Machining is the wide spread metal shaping process, it consist rapid wear rate of cutting tools due to high cutting temperature generated during the process. Thus effective control of the heat generated during machining is essential to ensure good workpiece quality. Different cutting fluids are applied to avoid the problem; however conventional cutting fluids are restricted due to their harmful health and environmental impacts.
The necessity to machine using less harmful cutting fluids has led the researchers to develop new cutting fluids which are less harm and the result of the investigation came up with a new system called Minimum Quantity Lubrication (MQL).
Minimum Quantity Lubrication refers to use the small amount of cutting fluid, typically in order of 500 ml/hr or less than that which is about 10,000 times less than that of conventional cutting fluids.
Use of MQL system in various machining processes
The purpose of studying the various machining processes using MQL system is to:
- Easily available and low cost technology.
- Need of such improved system in this generation.
- Develop technical skills.
- Improve machining characteristics.
- Utilize natural resources in lubrication field.
- Provide pollution free lubricants for the industries.
Types of Lubrication :
Basically, there are three types of lubrication systems.
One is Flooded type, second is dry machining and third one is Minimum Quantity Lubrication.
1.Flooded type :
Flooded type of lubrication system is what we see regularly in our industries. In flooded type of lubricating system, large amount of cutting fluid is subjected towards the workpiece for its cooling action.
2. Dry lubrication:
Dry lubrication is the lubrication in which use of cutting oil is totally prohibited. This type of lubrication is generally used where Material Removal rate is very less.
3. Minimum Quantity Lubrication (MQL):
As discussed earlier, this lubrication technique uses much less amount of cutting fluid as compared to conventional system.
What is MQL ?
MQL is the process of providing lubricant in various machining processes in minimum quantity.
Use of lubricating fluid is reduced up to 10,000 times than the conventional lubricating process.
The interface between tool and workpiece is coated with high quality of lubricant that is delivered in atomized spray to achieve lubrication properties.
Lubrication is achieved by use of oil while the cooling action is achieved by use of pressurized air.
Types of MQL :
Basically there are two types of MQL systems
One is External system and other is Through tool.
In external system, the lubricant is provided externally while in through tool system, lubricant is provided through the tool.
Though tool system is again classified into 1-channel and multi-channel.
MQL in Grinding Operation:
Grinding is metal cutting and surface finishing process. High heat evolved during grinding process causes the thermal deformation, residual stresses and micro cracks to generate on the workpiece.
To overcome these defects proper cooling and lubrication system has to adopt.
Use of MQL reduced the tangential forces, the cutting edges of the grinding wheels were observed to remain sharp.
MQL in Milling Operation :
Milling is the process of removing the material using rotary cutters.
The effects of depth of cut, feed rate and cutting speed were studied for the surface finish
From the experimental results, it was concluded that MQL system shows better results as compared to dry and wet machining processes.
MQL in Turning Operation :
Turnoing is a machining process in which non-rotary cutting tool describes helical tool path while the workpiece rotates.
The effects of depth of cut, feed rate and cutting speed were studied for the tool wear and surface finish.
MRR observed in was higher in MQL as compared to other lubricating processes.
- The process is friendlily.
- Minimum volme of cooling lubricant is required.
- Increased cutting speed.
- Improved chip evacuation.
- Clean in opeation.
- Easy to transport
- High initial cost.
- High maintenance
- Sepetaed system is requierd.
Tool wear is reduced which enhanced the tool life.
Surface finish improved mainly due to reduction of wear and damage at the tool tip by application of MQL.
MQL system can be applied efficiently over other lubricating systems.