International Journal of Precision Technology (12 papers in press)
Computer aided tool design for micro-ECM
by Pratik Shah, S.S. Pande
Abstract: This paper reports the development of a computer aided system for micro-ECM process to design tools to produce accurate internal features on workpiece. Mathematical model has been developed to compute the inter-electrode gap (IEG) for chosen shape of tool and process conditions. Axi-symmetric tools of different profiles such as cylindrical, conical, hemispherical have been analyzed to predict the shapes of work cavities. Model is validated with the reported results and some experiments conducted by us on typical tool shapes. Parametric studies have been carried out to study influence of various process variables on the accuracy of cavity shapes. Based on these studies, guidelines for improving profile accuracy in micro-ECM have been suggested.
Keywords: Micro-ECM; computer aided design system; inter-electrode gap; tool design; process model; parametric studies.
Carbon Nanofiber (CNF) Assisted Micro-Electro Discharge Machining (
by Prasanna Chougule, Rakesh Mote, Uday Dabade
Abstract: Titanium alloys have found growing applications in aerospace, biomedical and marine industry. However, extreme hardness and strength cause difficulty in machining of titanium alloys. This is further complicated by the requirements of micro features on hard to machine alloys. Micro Electro discharge machining (micro EDM) is being investigated to match the requirement. However, slower removal rates and thermal effects are the issues in thermal erosion based EDM process. In this work, we have investigated the efficacy of using carbon nanofibers (CNFs) mixed with the dielectric fluid for micro machining of Ti6Al4V using micro EDM. It is observed that the addition of CNFs not only improves electro-discharge frequency, material removal rate but also improves the surface roughness. Added nanofibers lowered the material migration and increased spark gap. We noted a significant influence of mixing CNFs in the dielectric fluid for enhancing machining performance characteristics in
Keywords: Micromachining; Micro-EDM; Titanium alloys; Carbon nanofibers (CNFs); Additives; Surface integrity.
Micro-Faraday cup array structures fabrication in Silicon using Deep Reactive Ion Etching
by JULFEKAR ARAB, Pradeep Dixit, Prakash Brahmankar, Raju Pawade, Arvind Kumar Srivastava
Abstract: Micro-faraday cup array (MFCA) detectors are used for the detection and analysis of incident ion particles. Over the years, MFCA played the vital role in the field ion detection with greater stability and precision. New and simple Micro FCA structures have been designed and fabricated considering the application of ion detection in devices such as Mass spectrometry and laser plasma techniques. MFCA structures were fabricated in n-type Silicon substrate with MEMS fabrication processes such as UV lithography followed by DRIE (Deep reactive ion etching). The UV lithography process was utilized for fabrication of Micro-Faraday cup array structure in photoresist (AZ4903) deposited on silicon substrate. After that DRIE process was used for creating array pattern in Silicon. Ultimately 1x16 arrays having 25
Keywords: Faraday Cups; micro-fabrication; characterization; UV-LED; DRIE.
Femtosecond Laser Assisted Generation of Micro-dimples on Moly-chrome film for Improving its Tribology
by Ezhilmaran Veeranan, Nilesh J. Vasa, L. Vijayaraghavan, Sivarama Krishnan
Abstract: Femtosecond laser ablation of the moly-chrome deposited piston ring and the influence of laser fluence and number of laser pulses on dimple morphology and geometry were analysed. The increase of laser fluence and pulse numbers beyond 8.4 J/cm2 affected the dimple surface by inducing severe cracks due to heat accumulation. Based on the experimental investigation, the ablation threshold for moly-chrome film was found to be 0.36 J/cm2. Textured surface was formed on the moly-chrome film with laser fluence near the ablation threshold and the tribological characteristics were studied. The piston ring surface was textured with dimple diameter of 100 m and dimple aspect
ratio of 0.2. Effect of different dimple area ratios, such as 2%, 16% and 38% were analysed by reciprocating type tribology testing. The textured surface with 16% dimple area ratio showed a reduction in friction compared to the plain and the remaining textured piston rings.
Keywords: surface texturing; micro-dimple; tribology; friction; femtosecond
Influence of wire feed rate on microslit width fabricated by Wire ECM process
by Subhrajit Debnath, Joydeep Kundu, Bijoy Bhattacharyya
Abstract: Miniaturisation of metallic structures has become a prime issue and to meet high demand, modern fabricators extensively use different micro machining techniques. Wire electrochemical machining (wire ECM) is such a process of removing excess material electrochemically. However, the process is still new and further research is needed. Hence, the present work aims in developing suitable wire ECM setup to find out the influence of wire feed rate at varying voltage settings on corresponding width of the generated microslits. For this, experimentations have been carried out with 50 m dia tungsten wire and machined micro features have been carefully observed under optical
microscope. Additionally, the experimental results have been represented graphically where the minimum average width of the microslit is found to be 83.117 m with an aspect ratio of 1.2. Moreover, complex microfeature with varying width has been fabricated by changing corresponding feed values in a single run.
Keywords: wire electrochemical machining (wire ECM) process; wire feed rate; applied voltage; microslits; slit width.
Contact behavior of elastic abrasive spheres during self-centering type magneto-mechanical deployment for Internal bore finishing
by V.S. Sooraj
Abstract: Elastic abrasive finishing, in its various forms, has been demonstrated for micro-finishing of engineering surfaces in the recent past. Conceiving the advantages of elastically controlled abrasion, a deployable type-internal bore finishing tool with self centring magnetic pads to hold elastic abrasive spheres has been introduced in this paper. Contact of such magnetically held elastic abrasives on target surfaces has been simulated, analysed with various contact hypotheses, and supplemented by experimental results. Spring-Dashpot analogy of elastic abrasive contact and characteristics of magnetically controlled abrasive deployment for surface finishing are discussed in detail. Reduced penetration depth of embedded grains due to significant reduction in elastic modulus at contact interface, through the action of elastomeric medium, is illustrated through simulations. With a significantly lower depth of cut under the action of controlled cutting velocity, elastic abrasive spheres are capable of generating fine finish without altering the surface form.
Keywords: Elastic; Abrasives; Magnetic; Deployable; Surface; Finishing; Roughness; Contact.
Molecular Dynamics Simulation of Mechanical Polishing
by Prabhat Ranjan, ANUJ SHARMA, Tribeni Roy, R. Balasubramanian, V.K. Jain
Abstract: Mechanical polishing, a nano-finishing process is extensively used for generating smooth surfaces on engineering materials. The mechanism of mechanical polishing is extremely complex due to its random nature of material removal at atomic scale. The need for a better understanding of the process at atomic scale is therefore necessary. Hence, molecular dynamics simulation (MDS) was carried out to understand the behaviour of material removal on two different types of engineering materials viz. aluminium and silicon. In the present work, material removal of rough asperities was modelled and simulated by abrading them with abrasive particles. It was observed that the nanometric abrasion occurs through adhesion de-bonding principle, recoverable phase transformation occurs during the nanometric abrasion on aluminium, and the non-crystalline debris formation during polishing of silicon as brittle crystalline structures. In addition, other attributes are also discussed such as force, stress, chemical stability, effect of abrasive particle, and temperature.
Keywords: MDS; mechanical polishing; nano-finishing; TERSOFF; EAM.
Fibre Laser Cutting of Thick Closed-Cell Aluminium Foam: Morphological Analysis and Its Parametric Optimisation
by Partha Saha, Mohammad Shahid Raza, Susmita Datta, Jogender Singh
Abstract: Laser cutting of 10 mm thick closed cell aluminium foam was performed using a 2 kW fibre laser. The parameters selected were laser power (1,350 W
Keywords: Fibre laser cutting; Closed-cell metal foams; Aluminium foam; kerf quality; Laser power; Scan speed; Response Surface Methodology; Parametric Optimisation.
Investigation of tool-workpiece interaction in nanoscale cutting: A Molecular Dynamics study.
by ANUJ SHARMA, D. Datta, R. Balasubramanian, Tribeni Roy, Prabhat Ranjan
Abstract: Ductile and brittle materials differ in their physical and mechanical properties and pose distinct interaction with the cutting tool while nano-machining. It is thus imperative to analyse the mechanism of material removal and tool-workpiece interaction. Towards this, molecular dynamics simulation (MDS) is carried out to study the diamond tool and workpiece interaction in the nanoscale cutting of Cu (ductile material) and Si (brittle material). Results show that material removal in Cu takes place through shear deformation by dislocations formation and their propagation while in case of Si, it takes place through phase transformation of the material in cutting zone. Force analysis of both the materials shows that machinability of Cu in nanoscale cutting is better compared to Si. Furthermore, tool wear while machining of Si with sharp edge tool is due to chipping whereas radial
distribution function reveals that graphitisation of the round edge tool occurs during machining of Si.
Keywords: cutting mechanism; tool wear; molecular dynamics simulation;
MDS; diamond turning; nanoscale cutting; subsurface damage; deformation; dislocation; silicon; copper.
Force analysis during spot finishing of titanium alloy using novel tool in magnetic field assisted finishing process
by Manas Das, Anwesa Barman
Abstract: Magnetic field assisted finishing process is a nanofinishing process which uses magnetic field for precise control of finishing forces. Magnetorheological fluid mixed with diamond abrasive particles in base medium of glycerol, hydrofluoric acid, nitric acid, and deionised water is used as the polishing medium. The novel tool is a magnet fixture made of mu-metal which is used to hold the magnet during finishing. In the present experimental study, finishing at a spot on flat titanium alloy is carried out to analyse the forces involved in the finishing. Normal force is the main force responsible for the indentation by the abrasive particles on the workpiece surface. Tangential force helps in removing indented material. The measured normal force and
tangential force during the spot finishing are 3.285 N and 0.43 N, respectively.
The final surface roughness achieved after spot finishing is 10 nm from initial surface roughness of 200 nm. The percentage improvement in surface roughness is 95%.
Keywords: nanofinishing process; MR fluid; magnetic field assisted finishing; MFAF; finishing force.
Fabrication of High Aspect Ratio Cylindrical Tungsten Micro Tool by Reverse Micro-ECM Process
by Partha Saha, Abhijeet Sethi, Biswesh Ranjan Acharya
Abstract: The present study was aimed at fabricating high aspect ratio tungsten micro tool using reverse micro-ECM process and studying the effect of different shapes of the brass cathode used on the geometry of fabricated cylindrical tungsten anode. The different shapes of cathode considered were a rectangular block, a wire and a disc. Tungsten rod of 1 mm diameter was first machined to 500 m and diameter was further reduced below 100 m by reverse micro-ECM process. The output parameters considered here were the average diameter, aspect ratio, tool diameter at 100 m from the tip and total tool length. Micro tool with an average diameter of 74.57 m with an aspect
ratio of 26.8 was successfully fabricated using a block cathode in reverse micro-ECM process. Finally, experiments were conducted to study the effect of process parameters like applied voltage and electrolyte concentration with the block-shaped cathode in the machining process.
Keywords: micro electrochemical machining; micro-ECM; micro machining; tungsten micro tool; high aspect ratio; tool geometry; cathode shape.
Constant work gap perpetuation in ball end magnetorheological finishing process
by Faiz Iqbal, Zafar Alam, Dilshad Ahmad Khan, Sunil Jha
Abstract: Ball end magnetorheological finishing (BEMRF) is an advanced finishing method employed for super finishing of flat, curved, intricate and complex surfaces. The surface finish achieved in BEMRF process is governed by machining parameters and fluid parameters. A main contributor towards super finishing by BEMRF process is the work gap. A constant work gap ensures a uniform finishing operation throughout the entire surface; however, there are many cases wherein the work gap between tool tip and workpiece varies over the surface due to geometric form deviations induced by preceding manufacturing process or linear positioner having a tilt error. This paper
describes a method to keep a constant work gap for finishing in BEMRF process. A confocal sensor is used to scan the surface in order to detect any height deviations that prevent a constant work gap. Experimental results show a considerable improvement in the surface quality while finishing with perpetuated work gap.
Keywords: work gap; perpetuation; nano finishing; non-contact measurement; confocal sensor; ball end; BEMRF; automated finishing; surface roughness; surface metrology.