Cutting Fluid Management Concepts

By Barrie Taylor | Coolant Management


Seems everyone these days has a version of the 6C’s to illustrate a point. From nursing to marketing to credit companies everyone is at it so why should Metal Working Fluids be an exception? This is our take on the thorny subject of cutting fluid management concepts and how it relates to our own range of equipment.

The concepts within this article should form the basis of best practice in any machine shop using metal working fluids. Properly implemented it will reduce costs and increase productivity. The problem is that its labour intensive and tedious to maintain. If you want an easier way then we can help, we are equipment suppliers after all, and our full blown coolant management systems will perform virtually every task of the 6C’s automatically every single day.

The significance of Metal Working Fluids is widely recognised, but very often treated as a support function, a necessary evil but not that important. What if I suggest that the average MWF 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 a MWF includes the cost of everything from the purchase of the neat product to its disposal at end of life. While it is easy to calculate the purchase and disposal costs the hidden costs in-between make it impossible to see with any clarity if the investment in MWF equipment is going to reduce TCO. No surprise then that payback figures to justify that new shiny piece of fluid management stuff get screwed when this information is either not available – or worst still mostly available but just plain ignored.

The TCO of MWF has 2 components, MWF Purchase and MWF Management. Of these, MWF Management is a significant contributor of TCO. Any lapse or gaps in fluid management 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 metal working fluids go wrong the consequences certainly don’t remain hidden. Many machine shop managers are trying to fix ‘problems’ when it would be better if they concentrated on eradicating the ’cause’.

Some predominantly common symptoms stemming from the use of metal working fluids in a machine shop are rancid smell, skin irritation, tool life, corrosion, residue, paint peel off, foaming issues I could go on.

If you were to do a root cause analysis from among the most probable causes, for example, concentration, pH, water quality, tramp oil, filtration etc, you will find high interaction among these variables making it difficult to pin down the actual ‘root cause. Therefore often a solution to a specific symptom or problem in one machine shop may not yield the same result for the same problem in another. Trouble is that this problem solving malarkey takes time and money. Isn’t it better to have a good systematic approach to coolant management that covers everything that happens to a MWF concentrate from the minute it arrives to the end of life disposal. This may well eradicate ‘problem solving’ altogether.

Cutting Fluid Management Concepts in Practice

So what is the 6C’s concept? Put simply its 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 because if implemented properly someone will have to pay for it, right?

We begin with the assumption 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. That said the 6C coolant management concept is generic and therefore ‘application-manufacturer’ independent. No matter what the brand all water mix coolants have a life expectancy depending on their chemistry when originally produced as a concentrate by the manufacturer. Unfortunately 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 competition’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 specification therefore reducing consumption and improving coolant performance characteristics and ultimately reducing disposal cost.

C1 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 you may get an unstable, reverse emulsion of water in oil, not good. Its best 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.

C2 Control
The cockpit of the coolant management system. Many cutting fluid manufacturers and service providers, who claim to offer coolant management services, 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 its the end also. Both service providers and users need to travel beyond ‘Control’ to complete the coolant management cycle.

C3 Contaminant
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 these pages.

C4 Cleanliness
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 tranquilisers. Yet skipping on this essential aspect, especially if the stand alone sump system has been heavily infected with bacteria or fungus, is just nonsense. Filling an infected machine with fresh coolant will not solve the problem either. Without using 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 here are ours.

C5 Cleaning
Not to be confused with Cleanliness. It is just not good cleaning that is essential, but a sustained cleaning schedule that ensures cleanliness of the sump in an ongoing manner. This scheduling could be part of Preventive Maintenance (PM) program or Condition Monitoring (CM) schedules. The adherence to a schedule should be driven from the top down otherwise this will become just a cleaning activity. 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 make up fluid. Another myth is that coolant will be given an infinite life, 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. However 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.

Its a fact that the C that most companies and service providers focus on is ‘C2 Control’. You will recognise the wall charts which are religiously maintained to show how well coolant checks are progressing. Unfortunately without the other pieces of the jigsaw it doesn’t really work. Total Cost of Ownership has to provide for the other functions and if that is done then machine shop cutting fluids will last and perform better. From our point of view, as a centralised system supplier, that’s good because now we have the TCO to stack up against the cost of a full blown central management system. By removing every bit of the labour intensive implementation of the 6C’s that a fully automatic coolant management will provide for we may just have a cost effective solution for you.

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(2) comments

Dan Sturgis April 26, 2017

How often should a 55,000 gallon system running 5% coolant require the entire system to be emptied and the coolant replaced?

If the coolant is kept clean is make-up water and coolant adds enough to prevent ever changing out the coolant?

    Barrie Taylor April 26, 2017

    Thanks for the question. Depends on the level of cleanliness that can be obtained. In a closed loop system like ours where machine coolant is constantly being returned to the separator the re-supplied clean coolant can have less than 1% tramp oil and much of the floating debris, which causes sludge build up, will have been removed. This happens automatically 24/7. Losses of coolant due to evaporation and drag out will also be made up automatically at the central plant. This means that the coolant is never under stress due to inconsistent dilution control and add hock cleaning. If you have a way to emulate the same level of cleaning without using a central plant then there is a more than even chance that the result would be the same. However I suspect that at this level it will be labour intensive. In addition our systems continue to circulate machine tool volumes so even when production has ceased, for example overnight or at weekends, coolant does not lie idle allowing bacteria to breed. Many of our systems have lasted years without any cleanout.

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