Cutting fluid
Cooling lubricants or coolants (abbreviation: KSS) - also known as drilling or grinding milk - used in manufacturing technology at the cutting and forming machine tools, the heat dissipation and reduce the friction between the tool and workpiece by lubrication. In addition they serve some machining processes chip removal by rinsing from the work environment, better dimensional accuracy of the workpiece, a better surface finish, reducing the built-up edge on the tool and the binding of the dust (for eg when grinding ). Side effect of the cooling lubricant, the anti-corrosion of the workpiece.
Lubrication
When machining and forming occurs mainly mixed friction. Cooling lubricant reducing friction by lubrication and thus reduce the wear of the tool, the heating of the workpiece and the energy requirements. The cooling lubricants may be added to reflect the highest standards additives. EP additives ( extreme pressure additive ) react at high pressures and temperatures with the material to be processed, thereby preventing roughness peaks. AW additives ( anti-wear additives ) form an adherent film on the surface of the tool and workpiece.
Cooling
Coolant to remove the heat as fast as possible from the site of action in order to avoid changing the structure in the outer layers of the tool and the material. The machining accuracy benefits from a good cooling. For water- mixed cooling lubricants in addition to the high heat capacity of the water content also contributes significantly to the evaporation of water for cooling.
Components
In addition to water and oils are commonly used additives, which are added prior to and during use. These include defoamers, biocides ( bactericides / fungicides) for pre-and re-preservation, disinfectant cleaner, stabilizers, emulsifiers, anti-corrosion additives, extreme pressure additives. Coolants and their preparations, the EC Dangerous Preparations Directive 1999/45/EC match. To this end, the EC safety data sheets must be provided by the manufacturer.
Types of cooling lubricant
A distinction is made between two types of cooling lubricants in accordance with DIN 51385:
- Neat ( nw ) coolants
- Water-miscible ( wm ) and mixed with water ( wg ) coolants
Neat KSS
Unalloyed (without chemical additives acting ) and alloyed oils. In most cases paraffin- naphthene or mineral oils, synthetic oils such as rare Hydrocracked oils, ester oils, Hydrieröle. For very simple edits enough "pure" mineral oil, but mostly chlorine additives are added to improve the performance of the oil phosphorus, sulfur, and in very rare cases. Chlorine-containing oils are highly effective, but health was precarious and in the disposal very expensive. Other additives provide corrosion protection, the reduction of foaming and oil mist, improve the flow behavior at low temperatures and the viscosity index. Neat KSS then come principally used when high lubricating effect is desired.
Water-miscible cutting fluids
Water-miscible concentrates or ready- emulsions. Mineral oil-based water-miscible cutting fluids contain, in addition emulsifiers and mineral oil and additives to improve lubrication, such as ester oils and sulfurized additives, anti-corrosion additives and additives to prevent foaming. Mineral oil-free water-miscible cooling lubricant emulsions may be, for example, on the basis of rapeseed oil, but also solutions containing for lubrication instead of oil, for example, polymeric alcohols. The properties of water-miscible cutting fluids are good heat dissipation, but lower lubricity. The oil content in the emulsions usually is from 5 to 8 percent.
Cleaning of the cooling lubricant
Usefully, the cooling lubricants are filtered in order to use them longer can. Clean coolant give a better surface finish. In machine tools with coolant through spindle and tool a filter device is often mandatory by the manufacturer. Use specific MWF filter, settling tanks or magnetic separators are used. The use of cooling lubricants is important for improving the tool life and the surface quality of the materials. Disposal is not a problem over all public waste disposal, on a regular monitoring of the KSS, the operator has to pay ( weekly measurements of the concentration of nitrate and nitrite value, as well as the pH value ).
Attack by germs
Water-miscible cutting fluids can be infected by bacteria and fungi. In particular, at some time in use KSS occurs during longer breaks (eg Christmas holidays ) to bacteria and fungi, which manifests itself in a strong odor and possibly discoloration of the KSS. Often resulting from the infestation health complaints among the workers who come into contact with KSS. In addition to frequent mild inflammation of everyday wounds may also cause rashes and allergic reactions. Technical problems can be caused by the clogging of pipes caused by fungal filaments and / or slime bacteria. To avoid this, biocides may be used. Neat cutting fluids are very rarely affected by microbial attack. Mineral oil-based cutting fluids are particularly vulnerable to bacteria and fungi, mineral oil-free KSS less because they contain less organic material.
Environment and Health
Coolant must be professionally applied and disposed of, otherwise threats to environment and operators arise. Disposal of KSS is costly and may be carried out by specialized companies. The proper disposal of KSS must be proven. In confined spaces, may cause an accumulation of oils in the air, which is why the oil content of air must be reduced by appropriate devices.