Higher Machining Rate Research Articles

Nanosecond laser grooving of water-immersed silicon carbide assisted by high intensity focused ultrasound (HIFU)

Silicon carbide (SiC) is a very important semiconductor and ceramic material with many applications. However, its micromachining is difficult and it is still challenging to achieve a good combination of high quality, productivity and low cost. The corresponding author previously proposed the “ultrasound-assisted water-confined laser micromachining” (UWLM) process, a new machining technology utilizing in-situ ultrasound to improve laser machining of a water-covered workpiece. The author's previous studies show that UWLM based upon a high intensity focused ultrasound (HIFU) transducer is able to produce a relatively high machining rate and quality for metals. Thus, it is natural to guess the HIFU-based UWLM process might also possibly help provide a good solution for SiC micromachining. However, SiC have properties very different from metals. An experimental study is critically needed to confirm whether or not HIFU-based UWLM can still produce a high machining rate and quality for SiC, and overcome additional challenge(s) arising (if any). However, such a study is seldom reported to the authors' knowledge. This paper reports a study on the micro grooving of SiC via the HIFU-based UWLM process. With the conditions in this study, it has been found that UWLM can produce a much better apparent groove quality (i.e., much less recast material and/or debris re-deposition) than the laser machining process in the ambient air, and a much higher machining depth per pulse than the laser machining process in water with no ultrasound. The likely fundamental mechanism is the in-situ cleaning effect due to ultrasound-induced cavitation flow and pressure waves in water. The laser machining process in water with or without ultrasound can produce cracks at relatively low pulse repetition rates (PRRs). Time-resolved pressure measurements in water have been performed to help analyze stress sources causing the cracks. The crack problem appears to be effectively solved by using a relatively high PRR of 5 kHz. One possible major reason is expected to be the inter-pulse thermal accumulation effect at the high PRR, improving workpiece fracture toughness and/or reducing temperature gradients.

Simultaneous electrochemical and electrodischarge machining process: An approach to sustainable manufacturing

Manufacturing of Net Finished Shape (NFS) microholes in Inconel 718 materials with faster machining rate can offer significant benefits in terms of reduced waste, improved efficiency, and lower production costs, which are essential for sustainable manufacturing. However, the existing manufacturing method, namely electrochemical machining (ECM), results in slow machining with uncontrolled dissolution, leading to increase production time, energy consumption, and carbon emission associated with the manufacturing process. The current manuscript investigates the reason attributes for these problems through potentiodynamic polarization test. Subsequently, a new machining process known as Simultaneous electrochemical and electrodischarge machining (SECEDM) has been proposed. This frugal manufacturing-based machining process offers high machining rate (MR) and better overall hole circularity (OHC) through the synergistic effect of anodic dissolution and electrochemical discharges. The obtained results reveal that the SECEDM process offers nearly 261 % and 141 % higher MR and 1.23 % and 3.78 % better OHC than electrochemical machining (ECM) and electrodischarge machining (EDM), respectively. Moreover, SECEDM outperforms the simultaneous micro-EDM and micro-ECM process (SEDCM) process by seven times in machining rate and promotes localized dissolution than ECM. Overall, SECEDM's benefits, including its high machining rate, superior surface quality, sustainability, eco-friendliness, and elimination of the need for secondary finishing processes, make it an ideal candidate for the next-generation manufacturing process.

Elucidating Powder-Mixed Electric Discharge Machining Process, Applicability, Trends and Futuristic Perspectives

Since the inception of electric discharge machining (EDM), it has facilitated the production industries, for instance, die & mold, automotive, aerospace, etc., by providing an effective solution for machining hard-to-cut materials and intricate geometries. However, achieving high machining rates and a fine surface finish is an inherent issue with the traditional EDM process. The emergence of the powder mixed electric discharge machining (PMEDM) process has not only provided the opportunity for enhancing productivity and surface finish but also opened a window for its potential application in surface modification/coating of biomaterials. The process incorporates simultaneous machining and coating of bioimplants, i.e., lacking in the already available chemical and physical coating methods while requiring costly post-treatment procedures. This study comprehends the influence of powder characteristics and EDM process parameters on the performance parameters. The impact of tool electrodes and additive powders on the machined and coated surface of commonly used biomaterials. Furthermore, the study depicts the most frequently used methods for optimizing the PMEDM process, future research directions, challenges, and research trends over the past decade.

An experimental investigation of wire breakage and performance optimisation of WEDM process on machining of recycled aluminium alloy metal matrix composite

Abstract In this research, a novel aluminium metal matrix composite (AMMC) was developed using recycled aluminium alloy as a matrix with 5% alumina as reinforcement. The machining experiments were conducted by varying the input parameters such as voltage (V s ), wire feed rate (F w ), current (I p ), pulse on time (ON T ) and pulse off time (OFF T ), on wire breakage. The effect of voltage level and wire breakage frequency was analysed. The parameter combinations for machining the slot of size 5 mm width and 10 mm height with high machining rate (MR) and less surface roughness (R a ) were analysed using the CRiteria Importance Through Intercriteria Correlation (CRITIC) and simple additive weighting (SAW) methods. The wire breakage frequency is lesser at minimum peak current. The optimal parameter combination for higher MR and lower R a is found to be at 30 V, 7 mm/min, 30 A, 120 μs (ON T ) and 70 μs (OFF T ). Analysis of variance (ANOVA) is performed to understand the significant factors affecting the WEDM process. ANOVA results predict that wire feed rate and voltage contribute 47.82% and 21.23%, respectively, to MR; and pulse on time shows a 23.06% influence on surface roughness. Scanning electron microscopy (SEM) was used to ascertain the pattern of wire breakage in WEDM, and based on the results obtained from employing this technique, it is inferred that the erosion and breakage of the wire are not instantaneous and that a cone shape is formed on the either portion of the wire.

Modernization of Electrode Composite Material Based on Copper Powder for Electrical Discharge Machining of High-Strength Alloys

As a result of implemented modernization of known electrode composite material based on Cu-3% wt BN copper powder successfully used for electrical discharge machining of high-strength alloys, composite material (Cu - 3% wt BN) – 0.5 % wt Al – 0.25 % wt in the form of high-density long thin-wall plates for operations of electrical discharge cutting and piercing of hard-to-machine materials was obtained. The new material was obtained with the use of the method of reactionary mechanical alloying of initial powder components in the attritor. Tool electrodes made of the new material during electrical discharge piercing of rectangular holes in titanium alloy sheets ensure a 1.6 times higher machining rate comparing to tool electrodes made of the Cu-3% wt BN prototype material. After replacement of rolled copper in tool electrodes with the new composite material the machining rate will increase 4.1 times. The tool electrodes made of this material have significantly lower electrical discharge wear comparing to the wear of tool electrodes made of the prototype material and rolled copper.

Special Issue on Advanced Manufacturing Science and Technologies

In recent years, manufacturing technologies have been progressing with the high demands of industry. In the automobile and aircraft industries, for example, the manufacturing processes have been requiring for technologies that allow for high machining rates of lightweight and/or difficult-to-cut materials. Medical device production includes the machining of biocompatible materials that have high mechanical strength. Information devices require high quality in ultra-precision manufacturing processes. Measurement and characterization technologies in manufacturing have also been essential in the progress. Along with evolution of manufacturing technologies, scientific studies have been done on manufacturing phenomena and the control of processes, based on physical and/or mathematical aspects. This special issue is promoted by the International Conference on Leading Edge Manufacturing/Materials & Processing (LEM&P2020), which was canceled to protect the health and wellness of our community from COVID-19, and by the Research Committee of Cutting Technologies in the Japan Society for Precision Engineering. This special issue includes 17 papers that detail progress and innovations in the following areas: - Characterization of materials - Fundamental study and modeling of material removal process - Manufacturing control and optimization - Manufacturing processes for new/hard materials - Micro-/Nano-scale manufacturing - Tool manufacturing and performance - Metrology and evaluation - Surface characterization This special issue also includes not only technical but also scientific discussions, suggesting new key technologies for future manufacturing. We hope this will help the readers to understand the manufacturing processes and improve their operations. We thank the authors and the reviewers for their generous cooperation and the editing staffs for their many contributions.

Mechanical properties and electrical discharge machinability of SPS sintered Y-TZP- and YGd-TZP-titanium nitride composites

Electrical discharge machining (EDM) of ceramics provides an opportunity to manufacture complex shape components from sintered blanks provided the material has a sufficiently high electrical conductivity. In this study yttria and yttria-gadolinia co-stabilized zirconia powders (Y-TZP, YGd-TZP) were produced by intensive co-milling. Fully dense composite ceramics with TZP matrix and 28–32 ​vol% titanium nitride dispersion were manufactured by spark plasma sintering and subsequently ED-machined by die sinking in oil based dielectric.The materials offer high strength of 1200–1450 ​MPa coupled with an attractive fracture resistance of 7–7.8 ​MPa√m. The ceramics exhibit a high electric conductivity of 21–74 ​kS/m with the highest values observed for the co-stabilized matrix and the higher TiN content. ED machining can be carried out at high machining rates of >1 ​mm³/min. The dominant material removal mechanism is melting. ED-machining leaves only a very thin glass-like process zone at the surface, the bulk material stays widely unaffected.

Delamination-free drilling of carbon fiber reinforced plastic with variable feed rate

A large number of drilling have been performed to assemble aircraft parts of carbon fiber reinforced plastic (CFRP). Although high quality is required in machining the holes with high productivity in terms of reliability of parts, delamination often occurs around the holes in drilling. This paper presents a novel drilling method with variable feed rate to machine the delamination-free holes at a high machining rate. In the drilling, the holes are machined at the standard feed rates when the chisel moves in material; and are finished with the negative thrust at higher feed rates after the chisel exits from the workpiece. Orthogonal cutting tests were conducted to measure the cutting forces and the friction angles for the uncut chip thicknesses and the rake angles. The negative thrusts were measured in large uncut chip thicknesses at large rake angles of the lips. Then, the drilling tests were conducted to verify the change in the cutting force in the variable feed rate drilling up to 100 holes. Negative thrust component appears consistently to raise the workpiece up in the exit process even though the tool wear progresses with repeating drillings. As a result, the variable feed rate drilling remarkably controls delamination compared to the constant feed rate drilling in the 100th drilling. The cutting process in the variable feed rate drilling is compared with the constant feed rate drilling in a cutting force model based on the minimum cutting energy. The negative thrust is verified when the friction angle becomes smaller than the effective rake angle with increasing the feed rate.

Effects of process parameters on jet electrochemical machining of SiC particle-reinforced aluminum matrix composites

Silicon carbide particle-reinforced aluminum matrix composites (SiCp/Al) are increasingly applied in high-end industries because of their excellent comprehensive material properties. However, as a typical difficult-to-cut material, machining of SiCp/Al using traditional processes faces serious challenges. Jet electrochemical machining (Jet-ECM) is a new-generation electrochemical machining (ECM) technology, which exhibits improved process flexibility and machining accuracy, in addition to the basic advantages of the ECM process. Jet-ECM appears to be a potential alternative machining technology for SiCp/Al to achieve high machining rate and damage-free surface. In the present work, the polarization curves obtained by electrochemistry study showed that a passivation-tanspassivation transition behavior with increasing the voltage occurs in NaNO3 electrolyte, while NaCl electrolyte causes active behavior. Thus, compared to NaCl electrolytes, the NaNO3 electrolyte is relatively suitable for Jet-ECM of SiCp/Al because of its potential to improve the machining localization. Besides, the effects of process parameters (including voltage, electrolyte type, and concentration) on the machining performance were systematically investigated. It was found that the voltage has the most significant influence on the machined dimple profile. A higher voltage helps in achieving a large depth. The surface roughness is dependent on the selection of the electrolyte and voltage. The NaNO3 electrolyte is preferred to realize smooth surface. Additionally, it was found that with increasing voltage, the surface roughness increases. Finally, this work was extended to be Jet-ECM with linear movement of the nozzle, and well-formed SiCp/Al grooves can be obtained using the selected process parameters.

Underwater Laser Turning of Commercially-Pure Titanium

Underwater laser machining process is a material removal technique that can minimize thermal damage and offer a higher machining rate than the laser ablation in ambient air. This study applied the underwater method associated with a nanosecond pulse laser for turning a commercially pure titanium rod. The effects of laser power, surface speed and number of laser passes on machined depth and surface roughness were investigated in this work. The results revealed that a deeper cut depth and smoother machined surface than those obtained from the laser ablation in ambient air were achievable when the underwater laser turning process was applied. The machined depth and surface roughness were found to significantly increase with the laser power and number of laser passes. The findings of this study can disclose the insight as well as potential of the underwater laser turning process for titanium and other similar metals.

Machining of thin sections using multi-pass wire electrical discharge machining process

The increasing application of fine metallic sections in various sophisticated areas has led to the growth of advanced machining technique to produce thin metallic sections. Wire electrical discharge machining process can prove to be an effective means to machine such sections. The current work identifies the thin wall machining of H13 tool steel using Taguchi's design. An optimal parametric setting is identified using a regression model for lower kerf width (kf) and higher machining rate. The decrease in kf and increase in machining rate is found to be highly dominated by the variation of the input parametric conditions. Machining of thin wall sections is performed to identify the extent of minimum sections that can be machined. A mesh-like structure is observed with wall thickness of less than 80 μm. Further, to improve the surface and edge characteristics, multi pass trimming process is incorporated.

Borealis and ADNOC sign Memorandum of Understanding to explore strategic opportunities in the polyolefin industry

Detail discussion on various advanced machining processes utilizing mechanical energy namely, Ultrasonic machining (USM), Abrasive jet machining (AJM), Water jet machining (WJM), and Ion beam machining (IBM) have been included. The fundamentals, material removal mechanism and related modeling, setup details, effects of process parameters on different outcomes, advantages and limitations of these processes have been presented in this chapter. The stationary ultrasonic machining (USM) as well as rotary ultrasonic machining (RUM) processes are applied for machining of hard and brittle materials like glass and ceramics with high accuracy those are highlighted. Rotary ultrasonic machining (RUM) is the recent development in USM which has higher machining rate and accuracy as rotary and ultrasonically vibratory abrasive bonded tool is used for machining. The abrasive jet machining (AJM) is applied for drilling, cutting, grooving and finishing operations on difficult to machine materials like glass and ceramics. In depth discussions on abrasive jet machining process have also been included. Water Jet Machining (WJM) process has been discussed in details which is utilized for cutting and drilling operation of various hazardous materials such as coal, rocks, asbestos, bones etc. for different field of applications such as mining, construction, mechanical and biomedical engineering. Ion beam machining (IBM) is one of the most advanced machining processes which utilize focused beam of ions to bombard and eject atoms from the workpiece surface by elastic collisions to crate desired shapes. IBM becomes attractive for fabrication of intricate structures especially in micro and nano range with high resolution. Recent advancements considering the latest research findings of all the advanced machining processes have also been highlighted.

Fundamentals of three-dimensional Yb-fiber Nd:YAG laser machining of structural bone

This work aims to understand the fundamental aspects of the laser-bone interaction in three-dimensional laser machining of the bone through an integrated experimental-computational approach. The study introduces 3-dimensional laser machining of bones through multilaser passes and attempts to establish the dimensional control over the laser-machined cavity through a finite element method based multiphysics computational model. A continuous wave Yb-fiber Nd:YAG laser (λ=1064nm) was employed with laser fluences ranging from 5.31J/mm2 to 25.46J/mm2 generated in combination of laser power (400 W–700 W) and machining speed (50 mm/s–250 mm/s). In multilaser pass machining, the optimum fill spacing of 0.2 mm was identified for higher machining rates with low deviation from linearity of machined edge (d=9μm). This resulted in high machining rates ranging from 16.49±0.2mm3/s to 45.26±0.66mm3/s for a given range of laser fluence. The optimization for machining efficiency and physical attributes of the machined cavity were comprehended through thermodynamics and kinetics of the laser interaction with the bone based on the computational model for varying laser processing parameters.

Micromachining of Stainless Steel Using TiAlN-Coated Tungsten Carbide End Mill

Abstract Micro-channels have been used for introducing chemical reactions, mass transfer and/or heat exchanger in some functional micro-devices. Micro-milling process using a micro-tool to mechanically shear off a work material is normally employed to precisely cut the channel. Although a number of published studies have revealed some effects of micromachining parameters on cut dimensions and process performance, a very little discussion has been made on the cut surface quality and material removal rate in the machining of micro-channel. Hence, this study aims at investigating the effects of machining parameters on these two aspects. AISI 304 stainless steel was selected as a work material to be machined by a TiAlN-coated tungsten carbide end mill. A set of experiments was carried out where the workpiece was cut under the different feed rates and depths of cut. Channel width, depth, surface roughness, burr height and material removal rate were considered as the process responses in this study. A multi-objective optimization was also performed to determine a machining condition optimally balancing both the cut surface quality and material removal rate. The condition associated with the feed rate of 30 mm/min and cut depth of 2 μm was found to be a suitable one to promote the good quality of micro-channel and high machining rate. The findings presented in this study could widen the understanding of process behaviors and offer a guideline for process optimization.

Optimization of the electrochemical machining parameters in drilling of AA6O6I-TIB2 in-situ composites produced by K2TiF6-KBF4 reaction system

Utilization of un conventional machining is increased exponentially due to its specific advantages like good machinabilty on the ceramic materials, ability to make complex profiles and supreme surface finish. Among the various un conventional machining, the electro chemical machining has unique identity including reasonably higher machining rate along with thermal and mechanical stress free machined surface. In-situ composites are made by reinforcing the micro size reinforcement by chemical reaction. The mechanical properties of these composites superior due its good interfacial bonding and smaller grain size of the matrix. The current paper deals the optimization of the electrochemical drilling parameters in machining of AA6061-5% T1B2 in-situ composites produced by K2TiF6- KBF4 reaction system. Current, concentration of the electrolyte and applied voltage are preferred as matrix whereas removal rate of the material and taper of the electrochemically drilled hole is identified to assess the machinbility. L27 orthogonal layout is followed for experimental work and Taguchi method deployed for optimization. Analysis of result and variance indicates that the preferred responses have significant influence on the responses.

Performance optimisation of electrochemical micromachining of micro-holes on Inconel 625 alloy

This work involves producing micro holes on Inconel 625 alloy through Electrochemical micromachining (EMM) process. The input parameters investigated are supply voltage, electrolyte concentration and duty ratio. The cathode tool used is a conical tipped stainless steel needle and the electrolyte is acidified sodium nitrate solution. Taguchi design of L9 Orthogonal Array is followed for experimental work. The performance analysis is done through process responses such as machining rate and overcut. The experimental results have given the optimum parameter combination for higher machining rate as 16 V supply voltage, 35 g/lit electrolyte concentration and 45% duty ratio and for lesser overcut as 12V, 35 g/lit and 45% duty ratio. The influence of input parameters on the process is also studied. The multi-objective optimisation technique used has produced 12 V, 30 g/lit and 45% duty ratio as the ideal combination for achieving higher machining rate and lower overcut.

Parametric optimization of powder mixed electrical discharge machining for nickel-based superalloy inconel-800 using response surface methodology

BackgroundElectrical Discharge Machining (EDM) is a well-established non-conventional machining process for the machining of electrically conductive and difficult-to-machine materials. But its applications are limited because of the slow machining rate and poor surface finish. Powder mixed EDM (PMEDM) is unitary of the recent progresses in the EDM process in which powder particles mixed in the dielectric fluid results in higher machining rate and better surface quality. In the past, limited work has been found on PMEDM of Inconel-800 material. Researchers have reported about machining with different powder particles like aluminum powder, silicon carbide, graphite etc. in the dielectric fluid of EDM, but the effect of powder particles, i.e. Tungsten carbide, cobalt and boron carbide along with tool material i.e. copper, copper-chromium and graphite on Inconel-800 material has not been explored. The purpose of the present work is to look into the issue of tool material (Cu, copper-chromium, and graphite) along with powder particles (tungsten carbide, cobalt and boron carbide) suspended in EDM oil on Inconel-800 material. MethodsThe present work includes optimization of Material Removal Rate (MRR) and Tool Wear Rate (TWR) for the machining of Inconel-800 material using Powder Mixed Elctric Discharge Machining (PMEDM). Different input parameters such as peak current, pulse on-time, pulse off-time, tool and powder materials along with effect of three micro powder particles, i.e. tungsten carbide, cobalt and boron carbide and three electrodes i.e. copper, copper-chromium, and graphite have been considered for the experimentation. The box-Behnken method of Response Surface Methodology (RSM) has been used for designing the experiments along with the Desirability Approach for multiple response parameters optimization. The adequacy of the proposed mathematical models have also been tested using analysis of variance (ANOVA). Microstructure analysis and transfer of different factors on the machined surface has also been investigated using Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS) and X - Ray Diffraction (XRD).ResultsThe results showed that peak current, pulse on-time, and tool material significantly affects the Material Removal Rate (MRR) while peak current, pulse on-time, tool material and powder materials affected the Tool Wear Rate (TWR). Pulse off-time has a trifling effect on both MRR and TWR, while powder particles on MRR. From desirability approach, the optimal combination of parameters found to be current 1 amp, pulse on-time 0.98 μs, pulse off-time 0.03 μs, tool material 0.31 and the powder (suspended particles) 0.64.ConclusionThe analysis of the experimental observations highlights that the current, pulse on-time and tool material have found to be the most decisive factors for MRR, while current, pulse on-time, tool material and powder particles for TWR.

Sequential procedure for selecting the ranges of process parameters in rotary ultrasonic machining

Nickel-based alloys have numerous potential engineering applications. However, their widespread applications have been hindered by the elevated machining cost. There is a crucial need for commercial and cost effective machining processes for Ni-based super alloys. Rotary ultrasonic machining (RUM) is a hybrid machining process that combines the material removal mechanisms through diamond grinding and ultrasonic vibration (USM), resulting in higher machining rate than those obtained by conventional USM. Before going to the production run, it is necessary to conduct performance analysis followed by pilot experimentation for newer material. Relationships between desired outcome and the controllable machining parameters have been deducing. However, the relationships have been studied by screening the experiments. In this paper, a three-factor two-level factorial design followed by steepest ascent is utilised to find conditions for final experimentation. [Received 16 September 2016; Accepted 12 March 2017]

Multi-performance optimisation of micro electro-discharge machining during deep micro-slots fabrication using foil tool electrode

This study attempts to investigate and optimise the effects of process parameters like voltage, sensitivity, duty factor and capacitance on performance characteristics such as material removal rate (MRR), tool wear rate (TWR), width expansion, length expansion and depth of slot during fabrication of deep and long micro-slots on brass work material by micro electro-discharge machining (micro-EDM). Copper foil is used as tool electrode of thickness 240 μm and width of 8 mm shaped by wire-cut electro-discharge machining. The randomised experiments were performed twice and mean response is considered for analysis to achieve accuracy in the results. Single-optimal parametric setting conditions obtained from the grey relational analysis (GRA) and confirmatory test results showed an improved machining performance of the process. Capacitance is observed to be the most influencing parameter followed by duty factor, sensitivity and voltage. Also, the feasibility of copper foil as a tool electrode is analysed and found high machining rate with more accurate micro-feature geometry.

Balancing of the transversal cutting force for pocket milling cutters: application for roughing a magnesium-rare earth alloy

Removing material efficiently in end milling usually involves taking a width of cut equal to the cutter diameter, i.e., to mill in full slotting as much as possible. However, in this case, end mills are very sensitive to the effects of cutting forces. Cutter deflection and vibrations may become limiting factors, especially at high machining rates and with long overhangs. To overcome these constraints, a new machining method to end mill workpieces can be considered. It is called “balancing of the transversal cutting force” (BotTCF). Indeed, this new machining method allows us to reduce deflection and vibrations and can therefore increase productivity. All the existing studies have used toroidal cutters with round inserts. Hence, the present study will focus on the application of the BotTCF to pocket milling cutters, considering their much more complex geometry. The goal is to determine the optimal inclination of the cutter axis, so as to minimize the transversal cutting force. In order to find this optimal inclination, a new cutting force model has been developed tailored to the pocket milling cutters. Then the BotTCF methodology has been applied to this type of cutter. An experimental validation has been carried out, and results validate the overall approach.