Minimum Quantity Lubrication

Nowadays, the challenge in machining industries is focused on achieving high-quality product on component accuracy, and high production rate. It is necessary to enhance existing technology and develop the product with reasonable cost. Thus, researchers have developed advanced technology such as high-speed machining. High-speed machining plays a very important role in achieving cost and time savings together with better surface finish and dimensional accuracy. High-speed machining is being widely employed in the aerospace industry. Aluminum 7075-T6 is one of the popular materials with attractive properties such as high tensile strength, toughness and high corrosion resistance. Minimum quantity lubrication is known as a technique to provide the best cutting performances. This paper provides the recent studies in minimum quantity lubrication and high-speed machining of aluminum 7075-T6. The influence of high-speed machining process parameters in term the surface roughness and relevant cutting fluid technique have been discussed based on the findings of the recent studies.

The paper presents a studyof the effect of operating variable parameter; cutting speed, feed rate, depth of cut and width of cut on heat being generated when end milling under MQL condition. The response surface methodology (RSM) was employed in the experiment, and a Box–Behnken design was used to determine the cause and effect of the relationship between the input variables and response. The investigated milling parameters were cutting speed (100 - 140 m/min), feed rate (0.1 - 0.2 mm/tooth), depth of cut (0.5-1.0 mm) and width of cut (0.2 -1.8 mm). Result of this study show ball nose end milling generates low temperature ranging from 69°C to 359°C. Experimental data and statistical analysis showed that heat generation was dominated by radial depth of cut, followed by axial depth of cut. Feed rate and cutting speed were found statistically not significant. The linear models were developed with a 92% confidence level. The optimum condition required for minimum heat generated include cutting speed of 117 m/min, feed rate of 0.11 mm/rev, axial depth of cut of 0.57 mm, and radial depth of cut of 0.21 mm. With this optimum condition, a minimum heat generated of 68°C was obtained.

Hybrid rolling element bearings are being considered for use in flight critical aerospace applications. The following work was undertaken to lay the foundation for future work that would permit the recommendation of appropriate quantities of lubrication for these advanced bearing systems. This was accomplished by focusing on the tribological performance of M50/M50 (or AISI M-50) and M50/Si 3 N 4 interfaces with minimum quantities of lubrication at two levels of speed and slide-to-roll ratio (SRR). Ball-on-ring tribological testing was conducted with stepped reductions of lubricant pump rate into the tribological contacts at initial lambda values of approximately 1.7 and 2.5, as calculated from the Hamrock and Dowson film thickness equation and surface finish measurements. Experiments were conducted with 5% and 45% slide-to-roll ratio (or SRR). Starting from these high initial lambda levels, the lubricant flow rate into the contact was reduced until severe damage occurred. Tests were then suspended due to excessive traction (traction coefficient greater than 0.2). The results of this work are in agreement with the starved lubrication literature and the bearing test literature. They provide some solid insight into the minimum quantity of lubrication recommended for M50/M50 and M50/Si 3 N 4 interfaces. In all of the tests conducted there was a clear trend that higher speed and increased sliding both require an increased supply of lubricant to the contact. The M50/M50 interface needed an order of magnitude higher lubricant pump rate into the contact for adequate lubrication as compared to the M50/Si 3 N 4 interface in the initial lambda ∼ 1.7 experiments. At lambda ∼ 2.5 with 5% SRR, the M50/M50 interface needed three times the lubricant pump rate that the M50/Si 3 N 4 interface needed. However, both M50/M50 and M50/Si 3 N 4 needed a similar amount of lubricant at lambda ∼ 2.5 with 45% SRR, in which the interfaces were severely damaged due to the extreme test conditions. These tribological test results are interpreted with an analysis of the wear morphology and surface chemistry of the test articles.