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CNC Coolant distribution

CNC Coolant distribution

CNC Coolant distribution

(OP)
Greetings all,

So here goes my first post. I am working on a new project to develop a centralized coolant distribution system for our CNC lathes. Currently we have a forklift drive around with a coolant tank and fill the machines individually as needed. In order to determine how much coolant we consume at each machine (they are not identical), I need to determine the flowrates of each machine during use. My question is what the best way to measure this flowrate short of simply standing at the machine with a bucket and a timer. I know there must be a better way. The machines are set at a fixed coolant flow (they dont have a flow control valve for the coolant). I am not sure if I am going to have to calculate the loss in pressure from the pump outlet to the machine turret. I know what kind of pumps we have and with some research could probably find the pump curves for each machine. Your help is greatly appreciated.

RE: CNC Coolant distribution

I don't know if there is a better way - sounds like a good plan to me. If your pumps are PD type (piston, gear or diaphragm) and you can find their design flow then you're pretty much there. Otherwise the design flow of your probably fairly small pumps could be higher or lower depending on some small differences in tubing length, nozzle size of flow control device fitted. Does the mfr not provide this info with each machine??

I assume from the above that each machine has it's own tank - does this re-circulate and filter and hence only need topping up ever now and then or a once through system??

Your only other option is to find a common flow line from your pump and insert some sort of small inline meter, but that seems a lot of effort and cost when you can do the same with a bucket and a timer...

A picture would be nice.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

RE: CNC Coolant distribution

A bucket and a watch are the most trustworthy way to gather the data you asked for.

But, are you measuring the right thing? Most machine tools recirculate the coolant locally. The only 'consumption' is evaporation, spray over the barriers, and 'carryout' on the workpieces. That number should be much lower than the volume of coolant recirculated locally.



Mike Halloran
Pembroke Pines, FL, USA

RE: CNC Coolant distribution

(OP)
I'm sorry by consumption I meant flowrate at the cutting point. I checked the manuals in addition to speaking with the manufacturer and could not find any information on coolant flowrates. Each machine has its own tank into which the coolant recirculates and is pumped out again. I guess what I'm really trying to do is find a way to calculate the head based on piping length, piping diameter, and change in height. With this I should be able to look at the pump curve and find the theoretical flow am I right?

I think the bucket method would be very difficult considering we have 73 CNC lathes many of which shoot the coolant out vertically or in awkward directions.

RE: CNC Coolant distribution

The tank typically slides out for cleaning.

Slide it out, and put a bucket in it, under where the machine tray drains into the tank.

Run the pump for a minute, and measure what's in the bucket.



If you're planning to replace the 73 individual coolant pumps and tanks with one single pump and big tank, consider that:

You're introducing a single point of failure that you don't have now.

That single point failure mode may include infection of the coolant, or contamination with anything that shouldn't be there, in addition to whatever can go wrong with the pump.

The changes you make to an individual machine may affect its warranty.

You will need flow control valves at each machine, and they will not be happy with the fine particles that are likely to be found in recirculated coolant.


Mike Halloran
Pembroke Pines, FL, USA

RE: CNC Coolant distribution

I have seen a few CNC lathe coolant systems, but not too many that used a central feed circuit. One reason is that most CNC lathes are designed with an integral coolant system that is satisfactory for most duty cycles. Chip removal from the coolant is also a big issue, and debris in the coolant can create problems with remote pumps and valves. Another consideration is that machining different metals requires different types of coolants.

Another problem I remember when running the CNC lathes "lights out" was the machines being unable to adequately clear the chips and causing the coolant to spill out onto the shop floor.

RE: CNC Coolant distribution

Coolant distributing system are typically a centralized mixing station and piping to send the coolant to the various machines. Coolant consumption is not normally needed except for having sufficient flow to meet usage on the system. Coolant consumption is not normally a critical issue except in the overall consumption of coolant. Bean counters need the overall consumption but knowing this machine used 4 gallons a day and the other machine used 3 gallons a day non-value added.

Coolant systems on most machining applications have three issues. One is tramp oil accumulating on the surface of the coolant tank allowing anaerobic bugs to grow in the coolant. This causes stinky coolant and dermatitis to operators. Proper makeup of coolant is another issue. Coolant should be made with distilled or deionized water. Tap water will cause precipitation of some coolant and even add other chemicals such as iron and other impurities reducing the life of the coolant. The final issue is maintaining the proper concentration of coolant to water. The active ingredients of the coolant are consumed and need to be adjusted.

There are numerous other factors such as allergic reactions, materials being machined, machining process being used, spitting in the coolant tank, etc...

You will still have to clean your coolant tanks on some regular basis removing sludge and other machining residue and foreign materials.

Good Luck

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