Why is it essential to remove tramp oil from machine coolants?
There are a lot of talks these days about “Green Business” and sustainable manufacturing practices. But one particular environmental concern, tramp oil in machine tool coolants, has been around for a long time. While most people think tramp oil is just a nuisance, it’s also bad for the environment, your equipment, and even your health.
Tramp oil is a common term for oils carried into a water-based synthetic or semi-synthetic coolant from external sources. These are non-emulsifiable oils, which means they tend to float on top of the coolant and form a layer.
It’s crucial to remove tramp oil from the CNC machine coolant because:
- Tramp oil contributes to emulsion failure and premature coolant disposal.
- Excessive tramp oil in the coolant causes rapid bacterial growth leading to a foamy, thick sludge.
- Tramp oil entraps the machining burr, chips, fines and causes a slurry which is a primary reason for excessive tool wear.
- A machine coolant free of tramp oil will have good surface wetting properties to prevent corrosion and improve surface finishes.
How does tramp oil get into the CNC machine tool coolant?
Tramp oil is a by-product of metalworking. The machine generates heat and friction, causing oil to oxidize and polymerize. It is then transported through the coolant system and recycled back into the coolant tank. As it is recycled, it accumulates in the coolant reservoir, forming a layer of floating oil.
Here are some common sources of tramp oils:
- Crankcase oil from CNC machine tools.
- Hydraulic oil from pumps, chucks, fixtures.
- Lube oil from spindle bearings, slides, bed ways,
- Lube oil from servomotor bearings.
- Coolant mist
- Workpieces- from previous operations
How do I know if my machines have a problem with tramp oil?
An increase in machine maintenance costs is the first sign that your machines have a problem with tramp oil. You may find that you are buying coolant filters more frequently or replacing the coolant more often. You may also find that you are adding too much coolant oil to the sump to achieve the desired concentration of your coolant.
A widespread symptom of tramp oil contamination is rough or dull tooling. The tiny particles of metal released as chips from your cutting operation are attracted to the tramp oil and form a slurry (metal fines suspended in oil). This slurry will coat your tooling and cause it to become dull, which results in poor performance and excessive wear on your tooling.
The most obvious sign of a tramp oil contamination problem, is when the tramp oil begins to float on top of the coolant in the sump. However, there is already plenty of damage done inside your machine’s components by this point.
The following are a few consequences of ignoring tramp oil from CNC machine coolants:-
- Degraded quality of machining coolant
- Increase in production downtime
- Increase in coolant consumption
- Risk to operator health- the tramp oil may contain toxic compounds leading to dermatitis and other skin problems
- Machine tool & workpiece damage
- Non-emulsifiable oils also clog up filters very quickly
Can you eliminate tramp oil in the machine coolant?
No, you cannot eliminate tramp oil in machine coolant. There are two methods to manage tramp oil-
1) You can prevent tramp oil from entering the sump by using a tube skimmer. A tube skimmer is a good solution if your primary concern is oily parts and oily coolant.
2) You can remove tramp oil from the sump with a coalescer (removes up to 95% of tramp oil). A coalescer is a good solution for those concerned about increasing tool life, improving surface finish, and extending coolant life.
