The primary functions of cutting fluid are chip evacuation, cooling, and lubrication between the tool and the workpiece material. If applied correctly, it will maximize the output, increase process security and improve the tool performance and component quality.
In some cases, it may be an environmental and cost-perspective benefit to machine without coolant (dry machining). Contact your Sandvik Coromant specialist to choose the best tool, geometry and grade if you opt for dry machining.
Many applications require coolant for tolerance, surface, and machinability factors. If coolant is required, it should be optimized to maximize its true potential.
There are different aspects of coolant that are important for the cutting process:
- Coolant media
- Coolant outlet
- Coolant pressure
There are a number of different coolant medias used when turning:
- Emulsion: a mix of water and oil (5–10% oil in the water) is the most common coolant media
- Oil: in some machines, oil is used instead of emulsion
- Compressed air: used for chip evacuation, but it does not take away heat in a good way
- MQL: minimum quantity lubrication – compressed air with a minimum quantity of oil for lubrication
- Cryogenic coolant: a liquefied gas is used as coolant to maximize the cooling effect
Emulsion, oil, and air can be applied through the coolant channels in turning tools. When mentioning coolant in general terms, we mean cooling with emulsion or oil. MQL and Cryogenic coolant require special equipment.
Most modern turning tools are equipped with internal coolant through the tool—many of these actually offer the combination of precision over coolant and under coolant. The outlets in the tool can be of the following types, giving different benefits to your machining:
Conventional coolant versus precision coolant
Precision coolant, or precision over coolant: a nozzle (or similar delivery system) directs a coolant beam directly toward the cutting zone on the rake side. Reduces temperature and improves chip control. Can be used with high pressure to improve chip breaking
Under coolant: a coolant beam on the flank side that effectively takes away heat from the insert, which gives longer tool life
Conventional coolant outlet: for example, adjustable nozzles that in most cases have a bigger outlet diameter than precision coolant nozzles. Meant to flow coolant over the insert and component during machining (may be referred to as flood coolant). These tools are not meant to be used with high pressure
Modern turning tools feature nozzles that deliver precision coolant directed exactly to the cutting zone on the rake side, which controls chip breaking and offers secure machining. To optimize machine capabilities and further improve tool life and chip formation, coolant delivery and velocity can be fine-tuned by changing the nozzle diameter.
The positive effects of precision coolant start at low coolant pressure. But the higher the pressure, the more demanding the material is to be successfully machined.
With precision coolant, you get improved chip control, longer tool life, better process security and higher productivity.
Without precision coolant, chip jamming may be a problem, causing machine stoppages, service call outs, increased tool wear and poor surface finish.
The most modern turning concepts are also featured with under coolant. The under coolant controls the heat in the cutting zone, which leads to improved tool life and predictable machining.
Under coolant is very efficient already at low coolant pressure, but the higher the pressure, the bigger effect we can see in tool life increase. It’s possible to increase the cutting speed or the feed to improve the output.