Development of magneto abrasive flow machining process

Abrasive flow machining (AFM) is a relatively new process among non-conventional machining processes. Low material removal rate happens to be one serious limitation of almost all such processes. Limited efforts have hitherto been directed towards improving the efficiency of these processes so as to achieve higher material removal rates by applying different techniques. This paper discusses the possible improvement in surface roughness and material removal rate by applying a magnetic field around the workpiece in AFM. A set-up has been developed for a composite process termed magneto abrasive flow machining (MAFM), and the effect of key parameters on the performance of the process has been studied. Relationships are developed between the material removal rate and the percentage improvement in surface roughness of brass components when finish-machined by this process. Analysis of variance has been applied to identify significant parameters and to test the adequacy of the models. Experimental results indicate significantly improved performance of MAFM over AFM.     

Effect of Curing Temperature on Mechanical Properties of Natural Fiber Reinforced Polymer Composites

Nowadays, growing environmental concerns have led many researchers to work in the area of natural fiber reinforced polymer composites. In this work, jute fiber has been used as reinforcement and epoxy as matrix material to develop partially biodegradable green composite with the help of hand layup followed by compression molding technique. The effect of curing temperature ranging from 80°C to 130°C on different samples was investigated for various mechanical properties. Results obtained from the various tests indicate that with increase in curing temperature, impact strength decreases, but tensile and flexural strength increases and decreases thereafter attaining the maximum value at 100°C between aforementioned temperature range. The trend obtained for mechanical properties is further justified through the study of morphology with scanning electron microscopy, and optimum curing temperature has been suggested.     

Optimizing Single Point Diamond Turning for Mono-Crystalline Germanium Using Grey Relational Analysis

In this paper the results of an experimental study conducted for precision machining of mono-crystalline germanium with single point diamond turning (SPDT) have been reported. The input parameters include the top rake angle, tool overhang, depth of cut, tool feed rate, and rotational speed of the workpiece. The flat profile is generated on a disk of mono-crystalline germanium possessing three performance characteristics: surface roughness (R_a), profile error (P_t), and waviness error (W_a). The process parameters are optimized to obtain the best surface finish with minimum profile and waviness errors by using the Taguchi method. The grey relational analysis is employed for carrying out multiresponse optimization of performance parameters. The best value of surface finish obtained after multiresponse optimization is 10.7 nm having a profile error and a waviness error of 0.202 µm and 0.046 µm, respectively.     

Parametric optimization of magnetic‐field‐assisted abrasive flow machining by the Taguchi method

Some hybrid‐machining processes have been developed in the recent past with a view to devising composite machining processes, which are able to overcome the limitations of one process with the help of advantageous features of another similar process. The present paper identifies the parameters of abrasive flow machining (AFM) that significantly affect the material removal when a magnetic field is applied around the workpiece. The Taguchi method has been adopted for studying the effect of magnetic‐field‐assisted AFM parameters, individually, on the abrasion rate of work materials. Optimization of the process parameters has been carried out for the purpose of off‐line monitoring of the process. Copyright © 2002 John Wiley & Sons, Ltd.     

Precision Deterministic Machining of Polymethyl Methacrylate by Single-Point Diamond Turning

Polymethyl methacrylate (PMMA) is widely used as substrate material for optical fabrication in infrared and visual applications. The single-point diamond turning (SPDT) being one of the deterministic precision machining technologies needs to be explored for the manufacturing of the optical components as it is capable of providing the required characteristics such as accuracy, quality, and repeatability. Therefore, it becomes imperative to study the role of influential factors in affecting the machining characteristics of PMMA. The present work is an experimental outcome of precision deterministic machining of PMMA with SPDT. The five input factors of depth of cut, tool overhang, tool nose radius, rotational speed of spindle, and cutting feed rate are considered for machining a flat profile. Surface roughness (Ra), waviness error (Wa), and profile error (Pt) are three output parameters. The process is optimized individually for Ra, Wa, and Pt by Taguchi method. Subsequently, Ra, Wa, and Pt are optimized simultaneously by grey relation to obtain an optimal solution which identifies rotational speed of the spindle, depth of cut, and cutting feed rate as significant parameters. Ra as 11.9 nm, Wa as 0.0289 µm, and Pt as 0.285 µm are obtained as minimum values. Effect of coolant on transmission of light is also studied.     

Performance evaluation of cryogenically assisted electric discharge machining (CEDM) process

The performance of cryogenically assisted electric discharge machining (CEDM) process has been evaluated in the presented research paper. The machining of cryogenically treated (CT) and cryogenically untreated (CUT) AISI D2 tool steel work specimens using cryogenically cooled (CC), CT, and CUT copper electrodes have been performed. The effects of various parameters, namely, workpiece condition, tool condition, nozzle flushing, peak current, duty cycle, pulse duration, and gap voltage, have been studied on the performance indicators, viz. the material removal rate (MRR), tool wear rate (TWR), and surface roughness (SR). The best parametric combinations have been suggested to obtain the desired quality characteristics. The interaction effects among various parameters have also been presented. An increase of approximately 18% in MRR and a reduction of 26% and 11% in TWR and SR, respectively, were observed, during the machining through CEDM in contrast to EDM. The confirmatory experiments suggested that experimental values were in permissible agreement with the predicted values for all the performance measures. Finally, the comparison of the CEDM with that of EDM process, in the light of SEM graphs, has been presented.     

Development of magnetically assisted lapping process for nano-finishing of alumina balls

The advanced ceramics have emerged as a successful alternative to the conventional materials used in ball bearing industry. However, extreme hardness and lower toughness of the ceramic balls make their finishing a challenging task. To address this problem, a novel process is developed and results are presented in this article. The process is termed as magnetically assisted lapping (MAL) wherein the lapping and the polishing action are supported by magnetic levitation. The process parameters are identified. The capability of the process in terms of surface finish, roundness and material removal rate of alumina balls is assessed. The process is carried out in two stages. In the first stage, the main focus is on material removal and sphericity while the second stage focuses on achieving nano level surface finish. A very high material removal rate of 2.5 µm/min is achieved in the first stage. In the second stage, diamond abrasive powder (0.25–1 µm) mixed with silicone oil is used as a polishing medium for fine finishing of balls. The final surface finish of 20?nm and roundness of 0.23 µm is achieved which meets the requirement of G10 grade bearings (as per ISO3290). Atomic force microscope images show remarkable improvement of the surface up to 8?nm. The developed process is capable of producing nanometric finish in quite lesser time as compared to conventional and eccentric lapping processes. The underlying mechanism of material removal is proposed with the help of scanning electron microscope and atomic force microscope images.