Hybrid micro-machining processes : a review

Micro-machining has attracted great attention as micro-components/products such as micro-displays, micro-sensors, micro-batteries, etc. are becoming established in all major areas of our daily life and can already been found across the broad spectrum of application areas especially in sectors such as automotive, aerospace, photonics, renewable energy and medical instruments. These micro-components/products are usually made of multi-materials (may include hard-to-machine materials) and possess complex shaped micro-structures but demand sub-micron machining accuracy. A number of micro-machining processes is therefore, needed to deliver such components/products. The paper reviews recent development of hybrid micro-machining processes which involve integration of various micro-machining processes with the purpose of improving machinability, geometrical accuracy, tool life, surface integrity, machining rate and reducing the process forces. Hybrid micro-machining processes are classified in two major categories namely, assisted and combined hybrid micro-machining techniques. The machining capability, advantages and disadvantages of the state-of-the-art hybrid micro-machining processes are characterized and assessed. Some case studies on integration of hybrid micro-machining with other micro-machining and assisted techniques are also introduced. Possible future efforts and developments in the field of hybrid micro-machining processes are also discussed

Frontiers in Ultra-Precision Machining

Ultra-precision machining is a multi-disciplinary research area that is an important branch of manufacturing technology. It targets achieving ultra-precision form or surface roughness accuracy, forming the backbone and support of today’s innovative technology industries in aerospace, semiconductors, optics, telecommunications, energy, etc. The increasing demand for components with ultra-precision accuracy has stimulated the development of ultra-precision machining technology in recent decades. Accordingly, this Special Issue includes reviews and regular research papers on the frontiers of ultra-precision machining and will serve as a platform for the communication of the latest development and innovations of ultra-precision machining technologies

A review on optimization of machining performances and recent developments in electro discharge machining

Electro discharge machining (EDM) is a popular unconventional machining process widely employed in die-making industries. Careful selection of process parameters such as pulse current, voltage, on and off time, etc. is essential for machining of hard and conductive materials using EDM. Previous researchers working in the area of EDM have extensively analyzed the machining performance through experimental study, modeling, and simulation and also by theoretical analysis. This article discusses the significant summary of the work performed by earlier researchers through a detailed literature survey. Relevant literature on EDM and impact of process parameters on performance measures such as surface quality, tool wear rate and material removal rate are reviewed. The challenge and limitation of EDM process are also highlighted in this article. It is observed that optimization of process parameters is essentially required for effective and economical machining. So, this article addresses the various issues related to EDM and also provides brief insight into some of the current generation applications of EDM process explored in various industries

High-precision micro-machining of glass for mass-personalization

With the fourth industrial revolution manufacturing industry faces new challenges. Small batches of personalized parts, where the geometry changes per part, must be produced in an economically viable manner. In such cases of mass personalization new manufacturing technologies are required which can keep manufacturing overhead related to change of part geometries low. These processes need to address the issues of extensive calibration and tooling costs, must be able to handle complex parts and reduce production steps. According to recent studies hybrid technologies, including electrochemical technologies, are promising to address these manufacturing challenges. At the same time, glass has fascinated and attracted much interest from both the academic and industrial world, mainly because it is optically and radio frequency transparent, chemically inert, environmentally friendly and it has excellent mechanical and thermal properties, allowing tailoring of new and dedicated applications. However, glass is a hard to machine material, due to its hardness and brittleness. Machining smooth, high-aspect ratio structures is still challenging due to long machining times, high machining costs and poor surface quality. Hybrid methods like Spark Assisted Chemical Engraving (SACE) perform well to address these issues. Nevertheless, SACE cannot be deployed for high-precision glass mass-personalization by industry and academia, due to 1) lack of process models for glass cutting and milling, relating SACE input parameters to a desired output, 2) extensive calibration needed for tool-workpiece alignment and tool run-out elimination, 3) part specific tooling required for proper clamping of the glass workpiece to attain high precision. In this study, SACE technology was progressively developed from a mass-fabrication technology towards a process for mass-personalization of high-precision glass parts by addressing these issues. Key was the development of 1) an (empirically validated) model for SACE cutting and milling process operations allowing direct relation of the machining input to the desired machining outcome, enabling a dramatical increase of automation across the manufacturing process workflow from desired design to establishing of machinable code containing all necessary manufacturing execution information, 2) in-situ fabrication of the needed tooling and 3) the use of low-cost rapid prototyping, eliminating high indirect machining costs and long lead times. To show the viability of this approach two novel applications in the microtechnology field were proposed and developed using glass as substrate material and SACE technology for rapid prototyping: a) fabrication of glass imprint templates for microfabricating devices by hot embossing and b) manufacturing of glass dies for micro-forming of metal micro parts

Principles and Characteristics of Different EDM Processes in Machining Tool and Die Steels

Electric discharge machining (EDM) is one of the most efficient manufacturing technologies used in highly accurate processing of all electrically conductive materials irrespective of their mechanical properties. It is a non-contact thermal energy process applied to a wide range of applications, such as in the aerospace, automotive, tools, molds and dies, and surgical implements, especially for the hard-to-cut materials with simple or complex shapes and geometries. Applications to molds, tools, and dies are among the large-scale initial applications of this process. Machining these items is especially difficult as they are made of hard-to-machine materials, they have very complex shapes of high accuracy, and their surface characteristics are sensitive to machining conditions. The review of this kind with an emphasis on tool and die materials is extremely useful to relevant professions, practitioners, and researchers. This review provides an overview of the studies related to EDM with regard to selection of the process, material, and operating parameters, the effect on responses, various process variants, and new techniques adopted to enhance process performance. This paper reviews research studies on the EDM of different grades of tool steel materials. This article (i) pans out the reported literature in a modular manner with a focus on experimental and theoretical studies aimed at improving process performance, including material removal rate, surface quality, and tool wear rate, among others, (ii) examines evaluation models and techniques used to determine process conditions, and (iii) discusses the developments in EDM and outlines the trends for future research. The conclusion section of the article carves out precise highlights and gaps from each section, thus making the article easy to navigate and extremely useful to the related research communit

National Educators' Workshop: Update 95. Standard Experiments in Engineering Materials Science and Technology

This document contains a collection of experiments presented and demonstrated at the National Educators' Workshop: Update 95. The experiments related to the nature and properties of engineering materials and provided information to assist in teaching about materials in the education community

National Educators' Workshop: Update 1993. Standard Experiments in Engineering Materials Science and Technology

This document contains a collection of experiments presented and demonstrated at the National Educators' Workshop: Update 93 held at the NASA Langley Research Center in Hampton, Virginia, on November 3-5, 1993. The experiments related to the nature and properties of engineering materials and provided information to assist in teaching about materials in the education community

Powder-mixed Electric Discharge Machining (PMEDM) of Inconel 625

In recent times, nickel-based super alloys are widely used in aerospace, chemical and marine industries owing to their supreme ability to retain the mechanical properties at elevated temperature in combination with remarkable resistance to corrosion. Some of the properties of these alloys such as low thermal conductivity, strain hardening tendency, chemical affinity and presence of hard and abrasives phases in the microstructure render these materials very difficult-to-cut using conventional machining processes. Therefore, the aim of the current research is set to improve the productivity and surface integrity of machined surface of Inconel 625 (a nickel-based super alloy) by impregnating powder particles such as graphite, aluminum and silicon to kerosene dielectric during electric discharge machining (EDM). Initially, temperature distribution, material removal rate (MRR) and residual stress were predicted through numerical modelling of powder-mixed EDM (PMEDM) process. In the experimental investigation, particle size analysis of the as-received powder particles was carried out to identify the distribution of particles. X-ray diffraction (XRD) analysis of particles indicated the presence of various phases including small amount of impurities. An experimental setup was developed and integrated with the existing EDM system for carrying out PMEDM process. The experiments were planned and conducted by varying five different parameters such as powder concentration, peak current, pulse-on time, duty cycle and gap voltage according to the central composite deign (CCD) of response surface methodology (RSM). Effects of these parameters along with powder concentration were investigated on various EDM characteristics such as material removal rate (MRR), radial overcut (ROC) and surface integrity aspects including surface crack density (SCD), surface roughness (SR), altered layer thickness (ALT), microhardness of surface and sub-surface regions, chemical and metallurgical alterations of the machined surface and residual stress. Results clearly indicated that addition of powder to dielectric has significantly improved MRR and surface integrity compared to pure dielectric. Among the powders used, graphite has resulted in highest MRR, lowest SCD, least ALT, least microhardness of surface and sub-surface regions. Least ROC, lowest surface roughness and least residual stress were obtained using silicon powder. Aluminum performed well in terms of MRR at low concentration range (upto 6 g/l).Therefore, optimal process performance under a given operating condition depends on judicious selection of powder materials, their size, concentration and process parameters

Energy Materials Coordinating Committee (EMaCC): Fiscal year 1996. Annual technical report

The DOE Energy Materials Coordinating Committee (EMaCC) serves primarily to enhance coordination among the Department`s materials programs and to further effective use of materials expertise within the Department. These functions are accomplished through the exchange of budgetary and planning information among program managers and through technical meetings/workshops on selected topics involving both DOE and major contractors. In addition, EMaCC assists in obtaining materials-related inputs for both intra- and interagency compilations. The EMaCC reports to the Director of the Office of Energy Research in his or her capacity as overseer of the technical programs of the Department. This annual technical report is mandated by the EMaCC terms of reference. This report summarizes EMaCC activities for FY 1996 and describes the materials research programs of various offices and divisions within the Department