RDWorks Learning Lab 40 Laser Output Power v Temperature
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- čas přidán 2. 02. 2016
- If you own a Chinese laser cutter this little series of videos about me learning how to use the free software provided, may solve the problem of trying to learn from a virtually unreadable manual.
I am nothing to do with RD Works, I am not an instructor and I am no expert. This series will document the essential bits of many hours of trial and error - Věda a technologie
One thing that I have seen is there is a clear difference in laser output when my water exceeds 77 degrees Celsius. In accordance to the manufacturers of the tubes, and a number of major laser repair shops I have spoken with, replacing distilled water is as important as cleaning the insides of your laser because you will have degrading quality and accelerated wear and tear of the machine and tube. I was rather surprised to hear you left your water in for the past 6 months!
+NFO Sec
I am slightly surprised myself, but as I mentioned, I do check it regularly. However, if you think about it logically, it was distilled water (not purified by osmosis or deionised) when it went into the system and as you have seen from the video I have a virtually closed system. There is no entry point for atmospheric ingress of spores that would pollute the water over time and make it green or feel slimy from proliferation of bacteria. Everything inside the tube is glass (except a small seam of epoxy around the tube exit window, so where will contamination occur? Fortunately I live in a cool climate which discourages bacterial growth.
As an engineer who works with evidence and facts, I ask how "degraded" water (please define) will have any less heat carrying capacity? What is the mechanism of "accelerated wear and tear" that I should be looking out for in the tube? and more interestingly in the mechanics of the machine itself? Please do not think I am being rude or sarcastic. Far from it. I still have a lot to learn about these little Chinese dragons and if there are evidence based facts to be had then I'm in.
I cannot envisage running a tube at 77C because as I mention in the video the highest recommended running temperature I was able to find was on Reci tubes where 40 max was stated. It's essential for the helium in the gas mix to transfer it's heat to the water jacket and thereby allow the dissociated CO2 to recombine and keep the efficiency of the lasing action steady. I therefore do not find it surprising you are experiencing output reduction at those high temperatures because you are reducing the rate of heat transfer and preventing efficient recombination. From all the reading I have done on the failure mechanisms of sealed CO2 tubes, I have not come across any scientific work on tube life reduction by running at elevated temperatures. However, I do suspect you will accelerate the demise of the tube if this is a regular running condition.
Back finally on the water purity. I occasionally manufacture small amounts of colloidal silver using a current limited generator. The generator runs at max 50v DC. As you will be aware, pure water is an insulator and it's only the impurities and dissolved solids that allow it to conduct current. Starting with pure distilled water when I dip the positive and negative electrodes in the water the voltmeter shows 48 or 49 volts for a few seconds during which time a few particles are stripped off one of the electrode and allows a minute current to flow between them. Because the current is limited to 10mA the process does not run away. And in fact it takes about 10 hours for the water to become "polluted" with 10ppm of dissolved silver at which point the voltage has dropped to 3 or 4 volts. I mention this because it would be a great way to test the condition of my system water.
Thanks again for stimulating lots of thought and I would genuinely be interested in any feed back from manufacturers or laser repair technicians on the subject of running tubes at 77C
Best regards
Russ
Awesome video and information !
Here in the US (Florida in particular) I have to combat heat. But I manage fine using the 3 Gal (11.5 Liter) bucket and using 2 liter soda bottles (3 in a rotating cycle as they thaw) filled and then frozen. Keeps my H2O at a pleasant 75 F (around 25 C). I do not have a meter to measure power output of my 30W but I can say that this system works well in hot and humid environments. I am now very curious about my lasers efficiency after watching several of your videos.
THX again for posting!
Russ I have a suggestion for a no cost water chiller. Use a carbonated soft drink bottle fill it with tap water and freeze it. Place the frozen bottle in the water reservoir whenever you need to. If you are worried about contamination of your distilled water you can place the bottle under your tank or in a ziplock bag.
+Paul Lecomte
Hi Paul
It's a great suggestion that I know several other people use (particularly those in Australia). Living in the UK near London we are not blessed with high temperatures and so for most of the year (especially with my low usage) I do not suffer with overheating issues. Most tubes are recommended to run up to 25C whereas the higher quality ones can run up to 40C. Without resorting to a chiller I have a couple of backup methods that I will investigate this coming summer.
Thanks for the info
Best regards
Russ
Another interesting video! I've just had to do a water change after a strange substance appeared in my tank. I've used de-ionised water. Can only assume something wasn't quite clean!
As ever great video, really interesting to see the performance change in that pattern as usual not what I would have thought! Slightly on subject I noticed when I was running a large design as my machine water temp went up from 8-20oC my mA went slightly down from 24-23 I'm not sure if that's a power supply anomaly. If not perhaps its another aspect in this mystery? Possibly the laser could resist more at different temps. Probably nothing but maybe. When you need more distilled have you thought about contacting anyone with a dehumidifier as its a by-product?
+patrick whelan
Hi Patrick
Good thought about the dehumidifier. We do have a condensing tumble drier which does the same thing and my first tank of water was from that source. Even though it was distilled water, there were traces of softener perfume carried through. When I noticed power issues with my first tube, I was ruling out every possibility and one change was to proper distilled water. I'll use condensate next time I need a water change, but, there's no hint of water degradation at present. My wife always uses the condensate for her steam iron.
Apart from the occasional 65% power reference tests, the machine was otherwise running continuously at 60% power (19mA). That 19mA was constant throughout the two and a half hour test period.. I'm thinking I may buy a cheap washing machine solenoid valve to control the flow of water through a copper cooling coil that I used to keep the temperature right down during the summer when I was trying to isolate my power loss issue. My "return to tank" temperature sensor could then switch my hosepipe flow on and off to keep the temperature levelish as I repeat this test to see if the oscillating power curve still exists. I suspect it will still be there.
Regards
Russ
The argon and krypton lasers I've worked with ran great with regular tap water. I used to think "it needs to be really cold" -- but you don't want condensation forming inside the laser. This can happen just as easily with a CO2 tube. You can use a water/glycol mix (use uncolored glycol), and avoid using anything with "stop leak" in it. Stop leak could potentially plug the small orifices these tubes have, and then you're screwed.
If water is working, there's no need to change it unless you're always worried about cracking the tube.
+pmgodfrey
Normally my tube water runs crystal clear and bubble-free. However, I did notice a gradual increase of minute air bubbles hanging on the inside of the water jacket as the temperature got above 25C. Must be dissolved air forced out by the increased temperature, it almost appeared to result from some sort of cavitation effect because water into the first 2"was clear and it was only after a couple of glass support legs inside the tube that the bubbles began. Interesting ,yes, but I wont normally be running at these temperatures so it's not a concern.
Before i got my machine I already set up a water reservoir in my workshop, as i am in central scotland, we are always colder, fortunately my workshop is very well insulated, and even dropping to closer to -10 outside, no ice forming in the reservoir. I did fall on my ass getting to my workshop though!
I have, however, a remote controlled heater if the temperature does drop now that my machine is in.
+Michael Edmond
We may share an island but fortunately not the weather.
your telling me! The day my machine came (bigger than yours... so huge crate... and a set of stairs to my workshop) it was mid storm... gales.. rain.... snow... and a full sheet of plywood flew past... Whats life without a bit of adventure!
No problem I have posted your link into the group so I hope your rating and views increase. I have a Cnc myself but looking to purchase a laser soon once I have made some space
+Carbon - G10 - FR4 - CNC Routing - 3D Design & Printing - Online Shop
Hi
Thanks for you interest and support. I have to be honest and admit to just doing this learning for fun. I'm naturally inquisitive and selfishly learn about the bits that interest me. Having been sold a 40 watt machine that I thought was going to be 50 watts, I am determined to wring every last ounce of performance out of it. That can only be achieved by understanding the technology. I owned and ran two 3kw metal cutting laser for 10 years but barely 5% of that experience is applicable to these little Chinese dragons. The fact that my other hobby is video allows you to come and look over my shoulder as I muddle through success and mistakes . I'm sure you will enjoy having a laser and along with your CNC routing and 3D printing you will have the complete suite of techno toys
Good luck
Russ
Russ, forgive my whining, BUT, it may be my poor hearing, my ambient noise hearing aids or the voice recording of the video camera . I know no other viewer will agree but might you compare a wireless dynamic mick accessory to your video production.
Also, hope you retain WORLD intellectual property rights to your labs. ron
Hi Ron
I have just received a Sony bluetooth wireless mic system for my productions . Should have been a simple plug and use. Sadly it's non-functional and am currently wrestling with Sony for a repair/replacement. Wll be happening soon.
Russ