I am currently building a VERY small cnc machine, 10cm by 10 by 10 volume. I have already(almost done) wrote my own software for it and am almost finished building it. I also have made myself some plans for an automatic tool changer due to it needing to surface AND due very delicate details on the things it will be machining. It looks quite similar to this....

http://www.gravers.com/mdx40large.jpg

I know it is possible but i am not sure if it will work or if it will work well, but here is my idea. I want the machine to load the stock(done), close its door(done), be completely sealed(done) and then completely flood the whole thing with coolant. No I will not be able to see the machine but i have worked around that, the software receives a ADC feed from the machine and shows it on the screen in 3d as far as what its doing and where it is, it also has high current protectors on all axis and on the spindle. All motors are brushless so no worries about electronics. I have an active pump that will be flowing coolant constantly through the machining chamber and through a filter then a radiator to cool it( I plan on running 10 hour plus programs, so i thought some form of "cooler" would be neccesary). It will hold about 4 litres of coolant in the mahining tank and 1 in the radiator/pump/filter assembly.

So basically, my question is can anyone see any problem with this system? I know a few dozen eyes can see problems better than 2....

Regards, Matt.

PS, sorry about that, I meant cm not mm- my bad.

If you flood the whole enclosure, wont the machine have to slosh coolant out of the way to actually move at all? Also, wont the rotation of the spindle tend to turn the whole thing into a blender? You'll have a chips and coolant milkshake IMHO.

Does it have to be flooded? Are you going to generate that much heat with the very small cutters I'm assuming you're going to use?

I would think that room temp coolant would be just fine, if you're worried about long run times heating it up, increase the volume. Or set up a chiller, just chilling the coolant would be easier than submerging the mill.

If you flood the whole enclosure, wont the machine have to slosh coolant out of the way to actually move at all? Also, wont the rotation of the spindle tend to turn the whole thing into a blender? You'll have a chips and coolant milkshake IMHO.

Lol @ digits “chips and coolant milkshake”.

He makes good points though:)

John

I think it depends on the material you are cutting. With a 1cc working volume and 10 hour cutting programs, I can only assume with that low a removal rate you are working in ceramics or very hard metals. Do you really mean 10x10x10mm and not cm? That is TINY!
I worked on a project where we developed a small mill doing highly detailed parts using full submersion. The coolant pump filled a container to overflow, and the spill-over went into a surrounding secondary container. With this double-container arrangement, the rest of the mill remained dry. Our ceramic chips were so small (dust) that it was simply carried in suspension over the overflow, and later filtered.

On the upside of a 10 x 10 x10 mm work area. It would only take a shotglass full of coolant to flood the whole thing. :)

I would think that would be very bad for the mill in general to be submersed.

First electronics and liquid dont mix well and your motors and spindle head are electrical.

Second it would be a mess having coolent everywhere which I would assume would promote rust and a whole other world of problems like chips flowing into areas they would never got to on thier own. And chips sticking to every nook cranny and surface instead of being able to be vacuumed or brushed away

Third As mentioned the blender effect if the mll electronics would even work under those conditions.

Chip floating in the coolant slurry will be re-cut and produce a bad surface finish.

Hmm... Is the material going to be magnesium ? Cutting submersed will help prevent any flash fires...

I knew about the chips and it is strained and filtered after the run, I couldn't see a problem with that part, but if you care to elaborate im all ears.

As far as the blender part I also don't see why it is a bad thing, and it will be very little effect most of the time because i am not using anything with flutes. All but one bit in its repetoire will be very small diamond tipped engraving bits which I have spun up in oil and not much happened other than very small swirls around the shank. One is an end mill which will only be used for rough surfacing and I have a diamond cylindrical bit for the final surfacing.

The reasons I'm going nuts about heat are
- The bits i use are VERY expensive($100 bucks a pop) and arent generic, there custom made by a friend of mine, about a week in the works for each. Obviously, breaking one in this situation would be a very bad thing. so i need as much on my side as possible.

-The parts i am making require a near perfect finish, preferably down to 0.0001mm but in actual use I'd expect something around 0.001-0.0005. And without coolant a simply surfacing routine results in a warped part.

-Standing there with dubya D for several hours is definately not my cup of tea, and a normal coolant system(spray coolant, collect, filter, repeat) has already ruined a pump due to the very fine dust comming off the part. and any filter i find that can protect it clogs in about 15 minutes. this way, there is no liquid pupmp involved, it pump air into the chamber when its done with the end mill spinning at max rpm just above the workpiece this creates a bit of a tornado kind of thing that does exactly as digit said, picks up the chips and swirls them around while draining them through the filter. No pump to fry from chips and because of it using air instead of water the pressure can be higher so where it would normally slow the flow rate low enough to be at a standstill the pressure can keep pushing the coolant through, and I can also use multiple filters and not have to worry about flow rate. Time is of no concern to me, if the part took a week to machine and it came out with a mirror finish, then I'm happy.

Lastly, for the finish I want, (mirror in some cases) I have been using a cut feed rate of 5mm per minute. It works like a charm for the first 2-3 minutes of having WD-40 sprayed on it constantly, producing a near mirror finish. then it all goes to heck and starts pitting and etcetera because of the metal melting and sticking to the bit. out comes the torch to clean it off and the olive oil to store it, then back to the drawing board. While at the drawing board I came up with this, it not onlycools the bits tip and the work-piece, but it cools the whole shank of the bit and keeps it cool. With an added benefit of cooling the steppers and spindle. Yes the feed is low but its the only way for the machine to function in my application.

-And it doesn't really have to do much pushing out of the way because of the feed rate, the jog on it is only 100mm/minute. I have everything running below its rated specs, motors at 7v instead of 8, 5mm/min rather than 250. I want this thing to last many years of hassle free running. And the only servicing I want to do is change the filter every few runs a the bits every few months. All of the motors are brushless to eliminate wear and tear, even the spindle is using a plettenburg brushless motor. Also because of the brushless motors the machine is whisper quite, all you hear is a slight hum when the Z axis kicks in.

If its of interest, Im milling titanium, carbon fiber(not while flooded), aluminum(6061/7075), magnesium, copper and fiberglass.

Chip floating in the coolant slurry will be re-cut and produce a bad surface finish.

I did not think of that one... Thank you very much, I will have to see how much of a degradation it will produce. I ill definately have to consider that one. Hopefully because of the dust rather than chips it wont damage the part.

On the upside of a 10 x 10 x10 mm work area. It would only take a shotglass full of coolant to flood the whole thing. :)

Yeah, sorry about that, it supposed to be 10cm not mm.... my bad



I would think that would be very bad for the mill in general to be submersed.

First electronics and liquid dont mix well and your motors and spindle head are electrical.


Steppers are brushless as is the spindle. Both were waterproofed and even if they leaked, no harm done, the coolant can't harm a bit of copper and a magnet.


Second it would be a mess having coolant everywhere which I would assume would promote rust and a whole other world of problems like chips flowing into areas they would never got to on thier own. And chips sticking to every nook cranny and surface instead of being able to be vacuumed or brushed away

The way I am running it there really is no chips, its all dust and it got everywhere anyway... even IN my toolbox which was closed. (yes i was wearing a mask...) The mill is 95% aluminum the only steel is the balls in the sealed bearings and the threaded rod fot the slides which i lube after each use anyway. I am not 100% as far as how well it will work but i have attempted to counter for the problem of them sticking everywhere. with the endmill(biggest most coarse bit i have) spinning up above the workpiece and creating a bit of a tornado as its drained, and like i said im getting dust not chips so I cant vacuum it I have to wipe it off anyway.



Third As mentioned the blender effect if the mll electronics would even work under those conditions.

I am trying to use that effect to my advantage.

I know few people have tried this if any but i have the time and resources to try something new. If it doesnt work, I can spend the next year or two making it work, but it will work well eventually. I am basically looking for your thoughts to account for certain scenarios before i get there, like preparing for the future.

I did not intend to have 2 posts, please delete the blank one..

Regards, Matt.

Please delete this, i did not intend to have 2 posts, they are collaborated into the one above this.

IMHO even brushless motors won't like being under water - I would bet that the leads that come out of the motors aren't the actual windings, but leads soldered to them. These joints will be underwater, and you will get electrolysis around them, which will cause them to quickly corrode, and quite possible electro-plate their surroundings. I also doubt that watery coolant will be the best thing for the motor's bearings...

i would like to see a couple pics of the parts made...

^^ What Project5k said :)