H. S. Shan

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.

Multi-Response Optimization of CFAAFM Process Through Taguchi Method and Utility Concept

Centrifugal force assisted abrasive flow machining (CFAAFM) process has recently been tried as a hybrid machining process with the aim towards the performance improvement of AFM process by applying centrifugal force on the abrasive laden media with a rotating centrifugal force generating (CFG) rod introduced in the work piece passage. For optimization of process parameters, an approach based on a Utility theory and Taguchi quality loss function (TQLF) has been applied to CFAAFM for simultaneous optimization of more than one response characteristics. Three potential response parameters i.e., material removal, % improvement of surface finish and scatter of surface roughness over the fine finished surface of a sleeve type work piece of brass are examined. Utility values based upon these response parameters have been analyzed for optimization by using Taguchi approach.

Wear behavior of materials in magnetically assisted abrasive flow machining

Abstract The finish machining of precision components constitutes one of the most challenging and expensive stages in a manufacturing process. Abrasive flow machining (AFM) is a non-traditional machining technique, which is capable of providing excellent surface finish on difficult-to-approach regions on a wide range of components. Not much research work has hitherto been reported regarding process behavior and performance improvement of AFM. This paper reports the results of an experimental study (mixed factorial design) conducted with the objective to understand the mechanism of material removal (MR) and the wear behavior of some materials when processed by AFM and magnetically assisted abrasive flow machining. Scanning electron microscopy (SEM) has been used to gain insight into the underlying wear pattern on the surfaces of different materials. The results suggest that the magnetic field has a strong effect on the MR in AFM. Furthermore, the nature of work material plays an important role in controlling the MR on the surface.

ABRASIVE FLOW MACHINING WITH ADDITIONAL CENTRIFUGAL FORCE APPLIED TO THE MEDIA

Abrasive flow machining (AFM) is one of the important non-traditional metal finishing technologies which was introduced during the late 1960s. The process has found applications in a wide range of fields such as aerospace, defence, surgical and tool manufacturing industries. Recently, an effort has been made towards the performance improvement of this process by applying centrifugal force on the abrasive media with the use of a rotating centrifugal force generating (CFG) rod introduced in the workpiece passage. The results have been encouraging. The present paper discusses the results of changing the parameters like shape and rotational speed of CFG rod, extrusion pressure, number of process cycles and abrasive grit size. The results indicate that all the input variables have significant effect on the response parameters, which for the present study were taken as material removal and surface roughness. An analytical model is proposed for the velocity and the angle at which abrasive particles attack the workpiece surface in the process.

Parametric Optimization of Centrifugal Force-Assisted Abrasive Flow Machining (CFAAFM) by the Taguchi Method

Extrusion honing, known as abrasive flow machining (AFM), deburrs, polishes, and radiuses surfaces and edges by flowing an abrasive-laden media over these areas. The process is particularly used on internal shapes that are difficult to process by other nonconventional machining processes. Because abrasive action occurs only in areas where the flow is restricted, tooling is used to direct the media to the appropriate areas. Like other nonconventional machining processes, AFM has the limitation of lower material removal rates. The application of centrifugal force (by using rotating rectangular rod inside the hollow workpiece) has been explored for the productivity enhancement of the process. This article reports that centrifugal force enhances the material removal rate (MRR) and improves the scatter of surface roughness (SSR) value in AFM. It outlines the development of a system that determines sets of viable process parameters for a new process called centrifugal force-assisted abrasive flow machining (CFAAFM). Cylindrical workpieces of brass are used for the experiment. During the experiments, parameters, such as rotational speed of rectangular rod, extrusion pressure, and grit size, were varied to explore their effect on material removal and scatter of surface roughness. Taguchis parameter design strategy has been applied to investigate the effect of process parameters on the MRR and SSR values.

Experimental Studies on Mechanism of Material Removal in Abrasive Flow Machining Process

In this article, the mechanism of material removal (MR) in Abrasive Flow Machining (AFM) process has been studied. Representative components of pure Aluminum and Brass were processed by AFM under similar process conditions. The processed surfaces were analyzed with the help of Scanning Electron Microscopy (SEM). SEM photographs reveal noticeable difference between abrasion patterns produced on the processed surfaces of both the materials. A mechanism of MR has been proposed by examining the nature of interaction between the flowing abrasive medium and target work surfaces of selected materials.

Analysis of Roundness Error and Surface Roughness in the Electro Jet Drilling Process

ABSTRACT A modern trend towards miniaturization has given a new impetus to the development of nontraditional small hole drilling techniques. Electro jet drilling (EJD) is one such promising technique, and is finding ever-increasing applications in several industries including aerospace, space, medical, automobile, and microfabrication (electronics and computers). This paper reports experimental findings on the effects of important process parameters such as applied voltage, capillary outside diameter, feed rate, electrolyte concentration, and inlet electrolyte pressure on the quality of small holes (<800 μm dia) produced by using the EJD process. Roundness error and surface roughness have been used as response parameters for evaluating the quality of the holes. The experiments were performed on SUPERNI 263A material. An analysis of variance (ANOVA) performed to test the significance of the variables at the 5% level indicates that applied voltage and electrolyte concentration significantly affect the response parameters.

Optimal Selection of Machining Conditions in the Electrojet Drilling Process Using Hybrid NN-DF-GA Approach

This article presents a hybrid neural network, desirability function, and genetic algorithm (NN-DF-GA) approach for optimal selection of the input process parameters for optimizing the multiresponse parameters of the electrojet drilling (EJD) process. EJD is a promising nontraditional machining technique that is used for machining microholes (<1 mm in diameter) in difficult-to-machine materials. The proposed approach first uses a back propagation neural network to formulate a fitness function for predicting the response parameters of the process. From the network output, the desirability method obtains a composite fitness function for further use in the genetic algorithm. The genetic algorithm predicts the optimal input parametric combinations and simultaneously optimizes the multiresponse characteristics of the process. Simulated results confirm the feasibility of this approach and show a good agreement with experimental results for a wide range of machining conditions.

Effect of Process Parameters on the Solidification Time of Al-7%Si Alloy Castings Produced by VAEPC Process

Casting is a manufacturing route that is of fundamental importance in the processing of metals because of its ability to produce complex shapes cheaply. A recent development, the Evaporative Pattern Casting (EPC) process, holds the promise of revolutionizing the manufacture of castings, making the process even more economically attractive. One serious limitation of this process is blow holes in the castings. The blow holes and/or gas porosity in EPC castings is because of the non-escape of the gas produced as a result of burning of polystyrene pattern in the sand mold. The hybrid-casting process is developed to improve the quality of castings. The developed hybrid-casting process has been termed as Vacuum-Assisted Evaporative Pattern Casting (VAEPC) process. This aricle investigates the effect of process parameters like degree of vacuum, pouring temperature, grain fineness number, amplitude of vibration, and time of vibration on the solidification time of Al-7%Si alloy castings. In order to evaluate the effect of selected process parameters, the Response Surface Methodology (RSM) is used to formulate a mathematical model that correlates the independent process parameters with the desired solidification time. The central composite rotatable design has been used to conduct the experiments. The analysis of results indicates that the solidification time decreases with increase in the degree of vacuum, amplitude of vibration, and time of vibration. However, solidification time increases with increase in pouring temperature and grain fineness number.

Percussion Laser-Drilled Holes: Characteristics and Characterization Procedure

Percussion laser drilling, being a thermal process, produces holes having widely differing characteristics than that of the mechanically drilled holes. In the present study, on the percussion laser drilling of through holes in a nickel-based superalloy (SUPERNI 263A), 21 characteristics were identified, and the methods of their determination were proposed. The effect of peak power of laser pulses on the identified hole characteristics were studied.