Clean coolant system for indoors?

[Luke Blades 1Participant @lukeblades1]

Hello,

I've recently bought a mini mill and done a CNC conversion. I'm a student and so unfortunately i don't have a shed or any real "workshop" space, i've been getting by with using the thing in the corner of my kitchen for the time being.

I've come to the point where i'd like to put the machine to work and i know that to make any substantial cuts in aluminium i will need coolant of some sort to spare my endmills.

I'd like some advice as to the best way to go about this, considering my living situation. From what i've read, it's possible to get bacteria/mold buildup in coolant sumps required for flood coolant systems. Also, i've read that mist coolant might end up coating everything in my flat (including my lungs).

Any thoughts or suggestions would be welcomed!

Best,

Luke

[Luke Blades 1Participant @lukeblades1]

[Nick_GParticipant @nick_g]

.

The 'go to' coolant / lubricant for aluminium for the hobby machinist in a home workshop is usually WD40 or paraffin applied with a small brush.

The good side is that you don't need a lot of it so cleaning up during and after sessions should me manageable. The bad side is it will stink the property out. – But that may be a preferable smell to normal student digs

I find when machining aluminium that ribbons and particles of swarf get EVERYWHERE.

Not sure what soluble coolants are best with aluminium (others will advise) but if good housekeeping is practiced it will not get to the stage where it starts to smell. However a bin left full of kebab and pizza boxes will.

Nick

[Anonymous]

Modern soluble oils do not seem to suffer from bacterial growth and nasty niffs, at least in my experience. And I have coolant sitting in the sump for months at a time.

I use coolant on my CNC mill for two main purposes when cutting aluminium, one to wash away swarf to prevent re-cutting, and two to prevent swarf sticking to the cutter. If you have decent cutters they won't be affected by coolant or no coolant in terms of life.

The practical problem, identified by Nick, is that swarf, and coolant, will get everywhere. Careful guarding can reduce the issue, but I still seem to end up with coolant on the floor. On aluminium I can't see any reason not to be running the mill at full speed, so I'm not sure there's a solution in terms of preventing coolant spray. In terms of coolant I use Hysol XF, which is fine on aluminium.

To remove swarf you might consider air blast, no coolant to contend with, but there will be the noise of a compressor; not that anyone will hear it over the loud music. Selection of cutters intended for aluminium (generally uncoated, polished and a maximum of three flutes) can help with the sticking problem.

Unfortunately there is no simple answer to the problem.

Andrew

[John HaineParticipant @johnhaine32865]

I generally machine ali dry on my Novamill, using the highest speed I can with slot drills (2 or 3 flute) not end mills, up to 10mm dia. Machine will go yup to ~5000 rpm. I have added an air jet to keep the working area clear of chips, and a front cover to stop the chips from covering the workshop.

[Luke Blades 1Participant @lukeblades1]

Thanks for the advice chaps!

Nick, I used WD40 before the CNC conversion but now it's automated, i don't fancy having to babysit the thing with a can, otherwise i might as well be turning the wheels right!? To avoid mess, i'm building a perspex enclosure, hopefully that will do the job.

Andrew, Thanks for the coolant recommendation, i'll look into it! What you said about running dry is contrary to what i've read/heard elsewhere, i've heard that coolant is essential for cutting any significant volume of aluminium and the chaps in the uni workshop always run coolant on their CNC jobs. Is this purely to improve the finish? I'm intrigued by the airblast idea as that would clearly be better for pocketing than flooding due to chip ejection. Are there any semi-quiet compressors available for this? The only compressors i've heard are much too loud but they also might be a lot bigger than what i need.

John, Interested again to learn that you're not using coolant either although you are using smaller tools that i'm intending to. I have a 50mm face cutter and a 20mm end mill which seem to get pretty toasty without any WD40. Not sure the air jet would give me enough cooling?

Thanks again for the advice guys,

Luke

[John HaineParticipant @johnhaine32865]

I use an airbrush compressor scored on eBay. The nozzle has a 1mm hole and there seems to be plenty of puff to keep the chips clear, in fact to throw them to the edge of the enclosure where they build up in little drifts.

On a mini mill and in ali, I wouldn't use anything like as big cutters as you mention. With CNC there's no need, you just leave the machine to mill down the surface with a smaller cutter. With my ER16 collets I'm restricted to 10mm cutters but I don't feel the need to use anything bigger.

[Bill MullParticipant @billmull]

Last company I worked for used Castrol Alusol exclusively, It was a great performer but I found the chemical type smell from it gave me headaches. Current employer uses Castrol Cooledge which doesn’t smell as strongly. As an aside, when I visited John Deere s vast transmission plant in Germany a few years ago they used no coolant on most of the CNC machines. When I asked the engineer tour guide, she replied that coolant was too much of a mess and they didn’t bother with it !!

[Nick_GParticipant @nick_g]

Posted by Luke Blades 1 on 10/09/2017 13:08:47:

Are there any semi-quiet compressors available for this? The only compressors i've heard are much too loud but they also might be a lot bigger than what i need.

Luke

.

There is amongst others a make called 'Bambi' who manufacture very quiet compressors. They get very good reviews but will make a big chunk of a hole your beer vouchers.

Nick

[Luke Blades 1Participant @lukeblades1]

Thanks for the responses fellas.

Following your suggestions i've been thinking about the best / cheapest way to tackle this with air cooling and being a true lover of efficiency, i reckon i might be able to kill 2 birds with one stone?

The first bird is the cooling of the part / tool.

The second:

My mill has a 500W brushless motor, these things use rare earth magnets which should not exceed around 90 degrees C due to the risk of damaging the magnets and loosing performance. Whilst running my machine for periods of 30 mins+ (which will clearly be the case when i'm using the CNC in anger), the motor gets hot. Not so bad that i can't bare to touch it but i'm thinking around 70 degrees perhaps more, meaning we could be getting too high internally if i push it much more.

How much of a mess do these mist coolers make? If i were to build a perspex enclosure for the mill (which seems necessary to stop chips flying into my kitchen, could i eliminate it? I'm thinking a sealed perspex box with a hinged front, extractor fan with an exhaust out the nearby window to clear the volume before i open it and let the contaminated air into the flat. Obviously i'd keep my windows open to ventilate the flat anyway but i don't want mist coolant settling on every surface!

To cool the motor, i'm thinking slap a couple of heat sinks on the side with a second mist cooler line run from the same compressor just directed straight at it. Might not even need the mist!

Thoughts? Cheers,

Luke

[Author]

Posts