Cooling a Laser Tube Part 2
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- čas přidán 24. 09. 2023
- In a previous session I examined the performance of the CW5200 industrial chiller that is widely accepted as a laser industry standard solution for cooling tubes of more than 100 watts. I proved that changhing the selected water temperature makes a HUGE difference to the cooling performance of the unit.
This session aims to disprove the many fantasies about what MIGHT happen if you raise or lower the temperature setting from the recommended 20 degrees C.. Will the tube grow or shrink thus affecting the power output? Will the glass crack because of thermal stresses? Is the tube manufacture's flow rate credible? Is the pink ionized beam over 1000 degres C? Will the intenal mirrors become unglued and fall off by running at high temperatures? Etc. etc.
It's amazing the myths that eminate from one simple manufacturer's temperature recomendation. What evidence did he gather to support this recomendation? - Věda a technologie
YOU SIR ARE A BLESSING TO THIS WORLD!! Seriously amazing work
The beams into the acrylic really helped me visualize what is happening. Thank you for putting this together
Thank you!
Love my CW5200 chiller…1.38amps/120.8v at idle, 4.4 amps under load…….ambient temp here in coastal SoCal avg 77F/25C and peak at 90F/32C😎
Youre on a whole different level of tinkerer my friend lol, much respect.
Really looking forward to your mini chiller setup as i am looking into a better method of cooling my co2 tube. Thanks for all the great informative video's you've allready made!
Hi
I already have all the mini chiller kit but other projects have pushed this down the queue. It will resurface soom. Thanks for the interst
@@SarbarMultimedia dear Russ. Are you familiar with the cooling off the tube with a portable ice machine. That's the way I am doing it right now but it's pretty inefficient. Do you thought about or thinking it be possible to convert one of those machines to a cw5000 style machine by dropping the cooling element directly into the water. The only thing that then needs controlling is the switch that switches the refrigeration.( I can't come up with the name right now). Pretty curious what you think of it because I think it's pretty close to whst you are planning to do with youre mini chiller machine. Best Regards Frank vE
@@vemusicworks
Hi All refrigeration systems rely on a heat transfer medium. That is always a substance that when you com[press it, changes from a gaseous state to a lquid. It requires lots of energy to achieve that change so the compressor supplies the enegy to achieve liquification. You can run that liqid through a cooling coil and just like water in a kettle nothing happens until you supply heat energy to whereupn it boils and chnges back to a gaseous state. So if you dip your cooling coil it into warm water it sucks the energystoored in the warm water in it's atempt to turn back into a gas. Hence the cooling effect. I suspect your cooling coil will have fins of some sort to suck in heat from the surrounding air/water.. Even a 150 watt tube does not require much heat transfer to remain at a steady temperature BUT it does mean that the system may be permenantly ON to balance the heating effect of your tube at ful power. The CW5000 has so much cooling power that it over cools and then swithces off. It is that dramatic overcooling capability that make s the CW5000 unsuitable for laser machines in its raw form. Allow the CW5000 to control the tempertature in a secondary reservoir that pumps water around your tube and the problem is solved. Howver, I suspect you do not have a chiller and want to create a neat low power workaround with a different and cheaper refrigeration unit. I see no issues in principle to what you are proposing because you will be controlling the temperatue of a remote reservoir with a submerged pump. Just make sure that the return water flows direcrly over the ccooling coil for maximum cooling effect. Also the bigger you can make the remote reservoir the more stable you will be able to maintain the temperature. Just like a 3kw kettle , if you put a cup of water in it, then boiling will occur in a minte of so , but fill it with 2 or 3 pints and its takes 10 minutes..As a guide, a laser tube creayes 2 or 3 times its rated output so a 150 watt tube has between 300 and 400 watts heating effect.
@@SarbarMultimedia Thank you for the detailed answer. I am currently running a mini ice machine as my cooling solution. In the future i will "convert" this machine to a cw5200 style chiller. I believe it will be a more efficient way of cooling then how it is running now. Thanks again for the many videos you have made, it is almost an online studying guide in co2 lasers. Cheers!
A fluorescent light tube also has ionized gas in it and also doesn't get very hot to the touch. As fgbhrl4907 mentions, there is very little mass involved thus there is a significant insulating effect. Also i believe heat concentrates at the mirrors more than along the rest of the tube. Thanks for another informative video!
That is a good way to solve the beam divergence problem on large laser beds... Just bring the tube with you as you travel down bed!
That was great and I liked seeing the carpet cutting machine
To the "thousands of degrees C myth" -- the ionized gas is at that temperature. But the gas pressure in that tube is peanuts -- it's about 0.2% of atmospheric pressure. So the number of ionized atoms buzzing around at that temperature is very small, especially in relation to the density of the water surrounding it. Water is ~1000 times denser than air, so our 0.2% near vacuum is 500,000 times less dense than the water.
You can take a simpler approach to calculating the required cooler power. Knowing the efficiency of the CO2 laser (15-20%)
If at the output of your laser tube the radiation power is 65 W, then approximately 350 W of energy is supplied to it, 65 W comes out in the form of radiation, the rest 285 W turns into heat. So you need a cooler that can compensate for these 285 Watts.
Fantastic as always Russ! Really interesting to see your friends machine, i think a similar set up would help me in a similar business for sewing patterns, does he have a VLOG of building it?
Hmmm....I have never asked the question. He had built the MK1 machine and asked me to help him get it running. What you see in this video is signifiantly different to what he originally built because although it moved around it was a bit like a CNC jelly.
Look at the compliments slip and email him for yourself. I think there wa some sort of video record but how much I cant say.
Also, perhaps people have stripes on their engraving when they turn on the cooler compressor due to a voltage drop when the compressor is turned on, this voltage drop is associated with the inrush current. In this case, the laser radiation power. may fall briefly.
Hi Anton
This has been suggested several times before , that is why I waited several seconds after the compressor started before carrying out the mode burn test during the cooling phase. A monmentary change of current would not produce the results you can see for yourself. and I did show the 2 second effect on current draw as the compressor kicked in.. That momentary power loss would be present at 10deg C running temperature as well as at 30C. I had previously tried checking power loss during cooling and detected nothing. As I supected, the average power does not change only the distribution of I|NTENSITY| within the beam if the cooling is rapid. At lower CW5200 settings the cooling is much "gentler" and there seems to be no effect on the intensity distribution,.
I will be investigating further when I run the new micro chiller.
Thanks for the thoughts. This has been a bit of a puzzle for several years because I have no need for a refrigerated system and thus not been able to investigate.
110v vs 220v
I believe alot of problems are result of dirty power. I run a 220v machine and have zero issues. Also remember most these machines are designed with 220v in mind. And then when converted to 110v they still retain the same wires.
People complain that lightburn drops files. I find they are usually on 110v.
The chiller is a small ac unit. The power draw spikes when it turns on. And then levels out at the 1amp once runing. Even firing the laser is going to have a spike.
Now if engraving very low that powersupply and therein the laser will be sensitive to power spikes or drops.
Rus, is there a way you can test the banding issue on photo engravings is or is not from compressors or chillers kicking in and causing a current drop, this is the largest myth about
Hi Sadly thr chiller has now been returned but you can see cocrete evidnec of the banding from a corresponent at 20:16 in this video czcams.com/video/uH0kYBsqIlM/video.html
The banding is far too wide to be an instant power kick problem.. My goal was not to prove the banding exists but to deterime likely causes for it. The only cause I could identify was the change of intensity distribution associated with rapid cooling. This affects the way that the lens focuses power, although it does not affect the total power. The difference my seem subtle but the effect can be significant if you look at the way cutting performance (for the same power) is affected by beam intensity distribution in this video. czcams.com/video/v7-VArJbJTs/video.html
@@SarbarMultimedia So maybe for these smaller watt machines a cw3000 is a better option Russ as most of these smaller watt mackines are targeted and used for engraving plus cutting. My 80watt i do alot of cutting 3mm acrylics but also a tonne of engraving, not running a chiller at all atm just 30L bucket and pond pump.
@@makesbyryandean
Hi Ryan
As you can see from my results the amount of heat output from the tube that is carried away by water flow is not very high.
I guess if you have n electric kettle it will hold maybe 2l of water but it has a 3000 watt heating effect going into the water, it will take about 4.5minutes to boil. If your kettle,could hold 30l then it would takemabout 65 mutes to boil. The point is that the greater the voulme of water in your "bucket" the slower it will heat up.. The fact that you have so little heat trying to heat this volume meand it will heat up VERY slowly.....in general. However in summer months when the air temperature is maybe 30C or more then the air will have a heating effect INTO your water also. AS I have demonstrated in this video , there is no loss of power just because yuor tube runs at 40C. For many yearsb I ran a 70 watt tube with a 12l reservoir and pond pump with zero problems.. In reality a CW3000 is just a fancy integrated version of the pond pump and bucket but with the addition of a fan blowing on the bucket (slight over simplification). A CW3000 is marginally more efficient but when the air temperature is high it does exactly the same to the water, it adds heat rather than extract it. but it has only a 5l reservoir.
Basically you have a cost effective cooling system so don't change it. Just invest in half a dozen "ice packs" that you can stick in your freezer and drop them into your bucket on the hot days.
MY two CW3000 70watt machines have never suffered from the banding effect that CW5000 users experience.
@@SarbarMultimedia thanks for the reply there Russ, appreciate what you do and the knowledge you're passing on. From a fellow tinkerer Melbourne Australia.
the loss of power of the laser beam is notice after 30 ºC, the machine starts not drilling the 9mm MDF, it happened to me
If the temperature is stable above 30C the beam does not change its intensity distribution or power. The more you go above 30C with a CW5200 chiller the more rapidly cooling occurs. It is the rapidity of cooling, not the temperature that causes loss of power. I have run tubes at 45C (no chiller)and yes, I have detected a 5% power loss. However, did not check the beam intensty profile at that temperature, so it may have resulted in reduced cutting ability.