Micro-cutting Mechanisms Research Articles

Experimental investigation of the tool radius and micro-cutting speed influence on micro-cutting mechanisms for marble based material

In this paper, a detailed experimental analysis of the effect of tool tip radius and cutting speed on the proposed mechanism of micro-cutting Plavi tok marble was performed. Although Plavi tok marble belongs to extremely brittle materials, experiments have shown that it can be processed in ductile mode (plastic deformation mode), i.e. without the presence of brittle fracturing of the material. Moreover, it has been established that the range of plastic deformation zone is a function of the tool tip radius and the cutting speed. The diamond tools used during the experiments had tip radius values of r = 0.15 and r = 0.2 mm, while cutting speeds were 15 and 25 m s−1. When using tools with higher tip radius values, with increasing cutting speed, the critical penetration depth (ductile-brittle transition) increased from 8.8 to 9.3 μm. On the other hand, tools with lower radius value led to a reduction of the plastic deformation zone range. This declining trend of plastic deformation zone continued during increased cutting speed, with critical penetration depths of 8.6 and 8.3 μm for cutting speeds of 15 and 25 m s−1, respectively. The intensity of lateral/radial destruction in the brittle fracturing mode was also directly dependent on the processing conditions. The reduction was achieved by using tools with a lower value of the tip radius while processing at lower speeds. In this paper, the identification of the components of the cutting force was carried out, whose intensities indicate the occurrence of the brittle destruction within the material.

Abrasive wear behavior of austempered ductile iron with niobium additions

Carbidic Austempered Ductile Iron (CADI) microstructures containing eutectic carbides can be produced by the addition of carbide stabilizing elements, such as chromium. Carbides formed from the addition of Cr are eutectic of M3C type. The presence of such hard phases can enhance the abrasion wear resistance of ductile iron. A new CADI can be produced by the addition of Nb. Niobium carbide particles are formed in the beginning of solidification and remain stable once they are insoluble in solid iron matrix. The dry sand abrasive wear resistance of ductile irons alloyed with 1.0, 1.8, and 2.4 wt% Nb were tested in both “as-cast” and “heat treated” conditions using standard ASTM G65. Results were compared to abrasive wear data obtained on ductile iron alloyed with 1 wt% Cr, CADI (1 wt% Cr), and the basic composition of iron without carbide stabilizing elements. In the “as-cast” condition, the addition of Nb did not lead to a reduction in wear, while CADI with Nb is a promising substitute for CADI with Cr addition, because both materials showed very similar values of abrasion resistance. Micro-ploughing and micro-cutting mechanisms were observed on the worn surfaces of ductile irons. Abrasive wear resistance of these alloys was correlated with the volume fraction of carbides.

Nano-finishing of the monocrystalline silicon wafer using magnetic abrasive finishing process

The monocrystalline silicon wafer is the key material for micro-electro-mechanical systems. The performance of these wafers depends on their surface and subsurface quality. This research aims to study the effect of process parameters on the reduction ratio rate in surface roughness (%ΔR˙) of monocrystalline silicon wafers during the magnetic abrasive finishing process using response surface methodology. The parameters studied are machining gap, rotational speed, abrasive size, and magnetic abrasive particle (MAP) size. Quadratic models are developed by applying Box-Behnken design. Also, experiments are carried out on the silicon wafer, and the results of surface roughness data are analyzed by using analysis of variance. The most significant factor on each experimental design response is identified. According to our findings, the maximum %ΔR˙ value and the best surface roughness of the silicon wafer achieve 3.70 and 31nm, respectively. Furthermore, the material removal mechanism in wafers is investigated by using atomic force microscopy. Our observations show that both micro-fracture and micro-cutting mechanisms might happen, and it highly depends on polishing parameters.

Numerical-experimental study on polishing of silicon wafer using magnetic abrasive finishing process

Silicon wafer as a brittle material is extensively used in semiconductors. The surface quality of this material significantly affects the quality and efficiency of related components. In this study, the coupled algorithm of SPH/FEM is used to simulate the surface polishing of silicon wafers with Magnetic Abrasive Finishing process. The effects of rotational speed and machining gap on percent change in surface roughness (%∆Ra) and material removal (MR) are comprehensively analyzed with simulations and experiments. Furthermore, the material removal mechanism in wafers was investigated by using AFM. Our observations showed that both micro-fracture and micro-cutting mechanisms might happen and it highly depends on polishing parameters. Results of the simulations and experimental data showed that MR and %∆Ra value increase with increasing rotational speed and decreasing machining gap. According to our experimental findings, maximum %∆Ra and MR are 65% and 39.09 mg, respectively.

Study of microcutting fundamentals for peripheral and end cutting edges in micro-end-milling

In the micro-end-milling of surfaces, thin walls, and micro channels, etc, both peripheral and end cutting edges of micro end mills are engaged in cutting. However, the microcutting fundamentals for end cutting edges have not been well studied, even though those for peripheral cutting edges have been studied widely. Key micromilling variable analyses show that the order of significance is the axial depth of cut (ap), feed per tooth (fz), and radial depth of cut (ae). It means that the microcutting mechanisms of the end cutting edge need to be studied and compared with that of the peripheral cutting edge in order to understand micro-end-milling mechanisms more thoroughly. Simulations using the finite element method (FEM) show that the minimum undeformed chip thickness (MUCT) is different for peripheral and end cutting edges, even though the cutting edge radius remains unchanged. The results of those simulations have been experimentally validated. It shows that the MUCT of the end cutting edge is larger than that of the peripheral cutting edge. That means the MUCT is not only the size of a certain proportion of the cutting edge radius, as mentioned in previous studies, but also has a close relationship with the location of the cutting edge. Therefore, ap could be several times larger than fz according to the relationship between MUCT and the micromilling parameters. It creates a solid basis for the selection and quantization of micro-end-milling parameters in the fabrication of complicated geometries as thin walls and micro channels.

SAFBM of Softer Materials: An Investigation into the Micro-Cutting Mechanisms and the Evolution of Roughness Profile

Swirling Fluidized Bed Machining (SAFBM) is a nontraditional machining process and novel variant of Fluidized Bed Machining (FBM) in which the former has overcome certain drawbacks of the latter such as roughness variation and shading effect. SAFBM generates significant material removal and surface finish on the workpiece surface during the machining process with consistency and flexibility. The present detailed study emphasizes on the machining of softer materials such as brass and aluminum using abrasive particles such as silicon carbide in order to analyze the effect of various micro-cutting mechanisms on the generation of surface texture. This study examines the evolution of surface roughness profile after progressive machining with abrasives ranging from coarse, medium and fine grades of SiC with the help of optical microscopic images of the machined surface. The research concludes that using SAFBM, flat and uniform surface finishing with modification ratio in terms of roughness parameters ranging from 5 to 7 is possible within 7–8 hours of processing.

Numerical-experimental study on the mechanisms of material removal during magnetic abrasive finishing of brittle materials using extended finite element method

Magnetic abrasive finishing (MAF) is an advanced machining process efficiently used for finishing of hard-to-machine materials. In this method, material removal takes place through nano-/microindentations in the presence of a controllable magnetic field generated via a permanent or an electronic magnet. Understanding the material removal mechanisms of the process is of particular importance for achievement of a high-quality surface with minimum surface defects. Therefore, in this work a numerical-experimental study was performed toward this issue using the extended finite element method (X-FEM). In this regard, the MAF operation was simulated as an indentation and sliding process of a sharp abrasive and the prevailing material removal mechanisms were obtained during MAF of BK7 optical glass. The constitutive material model for the specimen was defined according to the elastic-plastic-cracking model, which takes into account the tensile cracking and compressive yielding behavior of brittle materials. The X-FEM analysis revealed that both microcutting and microfracture mechanisms exist during MAF process of brittle materials depending on the process parameters. Among various parameters, magnetic particles size and abrasives size were the most influential factors affecting the dominant mechanism of material removal. The obtained numerical results were then validated experimentally by using scanning electron microscopy (SEM). The SEM observations revealed good performance of X-FEM analysis in prediction of material removal mechanisms during MAF of brittle materials.

Mesoplasticity approach to studies of the cutting mechanism in ultra-precision machining

There have been various theoretical attempts by researchers worldwide to link up different scales of plasticity studies from the nano-, micro- and macro-scale of observation, based on molecular dynamics, crystal plasticity and continuum mechanics. Very few attempts, however, have been reported in ultra-precision machining studies. A mesoplasticity approach advocated by Lee and Yang is adopted by the authors and is successfully applied to studies of the micro-cutting mechanisms in ultra-precision machining. Traditionally, the shear angle in metal cutting, as well as the cutting force variation, can only be determined from cutting tests. In the pioneering work of the authors, the use of mesoplasticity theory enables prediction of the fluctuation of the shear angle and micro-cutting force, shear band formation, chip morphology in diamond turning and size effect in nano-indentation. These findings are verified by experiments. The mesoplasticity formulation opens up a new direction of studies to enable how the plastic behaviour of materials and their constitutive representations in deformation processing, such as machining can be predicted, assessed and deduced from the basic properties of the materials measurable at the microscale.

Experimental Investigation of Microcutting Mechanisms in Marble Grinding

This paper offers an experimental study of the microcutting mechanisms in marble grinding to aid the optimization of the marble grinding process. The necessity for investigating these mechanisms is dictated by the increased use of marble in many applications and the fact that grinding and polishing processes are the dominant technologies used to meet surface finish requirements in this natural material. The experiments are aimed at the determination of the normal component of the cutting force and of the grain traces in microcutting with a single diamond grain. The investigations carried out make provisions for establishing critical grain penetration and cutting depths and allow the prediction of the normal cutting force component as a function of grain penetration speed and depth.