Papers by Keyword: Machining

Abstract: Silicon Carbide (SiC) abrasive machining solid particulates is one of the key engineering materials in the continuous development of wafer technology. Analysis of its packing behaviour is important to ensure the highest quality in the ingot cutting process to produce silicon PV wafers. One of the parameters that is monitored is the amount of fine particles present during the cutting operation and the subsequent separation technologies to recycle the material to reduce cost and allow environmental sustainability. This study presents results showing that with increasing circularity, less fines remain in the slurry suspension which is expressed as the percentage of total volume of particles in the slurry mixture. Furthermore, the work has gathered that there is a strong relationship between the % fines removed and the average diameter of the particles. An analysis of the relationship between the actual % fines remaining as a function of particle diameter reveals that the % fines remaining decreases as the particle diameter increases and this behavior correlates well with a power law equation. This agrees with a model of the fishhook effect during particle separation in a mini-hydrocyclone expressed as an equation raised to the fourth power.

Abstract: The purpose of this study is to investigate the phase transformation route of ZTA-MgO ceramic cutting tool in raw powder form, after sintering process and after machining process. This is to evaluate the effect of phase transformation to the properties of the cutting tool i.e hardness and fracture toughness. Samples of ZTA-MgO ceramic cutting insert were fabricated by wet mixing the materials, and then dried at 100°C before crushed into powder. The powder was pressed into rhombic shape and sintered at 1600°C at 4 hours soaking time to yield dense body. To study the effect of the phase transformation of the fabricated tool, machining was performed on the stainless steel 316L at 2000 rpm cutting speed. XRD analysis were performed on three type of ZTA-MgO samples which were the raw powder, the sintered samples and also the samples after machining process. Results shows that the m-ZrO₂ reduced to 0% when sintering process take place and reappear at 12% when the machining process take place proving the occurrence of transformation toughening during the machining process. The consequence of this condition is the hardness of the samples increased by 22% while the fracture toughness decreased by 21.1%.

Abstract: Single layer TiN coated and uncoated zirconia toughened alumina (ZTA) cutting inserts were fabricated and used to machine stainless steel 316 in a turning process. The powders of alumina, yttria partially stabilized zirconia and magnesia were mixed and uniaxially pressed into rhombic cutting tool inserts and subsequently sintered at 1600°C for four hours in air. The inserts were coated with TiN layer using the PVD process. Results of wear area illustrate that the coated ZTA inserts show 66.7% increase in wear resistance compared to uncoated ZTA inserts. Commercially available Si₃N₄ inserts were used to compare the wear performance. Results of Si₃N₄ flank wear show a 64% more wear resistance compared to coated ZTA inserts. This may be attributed to the lower strength of coated ZTA cutting insert flank. Therefore, it is shown that single coating of TiN provides a significant advantage in the ZTA cutting performance and better quality surface finish.

Abstract: The paper presents the results on research of machining anti-friction bushings of lever brake systems of rail transport, wherein the bushings are made of powder material based on iron and copper. Powder composition contains Fe-C-Cu with Ni and Mo content of less than 0.3%, and with reduced phosphorus content. The porosity of the bushings were in the range of 15 – 20 %. The main objective of the work was to determine the optimal machining parameters, as well as to evaluate the quality of the machined surface. The bushing were machined with cutting speed in the range of 130 – 150 m/min. To assess the quality of the machined surfaces the 3D roughness parameters were used, which allow to asses the surface roughness in more accurate details. The microstructure of the samples indicated the presence of pores onto the machined surfaces. It was found that to improve the quality of the surface it is necessary to adjust the parameters of the powder processing of parts with high porosity in the direction of their reduction. Studies of the microstructure and morphology of chips showed that the shape and structure of the chip is highly dependent on the porosity of the material and its processing conditions.

Abstract: Possibilities of miniaturization of products are constantly increasing and create numerous technological challenges at the same time. One of the important aspects of the machining process, which is the essence of this work, is the geometry of the cutting tool. This work aims to investigate the influence of three different radius of cutting edge on the minimum thickness of machined layer. The phenomena on a typical incremental step were described using a step-by-step incremental procedure, with an updated Lagrangian formulation. The machining process is considered as geometrical and physical non-linear initial and boundary problem. The finite element method (FEM) and the dynamic explicit method (DEM) were used to obtain the solution. The application was developed in the ANSYS/LS-DYNA system which makes possible a complex time analysis of the physical phenomena: states of displacements, strains and stresses. Numerical computations of the strain have been conducted with the use of methodology which requires a proper definition of the contact zone, without the necessity to introduce boundary conditions. Examples of calculations are presented and show what the depth of cut at a given radius of cutting edge allows achieving a minimum thickness of cutting.

Abstract: Paper deals with identification of the main causes of deformations of the thin-walled bearings and comprehensive analysis of the causes of bearing deformation and suggestion of the possible solutions. It deals with the analysis of bearing steel, its characteristics and causes of deformation of bearing rings during heat treatment and manufacturing process. Provides experimental measurement and report of uniformities on the surface of bearing rings - called oval and cradle, metallographic analysis of rings, as well as an analysis of various processes affecting the formation of deformations.​

Abstract: Technological processes of machining lead to plastically deformation of workpieces. Therefore it is needful to know influence of machining to machined material. The area of plastically deformation caused by friction of tool to machined surface was analysed. Local strain in structure was estimated by measurement of deformation of grains on metallographic cut using stereology. Local plastic deformation in deformation zone around the surface of drilled holes, local plastic deformation in deformation zone near the surface of milled workpiece and local plastic deformation near the surface of turned workpiece were investigated. The working piece was bulk from carbon steel CK45 (1.0503). Local plastic deformation was observed in case of drilling and turning, in case of milling no deformation of surface was present.

Abstract: Underwater laser machining process has a high potential over the typical laser ablation to remove materials with less thermal damage occurring along the cut. However, the formations of vapor bubble and cut debris in water can substantially disturb the incident laser beam, thereby reducing the ablation performance. Instead of performing the ablation in still water, the flowing water technique was applied to flush away the cut debris and bubble generated. In this study, the effects of laser pulse energy, traverse speed and water flow rate on the cut surface roughness and heat-affected zone in the laser grooving of silicon were experimentally investigated and analyzed. The findings revealed that the cut surface roughness decreased with the increases in laser pulse energy and laser traverse speed. Though a higher water flow rate resulted in a rougher cut surface, the heat-affected zone can be minimized when the increased flow rate was applied.

Abstract: Calibration curves of a multi-component dynamometer is of essence in machining operations in a lathe machine as they serve to provide values of force and stress components for cutting tool development and optimization. In this study, finite element analysis has been used to obtain the deflection and stress response of a two component cutting tool lathe dynamometer, for turning operation, when the cutting tool is subjected to cutting and thrust forces from 98.1N to 686.7N (10 to 70kg-wts), at intervals of 98.1N(10kg-wt). By obtaining the governing equation, modeling the dynamometer assembly, defining boundary conditions, generating the assembly mesh, and simulating in Inventor Professional; horizontal and vertical components of deflection by the dynamometer were read off for three different loading scenarios. For these three loading scenarios, calibration plots by experiment compared with plots obtained from simulation by finite element analysis gave accuracies of 79%, 95%, 84% and 36%, 57%, 63% for vertical and horizontal deflections respectively. Also, plots of horizontal and vertical components of Von Mises stress against applied forces were obtained.

Abstract: Silicon has widely been used as a substrate material in various microfabrication processes. Cut depth and surface morphology of silicon obtained from laser ablation process have to be well controlled to achieve the required features of micro-components being made. Though laser power has been known as a major factor affecting these responses, the detailed investigations of this factor on cut geometries and surface quality have still been deficiency. In this research, the cut geometries and surface characteristics of silicon induced by a pulse laser were experimentally investigated. The increase in laser power not only increased the cut dimensions, but also increased the debris deposition on and inside the cut channel. Furthermore, an analytical model was developed in this study to predict the cut depth of silicon in pulsed laser ablation, and an agreement between the prediction and experiment was also demonstrated.