Machined Surface Research Articles

Effect of Al7075 and activated carbon reinforced composite on optimizing WEDM responses

This paper presents wire cut electrical discharge machining (WEDM) response characteristics of Aluminium 7075 (Al7075) reinforced with powdered activated carbon (PAC) composite. In recent days WEDM has become a significant machining process in targeting its benefits of contributing improved material removal rate (MRR) and low surface roughness (SR). This is due the rising need for intricate, accurate, and superior structural components, the WEDM process emerges as a formidable alternative to traditional machine tools. In this work Pulse-on time (Ton), pulse-off time (Toff), discharge current (IA) and servo speed rate (SS) are the variables to be given as input and machining responses such as MRR and SR are studied. From Analysis of Variance (ANOVA) study it is found that discharge current and servo speed is the significant parameters. The optimal desirability condition is obtained with input parameters Ip: 2000 mA; Ton: 8.9 μs; Toff: 25 μs and SS: 150 rpm for the precision machining. The optimum response parameters are found as MRR 10.46 mm3/min and SR 3.32 μm. Results shows that the model designed for the prediction of MRR produces an above 98.27% and the prediction of SR is above 97.17%. The error percentage among the experimental and predicted MRR and SR were estimated. Additionally confirmatory test is performed with optimal results achieved from response surface methodology (RSM) and desirability technique. Metallurgical tests like electron backscatter diffraction analysis (EBSD) and microstructure are conducted to confirm the surface properties and atomic force morphology (AFM) analysis is applied to clarify the structural features of machined composites. The results revealed that the variation of hard deflection is caused by depression of eroded materials on the top layers of machined surface.

Assessment of the Impact of Jet-Abrasive Surface Machining on the Formation of Pitting Corrosion

Assessment of the Impact of Jet-Abrasive Surface Machining on the Formation of Pitting Corrosion

Experimental investigation on longitudinal torsional ultrasonic vibration milling for cortical bone

Efficient bone milling processes, producing high-quality machined surfaces, are crucial for enhancing arthroplasty surgery. This study introduces a novel Longitudinal Torsional Ultrasonically Vibration Milling (LTVUM) technique and conducts a comparative analysis with Conventional Milling (CM). The reduction in average milling force observed during the LTVUM process was systematically recorded. Orthogonal experimental analysis focusing on milling orientation, rotational speed, and feed velocity revealed that LTVUM diminishes the influence of orientation and rotational speed, while amplifying the impact of feed velocity. Subsequent response surface methodology experiments further demonstrated that LTUVM significantly augmented the impact of integrated parameters related to feed velocity. Moreover, LTVUM was found to improve machining surface quality and alter the shear mode. These results have profound implications for the theoretical exploration of LTVUM, supporting the design and development of innovative tools for arthroplasty surgery.

Analysis of Tool Load Concerning the Cross-Sectional Size of Removed Material

High-feed milling (HFM) represents a progressive manufacturing technology that has recently found widespread application across various industries. HFM is characterized by high machining speed, reduced cycle times, increased overall productivity, and increased tool life. Due to its versatility, HFM is a suitable technology for the application of various materials. The study deals with experimental analysis of cutting forces, machined surface integrity, and statistical evaluation in high-feed machining. In the present study, nickel-copper-based alloy (Monel) was chosen as the machined material, employing HFM with a monolithic ceramic milling cutter. The Monel material is characterized by its excellent mechanical properties and chemical resistance in harsh environments. During machining, cutting forces were recorded in three mutually perpendicular directions. This paper delves into the analysis of the impact of the depth of cut (ap), width of cut (ae), and lead-in angle (ε). The chosen evaluation characteristics encompass the tool load, primary profile, and the attained roughness of the machined surface. It is noteworthy that the technology under consideration predominantly aligns with the roughing phase of the manufacturing process. Additionally, the investigation incorporates a statistical analysis of the response surface pertaining to the cutting force components, namely Fx, Fy, Fz, and the resultant cutting force F.

Corrosion, wear and machinability studies on scrap aluminium alloy wheel based metal matrix composite

Recycled materials, especially scrap aluminum alloy wheels with reinforcement castings, are gaining applications in various fields such as aerospace, naval, military, and automobile. In this research, Honda car alloy wheels are stir-cast with 5% alumina as reinforcement and subjected to corrosion, wear, and machinability studies. Corrosion studies were conducted to evaluate the corrosion current density (ICorr), corrosion potential (ECorr), and corrosion rate for the cast aluminum metal matrix composite. The wear studies with different loads, i.e., 50 N, 60 N, 70 N, and 80 N, were performed on the specimen and investigated the coefficient of friction, frictional force, and pin temperature. The sliding load has a significant effect on wear performance, and for the sliding load of 80 N, the wear recorded was 2574.83 µm. The electrochemical machinability studies with voltage, duty cycle, and concentration of citric acid electrolyte are performed on the machining rate and surface corrosion factor. Analysis of the electrochemical machining process with PROMETHEE-II shows that 7 V, 60% duty cycle, and 30 g/L electrolyte concentration are estimated to be the best combination for a higher machining rate and a lower surface corrosion factor. KEY WORDS: Alumina, Machining rate, Nyquist plot, Electrochemical machining, PROMETHEE-II Bull. Chem. Soc. Ethiop. 2024, 38(4), 1163-1175. DOI: https://dx.doi.org/10.4314/bcse.v38i4.27

Investigate on material removal of 3C-SiC crystals in nano-polishing via molecular dynamics

While 3C-SiC crystals are widely employed in engineering applications such as aerospace, energy, chemistry, and electronics, the challenge of enhancing surface friction and wear mechanisms in 3C-SiC materials persists. This work focuses on the nano-polishing velocity effect on the material removal mechanism of 3C-SiC crystals in the course of nano-polishing, which is related to material removal, mechanical response, phase transformation, and stress distribution. By employing molecular dynamics (MD) simulations, nano-polishing velocity is modified within a specified range, and its influence on the atomic motion and structural transformation of the workpiece is examined. The simulation results reveal that higher nano-polishing velocities diminish the subsurface damage and the extent of phase transformation induced by nano-polishing. However, the higher velocities also result in reduced machined surface quality and increased residual stress in 3C-SiC crystals. Therefore, it is challenging to address both the surface quality and subsurface quality of the material solely based on nano-polishing velocity. A recommended range of nano-polishing velocity, ranging from 200 m/s to 400 m/s, is deemed appropriate. This work offers a comprehensive understanding of the material removal mechanism of 3C-SiC at the atomic level and holds significant guiding value for achieving ultra-precision machining of surfaces and subsurfaces.

Surface Integrity of Binderless WC Using Dry Electrical Discharge Assisted Grinding

AbstractBinderless tungsten carbide (WC) is preferred for manufacturing tools, mould, and wear-resistant components. However, due to its high brittleness and hardness, the machined binderless WC surface is prone to generate microcracks and the machining efficiency is extremely low. Aiming at this difficulty, a clean and eco-friendly dry electrical discharge assisted grinding (DEDAG) method without any liquid medium was proposed for the processing of binderless WC. DEDAG principle was revealed and the DEDAG platform was first developed. A series of DEDAG, conventional dry grinding (CDG), and conventional wet grinding (CWG) experiments were conducted on binderless WC under different processing parameters. The current and voltage waveforms during the DEDAG process were observed, and the discharge properties were analyzed. The chip morphologies, surface hardness, residual stress, as well as surface and subsurface morphologies were analyzed. The results show that the surface hardness and roughness obtained by DEDAG are smaller than that by CDG or CWG. The measured residual tensile stress after CDG is larger against DEDAG. The ground surface by DEDAG has better crystal integrity than that by CDG. DEDAG can soften/melt workpiece material and diminish grinding chips, thereby promoting plastic removal and increasing processing efficiency. The influences of DEDAG parameters on the ground surface quality are also investigated, and the optimal DEDAG parameters are determined. With the increase of open-circuit voltage or grinding depth, the surface quality improves first and then worsens. The optimal open-circuit voltage is 40 V and the grinding depth ranges from 10 µm to 15 µm. This research provides a new idea for promoting the efficient and low-damage processing of binderless WC.

Improving Maraging Steel 350 Machinability via Wiper Insert-Enhanced Face Milling

Despite the prevalent application of 18% Ni maraging steel in critical sectors such as aerospace and automotive due to its unique characteristics, including high ductility, yield strength, and hardenability, its machining presents enormous challenges, categorizing it as a difficult-to-machine material. The cutting tool’s geometry is crucial in machining, significantly affecting chip formation, cutting forces, power consumption, and obtainable surface quality. In particular, wiper insert technology, characterized by its multi-radius design, offers an increased contact area compared to conventional inserts, potentially enhancing the quality of the machined surface. This study explores the effectiveness of wiper inserts in the face-milling of maraging steel 350, conducting a comparative analysis across three distinct machining setups. These setups vary by alternating the number of wiper and conventional inserts within the same cutter, thereby examining the influence of insert configuration on machining outcomes. The research employs a reliable and well-established statistical approach to evaluate how different variables, such as cutting speed and feed rate, affect surface quality, power consumption, and material removal rate (MRR). It also sheds light on the material removal mechanisms facilitated by each type of insert. The findings reveal that incorporating a higher number of wiper inserts significantly enhances the surface finish but concurrently increases power consumption. Thus, the study successfully identifies an optimal set of process parameters that attain a balance between achieving superior surface quality and maintaining energy efficiency in the machining of maraging steel 350. This balance is crucial for optimizing manufacturing processes while adhering to the stringent quality and sustainability standards required in aerospace and automotive manufacturing.

Surface roughness prediction of AISI D2 tool steel during powder mixed EDM using supervised machine learning

Surface integrity is one of the key elements used to judge the quality of machined surfaces, and surface roughness is one such quality parameter that determines the pass level of the machined product. In the present study, AISI D2 steel was machined with electric discharge at different process parameters using Jatropha and EDM oil. Titanium dioxide (TiO2) nanopowder was added to the dielectric to improve surface integrity. Experiments were performed using the one variable at a time (OVAT) approach for EDM oil and Jatropha oil as dielectric media. From the experimental results, it was observed that response trends of surface roughness (SR) using Jatropha oil are similar to those of commercially available EDM oil, which proves that Jatropha oil is a technically and operationally feasible dielectric and can be efficiently replaced as dielectric fluid in the EDM process. The lowest value of S.R. (i.e., 4.5 microns) for EDM and Jatropha oil was achieved at current = 9 A, Ton = 30 μs, Toff = 12 μs, and Gap voltage = 50 V. As the values of current and pulse on time increase, the S.R. also increases. Current and pulse-on-time were the most significant parameters affecting S.R. Machine learning methods like linear regression, decision trees, and random forests were used to predict the surface roughness. Random forest modeling is highly accurate, with an R2 value of 0.89 and an MSE of 1.36% among all methods. Random forest models have better predictive capabilities and may be one of the best options for modeling complex EDM processes.

Diamond machining of additively manufactured Ti6Al4V ELI: Newer mode of material removal challenging the current simulation tools

Single point diamond machining (SPDM) produces smooth machined surfaces that other production methods cannot match. While the mechanics of machining of cast alloys with SPDM is well-explored, the realm of SPDM for additively manufactured parts remains largely uncharted. This work reveals new insights into the surface generation process of an additively manufactured titanium alloy, specifically, a Ti6Al4V Extra Low Interstitials (ELI) alloy workpiece. Our examination of the chip morphology unveiled a distinct mode of chip removal, previously unrecorded in existing literature. During SPDM of additively made Ti6Al4V ELI workpiece, identification of numerous pores and discontinuities in the chips flowing on the tool rake face, indicating periodic intermittent cracking during the material's plastic flow was seen. To examine this phenomenon, a finite element analysis (FEA) model was developed. While the FEA model can well explain the machining mechanics and chip morphology of SPDM of cast Ti6Al4V ELI reported in the literature, it failed to describe the chip morphology that are obtained during machining of additively made workpiece in this work. This disparity underscores the need for innovative simulation approaches tailored for additively manufactured components. The experimental observations in this study highlight a unique form of chip formation in contrast to conventional Ti6Al4V alloy machining processes. At lower feeds, there was a presence of short, discontinuous chip formation with tearing at the outer periphery. Conversely, at higher feeds, a long, continuous ribbon-like chip formation was observed. In addition, some typical additive manufacturing defects appear on the machined surface and chips. Through optimisation of the SPDT parameters, a surface roughness (Ra) value of about 11.8 nm was achieved on additively manufactured Ti6Al4V ELI workpiece. This work provides a fresh perspective on the mechanics of SPDM for additively manufactured components, offering a stepping stone for subsequent studies.

High-efficiency green machining of single crystal 4H–SiC based on tribo-oxidation

High efficiency, high quality and green machining of single crystal silicon carbide (SiC) is an important issue in the third-generation semiconductor industry. In this paper, a novel machining method for single crystal SiC based on tribo-oxidation is proposed. The formula and preparation process of polysaccharide bonded soft abrasive tool were designed. Dry machining of C-face of 4H–SiC substrate was carried out with the prepared environmentally friendly abrasive tool sample. The material removal mechanism of the proposed machining method was preliminarily analyzed, and the material removal rate, surface roughness and subsurface residual stress were studied. The experimental results show that the maximum material removal rate of 4H–SiC can reach 1.03 μm/min with a corresponding average surface roughness of Sa 0.816 nm. The machined surface has no brittle flaw, and subsurface residual compressive stress exists with a maximum value of 58.9 MPa. The material removal mainly attributed to the active oxidation of SiC surface induced by the friction between alumina abrasives and SiC substrate. The proposed machining method has potential application value in thinning of SiC wafers.

Enhancing the Machining Performance of Nomex Honeycomb Composites Using Rotary Ultrasonic Machining: A Finite Element Analysis Approach.

Nomex honeycomb composites (NHCs) are commonly used in various industrial sectors such as aerospace and automotive sectors due to their excellent material properties. However, when machining this type of structure, problems can arise due to significant cutting forces and unwanted cell vibrations. In order to remedy these shortcomings, this study proposes to integrate RUM (rotary ultrasonic machining) technology, which consists of applying ultrasonic vibrations along the axis of rotation of the cutter. To fully understand the milling process by ultrasonic vibrations of the NHC structure, a 3D numerical finite element model is developed using Abaqus/Explicit software. The results of the comparative analysis between the components of the simulated cutting forces and those from the experiment indicate a close agreement between the developed model and the experimental results. Based on the developed numerical model, this study comprehensively analyzes the influence of the ultrasonic vibration amplitude on various aspects, such as stress distribution in the cutting zone, chip size, the quality of the machined surface and the components of the cutting force. Ultimately, the results demonstrate that the application of ultrasonic vibrations leads to a reduction of up to 50% in the components of the cutting force, as well as an improvement in the quality of the machined surface and a reduction in the size of chips.

An Experimental Procedure to Study the High-Speed Orthogonal Cutting of Unidirectional GFRP

The aim of this paper is to establish a valid procedure for better understanding all of the phenomena associated with the high-speed machining of glass fiber-reinforced plastic (GFRP) composites. Both rectangular and circular specimens were machined at high cutting speeds (up to 50 m/min) in order to understand what occurred for all values of fiber orientation angles during machining operations. An innovative testing methodology was proposed and studied to investigate the phenomenon of burr formation and thus understand how to avoid it during machining operations. To this end, the forces arising during the machining process and the roughness of the resulting surface were carefully studied and correlated with the cutting angle. Additionally, the cutting surface and chip morphology formed during cutting tests were examined using a high-speed camera. Close correlations were found between the variations in the cutting forces’ signals and the trends of the surface roughness and the morphology of the machined surface.

Deformation mechanism of soft metal tin in micro machining

The deformation mechanism in the micro machining of soft metal tin significantly influences its machined surface quality. In this work, microscratching tests along different orientations are performed on the tin surface. Activation of slip systems induces the appearance of surface slip band, lattice rotation and stable cutting force. The crucial role of loading orientation in slip system activation and lattice rotation is investigated. The misorientation around 62° is detected in the region of the activated slip band, whereas the misorientation angle of the other deformation region is less than 15°. In addition, a part of the lattice rotation would be recovered to original orientation along with time.

Axis path planning of five-axis surface machining by optimizing differential vector of the axis movement considering tool posture limits

Axis path planning of five-axis surface machining by optimizing differential vector of the axis movement considering tool posture limits

Reducing Cf/SiC composite damages through collaborative control of laser ablating depth and grinding modes

Cf/SiC composites are regarded as difficult-to-machine aerospace materials. A low-damage surface machining of Cf/SiC composite by laser-ablating assisted grinding (LAAG) was conducted, and investigated the effects of laser-ablating depth and grinding modes on surface/subsurface damages. The results showed that ablated material depth reached 420 μm after 1200 times scanning, while the effective ablating rate was inhibited by the depth. Compared with down grinding, the grinding forces and temperatures were substantially higher in up grinding, with a maximum increase of 123.5 % and 140 % in normal and tangential grinding forces, respectively; however, micro brittle fracture and ductile removal were remarkably enhanced in normal and transverse fibers, and surface macroscopic damage has been suppressed; subsurface damage remained insignificant, mainly exhibited in internal micro cracks and minor interfacial debonding. It was attributed to cutting characteristics of up grinding. Furthermore, as grinding depth increased, the material removal behavior underwent a brittle-ductile transition and the surface roughness grew accordingly. Moreover, a laser scanning angle of 0° and up grinding facilitated the occurrence of longitudinal fiber debonding, producing larger sized fiber bundle chips. Combining up grinding with 90° scanning angle at low grinding depth was an effective method to improve the surface quality of Cf/SiC composite.

JUSTIFICATION OF NOZZLE PARAMETERS OF JET-TYPE WASHING MACHINES FOR CLEANING AGRICULTURAL MACHINES AND UNITS

Agricultural machinery and equipment are exposed to significant contamination by various types of pollutants, some of which can be easily removed, while others require the use of special cleaning agents and machines. To remove these contaminants, a pressurized water jet is used, the biggest disadvantage of such devices is the significant water consumption, so the issue of intensifying the cleaning process of agricultural machinery using a limited amount of water is an important scientific task. Cleaning of agricultural machinery and units from contaminants is a complex technological operation, therefore, there is a need to develop and justify the parameters and operating modes of a high-tech washing device that would ensure high-quality removal of all types of contaminants with high efficiency, minimal water consumption and minimal labor costs. The analysis of cleaning technologies showed that water jet cleaning is the most promising for removing dirt from the surface of agricultural machines and units, the technology allows to increase the level of mechanical impact by using additional energy, which can be the energy of a rotating jet. The study examines the efficiency of cleaning washing plants from various contaminants. The main focus is on studying the impact of nozzle design on the quality and productivity of the washing process. Nozzles determine the shape of water jets and their velocity, determining the cleaning efficiency. The dagger and fan nozzles, their advantages and disadvantages are considered. Nozzle parameters such as orifice diameter, spray angle, and number of fan jets are investigated. It is shown that properly selected nozzle parameters play an important role in achieving the optimal cleaning effect and water saving. Factors such as flow coefficient, drag coefficient, and velocity coefficient that affect the performance and energy of the jet are outlined.

Finite element and experimental analysis of surface integrity and surface roughness of precision machining SiCp/Al

The silicon carbide particle-reinforced matrix composites, or SiCp/Al, have excellent mechanical qualities, but producing them is quite difficult since the SiC particles’ and the Al matrix’s properties differ greatly from one another. During the cutting process, the Ra local oscillation phenomena takes place; that is, surface roughness seems to grow, decrease, and then increase as the cutting depth increases within a particular cutting depth range while maintaining the same cutting speed and feed. To find out why this behavior occurred, a cutting experiment and a simulation analysis of SiCp/Al composites were performed. Tests were conducted to find out how varied cutting depths affected surface roughness, and a finite element model for two-dimensional cutting was created. Based on the data, it can be concluded that Ra’s local oscillation phenomena is responsible for the surface quality at various cutting speeds. At 100 mm/s, 200 mm/s, 300 mm/s, and 400 mm/s, respectively, the mutation’s surface quality improved by 29.6%, 14.3%, 19.6%, and 30.7% prior to the cutting depth. The analysis is justified by the fact that the depth of cut is increasing, the way in which particles are removed has changed and the percentage of scratches appears to be decreasing. As aluminium is a plastic material, plastic deformation occurs during cutting by the sub-cutting edge of the extrusion, coating the machined surfaces and producing fine cracks rather than plough furrows. In a sense, increasing the cutting thickness results in larger chips, more force on the particles in the cutting path and easier removal. At the same time, it reduces the width of the chip in future cuts, improving the surface quality of the process.

Precise surface machining of fused silica using high stability atmospheric pressure microwave plasma jet with a new internal electrode

Plasma is a promising approach for machining of fused glass substrates. Developing high-performance microwave torch is the core element to ensure the processing accuracy of this technology. In this study, a spline curve-based microwave torch internal electrode structure was proposed, which increased the internal electric field strength by 54 %. The discharge dynamics simulation based on this electrode shows that the plasma is excited at the inner electrode tip and the bottom of the resonant cavity, then it expands to form a linear discharge region and eventually fill the discharge tube. It was revealed by CCD images that with the increase of carrier gas flow rate, turbulent flow state appears in the tail of the jet. OES data shows that microwave Ar plasma can effectively dissociate CF4, and due to the oxidation effect of oxygen, CFx and C2 content decrease significantly with the addition of oxygen. The machining experiment on fused silica shows that the material removal stability of this torch reaches 3.69 %, and the removal rate increases nYarly with dwell time due to thermal effect. Finally, the machining performance of the atmospheric pressure microwave plasma jet was verified by figuring of a planar fused silica surface reducing the form error from 108.1 nm RMS to 16.5 nm RMS.

Application of Taguchi Method, ANOVA Analysis, and TOPSIS Technique in Optimization of Process Parameters for Surface Roughness and Material Removal Rate in Electrochemical Machining of Al-SiC MMCs

Objectives: To evaluate the significance of advanced machining techniques, such as EDM, ECM, and USM, in increasing productivity and overcoming challenges associated with outdated Al-SiC MMC machining. To assess the surface roughness, tool wear, and machining cost implications of employing advanced machining methods for Al-SiC MMCs. Methods The parameters studied were voltage (V), feed rate (F), and electrolyte concentration (C) in electrochemical machining (ECM) of Al/15%SiC composites. To optimise process parameters, the Taguchi method for Design of Experiments (DOE) with an L27 orthogonal array was used. Signal responsiveness is optimised using the Taguchi approach. The Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS) is used to find optimal machining settings. Findings: The outcome of this research is that the parameters affecting surface roughness and material removal rate are voltage, electrolyte concentration and feed rate. The minimum Surface Roughness achieved by selecting the best combination level is A2, B3, C3 (smaller is better) i.e., voltage 20 V, feed rate (f) 0.4 mm/min., electrolyte concentration (c) 30 g/lit. The maximum Material Removal Rate achieved by selecting the best combination level is A3, B3, C3 (larger-is-better) i.e., voltage 25V, feed rate (f) 0.4 mm/min., electrolyte concentration (c) 30 g/lit. Novelty : In this work, TOPSIS technique paired with Taguchi method is used which is rarely studied by other researchers. TOPSIS technique provides the best optimal solution as compared to other techniques. Keywords: Al-SiC MMCs, ECM, MRR, Ra, Taguchi method, TOPSIS