Mechanical Machining Processes Research Articles

Study on magnetohydrodynamic internal cooling mechanism within an aluminium oxide cutting tool

One of the challenges in the transfer of heat during the mechanical machining process is the coolant substance used in the internal cooling method which is generally liquid water or a water-based coolant. This limits the heat transfer capacity insofar as the thermal conductivity of liquid water is concerned. The other difficulty is the requirement for an external mechanical system to pump the coolant around the internal channel, providing efficient transfer of the accumulated thermal energy. This study proposes a novel method to address this issue by using liquid gallium which provides the means to transfer the excess heat generated during the cutting process by integrating the design into an aluminium oxide insert. Combining this with a magnetohydrodynamic drive, the coolant system operates without the need for mechanical input. Liquid gallium is nontoxic and has a much higher thermal conductivity over liquid water. Investigations of the novel cooling system is performance compared against liquid water through numerical modelling, followed by an experimental machining test to ascertain the difference in heat transfer effectiveness, tool wear rates and workpiece surface finish when compared to dry machining and external cooling conditions on stainless steel 316L. Without cooling, experimental machining tests employing a cutting speed of Vc = 250 m min−1 resulted in a corner wear VBc rate of 75 μm, and with the magnetohydrodynamic-based coolant on, produced a VBc rate of 48 μm, indicating a difference of 36% in relative tool wear under the same cutting conditions. Increasing the cutting speed Vc to 900 m min−1, produced a corner wear VBc rate of 357 μm without the active coolant and a VBc rate of 246 μm with the magnetohydrodynamic-based coolant on, representing a decrease of 31% in relative tool wear. Further tests comparing external liquid water cooling against the liquid gallium coolant showed at Vc = 250 m min−1, a difference of 29% in relative tool wear rate reduction was obtained with the internal liquid gallium coolant. Increasing the cutting speed to Vc = 900 m min−1, the data indicated a difference of 16% relative tool wear reduction with the internal liquid gallium. The results support the feasibility of using liquid gallium as an internal coolant in cutting inserts to effectively remove thermal energy.

Numerical Modeling of a Sustainable Solid-State Recycling of Aluminum Scraps by Means of Friction Stir Extrusion Process.

One of the most important purposes of the modern industry is a sustainable production, considering the minimization of the energy and of the raw materials used, together with the reduction of polluting emissions. In this context, Friction Stir Extrusion stands out, since it allows to obtain extrusions starting from metal scraps deriving from traditional mechanical machining processes (e.g., chips deriving from cutting operations), heated only by the friction generated between the scraps and the tool, so avoiding the material melting phase. Given the complexity of this new kind of process, the objective of this research is the study of the bonding conditions considering both the heat and the stresses generated during the process under different working parameters, namely tool rotational and descent speeds. As a result, the combined approach involving the Finite Element Analysis and the Piwnik and Plata criterion proves to be a valid tool for forecasting if bonding phenomenon occurs and how it is influenced by the process parameters. The results have also demonstrated that it is possible to achieve completely massive pieces between 500 rpm and 1200 rpm, but at different tool descent speeds. Specifically, up to 1.2 mm/s for 500 rpm and just over 2 mm/s for 1200 rpm.

Methodology for Creating a Software for Structuring the Reconstruction Technologies by Laser Welding of Metal Moulds

Abstract Metal and plastic parts are made in moulds, in production processes such as plastic injection, metal alloy die casting and metal deformation. During operations, moulds are exposed to severe conditions: wear, impact, corrosion, thermal cycling and high mechanical stresses. Moulds reconstruction has advanced, precisely because to new technologies, such as laser welding. Laser technologies offers several benefits, including increase of work speeds, reduced thermally influenced zones and material losses and decreased additional working times for mechanical machining processes.

Non-Traditional Machining Techniques in Manufacturing Industries – An Overview

This comprehensive study provides an in-depth analysis of non-traditional machining techniques in the manufacturing industry. Focusing on mechanical, electrochemical, chemical, and thermal machining processes, the research explores recent advancements and their implications. The study adopts the action research method to gain a deeper understanding of the challenges associated with these techniques. Through a thorough examination of the machining processes, this work delves into various concepts, including the operations involved in each process and their corresponding outcomes. The analysis sheds light on the significance of non-traditional machining in the manufacturing industry, highlighting its potential for producing complex components and meeting design requirements that traditional machining methods may struggle to achieve. By exploring recent developments in non-traditional machining, this study aims to provide an overview of the advancements made in this field. It emphasizes the importance of understanding these techniques to unlock their full potential and enhance manufacturing capabilities. The findings of this research contribute to the existing knowledge base and serve as a valuable resource for professionals and researchers in the field of non-traditional machining.

Application of FUCA Method for Multi-Criteria Decision Making in Mechanical Machining Processes

Multi-criteria decision making (MCDM) is a very useful tool to find the best solution among many solutions. For most MCDM methods, the data must be normalized. However, the data normalization method has a significant influence on the results of ranking solutions. Choosing the right data normalization method is sometimes complicated. In many MCDM methods, FUCA is known as the method without using normalize the data. However, the FUCA method has a small limitation. All publications that were applied this method have not mentioned this limitation. In this study, this limitation was overcome and then used for multi-criteria decision making in some cases in the mechanical processing field. The ranked results of the solutions when determined by the FUCA method are compared with those ones when using other MCDM methods. The sensitivity analysis was also performed. The results show that the FUCA method can be used for multi-criteria decision making in mechanical machining. It is also expected to be successful when applying in other fields. The works in the future were mentioned in the last section of this article as well.

(Digital Presentation) HF-Free, Pulse-Reverse Electrochemical Machining of Tantalum

Electrochemical machining (ECM) is a manufacturing technology wherein metal is precisely removed by electrochemical oxidation and dissolution/dispersal into an electrolyte solution. ECM is especially well suited for “difficult to cut” materials (high strength/toughness, work-hardening, etc.) such as high strength steel, chrome-copper alloy (C18200), nickel alloy (IN718), cobalt-chrome alloy (Stellite 25) and tantalum-tungsten alloy (Ta10W) since the material removal process involves no mechanical interaction between the tool and the part. In ECM, an electrochemical cell is established wherein the workpiece is the anode and the tool is the cathode; by relative movement of the shaped tool into the workpiece while applying a suitable electrical voltage, the mirror image of the tool is “copied” into the workpiece. Production of parts with complicated and intricate geometries can thus be achieved in these challenging materials by design of a suitably-shaped tool made from a much more easily-machinable material. Compared to mechanical or thermal machining processes, where metal is removed by cutting or electric discharge/laser machining, respectively, ECM does not suffer from tool wear or result in a thermally damaged surface layer on the workpiece. Additionally, the use of pulse and/or pulse-reverse electrical waveforms can enable successful ECM of even highly passive materials using benign, HF-free electrolytes.Advanced materials such as refractories (e.g., W, Mo, Ta, and their alloys) provide highly desirable characteristics such as high strength, corrosion resistance, and survivability in extreme environments (high temperature, high chemical reactivity, plasma exposure, etc.). As motivation to adopt these materials has increased, conventional fabrication methods have proven progressively less able to successfully machine workpieces of the myriad needed geometries. ECM is a natural non-conventional fabrication method for these materials and workpieces, for the reasons described above. In this talk, we will present results from a proof-of-concept demonstration of pulse-reverse ECM of linear grooves in flat Ta and Ta10W alloy coupons using benign electrolytes, illustrating the potential for cost-effective, safe, environmentally-friendly fabrication using these exotic materials.

Application of topsis, mairca and EAMR methods for multi-criteria decision making in cubic boron nitride grinding

Determining the best cutting mode is a common problem for machining processes as well as for CBN (Cubic Boron Nitride) grinding on Computer Numerical Control (CNC) machines. It is even more important when it is necessary to choose a solution that meets many goals, which are in conflict. This paper presents the results of a multi-criteria decision-making (MCDM) study on CBN grinding of cylindrical-shaped parts on CNC milling machines. Three MCDM methods, including TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution), MAIRCA (Multi-Attributive Ideal-Real Comparative Analysis), and EAMR (Evaluation by an Area-based Method of Ranking) were applied in this work. Besides, MEREC (Method based on the Removal Effects of Criteria) and Entropy methods were used to determine the weights of the criteria. In addition, the Taguchi method with L18 orthogonal array (6^1+3^3) design was used for the design of an experiment, which has four input factors including the depth of dressing cut, the spindle speed, the feed rate, and the wheel diameter. Two criteria, including the surface roughness (SR) and the material removal speed (MRS) were selected as the response outputs. The reason for choosing these two criteria is because SR and MRS are two very important output factors of a mechanical machining process as well as of the CBN grinding process on a CNC milling machine. In particular, these two criteria are always in conflict with each other. Small SR requirements will require small values of the feed speed and the depth of cut. This will lead to the reduction of MRS. From the results of this study, the use of different methods for MCDM was evaluated. In addition, rankings of alternatives have been given according to MCDM methods. Furthermore, the best alternative to guarantee both the minimum SR and the maximum MRS has been found

Crack Propagation Behavior of Fused Silica during Cyclic Indentation under Incremental Loads

Fused silica is an important optical material with important applications, where the surface must be precisely machined without subsurface damage. In this study, multi-cyclic indentations under incremental loads were performed on fused silica using two kinds of indenters to clarify the mechanisms of crack generation and propagation induced by precision grinding. It was found that incremental loading cyclic nanoindentation induced various patterns of subsurface cracking and surface spalling. Four kinds of surface spalling were identified at different locations around an indent, the temporal formation mechanisms of which were clarified by microscopic observation and topographical measurement. Load–displacement curve analysis demonstrated that incremental propagation of lateral cracks during early indentation cycles caused large-scale brittle fractures during later cycles. Compared with a Berkovich indenter, a cube-corner indenter caused more significant brittle fractures and surface spalling. The findings in this study will deepen the understanding of subsurface damaging mechanism of fused silica and other brittle solids caused by cyclic tool-workpiece interactions in grinding and other mechanical machining processes.

A novel ensemble deep learning model for cutting tool wear monitoring using audio sensors

Tool wear is an important parameter in the machining because the production, cost and performance is highly depend upon its performance. Therefore, the monitoring of cutting tool wear plays an important role in mechanical machining processes. With this aim, the present work deals with the application of novel ensemble deep learning model for cutting tool wear monitoring using audio sensors. The tool wear data during machining was extracted with an audio denoising technique combined with Fast Fourier Transform (FFT) and bandpass filters and dependent component analysis (DCA). Then, the ensemble convolutional neural networks (CNN) detection model was trained and audio signals were converted into audio images with different algorithms. Finally, the results confirm that this novel method is very accurate to predict the tool wear values under different cutting conditions.

Life Cycle Inventories for Engine Blisk LCA

The aviation industry has been growing continuously over the past decades. To ensure sustainability and competitiveness for the aviation industry sector, a full understanding of the environmental impacts is required, not only during use phase but along the entire life cycle, including “Materials”, “Processes and Resources”, “Manufacturing and Production”, “Lifetime Services” as well as “Reuse, End-of-Life and Recycling”. Core engine components, such as integral rotors (Blisks), are comprised of high value metallic alloys that require complex and resource consuming manufacturing processes. This paper will introduce an approach for Life-Cy-cle-Inventory data acquisition during Blisk manufacturing as basis for a Life-Cycle-Assessment (LCA) according to ISO 14040. A particular focus will be set on the data quality and confidence level regarding measuring, acquisition, and analysis of in- and output flows within the Blisk manufacturing process chain in scope. This includes the stages of material generation, forming processes, heat treatments, machining, surface treatments and quality assurance. A greater emphasis is drawn to selected variations on mechanical machining processes. On this basis, first results of an LCA for Blisk-manufacturing will be presented.

Nd:YVO4 Laser Irradiation on Cr3C2-25(Ni20Cr) Coating Realized with High Velocity Oxy-Fuel Technology—Analysis of Surface Modification

The high-velocity oxy-fuel (HVOF) technique has been extensively used for the deposition of hard metal coatings. The main advantage of HVOF, compared to other thermal spray techniques, is its ability to accelerate the melted powder particles of the feedstock material to a relatively high velocity, leading to good adhesion and low porosity. To further improve the surface properties, a mechanical machining process is often needed; however, a key problem is that the high hardness of the coating makes the polishing process expensive (in terms of time and tool wear). Another approach to achieving surface modification is through interaction with a thermal source, such as a laser beam. In this research, the effects of laser scanning rate, scanning strategy, and number of loop cycles were investigated on an HVOF-coated surface. Cr3C2-25(Ni20Cr) was selected as the coating and Nd:YVO4 as the laser source. The results demonstrate the significance of the starting coating morphology and how the laser process parameters can be tuned to generate different types of modifications, ranging from polishing to texturing.

Low-Cost Tool Design for Pulse-Reverse Electrochemical Machining of Aerospace Alloys via Multiphysics Simulation

Electrochemical machining (ECM) is a manufacturing technology that precisely removes material from metallic workpieces via electrochemical means, typically oxidation, with subsequent dissolution/dispersal of the machining products into a working electrolyte. ECM is able to produce parts with complicated/intricate geometries, and is especially well suited for workpieces to be fabricated from “difficult to cut” materials, as no mechanical interaction occurs between tool and workpiece. In ECM, an electrochemical cell is established with the workpiece as the anode and a shaped tool as the cathode; a suitable electrical potential is then applied while the shaped tool is advanced into the workpiece, resulting in formation of a near-mirror image of the tool in the workpiece. Compared to mechanical or thermal machining processes, where material is subtracted by cutting or by electric/laser discharges, respectively, ECM does not suffer from tool wear or introduce a heat-affected zone to the workpiece. As a result, ECM has strong utility as a manufacturing technology for a wide variety of workpiece materials and ultimate part geometries, and encompasses machining, deburring, boring, radiusing and polishing processes, among others. As noted, ECM provides particular value when applied to high-strength/tough, brittle, galling-prone and/or work-hardening materials such as high strength steels, nickel alloys (e.g., IN718), titanium alloys (e.g., Ti-6Al-4V), cobalt-chrome alloy (Stellite 25), tantalum-tungsten alloy (Ta10W), molybdenum and tungsten.One challenge in practical execution of ECM is the tooling design process, which can require many costly and slow prototyping iterations and which often represents a significant barrier to entry for smaller manufacturing operations that might otherwise benefit from implementation of ECM. Multiphysics simulation has the potential to replace a significant fraction of the initial experimental prototyping effort with rapid, low-cost in-silico methods. This talk will present recent work by Faraday demonstrating a pulse-reverse ECM approach for fabrication of shaped Ni-alloy (IN625/IN718) and Ti-alloy (Ti64/Ti6242) workpieces, along with comparison of the experimentally-obtained results to simulated machined forms produced using the COMSOL Multiphysics® software package. For these preliminary simulation efforts, a 3D primary current distribution model was used to solve for the time-dependent electric field between a moving cathode tool and a workpiece surface, simulating deformation owing to metal dissolution. The simulated and experimental workpiece surfaces showed a satisfactory match for the complex, non-axisymmetric feature geometry embodying a notional form relevant to aerospace turbine and compressor blade manufacture, especially given the preliminary nature of the simulations implemented to date. A cost and lead-time analysis comparing a design process involving all-experimental tool prototyping iterations with one in which initial prototyping is performed computationally reveals the potential for significant cost/time reductions in the latter scenario. Thus, introduction of multiphysics modeling prototyping iterations to the tool design process has the potential to significantly reduce the barrier to entry for newcomers to ECM fabrication. Figure Caption Left to right: Non-axisymmetric tool fabricated by additive-manufacturing methods. Photograph and optical profilometry scan of indentation obtained by pulse-reverse waveform ECM. Indentation form predicted by multiphysics simulation. Figure 1

Force Control in Robotics: A Review of Applications

The aim of this article is to present an overview of the most important robotic processes in which force control methods are applied. In recent years, robotization has seen a rapid increase in the use of industrial robots in tasks that require simultaneous implementation of a given path of motion and the robot's force of interaction with the environment. In the field of industrial applications, this applies to issues related to the robotization of machining or some assembly tasks, but also the complex issue of cooperation between robots and people. One of the first applications of force control systems in robots were machining tasks such as grinding or blunting of sharp edges. Currently, robots are used in the following types of machining: grinding, polishing, chamfering, blunting, light milling. The implementation of such tasks requires the use of so-called position-force hybrid control. The task of such a control system is to implement the desired trajectory of the tool movement along the edge being machined or on the machined surface and to exert an appropriate clamping force of the tool. In the field of robotic machining, an important and still valid issue is the development and implementation of control strategies that ensure the quality of the mechanical machining process of the part despite the occurrence of unmolded phenomena, caused by, for example, significant errors in the geometry of the parts with local surface disturbances or its flexibility. Another of the basic applications of force control systems in robots are assembly tasks. In such processes, force control is particularly important, because too high interaction forces between the assembled components lead to large distortions and prevent the correct process from running. There are many papers in the literature that describe the problem of monitoring the machining process using force sensors. Monitoring the machining process is important in the industrial production of parts with a high unit cost. Any irregularity in the production of the part causing its non-compliance with the documentation is a cause of significant financial losses. Process monitoring aims to prevent irregularities during its implementation and to correct or discontinue the machining process. Friction stir welding is a method of joining materials without using consumable materials and without melting materials. In the process of friction stir welding, a cylindrical tool with a mandrel performs a rotary motion and at the same time is slowly moved along the joint area with simultaneous clamping. An industrial robot is responsible for the movement along the joint. The friction welding process is very sensitive to the temperature in the joint area. The temperature is not controlled directly, but by three other parameters: tool feed speed, tool speed and tool clamping force. For this reason, robots used for friction welding are equipped with position-force hybrid control systems. In recent years, the issue of cooperation in the human-robot system has become more and more important. The main area of application of this approach is assembly tasks. This solution has a number of advantages, such as the possibility of using the lifting capacity of the robot to lift heavy objects and the "ingenuity" of a human to maneuver the object. The robot, thanks to force sensor, is able to detect the method of maneuvering an object desired by a human. Summing up, it can be said that the use of force control has significantly increased the functionality of robotic systems in recent years.

A state-of-the-art review on sensors and signal processing systems in mechanical machining processes

A state-of-the-art review on sensors and signal processing systems in mechanical machining processes

Non-Linear through-Hole Fabrication By Electrochemical Machining

Electrochemical machining (ECM) is a manufacturing technology that precisely removes material from metallic workpieces by electrochemical oxidation and dissolution into a working electrolyte. ECM is especially well suited for workpieces to be fabricated from "difficult to cut" materials, and is able to produce parts with complicated/intricate geometries. In ECM, an electrochemical cell is established with the workpiece as the anode and a shaped tool as the cathode; after engaging a suitable electrical potential, the shaped tool is advanced into the workpiece and a mirror image of the tool is formed. Compared to mechanical or thermal machining processes, where material is subtracted by cutting or by electric/laser discharges, respectively, ECM does not suffer from tool wear or introduce a heat-affected surface layer to the workpiece. As a result, ECM has strong utility as a manufacturing technology for a wide variety of workpiece materials and ultimate part geometries, and encompasses machining, deburring, boring, radiusing and polishing processes, among others. As noted, ECM provides particular value when applied to high-strength/tough, brittle, and/or work-hardening materials such as high strength steel, chrome-copper alloy (C18200), nickel alloy (IN718), cobalt-chrome alloy (Stellite 25), tantalum-tungsten alloy (Ta10W), molybdenum and tungsten, since the material removal process involves no mechanical interaction between the tool and the part.This talk will summarize recent work performed to demonstrate the feasibility of non-linear through-hole machining in tubular metallic substrates by ECM, through application of a multi-step forming process. One category of feature that is often challenging to fabricate in hard-to-machine materials is a non-linear passage or through-hole. This is in contrast to a straight passage, which is generally uncomplicated to achieve with many methods, whereas in general non-linear through-holes in tube walls must be machined from both the inner and outer diameter of the wall. For easily-machined materials, machining steps taking place on the inner diameter of the workpiece can be accomplished with a sufficiently advanced multi-axis CNC mill, but for hard-to-machine materials it is difficult or impossible to achieve the necessary bearing force and/or angle of approach of the tool. Thermal machining methods (electric discharge machining, etc.) are viable in some cases, but as noted above will result in a heat-affected layer on the machined surface that is problematic in many applications. Experimental ECM results will be presented for fabrication of "chevron" through-hole features (~90° path axis deflection) in both planar and annular workpieces, embodying a proof-of-concept demonstration and an early step in development of an ECM methodology for fabricating integrated muzzle brake vane apertures directly into the barrel wall of large-bore cannon. Figure Caption (Top left) Patent drawing of modular muzzle brake concept for cannon, showing overall design and cross-section of a single vane, with vane passage geometry highlighted in orange. (Bottom left) Schematic 3D model of a cannon barrel with integrated muzzle brake vanes. (Top right) Schematic of two-sided ECM fabrication of nonlinear “chevron” passage in a composite stack of flat coupons. (Bottom right) Photographs of cross-sectioned flat steel coupons with fabricated “chevon” passages. Reference (from figure) Cler, D.L. and D. Forliti. U.S. Patent No. 7,600,461, issued 13 Oct 2009. Figure 1

Properties of Additively Manufactured Electric Steel Powder Cores with Increased Si Content.

In this paper, the best laser powder bed fusion (L-PBF) printing conditions for FeSi steels with two different Si content (3.0% and 6.5%) are defined. Results show very strict processing window parameters, following a lack of fusion porosity at low specific energy values and keyhole porosity in correspondence with high specific energy values. The obtained microstructure consists of grains with epitaxial growth starting from the grains already solidified in the underling layer. This allows the continuous growth of the columnar grains, directed parallel to the built direction of the component. The magnetic behaviour of FeSi6.5 samples, although the performances found do not still fully reach those of the best commercial electrical steels (used to manufacture magnetic cores of electrical machines and other similar magnetic components), appears to be quite promising. An improvement of the printing process to obtain thin sheets with increased Si content, less than 0.5 mm thick, with accurate geometry and robust structures, can result to an interesting technology for specific application where complex geometries and sophisticated shapes are required, avoiding mechanical machining processes for electrical steel with high silicon content.

Laser Grinding of Single-Crystal Silicon Wafer for Surface Finishing and Electrical Properties.

In this paper, we first report the laser grinding method for a single-crystal silicon wafer machined by diamond sawing. 3D laser scanning confocal microscope (LSCM), X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), laser micro-Raman spectroscopy were utilized to characterize the surface quality of laser-grinded Si. Results show that SiO2 layer derived from mechanical machining process has been efficiently removed after laser grinding. Surface roughness Ra has been reduced from original 400 nm to 75 nm. No obvious damages such as micro-cracks or micro-holes have been observed at the laser-grinded surface. In addition, laser grinding causes little effect on the resistivity of single-crystal silicon wafer. The insights obtained in this study provide a facile method for laser grinding silicon wafer to realize highly efficient grinding on demand.

Micro/Meso-Scale Mechanical Machining 2020: A Two-Decade State-of-the-Field Review

Abstract Micro/meso-scale mechanical machining (M4) processes are miniaturized versions of conventional machining processes such as milling, drilling, and turning, where material removal is accomplished by physical contact between the micro/meso-scale cutting tool and the workpiece. The objective of this review paper is to provide an assessment of the state-of-the-field related to M4 processes during the last two decades. Key systems-level issues related to the deployment of M4 processes including micro/meso-scale machine tool (mMT) design, sensing/calibration, cutting tools, and lubrication strategies are discussed. Emerging material systems are identified along with the specific challenges posed for the development of microstructure-based process models. The topic of micro/meso-scale machining dynamics is reviewed both in terms of recent research findings as well as unresolved challenges posed by the complexity of experimental characterization and modeling. Finally, key industry trends are discussed along with promising interdisciplinary drivers that are expected to influence this field in the upcoming decade.

Cold Tribo-Nanolithography on Metallic Thin-Film Surfaces.

This paper demonstrates a modified tribo-nanolithgraphy (TNL), micro- to nanometer scale mechanical machining processes, on metallic thin film surfaces which have poor machinability in micro scale under several mN normal loads. TNL is one of the promising atomic force microscopy (AFM)-based lithography processes which is more effective fabrication technology, as compared to conventional photolithography due to its relatively simple processes, high resolution, short processing time, and low cost. We propose ultra-precision machining at sub-0 °C temperatures using a lab-made micro polycrystalline diamond (PCD) tool on a retrofitted piezo stage with a Peltier device. The workpiece, located on the stage, is cooled artificially, and a normal load of several mN is applied by a micro PCD tool for micro scale machining processes. The machining results indicated considerably different machinability when the work was performed at sub-0 °C, as opposed to the ambient surface temperature, due to the changed mechanical characteristics of surface by the forced cooling of the workpiece. Although the normal load, machining speed, and machining area remained constant, the width and depth of machined grooves are significantly increased at sub-0 °C temperature conditions. In addition, we analyzed the TNL characteristics when machining with the PCD tool in four different machining directions. The mechanical surface properties, surface topography, scanning electron microscope (SEM) images, chip formation and other physical properties are investigated for more discussions.

Multiphysics Modeling Prediction of Electrochemically Machined Workpiece Geometries

Electrochemical machining (ECM) is a manufacturing technology that allows metal to be precisely removed by electrochemical oxidation and dissolution into an electrolyte solution. ECM is suited for fabrication operations using “difficult to cut” materials and/or producing parts with complicated and intricate geometries. In ECM, an electrochemical cell is established wherein the workpiece is the anode and the tool is the cathode; by relative movement of the shaped tool into the workpiece while applying a suitable electrical potential, the mirror image of the tool is “copied” into the workpiece. Compared to mechanical or thermal machining processes, where metal is removed by cutting or electric discharge/laser machining, respectively, ECM does not suffer from tool wear or result in a thermally damaged surface layer on the workpiece. Consequently, ECM has strong utility as a manufacturing technology for fabrication of a wide variety of metallic parts and components, and encompasses machining, deburring, boring, radiusing and polishing processes, among others. As noted, ECM provides particular value when applied to high strength/tough and/or work-hardening materials such as high strength steel, chrome-copper alloy (C18200), nickel alloy (IN718), cobalt-chrome alloy (Stellite 25) and tantalum-tungsten alloy (Ta10W), since the material removal process involves no mechanical interaction between the tool and the part.One notable difficulty with ECM is an inability to predict a priori the tool and process parameters required in order to satisfy the final specifications of the fabricated part. Currently, most practical applications of ECM require an iterative prototyping process for tool development, where a succession of tools and parts are fabricated until the desired final form is achieved. In this talk, Faraday will present results from ongoing development work of a multiphysics-based design platform to predict optimal ECM tool shapes and processing parameters using commercial multiphysics simulation software. Simulation results for both an axisymmetric tubular tool and a non-axisymmetric tool fabricated by powder-bed additive manufacturing methods will be compared to experimental data gathered from ECM tests on various materials of commercial interest (alloy steel, nickel and titanium alloys). A notional non-axisymmetric tool, the electrochemically machined indentation obtained in an IN718 alloy plate, and the indentation predicted from multiphysics modeling are shown in the Figure. The effect of including selected physical phenomena in the simulations (kinetic polarization, surface occlusion by insoluble dissolution products, etc.) on the quality of the predicted machined forms will be discussed, and general guidelines for successful multiphysics modeling of ECM processes will be highlighted. Replacement of most or all of a costly experimental prototyping cycle with a more-rapid and less-expensive in silico multiphysics modeling like that described herein, along with enhanced ECM process performance [1-3] and simplified management of ECM electrolytes [4] through the application of pulse/pulse-reverse electrical waveforms, has the potential to significantly advance ECM as a mainstream manufacturing technology. Figure Caption Left to right: Non-axisymmetric tool fabricated by additive-manufacturing methods. Photograph and optical profilometry scan of indentation obtained by pulse-reverse waveform ECM. Indentation form predicted by multiphysics simulation.