Cutting Fluid Management Concepts 

By  Barrie Taylor

This is our take on the thorny subject of the cutting fluid life cycle and management concepts and how it relates to our own range of cutting fluid management systems. The concepts within this article should form the basis of best practice in any machine shop using metalworking fluids.


Properly implemented it will reduce costs and increase productivity.

The importance of metalworking fluids are widely accepted but often they are treated as a support function, a necessary evil not as important as other commodities in the production food chain.

Probably the average cutting fluid cost to a production engineering company may be as high as 10%-20% of total production costs? Surprised? Don’t agree? That’s probably because the Total Cost of Ownership (TCO) isn’t on your radar – yet.

The TCO of metalworking fluids includes the cost of everything from the purchase of the neat concentrated product to its disposal at end of life. While it is easy to calculate the purchase and disposal costs the costs in-between make it difficult to see with any clarity if the investment in metalworking fluid equipment is going to reduce TCO. No surprise then that payback figures to justify that new shiny piece of fluid management stuff gets screwed when this information is either not available – or worst still mostly available but just plain ignored.

The TCO of metalworking fluid has two components, the original metalworking fluid purchase and metalworking fluid management – how it is used. Metalworking fluid management is a significant contributor of TCO. 

Any lapse or gaps in how coolants and cutting fluids are used will incur extra costs which may well remain hidden and, by definition, unaccounted for. Given time it becomes difficult to unravel the true support cost for your fluids without starting from scratch.More importantly when metalworking fluids go wrong the consequences certainly don’t remain hidden.

Some predominantly common symptoms stemming from less than adequate care are rancid smell, skin irritation, tool life, corrosion, residue, paint peel off, foaming issues and more. 

Many machine shop managers are trying to fix ‘problems’ when it would be better if they concentrated on eradicating the cause.

Cause and Effect

Finding the cause of any water-mix coolant issues is infinitely more constructive than treating the problem. Eradicate the cause once and further problems disappear right?

However often the cause is not one issue it’s a combination of variables that accumulate to bring about a specific outcome.

Take topping up a machine tool sump as an example. If the coolant mix comes from one outlet for the entire shop it’s unlikely that each machine will remain the same. Variable materials, cutting speeds and cycle times will affect each machine and consequently the coolant dilution. Treating the ‘problem’ of erratic dilutions by altering each top up dilution, if properly managed, will solve the problem.

However, it will not remove the cause, which is the single point outlet for top-up fluid at a single dilution.

To eliminate cutting fluid problems what is needed is a method to ensure  total control of every aspect of coolant  management from start to finish.

Cutting Fluid Management Concepts- The 6C's

It’s a process that will prevent metal working coolants becoming an issue and pay back the time invested. Interestingly it will also highlight the true TCO of any fluid used in your machine shop. The implementation of a new program of care should be treated like any other and properly costed at each stage.

From the outset we assume that the right coolant has been selected for the application. Coolant selection is ‘application-manufacturer’ dependent. Process variables are large and interactive. The same coolant may not be suitable for the same application across another industry segment. Therefore, coolant selection has to be investigated in conjunction with the cutting fluid manufacturer. 

However the 6C coolant management concept is also  ‘application-manufacturer’ independent. No matter what the brand all water mix coolants have a life expectancy depending on their chemistry . The ‘field life’ expectancy is determined by biology and the coolant environment encountered in use on the machine shop floor. 

Therefore, it is a bit of a fallacy for some coolant manufacturers to claim product X has a longer sump life compared to their competitor's product Y.

It ignores the environmental biology and coolant management regime of each individual machine shop.

The concept of 6C is to introduce a coolant management system that will increase coolant sump life at least to its design expectation therefore reducing consumption and improving coolant performance characteristics and ultimately reducing disposal cost.


C1-Coolant Combine
The beginning of the cutting fluid life cycle and the coolant management concept. Water mix coolant and cutting fluids are an emulsion of oil droplets and water. By adding concentrate to agitated water this will form a stable emulsion. Adding water to the concentrate is not a good idea as  an unstable, reverse emulsion of water in oil can result

It is better to use an automatic mixer of some type even a low-end venturi type can do a great job and it avoids untrained operatives fiddling around with concentrate.

The cockpit of the coolant management system. Many cutting fluid manufacturers and service providers focus their activities only on this segment of the 6c concept. The ‘Control’ section is the critical day to day activities that must be performed if the coolant is to remain in best condition. Coolant level, dilution, and pH need to be monitored so that any deviation from specification can quickly be normalised before damage to the incumbent fluid can occur.

Additionally, water quality should also be monitored dependent on what is known or guaranteed by the water supply. As water constitutes upwards of 85% of the mix poor water quality is hardly going to enhance cutting fluid performance. While this is only the beginning of CMS sadly for many it’s the end also.

Both service providers and users need to travel beyond ‘Control’ to complete the coolant management cycle.

This is a big one. Without doubt the most common cause of cutting fluid failure is contamination from the production process. Tramp oil from machine tool slideway lubrication, hydraulic leaks, grease and dirt from the process material all contribute to contamination levels. Add to that chips, swarf and particulate from the cutting zone and you have a heady cocktail that will seek to shorten the life of your coolant.

There are all types of equipment available to deal with each of these issues, you will find plenty in the pages on this website.

Stopping a production machine tool so that the sump contents can be emptied and the sump properly cleaned often have production managers reaching for their tranquillisers. Yet skipping on this essential aspect, especially if the stand-alone sump system has been heavily infected with bacteria or fungus, makes no sense.

Filling an infected machine with fresh coolant will not solve the problem either. Without using a system cleaner to kill off the bugs the new coolant will be infected in no time. Even coolants in good order still benefit from having accumulated chips and sludge removed on a regular basis. There are plenty of options on the market that automate the process.
Not to be confused with Cleanliness. Good cleaning is essential but also a sustained cleaning schedule is necessary which ensures machine tool sumps stay in good condition. Unless contamination from the production process is removed daily, tramp oil in particular, cutting fluid sump life will suffer. This scheduling could be part of Preventive Maintenance (PM) program or Condition Monitoring (CM) schedules which will initiate a sump change regime at intervals needed before complete coolant breakdown. The schedule should be driven from top management down to ensure adherence otherwise other factors will get in the way.

Therefore “Cleanliness” is an Activity and “Cleaning Schedule” is a Commitment. This could be implemented through a Total Productive Maintenance (TPM) program.

C6-Coolant Re-Cycling
Coolant re-cycling is attractive to users as on the face of it would appear that old coolant is transformed into new. Not the case. It is simply a reconditioning exercise that removes tramp oil and particulate, gives the opportunity to inject new additives before mixing with new makeup fluid. Another myth is that coolant will be given an infinite life, again not so, coolants that are continually contaminated and then recycled will eventually reach the end of their life.

Re-Cycling is going to need equipment and man power to operate it, there are many choices on the market. Our own coolant management systems operate 24/7 to remove coolant contamination at source and have sustained coolants well beyond the expectations of the coolant supplier.

Without establishing your cutting fluids true cost of ownership justification for equipment is never going to happen.

The cutting fluid life cycle is a complicated mix requiring each part of the jigsaw to be in place to maintain performance.

Take a look at each of these conditions and it compare it with your own coolant care procedures. Missed anything? Probably and that will be contributing to operating costs however you cut it.  

Organising and maintaining a comprehensive metal working fluid program is often some way down the list for many production focused machine shops yet the dividends can pay off handsomely. Those that get it right often invest in equipment to aid the process. Some, fortunately for us, are able to convince their masters regarding payback and have invested heavily in the comprehensive coolant management systems that you will find on these pages.

A fully functioning coolant management system connected to every machine tool in the machine shop will eliminate much of the work and manpower associated with the 6C's. Which brings us back to where we started. Without establishing your cutting fluids true cost of ownership justification for equipment is never going to happen.

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