Anirban Bhattacharya

Estimating the effect of cutting parameters on surface finish and power consumption during high speed machining of AISI 1045 steel using Taguchi design and ANOVA

The present paper outlines an experimental study to investigate the effects of cutting parameters on finish and power consumption by employing Taguchi techniques. The high speed machining of AISI 1045 using coated carbide tools was investigated. A combined technique using orthogonal array and analysis of variance was employed to investigate the contribution and effects of cutting speed, feed rate and depth of cut on three surface roughness parameters and power consumption. The results showed a significant effect of cutting speed on the surface roughness and power consumption, while the other parameters did not substantially affect the responses. Thereafter, optimal cutting parameters were obtained.

On Surface Finish and Dimensional Accuracy of FDM Parts after Cold Vapor Treatment

Fused deposition modeling (FDM) process is an additive manufacturing technology where objects are manufactured in layers. In the present days, FDM is commercially used to build prototypes, functional components; however, these parts majorly suffer from poor surface quality and dimensional accuracy even for basic part geometries. In the present paper, first the effect of part deposition orientation on surface finish and dimensional accuracy of FDM parts are studied. The part selected for this study is designed in such a way that different primitive geometric features at different directions are present. The parts are built at different orientations (0°, 15°, 30°, 45°, 60°, 75°, 90°) using acrylonitrile butadiene styrene P430 material, and surface finish and dimensional accuracy are measured at different surfaces. Next, the FDM parts are postprocessed by cold vapor treatment of dimethylketone (acetone) and improvement in surface finish and change in dimensional accuracy are investigated. The results show that surface finish of the components is greatly improved by this vapor treatment process with minimal variations in part geometric accuracy after the treatment.

Study of Material Transfer Mechanism in Die Steels Using Powder Mixed Electric Discharge Machining

The present article investigates the effect of process parameters and mechanism of material deposition in powder mixed electric discharge machining (PMEDM) on surface properties of EN31, H11, and High Carbon High Chromium (HCHCr) die steel materials. Current, powder, and interaction between workpiece and electrode affected the microhardness significantly. Copper electrode was found best for EN31 and H11 die steel, whereas tungsten-copper electrode was better suited for HCHCr steel to achieve higher microhardness. Graphite powder was found to be more suitable compared to aluminum in improving the microhardness of all three materials. Selected samples were analyzed for X-ray diffraction (XRD) followed by microstructure analysis using a scanning electron microscope (SEM). The results showed significant material transfer from the electrode as well as powder, either in free form and/or in compound form. For maximizing the microhardness of the machined surface, optimum parametric settings were identified for the three materials.

Optimization of powder mixed electric discharge machining using dummy treated experimental design with analytic hierarchy process

The analytic hierarchy process (AHP) is widely used for the optimization of multiple responses from an experimental study. In the present study, a method to obtain more reliable global weight of different alternatives has been described for a powder-mixed electric discharge machining (EDM) process. Seven different process parameters were tested to study their effect on material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR) using a specially designed Taguchi orthogonal array that could accommodate factors with varying number of levels. A three-level array L27 was modified to include two-level factors using dummy treatment. The process conditions that affected the three responses were identified and optimized together using AHP for high carbon high chromium (HCHCr), EN31 and hot die steel (HDS) workpiece material. Addition of powder in the dielectric improved the MRR as the electrical conductivity of powder reduces the dielectric insulating strength. Current, powder, and electrode material significantly affected the TWR. Kerosene as dielectric was observed to be a superior alternative than EDM oil. Graphite electrode worked best for HCHCr and EN31 and W–Cu electrode worked best for HDS as they globally optimize the three output variables. Also, Cu powder suspended in the dielectric resulted in an optimal solution for HCHCr and HDS and tungsten powder was seen to be a better choice for EN31 to globally optimize the responses. To overcome problems of poor finish at high current setting in EDM, the dielectric should be mixed with powder.

Formability and Surface Finish Studies in Single Point Incremental Forming

Incremental sheet metal forming (ISMF) has demonstrated its great potential to form complex three-dimensional parts without using a component specific tooling. The die-less nature in incremental forming provides a competitive alternative for economically and effectively fabricating low-volume functional sheet parts. However, ISMF has limitations with respect to maximum formable wall angle, geometrical accuracy, and surface finish of the component. In the present work, an experimental study is carried out to study the effect of incremental sheet metal forming process variables on maximum formable angle and surface finish. Box―Behnken method is used to design the experiments for formability study and full factorial method is used for surface finish study. Analysis of experimental results indicates that formability in incremental forming decreases with increase in tool diameter. Formable angle first increases and then decreases with incremental depth and it is also observed that the variation in the formable angle is not significant in the range of incremental depths considered to produce good surface finishes during the present study. A simple analysis model is used to estimate the stress values during incremental sheet metal forming assuming that the deformation occurs predominantly under plane strain condition. A stress-based criterion is used along with the above mentioned analysis to predict the formability in ISMF and its predictions are in very good agreement with the experimental results. Surface roughness decreases with increase in tool diameter for all incremental depths. Surface roughness increases first with increase in incremental depth up to certain angle and then decreases. Surface roughness value decreases with increase in wall angle.

Influence of Current and Shielding Gas in TiO2 Flux Activated TIG Welding on Different Graded Steels

In tungsten inert gas (TIG) welding, limited depth of penetration can be achieved during single pass welding. To achieve the desired depth of penetration, the speed of welding needs to be significantly reduced and hence, the productivity decreases. In the present work, the effect of TiO2 activated flux on penetration is evaluated for different workpieces namely AISI 1020, AISI 304, AISI 316, and Duplex 2205 steels at different currents and shielding gas compositions. The results show a significant increase in the depth of penetration and reduction in the width-to-penetration ratio using the activated flux for all the workpiece materials considered here. Current increases the depth of penetration, however, the influence of flux becomes more significant with higher welding current. Maximum of 37.8%, 44.3%, 47%, and 124% increase in depths of penetration is measured for AISI 1020, AISI 304, AISI 316, and Duplex 2205 steels, respectively, when activated flux is used. Also, maximum of 70% increase in the depth of penetration is further achieved when Ar along with 5% H2 is used as the shielding gas compared to that when pure Ar is used. The constriction of arc column increases the energy density, which increases the depth of penetration. Measurement of microhardness and metallurgical observations are carried out for samples after TIG welding and activated tungsten inert gas (ATIG) welding and compared to observe the solidification phenomenon during the process.

Mechanical and Metallurgical Studies in Double Shielded GMAW of Dissimilar Stainless Steels

In the present work, a simple arrangement is made to provide double layer shielding gas supply in addition to primary shielding during gas metal arc welding (GMAW) of two dissimilar stainless steels, i.e., AISI 316 and duplex 2205. Influences of double layer shielding in addition to five more process parameters like welding current, voltage, material of the electrode wire, the type of primary shielding gas, and flow rate on joint tensile strength and fusion zone microhardness are studied. An experimental design technique is used to design the experimental conditions and the results are analyzed to observe the influences of each process parameter and their interactions. The tensile strength is more influenced by the electrode material and the type of shielding, whereas current, interaction between current × voltage and current × flow rate significantly influence microhardness. Welding voltage influences both tensile strength and microhardness. Double layer shielding with CO2 as an outer shielding layer helps in controlling the cooling rate which improves the tensile strength and microhardness. Microstructural observations by scanning electron microscopy reveal that moderate to low heat input with a single layer of shielding results in poor joint strength and severe damage or lack of fusion, and the duplex 2205 filler gives the maximum joint strength due to the presence of a ferrite structure.

Mechanism of Material Deposition from Powder, Electrode and Dielectric for Surface Modification of H11 and H13 Die Steels in EDM Process

Surface modifications using the powder mixed electric discharge machining (PMEDM) process has gained a lot of research interest in recent few years. The present paper investigates the material transfer from the powder suspended in dielectric, electrode and dielectric material for enhancing the surface properties measured in terms of the microhardness of the machined surface for two kinds of die steels (H11 and H13). Four different powder materials aluminium, copper, graphite and tungsten were mixed with dielectric during machining with three different dielectric materials namely kerosene, EDM oil and refined mineral oil. Other process parameters were varied at suitable levels. Maximum increase in microhardness was observed with addition of tungsten powder and with tungsten-copper electrode even at lower current. Current significantly affected the transfer mechanism of material on the machined surface but was dwarfed by the very significant affect of powder which had the largest contribution. A relative comparison of microhardness between deposited and non-deposited regions showed an increase of 37% for H11 and 56% for H13 due to addition of powder. The photomicrographs of the machined surface also supported the material transfer from powder, electrode as well as dielectric forming compounds that suitably improve the surface properties of H11 and H13 die steel.

Material transfer mechanism during magnetic field–assisted electric discharge machining of AISI D2, D3 and H13 die steel

In this study, the surface modification and metallurgical analysis of three commonly used die steels were analyzed by microstructure and X-ray diffraction analysis after electric discharge machining and powder-mixed electric discharge machining. The effect of many process parameters was assessed for surface modification using magnetic field–assisted electric discharge machining process. It was observed that the microhardness of the machined surface increased by more than 200%. The analysis of machined surface confirmed material migration from added powder, dielectric and electrode. The magnetic field assisted in improving the material removal process. The strength of the magnetic field resulted in better expelling of material from workpiece and restricted the material migration from electrode especially in copper-based diamagnetic material. Deposition of tungsten and titanium carbide was observed, which increased the microhardness significantly. Titanium, tungsten and graphite powder aided favorably the increase in the microhardness.

Effect of process parameters on microhardness and microstructure of heat affected zone in submerged arc welding

The aim of the present work was to study the effect of flux, welding current, arc voltage, and travel speed on changes in microhardness and microstructure of the heat-affected zone (HAZ) and to optimize the process so that minimal changes occur in the material properties after completion of a submerged arc welding (SAW) process following suitable Taguchi experimental design. Micrographs of the welded samples were studied to analyse the changes in the microstructure of the material and the resultant changes in ferrite percentage, pearlite, bainite, and martensite formations. Welding current and type of flux were found to be the most significant factors leading to changes in microhardness and metallurgical properties. The microhardness tended to increase significantly with the increase of welding current from 350 to 450 Amp whereas higher hardness was observed when flux type I (basicity index 0.8) was used. Travel speed and arc voltage were found to be insignificant in relative comparison. Flux with basicity index of 0.8 showed a significantly higher microhardness compared to flux with basicity index of 1.6 (flux II). A higher amount of CaO and MgO present in flux II has a tendency to pick up carbon from steel workpiece, thus lowering the microhardness.