Machining or metal cutting is a tough business. With every passing year, customers demand higher quality components at a lower price. Moreover, to satisfy the growing demands, machine tool users need to increase their production capacity constantly, these factors put a huge strain on their profitability. If you are facing such issues, we definitely encourage you to read along.
In our experience, CNC machine users struggle to understand the correlation between the effects of tramp oil and their bottom line. Having studied this field of manufacturing for more than two decades, here is a list of hidden costs which a CNC machine shop owner incurs because of presence of tramp oil in the coolant.
Choice of coolant
Usually all cutting fluid or coolant suppliers have a range of products to offer. The most expensive ones are the ones which perform well even under harsh manufacturing conditions. Although I am not an expert, but having interacted with a lot of coolant manufacturers over the years, it has been observed that manufacturers end up paying a lot more over the long term because systems are not in place to monitor the quality, life and usage of coolant.
Only if the machine users realised that if proper systems like good quality tramp oil separators or skimmers are implemented for all the machines, they can use coolants that are less expensive! considering that good quality tramp oil separator or skimmers and good quality coolant filtration systems are a one-time investment, whereas using expensive coolant is a monthly recurring expenditure.
Following challenges reflect the hidden costs incurred by machinists:
Increased consumption of machining coolant
In the industry, the decision of whether the coolant is fit to use further or not is based mainly on crude parameters like odour, colour, visual appearance and rarely on quantifiable parameters like pH, concentration, bacterial count etc.
The presence of tramp oil in the coolant leads to higher bacterial count, lowering of pH which results in bad odour inside the shopfloor. This leads to the wrong conclusion that the coolant needs to be ‘topped up’. This not only causes higher consumption of water but also the actual coolant oil, which is expensive.
Increase in component rejects
In my experience, many manufacturers fail to consider the role that coolant quality plays in production. Tramp oil reduces the lubricating and heat dissipating abilities of the coolant. This degradation has an adverse impact on the component quality as tighter tolerances or specifications are difficult to maintain.
Again, the blame is not put on the ‘bad’ coolant. Manufacturers start adjusting or looking for issues in the machine and its setting.
Mostly, the solution is extremely simple- that of installing a tramp oil separator system which has a higher oil removal rate than the rate at which tramp oil is added in the coolant.
Surface finish
This point is similar to the earlier one as it is related to the component quality. However, there needs to be a special mention of it since presence of tramp oil in the coolant especially affects the surface finish and more so in case of aluminium components. Presence of tramp oil causes ‘pitting marks’ on aluminium. Pitting is a form of corrosion due to which white coloured spots are generated on the machined components.
Customer rejection cost
The issues of component quality discussed above are better to handle since it is assumed, that the quality issues are spotted and rectified before the components are shipped. However, we have had customers tell us horrific stories of how the entire shipment of components were rejected by their customer since they found rust on some components.
Although there are many factors at play here, however it has been observed that components made with good quality coolant have a lower chance of immediate rusting than the ones machined with coolant with high tramp oil.
Maintenance cost
Coolant is like the blood of the machine- it affects each and every component inside a CNC machine tool. The effects of continuously using bad coolant are not dramatic or sudden. Just like the build-up of blood cholesterol is slow and steady, similarly the effects of dirty coolant are also slow but steady. However, if these habits continue- permanent damage is certain.
Again, the blame is almost never put on these habits of coolant usage as the machine stops because of a bearing or a spindle failure. However, the reason why a bearing failed prematurely may be due to the presence of the tramp oil in the coolant.
The Human cost
The human cost is the most hidden and hence overlooked cost a CNC machine shop owner has to incur because of using dirty/oily coolant. Science tells us the following- tramp oil forms a layer on the coolant which does not allow atmospheric oxygen to mix with the coolant. This creates a healthy environment for ‘anaerobic bacteria’ to grow inside the coolant. When this dirty coolant comes in contact with operator’s skin it causes dermatitis. This leads to lower productivity, higher absenteeism and lowering of morale of the workforce.
The other cause for operator health concern is the nauseating smell of tramp oil on the coolant surface. Being in such an environment causes headache, dizziness, and nausea.
To summarize, one must be at least aware of all these hidden costs while running a CNC machine shop. A prompt action is recommended for the removal of tramp oil since the cost of inaction is going to be much higher in the long run.
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Dear innovationfilter.com owner, Your posts are always well researched.
Thank you
Hello innovationfilter.com admin, Good job!