Prediction of micro milling force and surface roughness considering size-dependent vibration of micro-end mill

When the characteristic structure size of the component is at the micron level, the internal crystal grains, grain boundaries and pore defects of the component material with the same size at the micron level cannot be ignored, so the micro-sized component will show different physical properties from the macro-sized component, which is called size effect. Since the tool diameter of micro-end mill is in the micron level, the micro-end mill will also show a significant size effect phenomenon. In addition, in micro milling process, because the surface roughness that affects the performance and service life of micro parts is mainly influenced by the vibration of micro-end mill, in order to enhance the machined surface quality, it is crucial to research the formation mechanism of surface topography in micro milling process. In this paper, a comprehensive method is proposed to predict micro-end mill vibration, micro milling force and surface roughness. At first, a size-dependent dynamic model of micro-end mill is presented based on the strain gradient elasticity theory (SGET). Secondly, considering the feedback of micro-end mill vibration, the micro milling force model is presented and solved through iterative method. Then the machined surface topography is simulated through the actual cutting edge trajectory considering the micro-end mill size-dependent vibration and material elastic recovery. The results show that the vibration of the micro-end mill will increase the micro milling force and surface roughness. In order to verify the accuracy and efficiency of the presented method, experiments are performed, and it is found that the experimental results are consistent with the predicted results.

Influence of Cutting Fluid Application Frequency in Micromilling Cutting Forces

Micromachining allows the production of parts and components on a micro scale with high precision and has become a key process to meet the growing demand for micro parts and micro components. To meet the quality requirements of the generated surfaces and reduce the cutting forces, strategies have been analysed, such as the use of the cutting fluid. Therefore, this research aimed to verify the effect of the frequency of the use of cutting fluid during the micro-milling of the Inconel 718 alloy. For this purpose, an ultra-refined cemented carbide micro end mill coated with (Al, Ti) N and 400 µm in diameter was used. A spindle speed of 20,000 rpm, a cutting speed of 13.8 m/min, a feed per tooth of 5 µm/tooth and an axial depth of cut of 40 µm were used as cutting parameters. Two frequencies of application of the cutting fluid were evaluated, corresponding to the flow rate of 40.7 and 270.0 ml/ h, in addition to the dry test. To measure the cutting forces, a Kistler dynamometer with operating range of -5 kN to +10 kN was used. In addition, the process simulation was performed using the AdvantEdge software by ThirdWave Systems. The results showed that the higher flow of the cutting fluid provided lower cutting forces and that, in dry machining, the cutting force increased significantly during the machining of a slot.

EXPERIMENTAL INVESTIGATION OF EFFECT OF CRYO-TREATMENT ON MICROMILLING OF INCONEL 718

In this paper, the effect of cutting parameters during micromilling on surface finish and material removal rate is presented. Inconel 718 alloy and high-speed steel micro end mill are used as work material and cutting tool, respectively. High-speed steel end mill of 1 mm diameter is subjected to cryogenic treatment. Machining studies are performed on Inconel alloy using untreated and cryogenic treated cutters. The milling tests are conducted at three different values of feed rate, cutting speed and depth of cut. Also, tool wear, microstructure and microhardness of different treated and untreated end mill are investigated and discussed in detail. The results showed that cryogenic treatment significantly improved the tool wear. The surface finish produced on machining the work-piece is better with the cryogenic treated tools than when compared with the untreated tools. The material removal rate is better with the cryogenic treated tools than when compared with the untreated tools. Improvement in tool life was up to 53.16% for Inconel 718 material when machined with cryogenically treated micro end mill.