Vigness]

My cooling water mix I pick up from one of the many hundreds of web sites I wandered when I first got my laser.

5 Gallons of water
5 drop of Tetra Algae control
5 drops of dish soap. Dawn was recommended for some reason but I can't say why, and it happens to be the brand we use.

I have my cooling water in a tote under the laser. Nice and close for my temp probes and it keeps it out of the way but moves with the laser if I pull it out away from the wall. Something that's happening a lot with all the upgrades and mods right now.

FYI - Russ hung his compressor to cut the noise. I went the other way and took a square of that super soft, crumbles all over the place in 1/4" balls, styrofoam that was shipped around the laser and set the pump on it. It's vibrated it's own mold into the foam, but it's quiet!

[Mark Malley]

Thanks to all of you for your help on this

Gene Uselman you were spot on. I left the pump on overnight with the water output side of the machine raised a little and all of my bubbles have gone.

When I filled the tank I poured the distilled water from a big carboy straight into the tank fairly fast (only way I could do it that carboy was heavy 25L of water = 25Kg if I still remember the physics right)

In doing so I think I aerated the water leading to my bubbles.

I am being hyper cautious at the moment because:

a) I'm new to this and don't want to make too many costly mistakes, (I'll make a few for sure, everyone does with these Chinese machines)

b) These tubes seem to be pretty delicate, touchy, things at the best of times and I would like to get at least some life out of the original before I upgrade to a "proper" tube.

I have already done my first machine "upgrades" A pair of good quality certified laser glasses of the right wavelength for CO2, and a CO2 fire extinguisher (suitable for electrical fires). I hope neither of them have to "fire a shot in anger"

I have checked the earthing which in my case was fine (0 Ohms from chassis to plug top) and will give all the connections a check before actually switching the "contraption" on.

I won't have the notorious fan connection issue as mine is slightly better model than some with an integrated axial fan.

Next step is beam alignment. I have done this before many times but with visible lasers that couldn't burn you and on thousands of pounds worth of optical bench. This is a little different.

IF I can get it aligned enough to actually cut I will be making one of Russ Sadler's red laser alignment pointers (probably as a first job.)

Best Regards Mark

[Dave Vigness]

Mark,

Your FIRST upgrade should be a Ma meter, followed closely by a temp gauge. The digital aquarium gauges work perfectly, and a dual will let you check main tank temp vs tube return temp.

The advertised, or max working current, is NOT your operating current. I discovered that the hard way as I was cutting before I found Russ' videos and this forum. My tube max is 28Ma, and I erroneously thought the manufacturer would set the machine up so it couldn't go beyond it normal operating parameters without me fiddling with things so I didn't bother with a Ma meter right away. Just cutting away at 100%.

WRONG WRONG WRONG !!!

My only saving grace was the in line flow switch failing and taking out the tube before it died on it's own. The manufacturer is sending a replacement laser tube as we speak. Several hundred dollars out of my pocket saved. If you get the chance, pull the in line switch and replace it with a pressure switch on a T. My particular in line switch reduced my coolant flow buy almost 50% ! I got mine at light object, a whopping $7.50. The connection was a bit weird, but then you'll get used to that with the chinese lasers. Email if you want the secret installation technique... LOL

My operating current on my 80W is 24Ma, equating to 62% power on my current controller. NOTE: The percentage is controller / power supply specific and varies from machine to machine. The current is tube specific but pretty close for most tubes. I think Russ runs his 60W at 22Ma.

I did make one improvement to Russ' cooling return line probe setup. I took an old 3/4" poly fitting and drilled the appropriate size hole for the temp probe in at an angle. It keeps the end of the tube from going where it wants to, and makes sure the water flow over the probe is 100% return line for accurate temp measurement.



If you're lucky enough to have one like mine ( NOT ) and can't get standard lens tubes, Russ makes adapter tubes reasonable. You'll also want to get his Dhicky for power tests to see just where your maximum power / percentage is. Both are very reasonable and the Dohicky is almost a necessity if you don't have access to a high dollar calorimeter. Drop him an email with your results, best three out of five for each reading, and he'll return your power curve between his other projects.

If you ever have to put a new tube in, seriously consider a SPT TR tube. It has the red dot integrated into the tube. I did my best to try and talk the manufacturer into that tube for a replacement, but no joy.

HINT: If there is anybody out there in the market for a new in the box EFR F2 80W, I'd consider a nice deal.

[Mark Malley]

Hi Dave

I have had a mA Meter on order since before I got the laser and it has just arrived from China. It actually arrived earlier than expected which is pretty good going with this Norovirus outbreak crippling china.

Like you I considered this essential as my machine is one of those digital display ones. I am running it at 15% indicated power to setup the optics which should be low enough not to overdrive the tube or anything but well powerful enough to pop a few holes in some masking tape.

At some later date I may change the whole panel and use the Ten turn pot and voltmeter method I've seen on the net. whilst The figures on the voltmeter don't mean much in themselves I can sort of calibrate it using the ammeter as a reference and even possibly put a voltage divider in the voltmeter circuit so I can set it to be similar to the ammeter.

What is the max safe mA for a standard K40 tube I've read various levels some say 12mA some 15mA and some 18mA.

I have my water pump on a separate supply from a switched power block not plugged into the back of the laser so I can't accidentally forget to switch the pump on (I also don't trust those horrible sockets on the back.)

My Machine claims to have a water flow switch in it to disable the laser if there is no water flow but I haven't actually checked it yet.

I am working on an Arduino project with 3 DS 18B20 temp sensors (Tank, Inlet and outlet) a hall effect flowmeter and a relay for the laser circuit.

But for now It's got to be mark 1 eyeball with laser goggles attached and a thermometer.

I have just started the mirror alignment and I will report progress or lack of in another thread

Once I have the mirrors set up and can actually use the thing I will invest in a dohicky I think Russ has come up with a clever idea there

Best Regards Mark

[Dave Vigness]

Your percentage on the control panel is completely arbitrarily... BUT !

You can safely run at 50% without worry. Most of the controllers seem to be at optimal wattage around the 60 to 65% from what I've read. The only exception would be if they oversized your laser power supply, and I don't see them doing that for free. My particular unit hits it's max 80W at 62%. That will change when I finally get my controller changed from a Top Wisdom to the RuiDa... or it could stay right where it was. Can you say Dohicky time?

I'm assuming you know to put your meter in the little wire coming off the mirror end and not in the big red wire... LOL I did something different with my analog / digital setup. I'm in the process of making an extension for my cabinet at the control panel, the RuiDa controller is too wide so it was a must do.

That being the case, I kinda went a bit wild on my electrical changes.

I had an unused switch ( Literally just filling a hole ! ) on the front along with my red dot and the lid switch over ride. I had three of those 'universal' outlets on the back for plugging in the air pump, exhaust blower, and water pump.

LET THE FUN BEGIN!

I preface this by saying my laser is in an unheated structure, so the pump / heater are not a generic change if you don't have that problem.

The back three universals became three duplex outlets, with two of them split. The top one is split between the Air Pump and the Exhaust Blower. The center one is split between a regular Aux that switches with the main power for my goose neck lamp, and an always on that connects in right at the power cord for the tank heater. The lower on is all one for the pump and the power for the temp gauge. If you don't need to have the heat for the winter you could eliminate the center split plug and leave the bottom one switched with the main power.

My high dollar tank heater is a birdbath heater. 50W keeps the 5 gal tank at a nice toasty 50 - 60 F all winter long.

So back to those three switch holes in the front angle. Since the blower takes a bit over the 10A the switch was rated for on start up, I took the lighted 15A breaker switch from a power strip and put it there, then the SPST switch for the Air Pump, followed by a SPDT switch for the water pump. In the winter the pump and temp gauge power are on regardless of the maser switch, in the summer they switch with the master switch. The SPDT selects the power source before or after the master.

On the panel extension, I extended it back for several things.

First off was for the analog Ma gauge, but instead of also mounting a digital gauge, I put a DPDT switch and then two posts on the end of the enclosure to connect my meter to when I need the digital. The red dot switch and the added Air Assist over ride are up there along with the dual digital temp gauge. Oh, and an extended LED for my water protect since I had a tube eat itself from bad cooling.

Speaking of cooling. Follow your input hose all the way. If you have an inline switch, get rid of it! Get a pressure switch on a T. My inline switch reduced my coolant flow by half! I had flow, but any serious cutting over heated the tube enough that I have to replace it six month in. If you had a lazy factory worker, he probably left the extra cooling tube wrapped around the tube.. that adds flow resistance. It would be a good time to trim that back as well.

Not sure what your working Ma will be, that's a part of what you find out with the Dohicky. It will tell you where you hit your normal cutting wattage. NOT your max wattage. Example - my 80W tube should max out at 95W. But at 95W it will eat itself. Hence running at 62% not 100% I only know the 62%, because my Dohicky told me I hit the 80W at 62%. The advertised Ma is just that, advertised. Stay two or three percent below where you think that will be until you can test wattage.

So now that I've scared the hell out of you, go enjoy your laser!

[Mark Malley]

Hi Dave

Sounds like you are doing almost a complete rewire !

But that's the thing with these Chinese machines they are sort of working test beds they almost never work perfectly out of the box. As a lifelong tweaker and customizer (professionally sometimes) I'm in my element. Not many people run them completely "stock" especially the smaller ones. They cry out for mods and upgrades. I've seen K40s on the net whose only original component is the casing and then highly modified.

I heed your warning about the ammeter it's definitely going in the LV (black side) that red wire is not Insulated so thickly for nothing,

I will probably not need to heat my laser as it is actually in my lounge along with one of my 3D printers, several computers and my audio recording gear.
(Yes I do live alone but open to offers from technically minded ladies who don't mind sharing with my "Metal Harem")

I will have a look at the pressure switch before I start doing any "real work" It will be replaced by a proper flowmeter shortly (when I've finished the Arduino project it's not far off now) and I must do something about where the hoses enter the cabinet. There are no bulkhead connectors on mine just holes and the tubes are so soft they tend to flatten. I've seen "spiroband" cable tidy used so I might try that.

I have hit a Snag with the Mirrors at the moment my beam is hitting the 1st mirror too high. It's described in another thread so I won't go into detail here but I'm not sure whether to lower the tube, raise the mirror or simply ignore it.

I've just printed a duct so that I can hang the end of the exhaust out of the window without crushing the flexible pipe and the laser does actually fire (got the burnt masking tape to prove it) so I'm on my way. Hopefully I will be cutting weird shapes out of acrylic very soon.

Best Regards Mark