Sunday, June 25, 2006

X1 Flood Cooling

It has been a while since my last post, but that's cuz I've been a busy little basement engineer! :-) I built an enclosure for the mill and implemented a flood cooling system. In addition to the cooling and lubrication benefits of a flood system, it is nice to keep the chips contained to a controlled area.

Basically it is an enclosure made from 3/4" MDF sitting on a base made of 2x4's.

What spurred me onto this was, while trying to make my pulleys, I discovered that the slow feed rates necessary with my ad hoc belt drive caused the 2024 aluminum to almost flake off. Airborne high strength aluminum dust can't be good! So, to solve that problem (plus gain other benefits) I built the enclosure.

The bottom is lined with 1/8" thick rubber that can be had from McMaster-Carr, 4 ft worth of P/N 86795K43. The filter setup is a food storage container with the bottom perforated, a large hole cut in the top and some nylon mesh sandwiched between the top and bottom for filtration. The mesh is also from McMaster (9318T48) and has .002" openings. It is about 40% open so flow isn't an issue. It doesn't let any solids past! The only issue I've found is that the coolant I'm using has a bit of a tendancy to foam, and that doesn't drain so well. I turned down the flow on my pump a bit and that took care of the problem for the most part. Speaking of which, the pump if from Harbor Freight, their P/N 45305.

I'm very pleased with the enclosure, and an unexpected benefit is that the 3/4" MDF really cuts down on the noise, which makes my wife happy! Most of the noise comes through the large front acrylic doors, but the ear protection knocks that down the rest of the way. Mainly it is nice that it keeps the noise polution out of the rest of the house.

I finished up the spindle pulley yesterday and will be working on the motor pulley today. I haven't test fitted the pulley yet, but if my calipers are accurate it should fit nicely!

BTW, the motor that I'm using is a 2.5 peak HP unit from Surplus Center.  Two things: they don't sell the correct speed controller for it and, if you work it hard, it will need a fan. 

All the DC speed controllers Surplus Center sells (currently) are of the SCR variety.  This motor is PWM rated.  Running it off a SCR controller will make it hot very fast, can fry the brushes and demagnetize the permant magnets.  Unfortunately, about the only PWM drive I've found that is rated to run this cheeta of motors is the KBWT-112 from KB Electronics.  It can be purchased through  It ain't cheap.  I'm getting away with running it on an SCR controller, but I've got a fan on it and try not to load it too hard.  The motor has a thermal switch (which can be wired in series with the armature wires) which will open at about 100 degrees C.  Having the motor abruptly shut down in the middle of a toolpath is frustrating, but the steppers will just get angry and it is better than smoking the motor.  The KB drive is definitely in my near future.

Speaking of the fan, with just a little creativity this is an easy thing to accomplish.  If you look closely at one of the pictures in the New Enclosure gallery at the right you'll see the fan... just look for the shiny propeller whizzing around at about 5000 RPM on top of the motor.  It is a 1/2" wide, 1/8" thick piece of aluminum stock.  I drilled a 9/32" hole at the exact center, put it in the bench vise and twisted a pitch on both sides.  I pressed (lightly hammered) it onto the stubby shaft coming out the top of that motor and VIOLA!  The motor now has a fan!

Ok, some might call that crazy to have an unshrouded "fan" whizzing around like that but keep in mind it is behind .220" thick acrylic.  There's no way I'd try this trick if it were just out in the open.  I've ran it for probably about an hour or two total now and it works great.  The air inside the enclosure is noticably warm when I open the doors after a long milling job so it is definitely cooling the motor.