Water cooled laser engraver help

Hi, I know this is somewhat off topic but OC is where the DIY water cooling knowledge is.

I have a Chinese built water cooled laser engraving machine which has specs that require the water in the reservior (a 25 litre plastic container) below 26 deg C. A small submersible pond pump circulates water through a glass jacket surrounding the laser tube to cool it and back into the reservoir. After a few hours use the water temp rises close and sometimes above 30 deg C. The pump pumps about 6 liters per minute through the tubing as it is set up. Haven't really measured it, that's an estimate.

My question is, what do you think is the best system to use to keep the water 4 degrees cooler than it gets to now? It doesn't seem like much but I don't know. I am restrained as to how far I can run the tubes (about 1/4" ID) because the manufacturer says the flow rate will fall off.

Also, there is a large commercial (noisy) extractror fan unit that pulls fumes from the back of the machine through a 6" dia plastic pipe at quite a high rate. I was hoping that this airflow that exits through the exterior wall could be used for cooling too.

The problem I may have with evaporative coolers I've seen on some posts is that they raise the humidity level which is not good for the machine, although I could exit the humid air out the wall. I know they are more efficient because of the latent energy and the change of state from liquid to gas. A closed loop system seems to require less maintenance but is less efficient it seems and restricts flow more. By the way, I am required to change the water every 16 hours of machine time anyway.

I just don't want to go out and buy an expensive industrial water chilling unit that is expensive and uses huge amounts of energy if I can help it for such a small change in temp.

Any direction or suggestions are welcomed. Thanks in advance for your input and I apologize if this post has no computer content. (It does have heat and water cooling though )

David

Is it possible to get pics of the current cooling setup?

Since you're not sure about the current pumps performance, I'd say replace it. You could use a submersible Eheim pump, or put a Laing D5 in series.

To cool the liquid use a radiator (eg. Swiftech MCR120) or heatercore.

What temperature is the air that goes through the extractor? If it's ambient temp then you could use that fan to cool a radiator/heatercore, if it's extracting warm air you'd be better off using a seperate fan.

Evaporative 'bong' coolers are excellent, but I dont think they're suitable in your situation.

Clockwork_Apple said:

Is it possible to get pics of the current cooling setup?

Since you're not sure about the current pumps performance, I'd say replace it. You could use a submersible Eheim pump, or put a Laing D5 in series.

To cool the liquid use a radiator (eg. Swiftech MCR120) or heatercore.

What temperature is the air that goes through the extractor? If it's ambient temp then you could use that fan to cool a radiator/heatercore, if it's extracting warm air you'd be better off using a seperate fan.

Evaporative 'bong' coolers are excellent, but I dont think they're suitable in your situation.

Click to expand...

I'm away from the machine for the next 10 days or so so pics are difficult but I can explain. The reservior is a 40cm dia by 60cm approx. plastic container into which the submersible pump sits powered by 220V. The feed tube exits out the top of the reservior connects to a flow detector in the machine and then enters the water jacket of the laser tube about a 2m run. The cooling jacket is intergral to the glass laser tube which is about 110cm long. A return tube rom the laser jacket follows the same route back returning the "hot" water back to the reservior.

The extractor is a metal fan box with a 15cm plastic vent tube from the back of the laser enclosure in one side and 15cm exhaust tube exiting out the other side which exits through the wall. The exhaust air is ambient temp. because it only removes fumes and smoke. very little heat if any heat builds up due to the laser.

I could construct an acrylic box with two chambers linked by the radiator and feed the exhaust air in one side and out the other before it exits through the wall. The exit water hose would connect to the rad and then out into the reservoir. I was also thinking of adding alum. fins to the reserivoir and blowing a fan on it. Seems primative, do you think it would work with a pastic container?

You could get a plastic 55 or so gallon barrel and fill it with water and pump from it. It would take a long time for the water to warm up, throw a couple bags of ice in the barrel before you start. One issue is you say you need lower than 26C water. That means your ambient water needs to be less than 26C, your work area needs to be below that all the time. A rad and fan will not cool the water lower than ambient, ever. Methinks you'll need a refrigeration unit to cool the water. How many watts of heat does the laser give out?

You need to cool below 26C which is close to most home/workshop ambient temps. Depending on the size of your initial res, the time you run the machine, how many watts of heat you need to dissipate will determine your chiller setup. I just don't think a radiator and fans will keep the water below your requirements.

We use compressors with radiators to chill the water at work to about 16C. The compressor is about the size of a large watermelon and I'm sure is in the $1000+, not counting the lines, radiator, motor starter, temp control circutry. It runs on 3 phase 480, not found in many homes. I'm sure there are smaller self contained units that run on 2 phase 220.

Evapo coolers work great, but a few considerations. You must have less than 40% humidity air to get any effective cooling. At 20% humidity, you will see an air temp drop of 20F, and SOME drop in the water temp. You could use that cooled water but it usually has high solids and contemenants from the cooling pads, which will cause scale build up inside the hoses, particles, etc. You could use the cooler air and pump it through a rad, that would work probably well enough as long as your outside air is less than 80F. You'll need to pump outside air through the evap cooler through the rad and back outside or your humidity will build up to the point where it won't cool anymore. Ohh another issue is evap coolers pump a TON of air. You'll need 3 120 rads all stacked up to make a big enough window for enough air flow, can't restrict the air flow through the cooler pads.

Hmm, evap would work for about $200 for the cooler, $250 for the water rads, $150 for pumps and tubing etc. But only if you have dry air for the evap cooler. Try the 50 gallon plastic barrel for your water source with 2 blocks of ice in it first. It should be enough for a day of running, if not add more blocks as the day progresses.

I missed the point about the coolant needing to stay below 26C.

In that case a simple rad setup may not be sufficient, depending on ambient temp. How much heat does that laser put out? What is your ambient temp in the work area?

Also, since the exhaust fan is taking out fumes and smoke, a radiator would become clogged very quickly.

As suggested above, a chiller would be an excellent solution; they're quite complicated and I dont have much experience with them, but here's a good place to look.

Hmmm..It's staring to sound complex...

I suppose the volumes of water and temp's I'm dealing with will require quite a big passive (air cooled) setup. It seems they make sense at the scale of a CPU but a 60W laser is a huge and inefficeint beast generating mainly heat and only directing 60W of that to the laser output.

From your descriptions of the cooling systems required to cool this thing, it may be cost effective to just import a chinese chiller unit for a few hundred Euro and keep it simple. They're not the most efficient or reliable but, neither would anything I built . The chiller would do away with the 25L tank because it doesn't need the thermal ballast.

What about inline cooling, like something you would have on a refrigerator door to dispense cold water. Anything like that available? Even if it couldn't handle the main coolant flow, I could use a secondary coolant loop that cooled the resevoir and hook it to a thermostat.

truedavi said:

The reservior is a 40cm dia by 60cm approx. plastic container into which the submersible pump sits powered by 220V. The feed tube exits out the top of the reservior connects to a flow detector in the machine and then enters the water jacket of the laser tube about a 2m run. The cooling jacket is intergral to the glass laser tube which is about 110cm long. A return tube rom the laser jacket follows the same route back returning the "hot" water back to the reservior.

Click to expand...

OK..am I missing something here? What cools the water?

If the "extractor" contains some kind of radiator, have you cleaned the dust out of it recently?

billb said:

OK..am I missing something here? What cools the water?

If the "extractor" contains some kind of radiator, have you cleaned the dust out of it recently?

Click to expand...

The water relies on the size of the reservior for cooling. I suppose, theoretically, if it was huge, like 60 litres, it would remain cool because the tank will dissipate the heat.

The extractor system is a completely seperate system and is simply a extractor fan hooked up to a flexduct, nothing to do with cooling.

it sounds like a evap cooling, like a bong.

Yeah, sounds like simplest but would have to route the humid air outside because machine is sensitive to humidity. Hey I'm in Ontario too. TO and also up at 3:00am at some reason.

haha, time for bed for me, got to get up and sit at the computer... looking for jobs

know anyone who need's a refrigeration apprentice?!?!! i have gas fitter 3, ODP, G2!!!!!!

truedavi said:

The water relies on the size of the reservior for cooling.

Click to expand...

"A small submersible pond pump circulates water through a glass jacket surrounding the laser tube to cool it and back into the reservoir"
If the pump is submersed, then it is dumping it's heat into the cooling water.
Removing the pump from the water may be an option. Perhaps just bypassing the pump and using a new aftermarket pump would also be an option.
Here's some info on pump heat dump, but it probably won't be usefull because you don't know the laser's heat load on the rez, nor the heat dump of the specific pump you are using. But you may find it helpful anyway: http://forums.procooling.com/vbb/showthread.php?t=10825&highlight=pump+heat+dump

UK & French Companies buy radiators from us (the standard PA Series rads) for use in Opthalmic lasers (lasic surgery)... they generally use PA120.2 or PA120.3. Been supplying them for a few years now... so there's no real reason why you can't just whack a PC Watercooling radiator inline, or a separate pump recirculating the reservoir contents thru the radiator and back to the reservoir.

He still needs to stay below 26C ambient water temp. If his workshop is at or above that then using a rad/fan setup is not gonna work.