Flood/mist lubrication

I have a 3 axis mill that I'm intending to cut anything from wood to steel on. Right now, I have the machine up and running on some MDF and aluminum plates for testing but already see that with aluminum a cooling/lubrication system would be a good idea since a spray bottle gets old quick. A quick look at options suggests that most people seem to prefer mist at this point. I have a pump that I was intending on using for flood but wondering if mist is really worth the effort? I have a pancake compressor in my shop but wondering if it's necessary.

FWIW, I'm running a PlanetCNC MK3/4 board so flood/mist controls appear to be available in software. I'm just looking for recommendations on what seems to work well and what doesn't so I can do more research.

EDIT: There are a few links that the forum added which are great references. But those are all over 10 years old. I don't know if things have changed much so still a valuable question I think.

Hi,
I have found that flood cooling is by far and away the best. I did try mist cooling and it does work, but not nearly as well as flood cooling.

About two months ago I finished a 200l coolant tank I had fabricated out of 2mm steel, and I made a 1hp three phase pump with dual outlets. One outlet about 10l/min and slightly higher pressure
to flood the tool, and the other outlet about 60l/min at a little lower pressure to wash all the chips down into the chip tray. This has vastly improved my CNCing, no blockages, coolant interruptions,
no leaks or spillages.

I refuse to put wood anywhere near my machine. The water soluble oil reacts with the wood fibres and forms a gel which blocks up everything. I did a small wood job for a friend about three months ago
and found that it took a month for me to finally get the coolant system working properly again. Never again!.

Craig

My mill is a tabletop style that fits nicely on a tub style Uline cart. I was planning on cutting a hole in the bottom and draining the water into a 5 gallon bucket with a small pond pump to circulate the water. I like the table you fabricated! The mill I built was from a class at my local university and a similarly designed table there has an in-work liquid collection tub similar to your design. I'm curious if you end up with all the fluid being collected or if there is enough splatter that you have to replenish frequently?

Hi,
until fairly recently I had a 12l tank with a single phase pump. I used it for eight years or so. With my first mini-mill it was fine, and even when I built this larger machine but retained the original
800W 24krpm spindle it did OK too.

About a year ago I bought a new spindle 3.5kW(S1), 3.4Nm(S1),10krpm(rated), 40krpm(max), 400V with an HSK32E tool interface. Has been a huge step up in my machines capabilities. Downside is that with the
huge increase in chips the small tank/pump combination could not keep up.

Firstly it has only a small area filter, and it would block up frequently resulting in flow interruptions which in turn would wreck jobs. Additionally when you are using a highspeed spindle you 'consume' a considerable volume
of coolant, typically 10L or more in an 8 hour day. Consequently my small tank required frequent top ups. All in all the flow interruptions, blockages and subsequent spills really pissed me off.

It was for that reason that I built a new coolant tank and pump. Large area filter which means I clean out the filter once a fortnight or so and no blockages resulting in coolant spills. Also I find that I need to top up
less frequently. Just recently I have been doing fewer jobs that require coolant, and I haven't topped up for a month. During times when I'm using coolant a lot then I'll top up 20l at a time every other day or so, maybe weekly.
The reduction in leaks and spillages has been exactly what I sort, which is just as well as the tank cost me $1000NZD! Remember, I designed and built my own pump, if I'd bought a suitable three phase pump, well they are
$680NZD so I can guess that a complete system had I bought it all is around $1800NZD. Crazy to think that I've spent about 1/3rd as much on a coolant system as I did the new spindle/VFD/tools/chiller....but I have.

Quote:

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I'm curious if you end up with all the fluid being collected or if there is enough splatter that you have to replenish frequently?

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You absolutely must catch all the coolant otherwise you'll have a god-awful mess to clean up. With My first mini-mill I used to put a huge big plastic bag over the top of the entire machine to try and
catch all the splatter and direct it into the tray. That got pretty old very fast. My new machine has an enclosure 1.1m x 1.3m x 1.2m high. So it does not have a roof. I can contain all the splatter no trouble,
but I suspect that much of the mist it lost out the top. You might be surprised just how much coolant is lost due to misting, certainly very VERY much more than evaporation even in summer.

Craig

Hi,
while I've sort of finished my tank and pump, there is, and was always, another phase to it.......that I've not got around to yet.

The idea of having two separate outputs to the pump was so that the larger volume/low pressure section be used for flood cooling and flushing chips into the tray/filter, while the lower volume/higher pressure
section was to pass through an in-line chip filter and then into two stainless magnetically driven gear pumps I have. I've attached a pic of the chiller that I use for the spindle coolant loop, and that includes
one of these gear pumps to which I have alluded.

These are great units, absolute top quality. Oriental Motors (quality Japanese) induction motor and a magnetically coupled stainless gear pump. They pump about 5l/min but at better than 100psi. They will make ideal jet coolant pumps,
but I want a prefiltered input to the pumps rather than wreck them. I paid $50NZD each for these pumps second hand. I don't know how they ended up in New Zealand, but there is a supplier whom had 50 of them and was selling them cheap.
I've bought three, and another two for a friend in Melbourne. If you want one....sing out and I'l see if there are still some left.

Craig

Hi,
just checked, the supplier still has six left. The price is up a little bit, now $59NZD.

Craig

Hi Mr Kenobi - I have a router that flood coolant wouldn't work on so have experimented with mist quite a bit. It has worked out very well for aluminium and brass. Not tried steel though. I'm very happy with it no mess (except the swarf) and the tools life is good and the surface finish very good. Datron use misting on their machines... but I expect flood is the go if you have the equipment.

https://youtu.be/UGHTZC2_pz4

Attached is the mister I eventually settled on and use methylated spirits for the coolant. High speed focused air keeps the swarf out of the cut zone and cools via evaporation and air flow. Peter

Hi,
there are three I think essential features of any cooling system that need to be evaluated:

1) Flushing of chips from the cutzone
2) Cooling (material and chips)
3) Lubricity.

I have listed them as I see their order of importance. Flushing the chips out of the cutzone is especially critical with aluminum. If a chip lies in the cutzone only to be recut one or more times by the tool
it will get hotter and hotter with each recut until the chip welds itself to other chips, the parent material or the tool. My experience is that if I use just pure water to flush the chip away that works nearly as well
as proper coolant. When I used air-blast I also found that if I could blow the chips away that worked fine, either with or without oil.

For aluminum then ANYTHING that flushes the chips away will work. I find flood cooling, a moderate flow of say 5 l/min at a velocity of about 1m/s to be the most reliable. Air blast is fine SO LONG as it is well directed.
If there is any obstruction to the blast then for that brief period the chips get re-cut and lo and behold the chips weld together wrecking everything. Thus if you are prepared to stand by and baby the air blast to always
flush away chips all well and good.....but the moment you turn your back then you'll have trouble.

The second feature is cooling. I find this is absolutely essential, especially with plastics. Acrylic is badly heat sensitive but ABS is worse. I try to avoid any polyethylenes as they don't form chips but long strings, and they are just
a plain bastard. All tools and all materials benefit by being kept cool. There are some schools of thought that suggest the the thermal shock experienced by ceramic and other high value tools means that coolant should NOT be used.
I am in the opposite camp, the higher the cost of the tool, the greater attention I take to keeping it cool and well flooded.....I cannot afford to wreck tools. Anyone who has blown out a CBN or a diamond tool in short order due to
overheating will know what I'm talking about.

The last feature is lubrication. This is important with hard and tough materials, steels and stainless.

Most water soluble coolant oils are recommended at about 20:1, or 4%.....unless doing tough metal in which case the recommendation can go up to 9:1or 10%. In interest of saving money I go for 4%. That works OK in steel
if you take it fairly easy. If you want to cut aggressively at production speeds then a higher concentration of oil is required.

Craig

Hi,
I've tried a few different oils. I have not found any particular one to be markedly superior to another, they all seem to work pretty well.

My latest purchase was from the company in the same block of building as my business, very convenient. They stock Quaker Houghton oils, lietrally dozens of different formulations.
The one I chose is one of the cheapest, CINDOL 305D. I paid $273NZD (inc tax) for 20L. It is everything I expected of it. There are many other formulations that look to be even better, but often up
to $400 to $500 per 20l.

Quaker Houghton, is, if I understand correctly, an Australian brand. Now I'm loath to say anything good about Aussies (lol) but I have to say Quaker Houghton is the 'bees knees', or 'duck nuts'!

Craig