Flood Cooling a Taig CNC Mill
Overview
One of the hassles associated
with running the CNC Taig mill (and actually all CNC
metal cutting systems) is the need to apply lubricant/coolant to the cutting
tool at periodic intervals. Flood
cooling offers the possibility of not only providing superior continuous
lubrication/cooling but also a somewhat greater level of “unattended”
operation.
I considered mist cooling which
offers a number of advantages as well as disadvantages. I decided on flood cooling largely because it
did not require a source of compressed air as well as I had a general concern
about mist getting in the air and getting outside of the general milling area.
One idea I pursued briefly that I
believe may be novel is the idea of a sort of “fling” cooling system. The idea would be to have a small spinning
wheel (envision a small plastic spur gear, maybe one inch in diameter) spun by
a small electric motor. The spinning
wheel would be placed near the cutting tool.
A coolant drip system would be arranged to drip coolant unto the
spinning wheel. The coolant would be
flung off of the wheel. The geometries
could be adjusted to direct the resulting spray of droplets onto the tool. The advantage over mist coolant would be
elimination of the need to have a compressed air source and the droplets would
be larger and therefore less likely to contaminate the air. A crude prototype looked promising but I
decided to go the proven, conventional route.
Design Goals
As much as possible, I wanted to
use easily obtainable and relatively inexpensive materials. I also wanted to minimize the amount of
custom fabrication needed; I didn’t want to turn the flood coolant system into
a major project unto itself.
The Design
The basic architecture is a “pan”
to catch the coolant runoff and collect it for recirculation with an enclosure
to prevent overspray/splash based on flexible curtains.
Front View of the
Completed Flood Coolant Enclosure
The pan I chose is a mortar
mixing tub (polyethylene) made by the Argee
Corporation that I bought from Home Depot.
The size used in this design is not available at their local stores; it
is only available via internet order. It
was reasonably priced (about $25 plus about $8 shipping). I hesitated at first because it was
significantly larger than I wanted but I decided to cut it down to a better
size. As shipped, the height was around
10” and tub included a lip around the perimeter. Using a saber saw, I cut it down to around 6”
in height and because of the sloping walls, reduced its footprint to around 40”
by 30”. The wall thickness was a healthy
0.080” or so and even with the lip removed, the tub is plenty stiff and sturdy.
For the frame of the splash
enclosure, I used ¾” vinyl water pipe and associated fittings. The key to this approach was to use
specialized fittings that are not commonly available, specifically three and
four way couplings. It turns out that
these fittings, while having no legitimate use for plumbing, are available via
internet order from companies that supply them for small garden greenhouse
construction. They also were quite
reasonably priced and fit perfectly with common ¾” vinyl water pipe.
Three and four way ¾” couplings.
Small “C” shaped
coupling is used to hold vinyl curtain to frame.
As you can see in the
accompanying photos, I used 45 degree fittings in pairs to provide a “jog” in the
leg structure to better fit the sloping sides of the tub. These fittings are commonly available as
plumbing parts. I used the four way fittings
on the of the frame as feet to raise the whole the curtain structure off of the
bottom of the tub by about ½” to allow better draining.
Frame Leg (Note use
of paired 45 degree couplings to provide jog in leg).
Also note use of
“C” shaped snap connector to clamp clear vinyl to pipe.
The curtain material is 0.020”
(20 gauge) clear vinyl obtained at a large local
fabric store. This gauge is relatively
flexible while still pretty tough. While not optically flat, it is generally
clear. It came in a roll of about 56”
width. I bought one and one half yards
for about $9. Ordinary shower curtain
can be used but I felt this stuff looked more “industrial” (who wants small
fishes and yellow flowers in their workshop décor?).
To attach the vinyl to the
plastic pipe frame, I used a specialized coupler (again obtained from the
greenhouse component supplier). These
couplers have a “C” cross-section and are used to snap together lengths of
plastic pipe. These couplers are about
5” in length. I cut each coupler into
three pieces to make three separate clamps to hold the clear vinyl on the
pipes. They worked surprisingly well and
can support two thickness of the 20 gauge material. They are readily unsnapped to remove the
clear vinyl for readjustment or cleaning.
The final touch on the enclosure
was to provide a mechanism to easily remove the front curtain of the enclosure
to provide ready access to the mill. As
seen one of the accompanying photos, I notched the couplings on both sides of
the front frame so that the front pipe section with attached curtain can be
quickly snapped/unsnapped. When I unsnap
the front curtain, I simply lay it down in the space between the front of the
frame and the tub while I am setting up the mill.
Front top right
coupling notched to facilitate quick removal of the front curtain.
The drain is a stainless kitchen
sink drain fitting obtained from Home Depot for around $9. I cut a hole in the front right corner of the
tub and mounted the drain using silicone caulking to prevent leaks. I kludged a drain tail fitting and a
dishwasher drain hose to the output end of the drain. The drain hose goes into a five gallon dry
wall bucket. The pump that powers the
system is a 360 gallon/hour common marine bilge pump (12 volts) that costs
about $25.
Drain in tub
To avoid multiple breaches of the
tub (and possible sources of leaks), I mounted the mill a frame I build out of
some structural iron that I had in my shop.
The iron frame sits on four rubber pads on the tub. The weight of the mill and the iron frame on
the pads keep it well secured.
Structural iron mount for the mill with rubber pad shown.
The coolant spigot is a LocLine product (they sell a coolant spray kit with LocLine, nozzles and fittings for under $10. I attached it to the column of the mill with
a simple clamp/strong magnet arrangement.
The coolant that I am using is Koolmist which is a synthetic concoction mixed with water
at a ratio of four ounces to a gallon of water.
It seems to work fine.
Results
So far, so good. I haven’t run the system very
much yet (just completed) but everything seems fine. The bigger question is whether flood cooling itself is something that is worth the added complexity…time
will tell but I think I am going to like this system.
Steve
Coolant flow in
operation
Links
The usual disclaimer: I have no
financial interest in these companies, use at your own risk,
I liked their products and services:
Source for specialized PVC pipe
couplings:
http://www.littlegreenhouse.com/accessory/pvc.shtml
Big orange store where I bought
(via internet) the tub:
Company that manufactures the tub
(45 gallon version):
http://www.argeecorp.com/HTML/mixatub.htm
Source for LocLine
flexible hose: