Machining Chips Research Articles

Impact of 6S (5S+Safety) Implementation in Machine Workshops on Occupational Safety

In this current study, the impact of implementing 6S (5S+Safety) in the machining industry on occupational safety was investigated by selecting the chip machining section of a factory producing flywheels. To facilitate the comparison of risk levels before and after the implementation of 6S, a Fine-Kinney risk evaluation was conducted in the sawdust department before the application of 6S. The 6S implementation process took 28 days, and subsequently, a Fine-Kinney risk evaluation was performed in the sawdust department, revealing a 77.4% reduction in risks. As a result, the 77.4% reduction in accident risks indicates that the implementation of 6S, which emphasizes safety within the framework of the 5S principles, leads to a more organized, cleaner, and safer machine workshop environment. We can indicate that this approach not only reduces the risk of accidents but also enhances work efficiency, preventing time loss and material waste.

A novel sustainable AZ31 based Mg matrix composite reinforced with recycled IN718 powder for circular materials economy

The pursuit of sustainable practices in manufacturing has sparked an increased interest in recycling and reusing materials to reduce waste and environmental effect. One interesting technique is incorporating recycled materials to develop advanced composite materials. In this study, we focus on utilizing recycled Inconel IN718 powders as reinforcement particles in AZ31D. Powders of IN718 finer than 37 μm, developed from machining chips through high energy ball milling process, are infused into AZ31 through friction stir processing (FSP), enabling a circular economy practice in advanced material development. The resulting composite material is evaluated for its microstructure and mechanical performance. Microstructural study reveals a uniform distribution of reinforcement particle inside the matrix throughout the processed zone. Strong interfacial bonding between the matrix and reinforcement, and the addition of dispersion strengthening mechanisms helped reducing the tension/compression yield asymmetry problem. The study highlights the use of recycled materials in composites to achieve sustainability in manufacturing.

Thixoforming of the Hot Extruded Aluminum AlSi9Cu3(Fe) Machining Chips

The main aim of this research was to investigate the aluminum AlSi9Cu3(Fe) machining chips recycling possibility utilizing a direct hot extrusion process and thixoforming. The thixo feedstock was prepared directly from the aluminum alloy AlSi9Cu3(Fe) machining chips waste without any remelting step. The machining chips were compacted, and direct hot extruded to create the solid samples and thixo feedstock. The aluminum alloy AlSi9Cu3(Fe) machining chips had a high degree of plastic deformation and after extrusion and heating in the semisolid temperature range, the suitable globular microstructure was achieved, which is a precondition for a successful thixoforming process. This approach can be characterized as a semisolid recycling process with a lower energy consumption, a higher material yield, and reduced greenhouse gas emissions into the atmosphere compared with conventional casting and recycling. Optical metallography, scanning electron microscopy accompanied with energy dispersive spectroscopy, electrical conductivity, and mechanical properties investigation were performed on the reference casted sample with a dendritic microstructure, the extruded sample with a severely deformed microstructure, and finally the thixoformed samples with a globular microstructure produced with different parameters, according to the Taguchi L4 (23) experimental plan.

Grain refinement of magnesium castings using recycled machining chips

A simple and effective recycling approach of magnesium alloys can offer economic and environmental benefits. This study demonstrates that by simply remelting AZ91/AZ80 machining chips and shape casting, the tensile properties of the castings can be preserved and substantial grain refinement can be achieved, compared to casting from ingots using the same alloy. Cooling curves for the samples, obtained through the immersion thermocouple method, showed that nucleation event density in chip melts consistently exceeds that in ingot melts, particularly at low undercoolings. Tensile tests showed that chip castings exhibit a slightly higher 0.2% proof stress than castings from ingots, with increases of 5% and 1% for as-cast and solution-treated conditions, respectively, due to the Hall-Petch effect. Elongation to fracture was similar for both chip and ingot samples, with fractography indicating entrainment defects, rather than grain size, predominantly determined this outcome. These combined results indicate that the shape casting of AZ91/AZ80 machining chips could be used as part of the closed-loop recycling of magnesium.

Mechanical and surface characteristics in laser-assisted machining of NiFeCr alloy: An atomic-scale understanding

This investigation explores mechanical characteristics and subsurface damage of NiFeCr alloy in laser-assisted machining through molecular dynamics simulation. The results of machining force, friction coefficient, local strain/stress, temperature distribution, subsurface damage, surface morphology, and worn volume are comprehensively explored, thereby revealing the mechanism of laser-assisted machining under different working conditions. Compared to conventional processing, average machining force, shear strain, subsurface damage, and dislocated length are all reduced in laser-assisted machining, which improves surface finish quality. Amorphization of removed chips in laser-assisted machining enhances the material removal efficiency. Analysis of various laser powers shows a decreased machining force with increasing laser power. However, residual stress and temperature rise, potentially impacting surface integrity. The subsurface damage depth exhibits nonlinearity with increasing laser energy, highlighting the competition between mechanical stress and thermal effect. The surface morphology and atomic flow demonstrate effective material removal with increasing laser power. The average machining force, friction coefficient, and subsurface damage depth show nonlinear relationships with cutting speed. The number of worn atoms is proportional to machining length and cutting speed, indicating enhanced material removal during high-speed machining.

Investigation of hybrid ultrasonic machining process of Nomex honeycomb composite using a toothed disc cutter

Nomex honeycomb composite (NHC) has been increasingly used in the automotive, aerospace and defence applications due to its excellent thermal and mechanical properties. Its complex cellular hexagonal thin-walled configuration along with heterogeneous, soft and brittle nature pose substantial processing defects such as burr formation, tearing of walls, surface roughness, dimensional inaccuracy and low machining quality during conventional machining (CM). These surface defects have a substantial influence on the operating life and functional performance of its sandwiched structural members. Hybrid ultrasonic vibration assisted machining (HUSVAM) technology has been introduced to overcome such limitations. For an in depth research on HUSVAM of NHC using ultrasonic toothed disc cutter (UTDC), three dimensional finite element model was developed and experimental validation was carried out. The numerical simulation and experimental results were found to be in good agreement with one another. The influence of various machining parameters including the ultrasonic tool vibration amplitude (UTVA), feed rate (FR), depth of cut (DoC) and spindle angular speed (SAS) on NHC cutting forces, chip formation and surface quality was investigated using both HUSVAM and CM techniques. Furthermore, stresses, deformation and forces near tool-workpiece interaction along with the surface topography and morphologies were also analysed and compared for various operating conditions. A reduction in the cutting forces was found with the increase of SAS and UTVA (up to 65.47 % and 65.74 %, respectively). Although, the cutting forces were observed to increase by increasing the DoC and FR (up to 159.45 % and 126.33 %, respectively). DoC has a greater impact on the cutting forces among all machining parameters according to 4 levels, 4 factors (L16) orthogonal experiments based on Taguchi method. The results show that the chip formation and machining quality of NHC core can be improved with HUSVAM technique using UTDC. HUSVAM also reduced the cutting forces (up to 73 %) compared to CM. The ultrasonic toothed disc cutter generated large number of burr with very short length, no tearing defects and no uncut fibers as observed from scanning electron microscopy of NHC hexagonal cell structure, walls and triple points. A burr formation of less than 10 % was realized during HUSVAM of NHC cores for Fx≤3N, while it was found up to 20 % if Fx>3N, compared to at least 40 % during CM. The finite element model developed can be used to investigate the influence of HUSVAM on modern difficult to machine materials for enhanced surface quality.

Machining of Ni-based superalloys using CAPVD coated carbide tools

The ever-increasing demand for cost-effective machining of Ni (Nickel) based superalloys has made it necessary to explore nanocomposite coatings as a potential surface engineering solution. The present study aims to investigate the variation in machining performance of new-generation hard wear-resistant coatings in milling of IN 718 (Inconel 718), IN 625 (Inconel 625), and IN 617 (Inconel 617). TiAlSiN and CrAlSiN coatings were grown in-house over tungsten carbide (WC) milling inserts through the cathodic-arc PVD route. The TiAlSiN coating improved the tool life by 80 % and 60 % in the case of IN 718 and IN 625, respectively. However, in the case of IN 617, the TiAlSiN-coated tool could not even reach the uncoated tool life. The CrAlSiN coating, on the other hand, improved the tool life by more than 200 % in the milling of IN 617. Tool-chipping was the dominant failure mode among all observed, which included flank wear and workpiece adhesion. The repeated adhesion and removal of the workpiece layer from the tool surface was a major cause of tool failure. The coating layer delayed the initiation of the chipping and prolonged the flank-wear-dominated machining time, resulting in improved tool life. The wear resistance of coatings in machining different workpiece materials was greatly influenced by the relative affinity of constituting elements of workpieces for employed coatings. The machining chips exhibited shear bands and saw-tooth (serrated/segmented) morphology in almost all cases. The degree of segmentation showed a direct correlation with tool life. The present work helps identify the optimum coating and machining conditions for three different grades of Ni-based superalloys. Additionally, the underlying mechanisms were analyzed and discussed with scientific observations.

Solid-State Synthesis of SiC Particle-Reinforced AZ91D Composites: Microstructure and Reinforcement Mechanisms

Safe and efficient recycling of industrially generated machined chips is a high-priority technological issue. In this study, the effect of SiC particles (SiCp) on the microstructure and mechanical properties of SiCp/AZ91D composites is systematically analyzed, and the reinforcement mechanism of SiCp on composites is investigated. Different contents of SiCp/AZ91D composites are fabricated by solid-state synthesis. The results show that the incorporation of SiCp refined the grains of SiCp/AZ91D composites, which is related to the uniform distribution of SiCp at the grain boundaries. The strong bonding of SiCp with the AZ91D matrix inhibited the generation and extension of cracks, which led to the simultaneous increase in the yield strength (YS) and elongation (EL) of the SiCp/AZ91D composites. The mechanical properties of the 3 wt.% SiCp/AZ91D composites are the most superior, with an average grain size, Vickers hardness, ultimate tensile strength (UTS), YS, and EL of 6.69 ± 4.48 μm, 89.5 ± 2.5 HV, 341 ± 11 MPa, 172 ± 8 MPa, and 4.43 ± 0.18%, respectively. The reinforcement mechanisms of SiCp/AZ91D composites are mainly grain refinement and dislocation strengthening. Solid-state synthesis is an effective method for recycling magnesium alloy chips.

Improving damping characteristics of epoxy by adding copper alloy wastes

Purpose The purpose of this study is to get benefits from manufacturing harmful wastes is by using them as a reinforcement with epoxy matrix composite materials to improve the damping characteristics in applications such as machine bases, rockets, satellites, missiles, navigation equipment and aircraft as large structures, and electronics as such small structures. Vibration causes damaging strains in these components. Design/methodology/approach By adding machining chips with weight percentages of 5, 10, 15 and 20 Wt.%, with three different chip lengths added for each percentage (0.6, 0.8 and 1.18 mm), the three-point bending and damping characteristics tests are utilized to examine how manufacturing waste impacts the mechanical properties. Following that, the optimal lengths and the chip-to-epoxy ratio are determined. The chip dispersion and homogeneity are assessed using a field emission scanning electron microscope. Findings Waste copper alloys can be used to enhance the vibration-dampening properties of epoxy resin. The interface and bonding between the resin and the chip are crucial for enhancing the damping capabilities of epoxy. Controlling the flexural modulus by altering the chip size and quantity can change the damping characteristics because the two variables are inversely related. The critical chip size is 0.8 mm, below which smaller chips cannot evenly transfer, and disperse the vibration force to the epoxy matrix and larger chips may shatter and fracture. Originality/value The main source of problems in machine tools, aircraft and vehicle manufacturing is vibrations generated in the structures. These components suffer harmful strains due to vibration. Damping can be added to these structures to get over these problems. The distribution of energy stored as a result of oscillatory mobility is known as damping. To optimize the serving lifetime of a dynamic suit, this is one of the most important design elements. The use of composites in construction is a modern method of improving a structure's damping capacity. Additionally, it has been demonstrated that composites offer better stiffness, strength, fatigue resistance and corrosion resistance. This research aims to reduce the vibration effect by using copper alloy wastes as dampers.

The Impact of Heating Temperature and Flux Ratio on the In-Situ Casting Technique as a Direct Recycling of AlSi7Mg Machining Chips

Recycling aluminium and its alloys is gaining popularity in reducing energy consumption and associated manufacturing expenses. The fluxing process is the preferred and often-used technique in the recycling sector for removing oxide inclusions from molten aluminium. The present study investigates the influence of flux ratio and heating temperature on the behaviour of aluminium alloy chips (AlSi7Mg) during in-situ casting. The primary objective is to create a more efficient and economical approach to recycling aluminium waste. The chips underwent heating for 30 minutes inside a controlled laboratory furnace. The temperatures used during this procedure were 750°C and 800°C. The chips were combined with flux in ratios of 1:0.1 and 1:0.2. The number of melted chips rose due to increasing the temperature and flux ratio. The heated samples were subjected to surface morphology and elemental analysis using a scanning electron microscope with energy-dispersive spectroscopy (EDS). The Energy Dispersive Spectroscopy (EDS) examination indicated the presence of oxygen on the surface of the unprocessed aluminium alloy machining chips. On the other hand, the X-ray diffraction (XRD) revealed that the observed condition may be attributed to the oxidation process, proven by the presence of Aluminium Oxide (Al2O3).

REUSING MANUFACTURING WASTES AS CRACK RETARDANT

Global production uses millions of metric tons of metals. The waste of these metals can be recycled to increase the economic benefit and lessen the negative impact on the environment. In this work, a manufacturing waste is used as a reinforcement material for epoxy to improve the fracture toughness and the stress intensity factor, where the machining chip is used with different weight fractions 5, 10, 15 and 20 wt. % and each percentage is added with three chip lengths 0.6, 0.8 and 1.18 mm. Three-point bending test of notched sample is used to test crack behaviour in addition to using Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), Differential Scanning Calorimeter (DSC) and Scanning Electron Microscope (SEM) to show the effect of chip on structure, bonding, glass transition temperature (Tg), dispersion and fracture surface of the epoxy. Results show that adding the machining wastes in the form of chips can enhance crack behaviour, and it is greatly dependent on the amount and size of chip. On the contrary, these chips change the glass transition temperature and change the fracture surface from brittle to ductile, thereby reducing the velocity of crack growth.

Production of Al-Cu multi-material billet from machining chips using friction stir consolidation (FSC)

This research investigates the production of Al-Cu multi-material billets through a recycling and welding approach. The method employed is the so-called friction stir consolidation (FSE), which involves the consolidation of machining chips by using a tool rotating at specific speed and feed rate. The microstructure and chemical composition of the resulting components are examined using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The findings indicate that this technique allows producing multi-material billets directly from machining chips with a solid structure and absence of voids.

Development of Highly Machinable Ti Alloy with Exceptional Tensile Properties by Er Alloying Element Addition

This study demonstrates that the addition of the rare earth element Erbium (Er) significantly enhances the machinability and tensile properties of titanium (Ti). Pure Ti alloys and Er-added Ti alloys with 0.5-1.1 wt.% Er content were prepared, and their microstructure, machinability, and tensile properties were compared. Two different types of Er secondary phase particles were identified in the microstructure: pure Er and Er-oxide. The amounts of these particles increased with higher Er content. The machinability of the Eradded Ti alloys was significantly improved due to the ability of Er secondary particles to cut machining chips or absorb heat from localized deformation within the Ti matrix. In addition, Er-added Ti alloys exhibited higher strength than pure Ti. The strength enhancement was attributed to grain refinement induced by the Er element. Er secondary phase particles reduced the β grain size during solidification, and they also served as preferential sites for α nucleation during the β → α phase transformation, resulting in a refined microstructure. In addition, the Er secondary phase contributed to the strength enhancement through the well-known precipitation strengthening mechanism. Although ductility decreased with higher Er content due to the increased amount of Er secondary phase particles, 0.5 wt.% Er-added Ti showed no such degradation; its ductility was comparable to that of pure Ti. Er-oxidation was expected to reduce oxygen content within the Ti matrix, enhancing intrinsic Ti ductility; this effect offset the adverse impact on ductility caused by the Er secondary phase particles. Above 0.5 wt.% Er, the adverse effects caused by the Er secondary phase particles overwhelmed the beneficial effect caused by the reduction in oxygen content. The present findings will contribute significantly to the development of highly machinable Ti alloys with superior tensile properties.

Vacuum-oxygen-low recycling process of aluminium composites manufactured from steel machining chips

Vacuum-oxygen-low recycling process of aluminium composites manufactured from steel machining chips

Creation of an Aluminum Alloy Template with a Surface Structure by Micro-Milling for Subsequent Replication of the Microstructure to Achieve Hydrophobicity

This research paper focuses on the fabrication of a microstructure based on a natural structure pattern of hydrophobic properties using micro-milling technology, followed by an investigation of the dimensional accuracy, roughness, and replication of the fabricated microstructure. Design, modeling (CAD system), fabrication, and replication are the steps of this process. Knowledge of biomimetics was used to select the microstructure. The main research aim of the experiments is to verify and extend the applicability of conventional CNC manufacturing technologies to obtain a functional surface structure. The micro-milling was carried out on a conventional DMG MORI CNC machine, a CMX 600 V three-axis horizontal milling center, using an external high-frequency electric spindle clamped to the machine. The machined material was aluminum alloy EN AW 7075. The tool was a 0.1 mm diameter double-edged ball mill made of sintered carbide and coated with TiSiN. The cutting conditions were determined according to the tool manufacturer’s recommendations. To compare the achieved accuracies, the same microstructure was fabricated using PLA technology. For subsequent replication of the sample, the negative of the selected microstructure was created and machined. Subsequently, a positive microstructure was created using the silicone impression material by the replication process. This paper and the experiments performed extend the technical knowledge in the field of manufacturing surface functional structures and confirm the possibility of manufacturing the designed structures using chip and laser machining technology, with achieved discontinuities in the range of 3 to 50 μm. They also highlight the issues of replication of such structures with respect to critical manufacturing locations (geometrical parameters of the structures affecting the functional properties of the structure, venting, replica defects, etc.).

Experimental Investigation on Machinability of α/β Titanium Alloys with Different Microstructures.

In the current study, Ti-6Al-4V (Ti64) and Ti-6Al-7Nb (Ti67) alloys were prepared by vacuum arc melting. The produced samples were then subjected to different heat treatment regimes. The evolved microstructures and their corresponding hardness were investigated. Computerized drilling tests using TiAlN-coated high-speed steel bits were performed to assess the machinability of the prepared specimen regarding cutting force, tool wear, and thickness of the deformed layer. It was observed that Ti64 specimens that were water quenched from either α/β or β range contained martensitic phase. In Ti67, samples showed martensite only when water quenched from the β-phase range (1070 °C). Formation of martensite resulted in higher hardness and hence led to higher cutting forces and increased tool wear during the drilling process. Machined samples with higher hardness formed a thicker subsurface deformation area (white layer) and increased burr heights. Surface roughness in Ti64 workpieces was generally higher compared to Ti67 specimens. The coat of the drilling bit was partially attacked in the as-cast specimens, which was evident by elemental N on the machining chips. The machining tool deteriorated further by increasing the workpiece hardness through martensitic formation, where elements such as Cr, V, Fe, etc. that came from the tool steel were detected.

Machinability analysis for drilling Ti6Al4V ELI under sustainable techniques: EMQL vs LCO2

As a result of the widespread use of Ti6Al4V ELI in the medical industry for implants that are subjected to high loads, these biomedical implants must be accurately machined to prevent unfavourable joint or muscular inflammatory conditions. This oftentimes involve drilling holes into the implants for joint assembly during surgery. It is well known that titanium is a very difficult to machine material and therefore, requires appropriate cooling and lubrication during machining. With the help of SEM and line-scan EDS analysis, the current study focuses on analysing various sustainable machining techniques, such as electrostatic minimum quantity lubrication (EMQL) and liquid carbon dioxide (LCO2 cryogenic coolant), while drilling Ti6Al4V ELI (Grade 23) holes in terms of hole surface quality, wear mechanisms, and chip morphology. Poor surface quality of the hole was produced under EMQL cutting, with around 42–71% larger surface roughness values (Rz) compared to cryogenic LCO2 conditions. The hole surface consisted of different defects such as adhesion, microfractures, smearing etc., as a residue of the drilling operation under both EMQL and cryogenic LCO2 conditions. Tool life was significantly improved under LCO2 cutting environment (approximately by 416%) in comparison with EMQL technique. Adhesion and abrasion were found to be the main tool wear modes. Likewise, the machined chips exhibited cracks and adhered particles further demonstrating that EMQL coolant did not provide sufficient lubrication and heat extraction capability. Cryogenic LCO2 coolant outperformed EMQL lubrication for all machinability indicators, according to the study, making it a superior cutting environment for machining Ti6Al4V. Moreover, cryogenic LCO2 coolant dissipates into air during the machining process rendering it a sustainable and environmentally friendly machining coolant fluid.

Solid state recycling of aluminium chips: Multi-technique characterization and analysis of oxidation

Solid-state recycling of metallic alloys is a promising alternative method which avoids remelting and reduces significantly the CO2-emission compared to remelting. Contamination being critical for solid-state recycling, the objective of this study is to quantify and localize oxygen contamination at each step of the process. Pre-compacted AA6060 aluminium alloy machining chips were hot-extruded. The oxygen intake and the formation of oxides were quantified and localized through a multi-technique characterization, including X-ray photoelectron spectroscopy and transmission electron microscopy. The overall oxygen content is found to increase at every step of the recycling process. Analyses reveal that the initial thin Al2O3 layer on the chips gets covered by a MgO layer during pre-annealing and hot extrusion. Thus, alloying elements, as Mg, are involved in oxidation. It results in a tenfold increase of the oxygen content in the extrudate accompanied by a complex network of oxides with an average thickness of 290 nm and a low density. Thus, tuning processing parameters is a promising leverage to limit oxidation and improve chip welding, which will probably depend on the alloying elements.

Microstructure evolution and properties comparation of industrial grade-maintained 7050-T7451 plate recycled from machining chips

There are 45%–71% machining chips generated during the manufacturing process of aviation components. Most of these MCs are down-grade recycled as cast alloy, causing resource waste. In this work, aviation MCs were added into the melt for grade-maintaining recycling. A systematic evaluation was conducted on the melt quality, microstructure evolution, and properties of industrial recycled 7050-T7451 plates with a capacity of 60t/furnace, as well as a comparison with the primary plates. The composition of the recycled 7050 melt is qualified, and the hydrogen content is below 0.075 mL/100gAl. The results of PoDFA and LiMCA show that the inclusions in the recycled 7050 melt are mainly below 40 μm in diameter, and the number of inclusions is 3 times that of the primary melt. TEM shows that the dispersed phase particles of the recycled plate are more uniform and finer. EBSD shows that the recrystallization ratio of recycled 7050-T7451 plate is 8.3%, much lower than the 23.9% of the primary plate. The mechanical and corrosion properties of the recycled 7050-T7451 all meet the AMS 4050 standard. The cost of grade-maintaining recycling can be saved by 6,130,000 USD per year for a production line with an annual output of 20,000 tons of plates. This work clarified the process, cost, microstructure, and properties of recycled 7050-T7451 plate, laying a foundation for the application of grade-maintaining recycled aviation aluminum alloys.

Destruction of Carbon and Glass Fibers during Chip Machining of Composite Systems.

Composite materials with carbon and glass fibers in an epoxy matrix are widely used systems due to their excellent mechanical parameters, and machining is a standard finishing operation in their manufacture. Previous studies focused exclusively on the characteristics of the fibers released into the air. This work aimed to analyze the nature of the material waste that remains on the work surface after machining. The dust on the work surface is made up of fibers and a polymer matrix, and due to its dimensions and chemical stability, it is a potentially dangerous inhalable material currently treated as regular waste. The smallest sizes of destroyed carbon fibers were generated during drilling and grinding (0.1 μm), and the smallest glass fiber particles were generated during milling (0.05 μm). Due to their nature, carbon fibers break by a tough fracture, and glass fibers by a brittle fracture. In both cases, the rupture of the fibers was perpendicular to or at an angle to the longitudinal axis of the fibers. The average lengths of destroyed carbon fibers from the tested processes ranged from 15 to 20 µm and 30 to 60 µm for glass fibers.