Lightobject.com Support Forum

Hi all
I did a comparison of the cooling water temperature and how much power is lost with the change of the temperature on 4 K40 machines.
all this machines are converted to the DSP
the best temperature for max output is between 18.5 degr C ( 66F) and 20.5 degr C ( 70 degr F)
every 1 degr C ( about 3 degr F) brings a loss of 10% of laser power.
for instance I can cut a 5mm ply wood or 6mm poplar at 18.5 degr C with 6mm/s and 40% power
now at at 21 degrC I need to cut the same with 5mm/s and 42 % power
at 23 degr C I already need 3mm/s and the full power of 48%.
above 24degr C I need already two or three passes at 3mm/s and 48% power
it was amazing what did come out.
all the machine tubes have around 500 hour mixed work engraving and cutting on it
I thought I let everybody know this especially that more and more new comer coming in who don't know what to watch for.
greetings
waltfl

Hi waltfl,
It's a very useful info. I tested my machine and same result. So I m thinking that should we put more water or change water in the sink to keep low temperature?
I have been using the tube like 3 hours a day for heavy cutting works. In the first hour, the temperature is ok, but after that the temperature in the sink increases to like 28,29 degr C. Will this temperature affect the tube's life? I have been using the tube for like 3 months and now have seen some decrease in the work quality.
How do you guys keep the water in the sink between 18.5 degr C ( 66F) and 20.5 degr C ( 70 degr F)? by changing it every 30 mins?

Hi there
the water should never go over 26 degr C or you will shorten the life of the tube dramaticly ( some have seen just 300 hours) the most important parts to hold the tube a live is to hold the water temperature below the ,max and the current should never go over 18ma ( that's already the max )if you did drive your tube with more then 25degr C then its normal that the tube loos power and I would recommend that you already looking for a spare tube
I use a 120 x 120 mm evaporator which is inserted in the outlet canal of a AC window unit.
some using the big kind of aquarium cooler or a water chiller like from marco.
greetings
waltfl

shizyo wrote:Hi waltfl,
It's a very useful info. I tested my machine and same result. So I m thinking that should we put more water or change water in the sink to keep low temperature?
I have been using the tube like 3 hours a day for heavy cutting works. In the first hour, the temperature is ok, but after that the temperature in the sink increases to like 28,29 degr C. Will this temperature affect the tube's life? I have been using the tube for like 3 months and now have seen some decrease in the work quality.
How do you guys keep the water in the sink between 18.5 degr C ( 66F) and 20.5 degr C ( 70 degr F)? by changing it every 30 mins?

I'll say it's pretty tough to keep the water under 25c on anything but very small jobs. If it really should never go over 26c then everyone running a k40 with just a couple of gallons of water is in trouble. Are you talking about water temp coming out of the tube? If so then those temps would be VERY hard to achieve without some other means of cooling.

I'm currently getting ready to put one of the small radiators with a fan to keep temps in check. It should be interesting to see if it makes much of a difference.

hi toasty
yes that's the problem what most K40 user don't realize that 25C ( 78F) is the max temperature of the cooling water coming out of the tube what can only be hold with additional means of cooling like ice cubes in the cooling water but only if the ice cube water is from distilled water no other water, or a other kind.
the tube live would be shorten by at least 30 to 50% even with reci tubes.
a small fan like from a computer will not do it even a big cooler system from one of the newer computer will not do it for a bit heavier cutting.
I try a 120mm radiator with a 120mm 120V fan and it would not be enough to do cutting for more then 15 minutes and a break of at least 1 hour.
that's why I now using my window AC where I installed the radiator inside the outlet canal the way that all the AC cooled air has to blow thru the radiator see picture.

greetings
waltfl

Toasty wrote:I'll say it's pretty tough to keep the water under 25c on anything but very small jobs. If it really should never go over 26c then everyone running a k40 with just a couple of gallons of water is in trouble. Are you talking about water temp coming out of the tube? If so then those temps would be VERY hard to achieve without some other means of cooling.

I'm currently getting ready to put one of the small radiators with a fan to keep temps in check. It should be interesting to see if it makes much of a difference.

Wow, I guess I'm doing everything wrong. I've always used distilled water but on the last big cutting job I had I was using normal ice cubes to cool the water from time to time. I do understand that distilled water is better but is putting in a few non-distilled ice cubes going to make that big of a difference?

I guess the one good thing about what I'm doing is that it is mostly engraving (I don't do much cutting normally) at no more than 13% most of the time. The water doesn't seem to get much warmer than where it started at the beginning of the job and that's without any added cooling. I do believe the water pump heats the water up more than the laser does on the engraving jobs I'm doing. In fact, I always turn the pump on and let the water circulated for about 15 minutes before starting the laser. The temp goes up more in that time than it does while engraving with those settings.

I asked this on a different thread but never got a reply... I'm getting ready to set up a small radiator with a 120mm fan on my k40 tomorrow. I assume I should have it in line after the laser tube water output, correct? I didn't think having the pump push the water through the radiator before the tube was a good idea. Any advice would be great.

It is always to use the radiator right After the tube because the temperature is highest and it is easy to tranfer into air. Think about of which one is faster; cooling of 100'C water to room temperature or cooling off 30'C water to to room temperature (25'C)? Or, consider 'non-linear' thermo effect and you should be more clear

Just my through. Correct me if I was wrong

Marco

Hi
OK my experience to this :
according to tongli tube manufacturer
first the water flow should be In to the tube side where the beam exit and return to the other site with a slight slope from IN to return without bringing the tube out of level doing so with twisting the tube
the cooled water should enter the tube because the beam exit site is where the most heat is generated
that's why my setup is from water reservoir the submerged pump min of 5LPM pumps the water in the radiator ( inside the window AC) from there in the tube IN ( beam exit site) runs thru the tube and back in the reservoir.
By the way the temperature difference between IN and return on the tube is by heavy cutting for more then 2 minutes around 5 degr C ( 8 degr F) .
greetings
waltfl

Tech_Marco wrote:It is always to use the radiator right After the tube because the temperature is highest and it is easy to tranfer into air. Think about of which one is faster; cooling of 100'C water to room temperature or cooling off 30'C water to to room temperature (25'C)? Or, consider 'non-linear' thermo effect and you should be more clear

Just my through. Correct me if I was wrong

Marco

Well, I got my new radiator with 120mm fan hooked up and running. Doesn't do much even when the laser isn't running. Like I've said before, I think the water pump is heating the water up more than the laser in my case so the radiator is fighting with that.

My shop is air conditioned but the ac is off when we're not there. So, the water for the laser tends to start at around 25 degrees every day. I was hoping the radiator would at least cool it down a bit before starting the laser. Nope, nada. Maybe one degree after 1/2 hour of running. Not really worth the effort.

I'll have to pick up a more powerful ac powered fan.

Hi toasty
like I said a fan alone is not enough to cool down the water you could use a big peltier element (at least 135W).
my normal starts with 27C the A/C unit need to run for about 30min to bring the water down to 19 C then when the laser is working the
temperature goes up to about 21C during engraving, by cutting it goes up to 23C the cool down time is about 10min.
this all by outside temperature around 32 to 35C.
this A/C solution cost about $120plus radiator. but you need a wall opening to the outside because to use the A/C inside brings nothing .
greetings
waltfl

Toasty wrote:Well, I got my new radiator with 120mm fan hooked up and running. Doesn't do much even when the laser isn't running. Like I've said before, I think the water pump is heating the water up more than the laser in my case so the radiator is fighting with that.

My shop is air conditioned but the ac is off when we're not there. So, the water for the laser tends to start at around 25 degrees every day. I was hoping the radiator would at least cool it down a bit before starting the laser. Nope, nada. Maybe one degree after 1/2 hour of running. Not really worth the effort.

I'll have to pick up a more powerful ac powered fan.

Hmmm, well, I'm going to have to figure something out. I don't have much a problem with engraving but those once in a while cutting jobs are gonna kill my tube if I don't figure out a better way to keep the temps down.

I'm really just shocked at how little that issue is talked about when it comes to the k40. From what I've seen almost no one is running any kind of cooling other than water in a bucket.

The window ac unit idea is great but the shop I have has central air and no windows near the laser so I won't be going that route.

Hi toasty
then the only way is to use a peltier element with a big heatsink from a old computer and use the fan to extract the heat from this and put the radiator on the other side.
yes I am surprised too that most guys don't even watch the temperature I try to tell everybody since years they need to watch the temperature and cool the water, but they also believe that's just mumbo jumbo and then crying if the tube is gone.
greetings
waltfl

Toasty wrote:Hmmm, well, I'm going to have to figure something out. I don't have much a problem with engraving but those once in a while cutting jobs are gonna kill my tube if I don't figure out a better way to keep the temps down.

I'm really just shocked at how little that issue is talked about when it comes to the k40. From what I've seen almost no one is running any kind of cooling other than water in a bucket.

The window ac unit idea is great but the shop I have has central air and no windows near the laser so I won't be going that route.

Or a real chiller but I don't want to go that far with a k40. I plan on getting another (bigger) laser in the near future so I hate to spend that kind of money on the small machine.

It would be interesting to find out the life (hours wise) difference between your tubes and someone like me who has been keeping the water around 25 degrees all the time. I suppose there's no real way of knowing since the quality of these tubes vary so much. I wish I would have put an hour meter on my machine when I built it.

I guess I'll just keep it as cool as I can for now and see how long this tube lasts. I use my machine about 4 hours a day and so far i've notice zero loss in power (knock on wood). I engrave the same items every day with the same power settings so it would be very obvious.

waltfl wrote:Hi toasty
then the only way is to use a peltier element with a big heatsink from a old computer and use the fan to extract the heat from this and put the radiator on the other side.
yes I am surprised too that most guys don't even watch the temperature I try to tell everybody since years they need to watch the temperature and cool the water, but they also believe that's just mumbo jumbo and then crying if the tube is gone.
greetings
waltfl

Toasty wrote:Hmmm, well, I'm going to have to figure something out. I don't have much a problem with engraving but those once in a while cutting jobs are gonna kill my tube if I don't figure out a better way to keep the temps down.

I'm really just shocked at how little that issue is talked about when it comes to the k40. From what I've seen almost no one is running any kind of cooling other than water in a bucket.

The window ac unit idea is great but the shop I have has central air and no windows near the laser so I won't be going that route.

hi toasty
if you just mainly engrave it would not be noticeable much even if the tube has only 30% power left, I use them on one machine where I just engrave and use the new ones on the machine where I do mostly just cutting.
if you wana get a bigger laser then you need a chiller anyway.
greetings
waltfl

Toasty wrote:Or a real chiller but I don't want to go that far with a k40. I plan on getting another (bigger) laser in the near future so I hate to spend that kind of money on the small machine.

It would be interesting to find out the life (hours wise) difference between your tubes and someone like me who has been keeping the water around 25 degrees all the time. I suppose there's no real way of knowing since the quality of these tubes vary so much. I wish I would have put an hour meter on my machine when I built it.

I guess I'll just keep it as cool as I can for now and see how long this tube lasts. I use my machine about 4 hours a day and so far i've notice zero loss in power (knock on wood). I engrave the same items every day with the same power settings so it would be very obvious.

waltfl wrote:Hi toasty
then the only way is to use a peltier element with a big heatsink from a old computer and use the fan to extract the heat from this and put the radiator on the other side.
yes I am surprised too that most guys don't even watch the temperature I try to tell everybody since years they need to watch the temperature and cool the water, but they also believe that's just mumbo jumbo and then crying if the tube is gone.
greetings
waltfl

Toasty wrote:Hmmm, well, I'm going to have to figure something out. I don't have much a problem with engraving but those once in a while cutting jobs are gonna kill my tube if I don't figure out a better way to keep the temps down.

I'm really just shocked at how little that issue is talked about when it comes to the k40. From what I've seen almost no one is running any kind of cooling other than water in a bucket.

The window ac unit idea is great but the shop I have has central air and no windows near the laser so I won't be going that route.

waltfl wrote:hi toasty
if you just mainly engrave it would not be noticeable much even if the tube has only 30% power left, I use them on one machine where I just engrave and use the new ones on the machine where I do mostly just cutting.
if you wana get a bigger laser then you need a chiller anyway.
greetings
waltfl

I do cutting from time to time too. In fact I had to cut around 100 pieces for a job today. I'm still using the same settings on that process too so the tube doesn't seem bad at all right now (again, knock on wood).

I will say that the radiator seemed to help a bit today when I was cutting. It doesn't lower the water temp much from the start but it does seem to hold that temp for a MUCH longer time than without it.

Funny though, I was reading around on Full Spectrum's site looking for water temp discussions. FS doesn't seem to think higher temps (higher than 25 degrees C) are a problem at all. Then again, they sell replacement tubes. lol