Thoughts on mist coolant for machining - Editted MQL not Mist

[ATGNI]

I think you have the wrong end of the stick. You absolutely don’t want a squirter! It won’t be a drip as the pump is used to dose a compressed air stream with a tiny amount of oil pointing at the tool. The oil provides the cutter a little lubricant and the compressed air cools the cutter and blows away the chip.

 

[ukracer]

Air use could be an issue for me as I don’t want my shop compressor kicking in as I may not have the electrical capacity. Again interesting to see if the air supply would need to be on constant or could it be pulsed.

I also wonderful if one of the larger diaphragm pumps would be capable of moving the chips

I wouldn’t beat yourself on setting up those Venturi based misters I don’t think anyone had much luck with the cheap ones. But for £7 they are a useful source of parts

What's a venturi based mister?

 

[ATGNI]

What's a venturi based mister?

It uses the compressed air stream to suck up the oil from the storage tank. Same principle as a carburettor. It’s used on the cheap mister systems sold on Amazon and eBay

Venturi effect - Wikipedia

en.wikipedia.org

 

[ATGNI]

Video about a commercial MQL system

 

[ukracer]

I have been doing a bit more research and I should probably retitle the post. So looks like I am looking to build a MQL minimum quantity lubrication system. So the oil isnt atomised it just introduced at the end of the air nozzle via a metering pump. So there should not be clouds of mist etc. I suspect the casual reader won’t appreciate the difference, i didn’t before the research today.

How does what you want/need differ from in this video?

 

[ukracer]

It uses the compressed air stream to suck up the oil from the storage tank. Same principle as a carburettor. It’s used on the cheap mister systems sold on Amazon and eBay

Venturi effect - Wikipedia

en.wikipedia.org

So you could use an aquarium pump like we use as a cheap laser compressed air blower?

 

[Misterg]

A few people have already tried what you propose using both DC motor and stepper motor driven peristaltic pumps like this one:

Mini Peristaltic Pump Head With Tube Small Flow Stepper Motor OEM Package | eBay

Find many great new & used options and get the best deals for Mini Peristaltic Pump Head With Tube Small Flow Stepper Motor OEM Package at the best online prices at eBay! Free delivery for many products.

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I think they sourced some 1mm bore tubing separately (to reduce the flow rate).

Link (Not sure if you need to be a member to see it or not.

The problem with driving it off the 'A' axis is that you need to program an A axis move to turn the pump on. When the move finishes, the pump stops. In the discussion above, I think they resorted to using a stand-alone, variable speed stepper driver.

Despite the blurb on the 'Kool-aid', it has an OEL on the datasheet, so isn't "harmless" - in a commercial setting, you'd need to have extraction, or at least carry out air monitoring.

I use isopropyl alcohol fed from a pressurised reservior and delivered to the tool by a low pressure air jet ( <10 PSI). It spits a drop of liquid onto the work every 1-2 seconds and works well enough for me.

(The gauge is reading high as there isn't any flow and the regulator isn't very good). I'm aware of the fire hazard (and the potential health risks), but I rationalise it in the same way that Stefan Gotteswinter in the video below. I saw a recommendation for a water soluble cutting fluid for misting systems some time ago, but I can't remember what it was, or where I saw it! (It was a UK supplier). I'll probably give it a try if I can ever remember.

This is my system in operation - it is turned up quite high here - look for the puff of liquid from the brass nozzle every second, or so. It is enough to wet the workpiece.

 

[ATGNI]

Lots of good information thanks

incase it doesn’t work off the spare axis I have already got a stepper driver to make it stand alone And take a output from the cnc controller.

never would have thought of alcohol but it has a low temperature of evaporation, is there a fire risk?

 

[ATGNI]

So you could use an aquarium pump like we use as a cheap laser compressed air blower?

I did wonder on trying the diaphragm pump of my laser but I think it would need something more substantial.

 

[ATGNI]

How does what you want/need differ from in this video?

That’s a mist system so has a lot of atomised particles. The MQL should use much less oil or so it says on the packet

 

[ATGNI]

yes something much like this. I am not brave enough to use isopropyl as a cutting fluid

 

[Brad93]

Kool Mist is safe for people, machines and parts
Kool Mist contains no halogens or sulfides and is totally free of dangerous or otherwise troublesome chemicals. It is harmless to operators and ends problems of mist fog fumes. Kool Mist will not cause corrosion, buildup, dermatitis, rancidity or objectionable odors. Properly diluted with water Kool Mist does not create rust or stains on machined parts. As a result, it sharply reduces parts spoilages, eliminates employee health claims, and precludes problems with health and environmental agencies such as OSHA, NASA, AEC, and the EPA.

Yeah funny how many companies say things are safe... especially US based companies.
Until they get taken to court and it comes out that no studies were ever done, so called experts were nobodys and backhanders were given to OSHA officials.

 

[outofthefire]

The only time i've seen any one from health and safety actually come into the workplace was in my last job. They were targeting machine shops to because they're worried about coolant misting and being breathed in. They ended up spending thousands on extractors including one for the welding bay, and it's the 1st place i've worked where they started to take h&s seriously. They, h&s, said there wasn't a lot of evidence it caused health problems, but there must have been enough worry to get them out and about visiting machine shops.

 

[Brad93]

The only time i've seen any one from health and safety actually come into the workplace was in my last job. They were targeting machine shops to because their worried about coolant misting and being breathed in. They ended up spending thousands on extractors including one for the welding bay, and it's the 1st place i've worked where they started to take h&s seriously. They, h&s, said there wasn't a lot of evidence it caused health problems, but there must have been enough worry to get them out and about visiting machine shops.

There are multiple documented cases in UK machine shops where centralised sumps caused occupational asmtha. Less likely to happen with small sumps but still, why take the risk.

It doesn't take a lot to realise breathing in an vaporised oil is probably bad for your health.

 

[minimutly]

I think you have the wrong end of the stick. You absolutely don’t want a squirter! It won’t be a drip as the pump is used to dose a compressed air stream with a tiny amount of oil pointing at the tool. The oil provides the cutter a little lubricant and the compressed air cools the cutter and blows away the chip.

Ah, you’re using air as well? Thought you didn’t want your compressor running? Perhaps, I got that wrong?
With air and an added liquid a peristaltic could work.
With the caveat from @Brad93 of course...
I would still use a timed squirt.

 

[ATGNI]

Firstly I wouldn’t discount anyones safety concerns. But you Know the recommendations for drinking alcohol is something daft like three teaspoons per year and I’m on my third gin and tonic Tonight. Health and safety information means very little unless balanced against other risk factors like, drinking, crossing the road, going up a ladder. In the case of these MQL systems the exposure is clearly designed to be extremely low given that only a few ML of fluid are used over a 6 month period. I suspect this is less exposure to vegetables oil than someone working in a fish and chip shop. I won’t presume to tell anyone that this is 100 percent safe, but nothing is. As Individual we make decisions about risk all the time this isn’t any different. I wouldn’t let the perfect become the enemy of the good.

 

[ATGNI]

Let Battle Commence

 

[outofthefire]

There are multiple documented cases in UK machine shops where centralised sumps caused occupational asmtha. Less likely to happen with small sumps but still, why take the risk.

It doesn't take a lot to realise breathing in an vaporised oil is probably bad for your health.

I completely agree, our coolant wasn't vaporising though. It sounded like H&S were covering their arses, they also got my boss to start testing the coolant sumps weekly for bacteria. It was quite a shift in the companies attitude to health and safety generally.

 

[Brad93]

I completely agree, our coolant wasn't vaporising though. It sounded like H&S were covering their arses, they also got my boss to start testing the coolant sumps weekly for bacteria. It was quite a shift in the companies attitude to health and safety generally.

I think due to our cooler climate and greater use of flood coolant than mist, the cases occur less frequently here than in the USA.

However, you definitely see many cases of contact dermatitis here.

A company called pennine oils who advertise on Instagram have a service where they will come and carry out a complete clean, carry out regular sampling, etc. Some of the growth they find in the sumps is horrendous.

 

[ATGNI]

not sure how well it will work when it’s connected to the compressed air support but it’s looking good so far. The oil dose can be adjusted by varying the speed of the steppers motor peristaltic pump and the air mark space ratio is variable. I found good results intermittently clearing the chips using a manual air line. I’m hoping this may let the compressor run for less time. The lubrication system receives a start command from the CNC controller.