Effect of Minimum Quantity Lubrication on Tool Wear and Surface Roughness in Micro-Milling

Author(s):  
Kuan-Ming Li ◽  
Shih-Yen Chou

Micro-milling is a suitable technique for manufacturing of microstructures with high aspect ratios and intricate geometries. The application of the micro-milling process in cutting hardened tool steel is particularly challenging. The low strength of the miniaturized end mills implies accurate control of the chip load in order to prevent the tool break and product dimension errors, which requires high positioning accuracy. It is known that the application of cutting fluids can improve the performance of machining operations. However, the supply of cutting fluids in a conventional way is not appropriate for miniature machine tools due to the plentiful electronic components used to construct micro-scale machine tools. Minimum quantity lubrication (MQL) presents itself as a possible alternative for micro-cutting with respect to the minimum impact on the electronic components as well as low tool wear, better heat dissipation, and machined surface quality in metal cutting. This study compares the mechanical performance of MQL to completely dry condition for the micro-milling of SKD 61 steel based on experimental measurements of tool wears and surface finish. The effect of MQL on the burr formation is also observed. Results indicate that the use of MQL leads to reduced tool wears, better surface roughness, and less burr formation.

Author(s):  
S. Vignesh ◽  
U. Mohammed Iqbal

This paper is concentrated on the exploration of carbonaceous nanocutting fluids with the concept of tri-hybridization with improved lubricative and cooling properties by using multi-walled carbon nanotubes, hexagonal boron nitride , and graphene nanoparticles with neat cold-pressed coconut oil in a fixed volumetric proportion. The rheological properties of the nanofluids were studied to assess their performance in real-time end milling operations using an AA7075 work piece on a CNC lathe machine under a minimum quantity lubrication environment. At the outset, the carbonaceous nanofluids gave good performance when compared to conventional cutting fluids. Furthermore, the surfaces of the tribo-pairs and the chips formed were analyzed using a profilometer and high-end microscopes. The results obtained from the experiments confirm that the tri-hybridized carbonaceous nanolubricant has reduced the cutting force, tool wear, and surface roughness when correlated to monotype nanofluids. The scanning electron microscope images of the surface and tool were studied and it was found that the surface quality was maintained while end milling with tri-hybridized carbonaceous nanofluid. Improvement of ∼17%, 20% and 25% in cutting forces, surface roughness and tool wear was found in tri-hybrid fluid when compared to other fluids. Thus, the present work indicates that the addition of carbon-based nanoparticles with coconut oil has offered better performance and is found to be a credible alternative to existing conventional cutting fluids.


Author(s):  
Xueming Yang ◽  
Xiang Cheng ◽  
Yang Li ◽  
Guangming Zheng ◽  
Rufeng Xu

Machining conditions such as cutting fluids exert a crucial function in micro-milling, which removes chips from the cutting area and lubricates the interface between the tool and workpiece. Therefore, it is necessary to identify suitable cutting fluids for processing different materials. In this article, the effects of cutting fluids (dry, flood cooling, minimum quantity lubrication, and jet cold air) on tool wear, surface roughness, and cutting force were studied. The Pugh matrix environmental approach was used to compare different cutting fluids in terms of sustainable production. In addition, a curved thin wall was processed to demonstrate the value of minimum quantity lubrication in industry. The experimental results illustrated that the minimum quantity lubrication can not only effectively reduce tool wear and cutting force but also improve the finished surface quality. According to the sustainability assessment results, minimum quantity lubrication was superior to other cutting fluids in terms of environmental impact and production quality. The curved thin wall size error was only 2.25% under minimum quantity lubrication condition. This indicated minimum quantity lubrication was particularly suitable for micro-milling of H59 brass and 6061 aluminum compared to other cutting fluids.


Author(s):  
S Vignesh ◽  
U Mohammed Iqbal

The current paper is concentrated on the mechanical and machining process exploration of metallic nano-lubricant with the concept of tri-hybridization with improved lubricative and cooling properties by using TiO2, ZnO and Fe2O3 metallic nano particles with neat cold-pressed coconut oil in a fixed volumetric proportion (10:90). End milling of gummy material like aluminium requires a solution to the conventional dry and wet machining due to high productivity requirement and to obtain good surface quality. So, the prepared nanofluids were tested for their rheological behavior and latter introduced into milling of AA7075 as a solution to the above stated problem. Overall, the nanofluids gave good performance when compared to conventional methods. Furthermore, the results obtained from the experiments confirm that the trio-hybridized lubricant has reduced the cutting force, tool wear and surface roughness in an improved way when related to monotype nano fluids. The response surface methodology is performed to evaluate the interaction of process parameters in minimum quantity lubrication environment with nano fluids. The results show that the cutting forces, surface roughness, tool wear was minimized while machining with hybrid cutting fluids and well within the desirability.


Author(s):  
Pushparghya Deb Kuila ◽  
Shreyes Melkote

Laser-assisted micromilling is a promising micromachining process for difficult-to-cut materials. Laser-assisted micromilling uses a laser to thermally soften the workpiece in front of the cutting tool, thereby lowering the cutting forces, improving the dimensional accuracy, and reducing the tool wear. Thermal softening, however, causes the workpiece material to adhere to the tool and form a built-up edge. To mitigate this problem and to enhance micromachinability of the workpiece in laser-assisted micromilling, this article investigates the following lubrication and cooling methods: (1) minimum quantity lubrication and (2) vortex tube cooling. Experiments utilizing the two methods are carried out on a difficult-to-cut stainless steel (A286), and the surface morphology, tool condition, burr formation, groove dimensional accuracy, surface finish, and cutting forces are analyzed. Results show that the combination of laser-assisted micromilling and minimum quantity lubrication yields the least amount of tool wear, lower resultant force, better groove dimensional accuracy, and no built-up edge. While vortex tube cooling with laser-assisted micromilling produces smaller burrs compared to minimum quantity lubrication, it yields larger changes in groove dimensions and is characterized by built-up edge formation. Possible physical explanations for the experimental observations are given.


2012 ◽  
Vol 579 ◽  
pp. 193-200 ◽  
Author(s):  
Kuan Ming Li

Mechanical micromachining is a promising technique for making complex microstructures. It is challenging to apply mechanical micromachining in the industry due to the low strength of micro tools. Therefore, it is not easy to accurately control the product dimension error and to raise the production rate. In this paper, the applications of minimum quantity lubrication (MQL) in micro-milling and micro-grinding are presented. MQL is considered as a green manufacturing technology in metal cutting due to its low impact on the environment and human health. This study compares the tool wear and surface roughness in MQL micromachining to completely dry condition based on experimental investigations. The supply of MQL in vibration-assisted grinding is also studied. It is found that the use of MQL results in longer tool life and better surface roughness in mechanical micromachining.


Author(s):  
Yuk Lun Chan ◽  
Xun Xu

Traditionally, metal cutting fluid or lubricant is used in finishing operations of high-speed machining process to reduce the rate of tool wear, which in turn will improve surface quality. In automobile and aerospace industries, minimum quantity lubrication technique is considered to provide the same level of performance as the flood coolant method and offers financial benefits by saving coolant direct and associated costs. However, scant research work has been done on minimum quantity lubrication applications in the die and mould manufacturing industry. In this study, the effects of dry, flood and minimum quantity lubrication machining on surface roughness, tool wear, dimensional accuracy and machining time of hardened steel mould inserts were compared. The results revealed that there were no significant differences between these three lubrication methods. More in-depth experimental study of dry and minimum quantity lubrication machining was then carried out using the design of experiments technique. In terms of surface roughness and tool wear, there were again no significant differences. Nevertheless, minimum quantity lubrication machining produced more accurate results than dry machining in dimensional deviation. The regression models show that feed-rate ( fz) has a larger effect on surface roughness and machining time than step-over ( ae), while depth of cut ( ap) has no significant effect on surface roughness. Based on the test piece shape, a shortest possible machining time of 3.55 h and a good surface finish of 0.28 µm can be achieved using a small feed-rate (0.03 mm/tooth), a large step-over (0.1 mm) and a large depth of cut (0.2 mm). This work shows that when combining the minimum quantity lubrication technique with the right cutting conditions in modern die and mould manufacturing, machining time and polishing time can be saved, which leads to an overall saving in production cost. Using the dry and minimum quantity lubrication techniques for different finish machining situations can therefore be a good economical solution.


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