Machining Of Materials Research Articles

Characterization of 3D printed composite for final dental restorations.

This study evaluated the mechanical, optical, microstructural, surface, and adhesive behavior of a 3D printing resin comparing it with a machinable resin composite. Specimens of different sizes and shapes were either printed (Vitality, Smart Dent) or machinable (Grandio Blocs, Voco GmbH) resin composites with similar composition were prepared. Surface and mechanical characterization were performed with Knoop hardness, flexural strength (three-point-bending), and elastic modulus tests. The wear of the tested materials was evaluated against steatite antagonists. The optical properties stability (color change, ΔE00, and translucency, TP00) were observed after staining in red wine. In addition, the bond strength of the resin composites to two resin cement protocols were investigated with microshear bond strength tests at baseline and after thermocycling. Scanning electron microscope (SEM) coupled with Energy-Dispersive X-ray Spectroscopy (EDS) was used for microstructural and chemical characterization. Statistical analyses were performed with t- and ANOVA tests. Hardness values (132.76 (16.32) KH- Machinable and 35.87 (2.78) KH - Printed), flexural strength (172.17 (26.99) MPa - Machinable and 88.69 (8.39) MPa - Printed), color and translucency change (1.86 (0.31)/0.06 - Machinable and 3.73 (0.36)/9,16- Printed), and wear depth (24.97mm (3.60)- Machinable and 7.16mm (2.84) - Printed) were statistically different. Average Regarding bond strength, mean values (MPa) for non-aged and aged groups were respectively 21.76 (6.64) / 31.9 (12.66) for Bifix cement (Voco GmbH, Cuxhaven, Germany) and 26.75 (5.14) / 24.36 (6.85) for Variolink cement (Ivoclar Vivadent, Schaan, Liechtenstein) in Printed and 17.79 (3.89) / 9.01 (3.36) ) for Bifix cement and 22.09 (6.55) / 11.01 (3.77) for Variolink cement in Machinable materials. The material and aging factors did affect bond strength but the cement factor did not (p = 0.202). No statistical differences were observed for mean roughness (Ra) between materials. The better dispersion and larger size of the inorganic particles in the Machinable resin were contrasted with the clustered smaller particles of printed resin, under SEM. The mechanical properties and color stability of the machinable resin were superior to those of the printed resin, probably due to the greater amount and dispersion of inorganic particles in the Mach resin, but bond strength after aging was stronger and more stable in the printed resin. 3D-printed resin composites with similar compositions to machinable resin composites do not necessarily exhibit the same properties, which can impact clinical performance. Understanding these differences can assist manufacturers in improving their materials and help clinicians distinguish between materials appropriate for provisional and final restorations.

Research on the Risk of Drilling Phases Based on the Development Model of Shallow-Water Subsea Trees

China is actively advancing offshore oil and gas exploration and development, focusing on addressing the technical challenges associated with resource extraction in shallow waters. The shallow-water subsea tree development model has gradually been applied in such environments, alleviating some construction difficulties. However, it still poses well control risks that require systematic analysis and quantitative evaluation. Given that the blowout preventer (BOP) is located on the platform and the shallow-water subsea tree is only used during certain drilling stages, this study divided the drilling process into two phases: the first three sections and the fourth section. Based on the “man–machine–material–environment” analytical framework and an improved system-theoretic process analysis (STPA), a control model for the construction phases was developed. Fault tree analysis (FTA) was then employed to identify comprehensively the potential risks from the platform to the wellbore in both phases. Subsequently, the decision-making trial and evaluation laboratory (DEMATEL) method were used to assess quantitatively the well control risks. Using the average weight as the evaluation criterion, high-risk factors exceeding the average weight in each phase were identified. The results indicate that in the shallow-water subsea tree development model, well control risks in the first three drilling sections primarily stem from human errors and equipment failures, while risks in the fourth section are mainly caused by damage to the subsea tree itself. The identified risk factors provide a theoretical basis for enhancing well control safety management in the shallow-water subsea tree development model.

Physical-Vapor-Deposition-Coated Natural Rocks as Sustainable Cutting Material: First Insights into the Effect of Substrate Integrity on Properties of TiN Thin Film

The most important cutting materials for machining are carbides. Their production requires both tungsten and cobalt; however, these materials are becoming increasingly difficult to obtain and are sometimes mined under ethically questionable conditions. As a result, increasing efforts are being made to expand the range of cutting materials. The basic suitability of natural rocks for cutting tools in less demanding processes has already been demonstrated. PVD coating of the natural rocks could improve their performance. The adhesion mechanisms in TiN-coated natural rock samples are discussed below. The TiN thin film is characterized in depth.

Comprehensive Evaluation Method for High-Performance Milling of Inconel 718 Alloy

The aim of this paper was to develop and verify a method for evaluating the high-performance milling of Inconel 718 alloy under accelerated tool wear conditions. The method considered parameters such as cutting-force components, total machine power consumption, cutting-edge wear, and material removal rate. The study compared high-feed milling and plunge milling, using sets of cutting parameters that are appropriate for both techniques. The results indicate that high-feed milling was more efficient, achieving higher material removal rates and lower tool wear. On the other hand, plunge milling was characterized by a lower axial force component (Fz), which can positively affect machining accuracy. The paper highlights that the proposed evaluation method can also be applied to other hard-to-machine materials, and plunge milling offers a competitive alternative for roughing operations in the milling of Inconel 718 alloy.

Influence of WEDM input variables on the machinability of Ni–Cu superalloy

ABSTRACT The study investigates the influence of Wire-cut Electrical Discharge Machining (WEDM) input variables on the Ni–Cu superalloy, crucial in marine environments. Input variables include Input current (Ic), Pulse on Time (TON), Pulse off Time (TOFF), Servo Voltage (SV), and Wire Feed (WF) rate, while output variables are Machine Speed (Mc), Kerf Width (K), and Material Removal Rate (MRR). Utilizing an L16 orthogonal matrix, experiments were conducted. The Taguchi method examines single output variables, while the Grey Relational Grade Algorithm (GRA) assesses multi-objective outputs. GRA identifies optimal input combinations, crucial for maximizing the machining performance. ANOVA of GRA results highlights Pulse on Time (TON), Input current (Ic), and Servo Voltage (SV) as significant factors affecting Mc, K, and MRR. This analysis underscores their importance in optimizing the WEDM process for Ni–Cu (MONEL K-500 superalloy).

Rapid manufacturing of copper-graphene composite EDM electrode for improved machining performance

ABSTRACT Recently, graphene has emerged as reinforcing material for copper-based electric discharge machine (EDM) tools because of its superior electrical, thermal and high melting properties. 3D printing methods to fabricate electrodes are convenient and faster compared to conventional methods. Therefore, this study investigated the fabrication of copper-graphene composite electrodes for EDM using rapid tooling and pressureless microwave sintering. The influence of graphene content on the machining performance was examined, revealing enhanced electrical conductivity and machining efficiency. Electrical conductivity of the composite electrodes having 0.25 and 0.5 wt% of graphene was higher than pure copper. Additionally, upto 89% improvement in material removal rate and upto 14% reduction in electrode wear rate was obtained. Optical study showed an improvement of upto 28% in surface finish of the workpiece machined using composite electrode having 0.25 wt% graphene. A complex shaped composite tool was successfully fabricated and machined cavity was obtained.

A Study on Microstructure Evolution and Mechanical Properties of Inconel 690 Subjected to Milling Process

The metallic materials subjected to machining‐induced severe plastic deformation can experience alterations of microstructures and mechanical properties, affecting the functional performances of the components. This study concentrates on the microstructure evolution and mechanical properties analysis of Ni‐based superalloy Inconel 690 under severe plastic deformation induced by milling process. The obtained results show that the microstructures of the machined surface and subsurface exhibit the characteristic of gradient distribution. Plastic behaviors involving dislocation multiplication, grain deformation and refinement, increment of local misorientation and average intragranular misorientation, and transition from high‐angle grain boundaries to low‐angle grain boundaries occur in the superficial layer of the machined workpiece. Both the intensity and the affected depth of plastic deformation for the superficial layer are strengthened following the cutting speed and feed increase, which is attributed to higher cutting forces. No white layer and phase transformation is found under all cutting conditions. In addition, the nanohardness of the superficial layer shows the reduction tendency of hardening effect from the surface to the bulk of the machined workpiece material. With the increase in cutting speed and feed, the affected zones of residual stresses and work hardening below the machined surface become wider.

Determination of Chip Compression Ratio for the Orthogonal Cutting Process

The chip compression ratio is the most important characteristic of various machining processes with chip generation. This characteristic enables the determination of kinetic and other energy loads on the tool and the machined material. This provides an overall evaluation of the machining process and the possibility of its subsequent optimization. This paper presents the results of determining this cutting characteristic by experimental method, analytical calculation, and numerical modeling. For the analytical calculation of the chip compression ratio, an analytical cutting model developed based on the variational principle of the minimum potential energy was used. A finite element model of orthogonal cutting was used for the numerical simulation of the above process characteristic. Experimentally, the chip compression ratio was determined by the ratio of the chip thickness to the cutting depth (undeformed cutting thickness). The chip thickness was determined by direct measurement using chip slices obtained during the cutting process. The Johnson–Cook constitutive equation was used as the machined material model and the Coulomb model was used as the friction model. The generalized parameters’ determination of the constitutive equation was performed through a DOE (Design of Experiment) sensitivity analysis. The variation range of these parameters was chosen based on the analysis of the effect of individual parameters of the constitutive equation on the chip compression ratio value. The largest deviations between the experimental and analytically calculated values of the chip compression ratio did not exceed 21%. At the same time, the largest deviations of simulated values of the indicated cutting characteristic and its experimental values did not exceed 20%. When comparing the experimental values of the chip compression ratio with the corresponding calculated and simulated values, the deviations were within 22%.

Design of a test rig for the characterization of friction and wear in hot-metal gas-forming of AA 5083 aluminium sheets

Advanced aluminium sheet-forming processes such as the hot-metal gas-forming represent a challenging solution for producing small lots in the high-end car bodies industry, and the adoption of single cavity moulds made from low-cost, easily machinable materials such as cast iron reduces the overall sheet-forming costs. The tribological properties of the mould-sheet tribopair are of great interest for optimizing the sheet forming obtaining an acceptable esthetic surface finishing. This study presents the design and construction of a lab-scale experimental test rig for the tribological characterization at high temperatures of the mould-sheet tribopair. The proposed test method reproduces the sliding at the mould-sheet interface with contemporary sheet straining up to ε = 0.8 at strain rates in the 1.2*10-3 to 2*10-2 s-1 range. A series of experiments were carried out in dry and lubricated conditions for a ductile iron EN-GJS grade sliding against a AA 5083 aluminium alloy while straining. After comparing the experimental results with the literature data from other test rigs, comparable results were obtained as COF regards, ranging between 1.2 to 2.5 in dry sliding and between 0.05 to 0.2 in lubricated sliding. The morphological characterization of the sliding surfaces and cross-sections highlights the strong tendency to galling in dry sliding conditions expecially for low strain rates.

Influence of machining conditions on dry EDM with workpiece cooling of Inconel 625 alloy in the milling kinematics

One potential eco-friendly variant of electro-discharge machining is dry electro-discharge machining (EDM), in which the liquid hydrocarbon–based dielectric is substituted with a gaseous medium. The primary challenge associated with dry EDM is the excessive dissipation of heat within the machining gap, which restricts its utilisation only to a microscale machining. Consequently, further modifications to the underlying mechanism of the process are being undertaken with the aim of efficient industrialising it on a larger scale. In the present study, a novel approach is proposed to enhance the efficiency of dry-EDM process while using carbon dioxide as a gaseous medium together with introducing additional external workpiece cooling with deionised water. A series of experiments were conducted to determinate the impact of external workpiece cooling with deionised water and the main machining parameters, namely pulse-on time and current intensity gas pressure, on the material removal rate, working electrode wear, and surface integrity of Inconel 625 during EDM in milling kinematics. The results demonstrated that, under the same machining parameters, the wear of the working electrode, the surface roughness, and the thickness of the recast layer were significantly reduced in the EDM with external workpiece cooling in comparison to the dry-EDM process without water cooling. Furthermore, the EDM with coolant exhibited superior performance in comparison to the dry-EDM process due to the fact that there were fewer changes in the surface morphology and chemical composition of the machined material.

Investigating micro-EDM machinability of Ti-35Nb-7Zr-5Ta (TNZT) alloy

ABSTRACT Titanium and its new-generation alloys are widely employed in high-end applications due to their special properties. Modern industries frequently use micro – Electro Discharge Machining (μ-EDM), a non-conventional machining technique that is especially useful for processing hard to machine materials like titanium alloys. μ-EDM can produce intricate shapes with excellent dimensional precision. The main emphasis of this work is an experimental analysis of the μ-EDM of TNZT alloy (Ti-35Nb-7Zr-5Ta) employing a tungsten carbide (WC) electrode. The results showed that with the increase in capacitance (C) 10nF to 100nF at Voltage (V) 80 V, the machining performance parameters such as material removal rate (MRR), overcut (OC), crater area, surface microhardness, and surface roughness increase by 6.38, 1.52, 4.66, 1.07, and 3.29 times, respectively. However, the circularity error of the µ-hole increases by 1.81 times. This study intends to show how the two key machining factors (C & V) influence significant machining performance parameters.

Alte Werkzeugmaterialien im neuen Kleid

Abstract The most important cutting materials for machining are carbides. Tungsten and cobalt are required for their production, but these are becoming increasingly difficult to obtain and sometimes under ethically questionable conditions. Therefore, increasing efforts are being made to expand the range of cutting materials. The basic suitability of natural rocks for cutting tools in less demanding processes has already been demonstrated. The possibility of their PVD coating is discussed below.

Exploring the machined surface characteristics of Haynes 25 superalloy: Cost mitigation and quality enhancement perspective

The current study investigates the surface characteristics and machining cost of electrical discharge machining (EDM) of Haynes 25 superalloy using tools made by additively manufactured CuCr1Zr, pure copper and graphite. Before assessing machinability, the workpiece and tool materials were characterized using Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD) and evaluations of tensile strength, micro-hardness, density and thermal conductivity. The effects of current (I), voltage (V), pulse duration (Ton), duty cycle (τ) and flushing pressure (Fp) is analyzed on surface characteristics viz. surface roughness (SR), surface crack density (SCD), recast layer thickness (RCT), heat-affected zone (HAZ), micro-hardness (MH) and machining cost (MC). Post machining XRD analysis revealed the formation of cobalt oxides like (CoO and Co3O4) affecting the micro-hardness of the machined surface. Alongside, a field emission scanning electron microscopy (FESEM) is carried out which confirms, the deposition of metal carbides and oxides on the EDMed surface. Current and pulse-on-time significantly influenced performance, with optimal EDM parameters identified and validated through confirmative experiments, resulting in a mean error of ∼2.84 %. It is seen that the use of additively manufactured CuCr1Zr tools resulted in improved machined surface characteristics and a more cost-effective approach for producing intricate profiles with minimal surface defects.

Analisis Efektivitas Mesin Bordir Komputer Menggunakan Metode Overall Equipment Effetivenes (Oee) dan Six Big Loses pada UD. Jadi Gumilang Sukorejo

The garment company UD. Jadi Gumilang is a home-based industry located in Mojotengah Village, Sukorejo District, Pasuruan Regency, East Java. UD. Jadi Gumilang engages in the production of bags, clothes, uniforms, and embroidery, which are produced only when there are customer orders. Frequent damage to the computerized embroidery machine occurs because operators do not perform routine maintenance as per the garment's regulations. To address this issue, the Overall Equipment Effectiveness (OEE) value was calculated to analyze the major factors causing downtime. OEE itself is the result of multiplying the variables of Availability (90%), Performance (95%), and Quality (99%). After calculating the OEE value, the six big losses values were calculated to identify the highest losses that cause low OEE values. Then, from the highest loss values, a fishbone diagram (cause-and-effect diagram) analysis was conducted to identify the factors causing damage to minimize the recurrence of similar issues in the future. The results of the study show that out of the 2 computerized embroidery machines, one machine has an OEE value below 85%, which is the computerized embroidery machine 1 (84.64%). From this value, the six big losses calculations reveal that the largest loss is idling and minor stoppages losses, amounting to 20.02%. After conducting a fishbone diagram analysis, the factors causing idling and minor stoppages losses were identified as Human, Machine, Method, and Raw Material. Suggestions to prevent idling and minor stoppages losses include frequently cleaning the production area after production, regularly lubricating the machine to prevent wear, always checking the machine's condition before use, and others.

Comparison of Modulation-Assisted Machining Strategies for Achieving Chip Breakage When Turning 17-4 PH Stainless Steel

Chip morphology is an intrinsic characteristic of the machining process that determines the quality of the process. When machining low machinability materials, the chips formed are usually long, continuous, and difficult to break. Due to the negative effect of the accumulation of the chip along the process, chip breakage and the correct extraction out of the machining area have become indispensable requirements. Although numerous chip-breaking methodologies have been proposed, modulation-assisted machining (MAM) is one of the most promising approaches, due to its independence from the workpiece material, tool geometry, and cutting conditions. In this work, a comparison of different modulation-assisted machining strategies, based on the modulation of the feed (F-MAM) or the depth of cut (D-MAM), were experimentally evaluated and compared to conventional turning in terms of chip morphology, surface roughness, and tool wear. Results showed that both MAM strategies enabled chip breakage and improved chip evacuation in comparison to conventional turning; however, D-MAM showed a better performance in terms of tool wear and surface roughness.

Effects of Ar ion bombardment on the structure and properties of β-quartz

β-quartz is an important component that affects the physical and chemical properties of glass-ceramics. The material removal process of ion beam machining is complicated as one of the ultra-precision machining forms. Therefore, it is important to understand the removal mechanism of ion beam machining materials. The methods of molecular dynamics (MD) and first-principles were adopted to investigate the microscopic mechanism of ion beam bombardment of the β-quartz structure. The damage evolution of structures and the evolution of material properties caused by defects respectively from the atomic and electronic levels. Through MD analysis, we find that the random collision between incident ions and matrix atoms can lead to the formation of sputtered atoms. The incidence of ions will increase the disorder degree of the matrix, and the influence on the disorder degree at different depths of the matrix is different. The degree of disorder increases obviously in the range of 50–70 Å from the surface of the matrix. It has a significant impact on the surface topology of the matrix, the number of defects, surface roughness, and matrix density. The results of first-principle calculation show that the refraction, absorption and other characteristics of the system are significantly different with different doping forms, and the energy loss is most affected by substituted doping. And the substituted doping defects have the most significant effects on the structural energy loss. Among, the Ar-substituted O doping structure leads to higher energy loss, and the peak energy loss intensity reaches 5.146. In contrast, the Ar-substituted Si doping structure causes the least energy loss, the intensity is 2.543. This study provides a theoretical basis for the selection of parameters and the realization of ultra-smooth surface in actual ion beam machining.

Analysis of Overall Equipment Effectiveness (OEE) as an Effort to Increase The Productivity Filling Line of Lithos Packaging Lubricant

This research was conducted at a company engaged in the lubricants business. This study examines the filling station lithos packaging. The lithos packaging filling station consists of 6 filling lines (FL), namely FL-1, FL-2, FL-3, FL-4, FL-5, and FL-6. From each filling, the line will be observed and analyzed in the format of the automation machine program. Based on the observations and analysis, it was found that FL-4 has an availability rate, performance rate, and quality rate below standard, so it is necessary to identify the cause of the low Overall Equipment Effectiveness (OEE) value of FL-4. This study analyzes the factors causing the low Overall Equipment Effectiveness (OEE) score on FL-4 using Six Big Losses and Fishbone diagrams. From the research results, it was found that several factors caused the less productive FL-4, namely breakdown losses with a value of 48%, setup and adjustment losses with a value of 3%, idling and minor stoppages with a value of 7%, reduced speed losses with a value of 41%, and defect losses with a value of 1%. An analysis was carried out using a fishbone diagram to determine the root cause of the high value of breakdown losses, reduced speed losses followed by idle and minor stoppage losses, and setup and adjustment losses. Based on the fishbone diagram, it was found that the factors causing the FL-4's unproductivity in terms of machine factors, method factors, human factors, material factors, and environmental factors. The causes of unproductive FL-4 are damage to the machine, downtime, the operator's less responsiveness to machine problems, operator expertise, decreased work ethic, defective materials, late material stocks, and hot room temperatures. Based on this, the proposed improvements given are to schedule machine maintenance at a specified time (preventive maintenance), not by the factor of damage (breakdown maintenance), make data guide for product change for each machine and attach it to each machine in full so that This downtime can be reduced, placing technical operators who focus on each filling line at least one technical operator, to speed up downtime and not disrupt the production process, add fans to speed up air circulation to reduce heat in the area and change material suppliers to get better quality.

A REVIEW OF THE RECENT RESEARCH ACTIVITIES IN THE FILD OF ELECTRICAL DISCHARGE MACHINING

Electrical discharge machining (EDM) is one of the earliest non-traditional machining processes being considered one of the most popular machining methods today. The EDM process basis on thermoelectric energy between the workpiece and an electrode, so that the discharge energy generated during the operation characterizes the productivity of the process. Due to the well-established machining options utilized in the industry of aerospace, automotive industry and surgical components for precision machining and making complex geometrical shapes in hard-to-cut materials, a significant amount of research interests has been created in this field. This paper provides a review of numerous academic research activities carried out in the previous years, as well as numerous developments in the field of EDM related to increased machining rates, improved performance, materials and dielectrics used, electrode design and manufacture.

EXPERIMENTAL DETERMINATION OF TORQUE FOR THE DRILLING OFAL7SIMG ALLOY

The productivity of a machining process is closely related to the value of the cutting force.For the calculation of the cutting forces, a series of models have been developed to allow the determination of these forces according to the machined material and the specific conditions in which the process is carried out. Usually, for a better approximation of the value of the cutting force, the unitary specific cutting force is used, which depends on the machined material. For common materials, the values of specific unitary cutting forces are presented in the specialized literature, but for less frequently used materials, for example, those with reduced machining properties, the respective values are difficult, sometimes impossible to find. In this paper, determining the unitary specific cutting force for an aluminum alloy with a high silicon content is intended, recognized as difficult to machine. The determination of the value of this force is done starting from the measured values ofthe torsional moment at the drills.

Influence of sequential machining process on the surface topography of dies

Near net-shape manufacturing of components is a trend that aims to significantly reduce machining times and material waste, trading the machining efficiency for smaller lead times. Cold forging of gear-shaped components is one such operation that generates a component with superior geometrical accuracy and precision, however, the machined cavity is often subject to high mechanical loads and fatigue failures. The usual manufacturing chain involves hard machining, die-sinking electro-discharge machining, and mechanical polishing with abrasive media. Without proper knowledge of the resulting surface roughness and morphology, the tribological aspects of the surface can be neglected. Therefore, this study aims to investigate the manufacturing chain of gear-shaped cavities in terms of surface roughness, surface morphology, and surface residual stresses generated after die-sinking electro-discharge machining (roughing and finishing regimes), as well as mechanical polishing. The surface of the gear tooth was evaluated in three distinct regions: flank, top, and bottom. The results showcased that, even though the surface roughness/texture of the different regions of interest illustrates similar magnitudes, the surface morphology presented completely adverse features, highlighting the importance of a thorough analysis of the machined surface. Residual stress analysis indicated that the mechanical polishing operation was not enough to remove the high-magnitude tensile residual stresses.