Oil Skimmers for CNC Milling Machines
Coolants that are free of tramp oil prevent premature replacement and are important for maintaining the desired coolant properties – not only on CNC machines.
Problem
Coolants used in CNC milling and turning machines for metalworking need to fulfill a lot of requirements and are under constant stress. The effectiveness of the oil skimmer depends on your specific conditions and the choice of the right model. Especially with CNC milling and turning machines, there are significant differences in tank sizes and installation conditions that must be taken into account.
Which oil skimmer is best for coolant tanks of CNC milling and turning machines?
CNC milling machines can vary greatly in their design, so there is no simple answer to which skimmer is the optimal one. To select the best possible model, a detailed assessment of the individual conditions on site should be carried out.
In general, the surface area of the coolant tank on your CNC machine should be the decisive factor when choosing the correct oil skimmer model. While belt skimmers perform well in smaller tanks, these models are less effective for larger tanks. In practice, the individual circumstances of the CNC milling system must be considered.
To ensure that a belt skimmer works effectively, the surface of the coolant tank should be as small as possible so that the oil layer can be completely removed by the suction effect of the immersed belt. This is a challenge where many models of belt skimmers fail.
From a certain tank size onward, the flow of the oil film towards the belt breaks off. The belt, which usually dips vertically into the tank, can only create a suction effect within a limited radius. Everything beyond that forms dead zones that the belt cannot reach, meaning the oil film is only partially removed, namely in the direct surroundings of the skimmer itself.
The low mixing and the constant oil film in these dead zones promote microbial contamination of the coolants due to insufficient oxygen input. This results in the need for much more frequent and costly coolant changes and significantly increases health risks for operators.
For which CNC machines is a belt skimmer ideal?
Small CNC milling systems usually also have smaller coolant tanks. Due to structural characteristics of the coolant tank, such as chip conveyors, pumps, level sensors and piping, sometimes in larger tanks there is only enough space to use a belt skimmer. In this case, belt skimmers are also used on CNC systems with larger coolant tanks. To cover as much surface area as possible, multiple belt skimmers can also be used, as this is often the only way to achieve satisfactory results.
Which oil skimmer for CNC machines?
For smaller tanks or when there are structural obstacles:
Belt skimmer
Here are two durable belt skimmers from FRIESS:
- Model WBS (guide rollers increase the contact with the surface)
Advantage:
Belt skimmers can also be used where structural features only allow limited access to the coolant tank and where skimmers with a larger area of operation, such as tube skimmers, cannot be implemented, for example due to chip conveyors and pumps located in the tank.
Disadvantage:
The oil film is only captured within a limited radius around the immersion point of the skimmer belt. The model WBS (angular belt skimmer) improves on this issue by increasing the radius, but does not fully solve it. To achieve sufficient results, several belt skimmers should be used for larger surface areas (if the conditions for a tube skimmer are not available).
What is the ideal solution for larger CNC milling machines and coolant tanks to remove oil from the coolant with an oil skimmer?
Tube skimmer
The ideal oil skimmer for keeping coolant in CNC machines free of oil is one that removes oil from the entire surface, removes a large amount of oil while removing very little coolant, and ideally continues removing oil reliably even with fluctuating levels. For tanks above a certain size, the tube skimmer is the first choice.
The Friess range includes various tube skimmer models with different performance characteristics
The length of the floating tube can be adapted to the size of the tank, which represents an unbeatable advantage compared to other types of oil skimmers. In this way, the oil film can be removed across a large surface area. The special skimmer tube, with its oleophilic properties, ensures that as much oil as possible adheres to the tube and that as little coolant as possible reaches the scrapers. The circular motion of the oil collector tube ensures widespread oil removal and even pulls the floating oil out from the corners of the tank. Therefore the entire surface of the coolant remains oil-free, so that anaerobic bacteria has very no viable environment to prosper. As a result, the coolants remain fresh and usable for longer.
Here are the proven FRIESS tube skimmers for different coolant tank capacities:
- Oil skimmer model S 100 → specially designed for very large basins and tanks that may experience strong level fluctuations. Often used for centralised coolant systems
- Model W40 → for tanks of various sizes with a width starting at 800 mm
- Model W20 → for very narrow tanks with a width of 500 – maximum 1000 mm
- Model 1U → for small coolant tanks. The standard model for most CNC machines
- Model 1S → for vertical use in smaller emulsion containers. Perfect model for underground coolant tanks
Advantage:
There is virtually no upper limit to the size of coolant tanks on CNC milling machines. The FRIESS product range includes a series of powerful oil skimmers that are perfectly suited for large CNC systems as well as smaller tanks. The tube length can be flexibly adapted to the tank size. The models are also equipped with different motors designed to meet the required performance characteristics.
Disadvantage:
Depending on the structural conditions of the tank, tube routing may be hindered by obstacles such as chip conveyors, pumps, or similar components located in the tank. Especially with space-saving CNC milling cabins where an integrated coolant tank is located in the lower section of the machine, free tube routing may not always be possible. In such cases, customized solutions can be coordinated together.
We will be happy to advise you on your individual application and support you in finding the optimal solution!
Conclusion on oil skimmers for CNC machines:
An individual assessment is always recommended in order to achieve satisfactory results. We would be happy to advise you on our versatile oil skimmers and help you achieve maximum performance for your coolant in your CNC milling and turning machines. Your goal—and ours—is the significant extension of the service life of costly coolants and the associated economic benefits. As a rule, FRIESS skimmers pay for themselves after a short time due to the considerable extension of coolant lifespan. Purchase and disposal costs are significantly reduced.
Checklist so we can help you:
- How large is the tank or basin for the coolants?
- Are there obstacles that restrict access to the system?
- Are there obstacles inside the tank that prevent large-area capture of the oil film?