Analytical Investigation of the Micro Groove Surface Topography by Micro-Milling

Effect of Milling Processing Parameters on the Surface Roughness and Tool Cutting Forces of T2 Pure Copper

In this paper, the responses of machined surface roughness and milling tool cutting forces under the different milling processing parameters (cutting speed v, feed rate f, and axial cutting depth a_p) are experimentally investigated to meet the increasing requirements for the mechanical machining of T2 pure copper. The effects of different milling processing parameters on cutting force and tool displacement acceleration are studied based on orthogonal and single-factor milling experiments. The three-dimensional morphologies of the workpieces are observed, and a white-light topography instrument measures the surface roughness. The results show that the degree of influence on S_a (surface arithmetic mean deviation) and S_q (surface root mean square deviation) from high to low level is the v, the f, and the a_p. When v = 600 m/min, a_p = 0.5 mm, f = 0.1 mm/r, S_a and S_q are 1.80 μm and 2.25 μm, respectively. The cutting forces in the three directions negatively correlate with increased cutting speed; when v = 600 m/min, F_x reaches its lowest value. In contrast, an increase in the feed rate and the axial cutting depth significantly increases F_x. The tool displacement acceleration amplitudes demonstrate a positive relationship. Variation of the tool displacement acceleration states leads to the different microstructure of the machined surfaces. Therefore, selecting the appropriate milling processing parameters has a positive effect on reducing the tool displacement acceleration, improving the machined surface quality of T2 pure copper, and extending the tool's life. The optimal milling processing parameters in this paper are the v = 600 m/min, a_p = 0.5 mm, and f = 0.1 mm/r.

Development of Tool Wear Standards and Wear Mechanism for Micro Milling Ti-6Al-4V Alloy

With the rapid development of high-precision-device technology, new demands are put forward for micro milling. The size effect and low cutting energy of micro milling make the process expensive and difficult, especially for Ti-6Al-4V alloys. The wear of the micro-milling cutter lacks corresponding international standards and its cutting mechanism is complex. In this paper, four kinds of micro-milling cutters with different wear states were obtained by designing micro-milling experiments, and the wear process and wear mechanism were observed and analyzed. The cutter diameter reduction, end face wear, flank wear and edge radius are comprehensively analyzed. It is considered that the formulation of a micro-milling-cutter wear standard needs comprehensive consideration, and the wear of end face 30 μm, wear of flank 35 μm and tool diameter reduction 55 μm can be used as the failure criteria of the micro-milling cutter. The wear forms mainly include abrasion marks, material adhesion, built-up edges and micro-collapse blades. Adhesive wear exists in the whole cutting process and plays a major role. Abrasive wear, diffusion wear and oxidation wear will occur when the cutting temperature reaches the melting point of Co. The wear of the micro-milling cutter is analyzed more comprehensively, a new wear-failure standard is formulated and the complex wear mechanism is revealed.

Dimensional Accuracy and Surface Quality of AZ91D Magnesium Alloy Components after Precision Milling

This study investigates a precision milling process conducted with the use of conventional end mills and a standard CNC (Computer Numerical Control) machine tool. Milling tests were performed on samples of AZ91D magnesium alloy using TiB₂- and TiAlN-coated three-edge end mills measuring 16 mm in diameter. The following technological parameters were made variable: cutting speed, feed per tooth and axial depth of cut. The effects of precision milling were evaluated by analysing the scatter of dimension values obtained in successive tool passes. In addition to that, deviations from the assumed nominal depth as well as obtained ranges of dimension varation were analysed. The study also examined surface quality obtained in the precision milling process, based on the basic surface roughness parameters: Ra, Rz and RSm. Results have confirmed that the use of conventional cutting tools and a standard CNC machine tool makes it possible to manufacture components characterized by relatively small scatter of dimension values and high accuracy classes. Additionally, the results have shown that the type of tool coating and variations of individual technological parameters exert impact on the dimensional accuracy and surface quality obtained.

Characterization of Machined Surface Topography Based on the Normal Declination Angle of Microfacets

It is important to characterize surface topography in order to study machined surface characteristics. Due to the features of periodicity and randomness of machined surface topography, the existing topographical parameters may not describe its features accurately. A novel characterization method called the normal declination angle of microfacet-based surface topography is thus proposed for this task. The topography of machined surfaces is measured and the data on the normal declination angle are obtained. Then, surface topography is analyzed via the distribution of the normal declination angle. The lognormal distribution characterization model of machined surface topography is established, and the accuracy of the model is verified by error analysis. The results show that the calculated results of the present characterization model are generally consistent with the distribution of the normal declination angle, where the maximal root mean square errors (RMSE) is 4.5%. Therefore, this study may serve as an effective and novel way to describe the characteristics of the machined surface topography.

Force Prediction and Cutting-Parameter Optimization in Micro-Milling Al7075-T6 Based on Response Surface Method

Optimization of cutting parameters in micro-milling is an important measure to improve surface quality and machining efficiency of the workpiece. Investigation of micro-milling forces prediction plays a positive role in improving machining capacity. To predict micro-milling forces and optimize micro-milling cutting parameters (per-feed tooth (f_z), axial cutting depth (a_p), spindle speed (n) and tool extended length (l)), a rotatable center composite experiment of micro-milling straight micro-groove in the workpiece of Al7075-T6 were designed, based on second-order response surface methods. According to the experiment results, the least square method was used to estimate the regression coefficient corresponding to the cutting parameters. Simultaneously, the response prediction model of micro-milling was established and successfully coincide the predicted values with the experiment values. The significance of the regression equation was tested by analysis of variance, and the influence of micro-milling cutting parameters on force and top burrs morphology was studied. The experiment results show that in a specific range of cutting parameters, a_p and f_z have a significant linear relation with the micro-milling force and the top burrs width. According to the optimal response value, the optimized cutting parameters for micro-milling obtained as: n is 11,393 r/min, f_z is 6 µm/z, a_p is 11 μm and l is 20.8 mm. The research results provide a useful reference for the selection of cutting parameters for micro-milling.