Minimum quantity lubrication For minimum costs and maximum protection of the environment Cooling lubricants and coolant systems have various tasks in metal cutting. Primarily they conduct heat and reduce friction. They ensure a uniform temperature of the workpiece and tool and help to maintain tolerances. Moreover, in many applications the cooling lubricants also transport chips. Supply, preparation, and disposal of cooling lubricants can cause considerable costs. Additionally, these substances pollute the environment. Therefore, it is worthwhile to think about alternatives. A possible solution in searching for the optimum lubrication system is minimum quantity lubrication (MQL), which is becoming increasingly important. This is an alternative between wet and dry machining. In the case of minimum quantity lubrication, the quantity of the applied lubricant is reduced to a minimum. The maximum volume flow rate with MQL is less than 50 ml/hour. Compared to conven- tional wet machining, where up to 12,000 liters of coolant is used per hour and must be reconditioned again, the user of the MQL system does not need a higher quantity than a few milliliters. The air-oil mixture (aerosol) is either directly fed to the point of application, or sprayed via a compressed air stream in the cutting area. The optimum lubrication considerably reduces the frictional heat. With MQL, the machining costs can be reduced considerably. The environment is also protected and possible health risks for the machine operator are reduced. Workpiece and metal chips stay almost dry MQL is a loss or consumption lubrication. The applied medium almost completely evaporates at the point of application. Through the evaporation as well as through compressed air stream, the workpiece is additionally cooled. The remaining heat is conducted via the tool and the metal chips. The chips, workpiece and tool stay almost dry if the system is ideally adjusted. 01 – Minimum quantity lubrication
Transcript
Minimum quantity lubricationFor minimum costs and maximum protection of the environment
Cooling lubricants and coolant systems have various tasks in metal cutting. Primarily they conduct heat
and reduce friction. They ensure a uniform temperature of the workpiece and tool and help to maintain tolerances. Moreover, in many
applications the cooling lubricants also transport chips. Supply, preparation, and disposal of cooling lubricants can cause considerable costs. Additionally, these substances pollute the environment. Therefore, it is worthwhile to think about alternatives.
A possible solution in searching for the optimum lubrication system is minimum quantity lubrication (MQL), which is becoming increasingly important. This
is an alternative between wet and dry machining. In the case of minimum quantity lubrication, the quantity of the applied lubricant is reduced to a minimum. The maximum volume flow rate with MQL is less than 50 ml/hour. Compared to conven-tional wet machining, where up to 12,000 liters of coolant is used per hour and must be reconditioned again, the user of the MQL system does not need a higher quantity than a few milliliters. The air-oil mixture (aerosol) is either directly fed to the point of application, or sprayed via a compressed air stream in the cutting area. The optimum lubrication considerably reduces the frictional heat. With MQL, the machining costs can be reduced considerably. The environment is also protected and possible health risks for the machine operator are reduced.
Workpiece and metal chips stay almost dry
MQL is a loss or consumption lubrication. The applied medium almost completely evaporates at the point of application. Through the evaporation as well as through compressed air stream, the workpiece is additionally cooled. The remaining heat is conducted via the tool and the metal chips. The chips, workpiece and tool stay almost dry if the system is ideally adjusted.
01 – Minimum quantity lubrication
The minimum quantity lubrication concept can be used wherever friction needs to be minimized by using lubricants. It is ideal for drilling, deep hole drilling, milling, tapping, and turning. The lubricant consumption and adjusted values differentiate depending on the cutting performance, material, tool design, or volume of chips. Many practical applications in MQL have shown that the coolant consumption for metal cutting applications lies between 5 and 30 ml/h.
Depending on the environmental conditions, MQL requires minimal up to farreaching changes of the machine and the tool. It is important to ensure a proper removal of metal chips from the machine as well as an efficient extraction of aerosol steams. For high performance cutting and specially-designed machines, tools, and toolholding systems suitable for applications with MQL are used.
u Special Coolant tube HSK-Av Coolant tube nutw Tool shank x Top part LVS (depending on the diameter)y Actuation (radial length adjustment)U Length adjustment screw (radially actuated) with guide pinV Connecting tube
u KMR HSK-A coolant tubev Coolant tube nutw Tool shank x Adjustable insert VZSy Intermediate sleeve type GZB-SU Length adjustment screw LVS with connecting tube / MQL
Two possibilities for coolant supply
The coolant with MQL can be supplied in two different ways: Systems with external supply
In case of external supply, the minimum quantity is supplied to the tool or the required point via a nozzle which is installed in the machining area of the machine.
Systems with internal supply
The internal feeding of the MQL medium in turn is done through the machine spindle, the toolholding system, and the tool directly on the cutting edge. This allows an optimum moistening of the involved components at the point of application. The group of MQL systems with internal supply is divided into one-channel and two-channel MQL systems. In case of the one-channel systems, the aerosol is mixed outside the spindle, whereby the lubricant of a two-channel system is mixed directly inside the spindle.
SCHUNK-Toolholding Systems offer process reliability for MQL applications
The design of the toolholder components for MQL systems are similar to a nozzle system. The lubricant-air mixture is directed to the contact zone of the tool. At this point it reduces friction and heat development.
The toolholder has to accomplish important functions. It has to clamp the tool safely and in case of internal feeding, has to ensure an unhindered loss-free flow from the end of the spindle to the tip of the tool. Most important is that the coolant is safely regulated and directed into the tool. This also has to be ensured in case of frequent tool changes and the use of different cutting tools. Dead spaces or notches inside the tooldholder have to be avoided. The excellent run-out and repeat accuracy are an absolute must as well as safe holding forces and high balancing qualities.
Therefore, TENDO hydraulic toolholders and TRIBOS polygonal clamping technology from SCHUNK are excellently suited for MQL applications. The excellent run-out of less than 0,003 mm and the vibration dampening characteristics increase tool life and cutting volume of the clamped tools. Com-pared to the heat-shrink toolholders, TENDO and TRIBOS ensure a very high process reliability. Both toolholding systems from SCHUNK can be individually modified for MQL applications.
SCHUNK has a close partnership with MQL-machine-builders, tool manufacturers and well-known end-users to provide the necessary technical focus and application experience needed when using MQL technologies.
Additional Product Information onMQL
You can find detailed information on MQL in the SCHUNK Toolhol-ding Systems catalog. A free cata-log can be requested by calling
800.772.4865or by visiting the SCHUNK website at www.schunk.com.The catalog pages for each SCHUNK product are also availa-ble for download atwww.schunk.com.
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Numerous advantages for the userUsing MQL in metal cutting offers many advantages:
Financial advantages
• Due to the omission of supply and disposal of coolant, high savings are possible.• After optimization of processes, a higher tool life can be expected.• Optimized processes reduce the machine cycle time up to 30 %.• Purchase, warehousing and transportation costs as well as disposal costs of the
coolant will be reduced considerably.• There will be no expenditures for control and care of coolant.• Depending on the application, extensive follow-up processes for cleaning/
washing of the workpieces will be reduced or can be completely eliminated.• Compared to wet metal chips, which are treated like hazardous waste, dry metal
chips can be sold as recycling material.
Ecological advantages
• No used emulsions will accumulate.• Accidents due to large quantities of leaking coolant are avoided.• Due to a dry machine, the risk of accidents at work are reduced.• Airway or skin diseases caused by coolants can be avoided.
There are many reasons to think about a change to an MQL-system. The environment and your wallet will thank you.
