Coolant Filter Retrofit for VMC

[Hoffman7]

I did quite a bit of searching here before making this post but never found info that addresses what I'm trying to do.

I run a two man automotive machine shop and we have a Milltronics VMC that we use for machining aluminum cylinderheads after weld repairs. It's not worked super hard daily like a parts manufacturer would but it does get pretty steady work.

We've been running Monroe Fluid Technology's Astro Cut C for six or seven years. We've been happy with the results but would like to see if we could extend the life of the coolant by filtering it. I'm going to start skimming to deal with tramp oil so I'm not super concerned with trying to filter out tramp oil (though that would be nice.)

The tank holds 50 gallons and has baffles to keep sizeable chips from the pump sump, though I'm sure we're getting some fines. Like I said my goal is to extend the life of the coolant and filter out fines, though frankly for the work we do the fines haven't been a problem.

The concept I'm envisioning is a retrofit that utilizes a separate external pump to draw coolant from the sump tank drain outlet, pump it through a couple of cannister filters, and dump it into the cabinet where it will drain back to the other side of the tank from the sump for good circulation through the entire tank. Make sense?

Was hoping that maybe someone here has tried this approach (or a better one) and could provide some feedback and technical ideas, like what pump and filter system they used.

Thanks in advance for any responces.

 

[2outof3]

Just add a Rosedale cannister filter between the existing pump and the return to machine coolant infeed to the machining area. Probably need some more hose.

 

[Hoffman7]

Thanks for the reply. That looks like a good system. Think I'll try that before I jump to something more elaborate like I described in the original post. What micron bag do you recommend?

I thought about the Nexgen system, but I'd have to modify my tank to accomodate the floats. Not sure if it's worth it since I have a belt style skimmer that I can more easily adapt and I know it does a great job in the wier tank on our large ultrasonic cleaner. That should handle the tramp oil.

 

[guythatbrews]

I have a screw machine running neat oil. Both the high pressure pump and the oil chiller have 5 micron bag filters. It works very well.

Both throw an alarm when the pressure differential across the bag drops below a certain level. I do not notice any coolant flow drop as the bag approaches full. If you don't have a good coolant pump you may find there is some loss of coolant flow as the bag approches end of life.

Try what 2outof3 says and just put it inline. Worst case add another pump later if you need to.

This machine has a single coolant return from the conveyor into the tank, easily accessible from the front of the machine. To keep some fines out of the tank I tie a five gallon paint strainer bag over the return. It really traps a bunch of fines and when it's full I just let it drain in a pail and toss it. It's a good cheap move if you can make it work.

 

[Hoffman7]

Thanks for the micron recommendation Guythatbrews.

I’m going to go with the Rosedale bag filter plumbed with the existing pump. I think it has enough ass to handle it. But like you said I could upgrade the pump if it doesn’t.

 

[gkoenig]

Thanks for the micron recommendation Guythatbrews.

I’m going to go with the Rosedale bag filter plumbed with the existing pump. I think it has enough ass to handle it. But like you said I could upgrade the pump if it doesn’t.

Be aware, you can't filter normal emulsive coolant down to 5 microns without stripping it (in the vast majority of cases). 10um is about as low as you want to go, though some coolants strip at 20um.

Some of the latest/greatest coolants go down to single micron filtration without stripping (Ometa promises this, as does QualiChem in a couple of their offerings). I am sure there are others, but I have worked directly with those two on these applications.

 

[Hoffman7]

Hmm. Thanks for the real world experience gkoenig. I had not considered stripping as issue before. Glad you brought it up.
I was more concerned with decreased flow with super low micron filters, but not stripping the base out of suspension. I'll send the question to Monroe Fluid Tech, but who know's if I'll get an answer. If I don't hear anything back I guess I'll play it safe and go with 25um?

Wonder what size strips tramp oil?

 

[gkoenig]

I was more concerned with decreased flow with super low micron filters,

If you go with the #8 bag size, you'll have more than enough flow overhead that there will be hardly any impact at the coolant nozzle. They are bigger than the #4 bag Rosedale housings, but don't cost much more or take up that much more floor space.

 

[YDCHEN]

If your cutting fluid is emulsion or semi-synthetic type, the filter should not be less than 20um, otherwise you will experience serious foam problems. Synthetic is Ok to use 5um, but some pumps do not support the use of full synthetic，causes wear issue.

 

[Hoffman7]

I’m getting good info here. Much appreciated! I have over thirty years of manual machining experience but this is my first cnc and I never worked around any either so it’s been a learning curve that’s been steep at times.

I’ve recently experienced some odd coolant conditions that have been hard to find explanations for. It separated somewhat after a few hours of running. Added a couple of gallons of distilled water and it turned into a very thick milkshake like substance. I can’t figure out if it was bacteria or tramp oil emulsification adding viscosity. Adding more water made it even more viscous. Weird. It happened suddenly.

The coolant was Monroe Fluid Technology Astro Cut C . A couple of years old. The machine isn’t run daily. Sometimes we’ll go a couple of weeks without using it. We only run aluminum.

Would love to hear if anyone else has run into this.

I plan to start overnight tramp oil skimming and running the coolant through a filter. I have to figure that will help extend the life.

 

[DouglasJRizzo]

@Hoffman7
Filtration and skimming are key. You'll have a big increase in coolant life. Also, an aquarium bubbler to oxygenate the coolant - it will kill off the anaerobic bacteria.

 

[Hoffman7]

I'll definitely install an aquarium bubbler. Best to run it every night, or just every few days?
Thanks for the tip.

 

[marccongdon]

I run the skimmers and bubbles on those cheapo "vacation" timers. Skimmer runs from 530-6 before I start the day and the bubbler comes on for 5 minutes every hour except for 2 hours before the skimmer comes on to give the oils time to collect on the top.

 

[DouglasJRizzo]

I'll definitely install an aquarium bubbler. Best to run it every night, or just every few days?
Thanks for the tip.

Every night. Coolant will stay fresh that way.

 

[Hoffman7]

Every night. Coolant will stay fresh that way.

Great info. Thanks everyone!

 

[garyhlucas]

The biggest thing to know about filters is they need to be really much bigger than you think. I worked in waste water and filters were a constant maintenance item until I started building some really big filters. My jobs went from needing filters cleaned every day to maintain flow to getting a week or more. We did lots of ultrafiltration work for the automotive machining industries to dispose of used coolants. An ultrafilter will strip all the metal fines and every last bit of oils and emulsions and leave the water cystal clear like bottled water. If there were dissolved metals we used acids or bases to precipitate the metals and we could then remove them too.

 

[Hoffman7]

I'm leaning toward a #12 bag size filter unit. That should handle my needs okay, I think.Especially since we're not trying to reduce it down to clear water. Won't be as much waste production.

 

[Duc]

I went with a #4 bag filter housing between the pump and the coolant nozzles. Works well for capturing the chip fines with a 100 micron bag. Has a ports for pre and post pressure gauges to monitor how clogged the bag is getting.

mcmaster 5168K249

 

[Hoffman7]

I have a couple of questions about the bubbler(s). My tank is 50 gallons. Would it be most effective to have several bubblers positioned around it? Also, will a typical pond bubbler hold up in the coolant? I've searched for coolant specific bubblers but get nothing. I'm looking at the 12" long bubblers.

I'm now leaning away from the #12 bag filter. Based on feedback here from users it looks like overkill and a cursory search of bags indicates prices are high for the #12 and not as readily available as the #4 & #8. Not to mention the #12 filter housing is $$.

Thanks guys for sharing your actual experiences!

 

[DouglasJRizzo]

@Hoffman7
I would think two at most. One at each end. More than adequate.