Mist coolant

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Anybody used a mist coolant system. - Good / bad.?

Nick

Nick

Have not used it myself but I seen several you tube videos were it's used and seems to be very good , Tom at https://www.youtube.com/user/oxtoolco give a good account of his system in one of his videos.

H

Link here

Edited By Harry Wilkes on 05/02/2015 15:42:39

I have a pair of ex-industrial Bijur Spraymist systems. One on the lathe and one on the mill. Very effective but a touch tricky to set just so. The mill one in particular as the main unit is on the main column a couple of feet lower than the nozzle so things tend to drain back, despite having a check valve, so start-up can be iffy unless the volume valve is opened until flow established. Which is a pain. The one on the lathe is mounted above the nozzle at the back of the machine and does not suffer so but has to be lifted down to refill.

Its important to direct the flow accurately onto the workpiece so that the minimum amount of coolant is used. Its easy to create an evil fug by using too much flow. With the Bijur system a certain amount of fiddling with flow volume and air pressure allows a well controlled spray to be directed at the cut so virtually all the coolant condenses onto the work throwing very little into the air. Still gets everywhere on the working area of the machine tho'.

Having the mist systems lets me use coolant all the time except when working dry is best which helps enormously in getting good finish as well as extending tool life. You do get overconfident tho' and tend to exploit industrial level speeds and feeds. If the system glitches things go wrong fast!

Despite having pumps and sumps I only used normal free flowing liquid systems when unavoidable due to the splashy mess and long clean up times. An adjustable nozzle hand squirt bottle was better than nothing but still pretty messy and not that effective.

Despite their effectiveness I'm unsure as to whether mist systems are really worth the effort in a Model Engineers workshop where its rarely necessary to move lots of material fast. The systems are relatively expensive and a reliable supply of compressed air essential.

Clive

The Mercans seem to use it quite a bit, as they seem more likely to have air lines in their (work) shops. Also known as Minimum Quantity Lubrication (MQL), AFIK. The clue's in the name - it delivers lubrication of the cutting edge but no significant cooling. The small air jet also clears the swarf, so the surface finish benefits on both accounts.

I tend to use flood coolant if anything and even then it's primarily for preventing the work piece and tool from overheating (ie to protect the tool) or for parting. For machining aluminium, I use WD40 and a brush which really isn't ideal, especially for milling - probably a situation where a mist / MQL system would be helpful.

I've been considering getting a mini compressor for this purpose but I'd want to convince myself it was fairly quiet - anyone got any recommendations for small, quiet compressors?

Murray

Examples here

Edited By Muzzer on 05/02/2015 17:02:56

When it comes to small, quiet, compressors best to look at the tank mounted dentist / lab / industrial type such as Bambi or Jun-Air. I've used both and can confirm the low noise level. Not cheap new but turn up fairly often on E-Bay at acceptable prices. There are other makes too. Being intended for continous running they are durable so generally safe to buy used. Bambi have a decent spares policy. Twin or triple "cylinder" versions of the diapharm compessors intended for airbrush and similar use will probably handle the air requirements but generally are priced to meet the market so are less durable. Often not happy at continous running. The baby vertical 40 psi rated Burgess / Hydrovane intended for spray gun duties is another possibility. But getting rare now and no tank either.

Given appropriately diluted coolant, say 2 or 3 %, mist systems provide a fair degree of cooling due to evaporation of the water content. Change of state from liquid to vapour absorbs a fair bit of energy right at the cutting point. The air blast contributes too. The neat oil film left behind is effective at controlling buit up edge tendencies.

Air blast is great when milling as it clears chips preventing double cutting which not only ruins finish but also hits tooling life. been known to just use neat air for this reason when the work piece is going to be a PIA to clean.

Clive

Another good source of practically silent compressors is old refrigerators.

Mike

If you look at the HSE website on the perils of machining, the health effects of cutting fluids are one of their greatest worries, certainly it seems to cause very many health problems. Spraying a mist of coolant suggests to me that at the very least the choice of a safe fluid must be important.

www.hse.gov.uk/pubns/indg365.pdf

Best advice in that guide - don't put oily rags in your pockets...

Neil

I have a home made compressor using a twin cylinder fridge unit and have sprayed cars with it.

It is very quiet compared to an Aldi compressor I bought to replace it but that was so noisy it's never used as I don't want to annoy the neighbours.

Hmmm, may have to rethink the mist system & just use hand spray / air blast methodology...

George

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I have ordered a Vertex mist coolant set up. I will let you know how I get on with the rascal.

Nick

Some of you on here will know of my obsession s about coolant (metal working fluids). No mention gets ignored by me.

Has anyone tried through tool coolant?

Jerry

The last thing you want in the workshop is coolant mist, the resultant fog of coolant suspended in the air will very soon have you coughing your lungs out.

Mist coolant is a bit of a misnomer for these air/coolant devices, take a look at the Hench Fogbuster, specifically designed NOT to produce a coolant mist, in reality what you get with these is a stream of liquid droplets carried along in the air jet. The coolant does not get atomised hence no mist of coolant. These devices are very effective, I've made a couple using this principle and never have a problem with coolant fog around the machine, good cooling and lubrication and minimal cleanup.

I did look at the Vertex but these rely on a venturi principle similar to the Koolmist unit I have and I find the coolant delivery to be somewhat intermittent, the fogbuster presurises the coolant tank at about 5psi to ensure reliable fluid delivery.

I have a Koolmist spraying water only, for cooling woodworking tools whilst grinding. Surprisingly cold and very little loose water - leaves tools damp rather than sopping. Lots more water gives little cooling advantage. The official additive for machining appears only to be on sale in the USA. Water miscible oil should not be used for health reasons.

I did not buy a tank, but use a mains water filter case, which could be easily rigged to give pressured fluid delivery. Paint spraying with a pressure pot gives good control of droplet size; going in the "wrong" direction for paint (larger droplets) is quite possible, so I don't see why adjustment of fluid pressure and air should not do the same for the Koolmist - but I've not tried it!

Thanks for the clarification Coalburner.

Neil

I have a Bijur system, a lot of Bridgeport milling machines were fitted with these. The fluid container is pressurised, I think the makers recommend about 10-15 PSI, air and fluid feed to the nozzle through separate tubes at the same pressure, the idea is that relatively large droplets of fluid are carried by the air leaving the nozzle. There should not be any fog but if you really need one, cranking the air pressure up to max should do it!

Well I think there are two different lubrication systems discussed here. So I hope I can bring a bit more clarification into that matter and tell about my experience - not all good as you will see.

Many years ago I saw a minimal quantity lubrication system at a machine tool exhibition. This was (is) NOT a 'mist system' - just to make that clear. This system came from a manufacturer called Vogel; to my surprise when I looked it up today it goes now under the name of SKF (yes the ball bearing firm). So I bought such a system and had soon to discover the drawbacks.

Maybe best to show the link to that system as sold by SKF:

**LINK**

As you see this is a fully pneumatic system. The oil is metered by a small pneumatic pump, and the air blow can be regulated separately. But, and that was the drawback, it needs a constant pressure of 5-6 bar in the air line, and the air stream empties my 50 l tank in a couple of minutes below that level. I know my compressor is not very large and is unable to keep the pressure high enough. What I want to say is that this system needs air in copious quantity - you could never use it with a Junair. Bambi or fridge compressor.

The other problem is that it does not start immediately (as mentioned above for another system also). In practice I have to start it 15-20 min before I want to use it, and have also to set oil volume and air to the max ant then - when it finally starts to work - regulate it back again. A big nuisance to say the least..

The reason why I wanted such a system was, that I heard good reports about a U.S. product named Micro-Drop (iirc). This uses a pressurized oil reservoir, which imho is much easier to work with. This is (was) available here also, but again 50% more expensive than the Vogel/SKF system.

So if you have a big, powerful compressor then go for it, otherwise I would say no.

Just to finish that narration, somewhere in the distant back in the American 'Home Shop Machinist' there was a construction article about a lubrication system in which the oil was sputtered out by the action of a magnetically moved iron core (solenoid) hitting the back end of an oil filled tube. This just from a not too good memory. so the details are a bit vague...

Regards, HansR.

One of the last things I almost got involved in before retirement, was the use of compressed air as a coolant, just an accurate blast of air. Most (90%) of the material was Al. Alloy usually 6061 T6, 2024 T3, 7075 T6. Air cooling probably wouldn't work on steel alloys. The theoretical advantages were several, no mess, clean swarf ready for compacting (normally the compacted swarf contained a fair amount of coolant which had to be filtered and cleaned prior to reuse) supposedly better cutting, as long as the tools were sharp.

Any thoughts??

cheers

Bill

Full details of a mist unit I use on my milling machine are in my Photo folder. Simple to make and effective in use.

It does not fill the air with mist as some professional units so may not be effective for your use, it has an air supply (25psi is sufficient) that syphons coolant from a bottle, coolant is sprayed onto the job in droplets rather than mist, amount of coolant is controlled by raising the coolant bottle above the block height.

The unit can be used without coolant to keep chips clear by forced air. The unit can be seen working in some of my Emco F1 videos on Youtube at ukmwg

http://youtu.be/KRiiEywpzZk

Emgee

Edited By Emgee on 07/02/2015 22:06:24

Here's an example of an MQL system. They claim the actual qty of lubricant used is minimal ("typical applications use only 1oz. of lubricant per 8-hour shift" and this accords with Mr Saunders across at NYC CNC, who made a short video about his experiences using the Trico system.

The downside of this particular system is the cost (over £400) but it can operate down to 60psi / 4 bar and requires about 1.7cfm per nozzle.

Murray

I have a Noga bought to get me out the proverbial some years back. These work on droplets and require around 15psi regulated. The amount of air wont shift debris, might just about move small miniscule stuff but does an ok job of coating cutters and relieving of heat. Certain boring bars wouldn't have it no better than nothing. General o/d turning and shaping marginally better than nowt. For these to work they need to deliver at least double the capacity before it goes in to a mist. Increasing pressure turns in to a mist which will be the same as what happens on all others.

Used it for the two weeks, was real hard work percevered as some tools only work with coolant. Lathe work its pretty useless unless taking minute cuts often ie cant keep a Ceratizit drill/turn/bore tool with through coolant going sprayed direct in to and in to work piece, just clogs up at mildest touch.

Mill work theyre better suited unless doing deep slots. Three years on dont think I have used it since, just using a bottle topped up with coolant squirted on to the jobs.

Cant beat flood coolant unless its a high flow specialist mister along the lines fitted to Haas and so on.