Non Traditional Machining

Abrasive waterjet machining (AWJM) is a new machining process, the advantages of which include low cutting temperatures, no heat damage to the material being cut, minimal dust, and low cutting forces. This paper presents a state of the art review of research in this new process. The main topics discussed are mechanics of material removal, productivity, cutting forces, surface quality and nozzle wear.

Electric discharge machining (EDM), sometimes colloquially also
referred to as spark machining, spark eroding, burning, die sinking or
wire erosion, is a manufacturing process whereby a desired shape is
obtained using electrical discharges (sparks). Material is removed
from the workpiece by a series of rapidly recurring current discharges
between two electrodes, separated by a dielectric liquid and subject
to an electric voltage. One of the electrodes is called the toolelectrode, or simply the ‘tool’ or ‘electrode’, while the other is called
the workpiece-electrode, or ‘workpiece’. EDM will help and support
the drive to quality cost and delivery. Knowledge of EDM will provide
the ability to design parts that are not possible or cost effective to
produce by any other method. The prospect of machining complex
shapes in hardened or exotic materials will continue to attract
engineers and designers to produce more challenging parts and
profile.

This article highlights and focuses on laser beam machining (LBM) of aluminum and its alloys. It begins by providing a brief overview of various conventional (chip forming) and nonconventional machining techniques employed for aluminum-based materials. Later, it explicitly provides features of LBM techniques employed for aluminum and its alloys for different types of machining.

Despite the large number of abrasive waterjet machining (AWJM) models developed so far, there still has been confusion about the nature by which workpiece surfaces are eroded. The finite element method (FEM) could provide both qualitative and quantitative means in order to explain the AWJ erosion process. This paper presents an attempt to model the AWJM process using the powerful tool of the finite element method. The main objective is to develop an FE model which would enable to predict the depth of cut without any cutting experiments. The new model takes into account the precise representation of the constitutive behaviour of the workpiece material under AWJ dynamic loading conditions. Interaction of the abrasive particle with the workpiece material is traced at small time increments. The model accurately predicts the depth of cut as a result of AWJ impact and the results are in good agreement with experimental results.

Despite the large number of abrasive waterjet machining (AWJM) models developed so far, there still has been confusion about the nature by which workpiece surfaces are eroded. It is believed that analysis of stresses generated at the AWJ cutting interafce could provide deeper insight to explain such an erosion behavior. This paper presents a stress analysis of AWJM using a nonlinear dynamic finite element (FE) code in order to explain the behaviour of the process. The main objective is to develop an erosion mechanism which would correctly describe the abrasive-material interaction. The new model considers both AWJ dynamic loading conditions and nonlinear material behavior. The results show that the workpiece material fails due to highly localized plastic deformation caused by compressive stresses, specially at the AWJ cutting interface. Also AWJM causes residual stresses to remain in the workpiece material after machining.

Conventional machining of polymeric composite materials is often both technically and economically less effective because the structural characteristics inherent in fibre reinforcement promote excessive tool wear. In recent years, abrasive waterjet machining (AWJM) has been proving to be successful in the machining of such materials. This paper presents a state of the art review of research in AWJM of polymeric composite materials. Among the main topics discussed are mechanisms of material removal, productivity and surface quality

Erosion of ductile materials by abrasive waterjet machining (AWJM) is still a complex phenomenon. This paper presents a first attempt to simulate the abrasive waterjet machining (AWJM) process using the finite element method (FEM) in order to determine the workpiece response in this erosive wear process. Additionally, deformations occurring in the workpiece material in the vicinity of the cutting interface as a result of the high speed AWJ impact could be obtained. The results indicate that the finite element method is a useful tool in the prediction of the AWJ deformations.

Understanding the exact nature of erosion of workpiece materials by abrasive waterjet machining (AWJM) is still confused, although it is important for successful modeling of this promising process. This paper presents a first attempt to model the AWJM process using the powerful tool of the finite element method (FEM) in order to explain the abrasive particle-workpiece interaction. Also the model predicts the behaviour of the process. The main objective is to develop an FE model which would enable to predict the depth of cut without any cutting experiments. The new model takes into account the precise representation of the constitutive behaviour of the workpiece material under AWJ dynamic loading conditions which was ignored in previous AWJM models in which the flow stress was represented by a constant value. Additionally, deformations, stresses and strains occurring in the workpiece material in the vicinity of the cutting interface as a result of the erosion impact by AWJ, could be obtained. In the present model, forces acting on the abrasive particle need not be initially determined, as in previous AWJM studies, as they are automatically calculated at each time step. The results show that the finite element method is a useful tool in predicting abrasive-material interaction and AWJ depth of cut.

Modeling of abrasive waterjet machining (AWJM) has been finding widespread interest for the past twenty years. Due to the complex interaction of several AWJM parameters, combined with the nonlinear dynamic high speed impact of several thousands of small abrasive particles on the workpiece surface, the mechanism of material removal has not yet been fully understood. The current paper presents an attempt to explain the mechanism of material removal in AWJ, as a result of abrasive particle impact through step by step tracing of the abrasive particle as it is interacting with the workpiece material. The new model considers the elastic-plastic behavior of the workpiece material. Also the non linear dynamic loading conditions which are characteristic feautres of AWJM are accounted for in the pesent study. The failure of the workpiece material is examined analytically, by means of a virtual finite element (FE) AWJ experiment, and experimentally, by means of scanning electron microscopy (SEM) and surface topographies. Stress results indicate that the workpiece material is subject to severe highly localized plastic deformation and as a result, small overlapping craters are generated. These craters are formed by high compressive stresses at the cutting interface. The finite element results indicate a good agreement with experimental results.

In order to realize the manufacturing/machining demands thrived by newer, hard and difficult-to-machine materials being utilized in the present day industries, an assortment of non-traditional machining (NTM) processes has been developed over the past few decades. These processes are capable of generating intricate and complex shapes with high degree of accuracy, close dimensional tolerance and better surface finish. In this paper, a decision guidance framework is developed in Visual BASIC 6.0 to help the process engineers in selecting the most appropriate NTM process for a specific work material and shape feature combination. It also assists in identifying the ideal process parameter combinations for the most suitable NTM process. The derived results highly corroborate with the opinions of the experts in the related field, demonstrating the acceptability of the developed system.

Although several theoretical and experimental models have been developed for abrasive waterjet machining #AWJM), the exact nature of
erosion is not yet understood. This paper presents an attempt to model AWJM using the ®nite element method #FEM) in order to explain the
abrasive particle±workpiece interaction process. Also, the model predicts the depth of deformation as a result of abrasive particle impact.
The main objective is to develop an FE model which would enable the prediction of the depth of cut without any cutting experiments. The
new model takes into account the precise representation of the constitutive behavior of the workpiece material under AWJ dynamic loading
conditions which was ignored in the previous AWJM models. In the present model, forces acting on the abrasive particle need not be
initially determined, as in previous AWJM studies, as they are automatically calculated at each time step. The results show that plastic
deformation is very localized. Finally, the present FE results are consistent with experimental results.

Erosion of ductile materials by waterjet machining is still a complex phenomenon. This paper presents a finite element model of the waterjet machining (WJM) process. Cutting forces, deformations and stresses occurring in the workpiece material in the vicinity of the cutting interface as a result of erosion impact by the waterjet could be obtained. The results indicate that the finite element method is a useful tool in the analysis of  this process. Further research work is currently being conducted by the authors.

The main functions which feature the developed wire vibration detection and analysis system are: To be able to measure the wire position and displacement during machine idling as well as during EDM cutting. To perform a vibration analysis, based on the gathered data during the wire vibration measurements. This also in both modes, machining and idling. The vibration analysis includes, graphical output of the wire displacement data in a 2-D plane, Past Fourier Transform calculation (PFT), calculation of wire damping ratios, and frequency spectrum analysis.

This paper reports the effects of machining parameters on surface roughness in cylindrical wire electrical discharge grinding (WEDG) process. In this research tungsten carbide is used as workpiece. A rotary axis spindle is set up in the electric discharge machine in a submerged dielectric environment so as to machine cylindrical parts. The speed of the spindle is maintained constant at 200 rpm. Experiments have been under different process conditions like peak current, voltage, pulse off time and number of passes. Number of passes in the wire electric discharge grinding decreases the surface roughness.

The experimental investigation of material removal rate, and micro hardness during machining of OHNS steel using
EDM machine was study in this paper. The input parameters include peak current, pulse on time; voltage gap and
flushing pressure were used for experimental work. Mean effect plot and S/N ratio graphs have been used to
optimize the machining parameters of EDM on OHNS steel using the Taguchi method and ANOVA methods. It can
be observed that Current has the largest effect on the material removal rate of OHNS steel by machining. It can be
observed that flushing pressure has the largest effect on the hardness of OHNS steel by machining. The optimum
machining condition for material removal rate (MRR) with positive polarity are Current (30 A), Pulse-on (100 µs)
Voltage Gap (10 v) and flushing pressure (20 lb/in2). The optimum machining condition for with positive polarity
for hardness are, Current (10 amp.), Pulse-on (100 µs), voltage gap (20 volt) and flushing pressure (10 lb/in2).

Aim of the experimental investigation was to determine the
effect of electric discharge machining parameters on surface
roughness of oil hardened non shrinkable (O6) steel. Though
vast research has been done to improve the surface finish of hard
metal machined by EDM, optimal choice of parameters for best
performance measures is still challenge. The experiments were
carried out on adequate range of machining parameters. Selected
input parameters for this study were peak current, pulse-on-time,
and pulse-off-time. Pure copper electrode with positive polarity
in dielectric medium was used to perform the investigation. The
optimal machining parameters peak current (8 Amp), pulse on (45
μs) and pulse off (9 μs) were originated by using Taguchi method
and ANOVA analysis. Design of experiment approach was used to
model the experimental data. It is found that interactions between
Peak current, pulse on, Voltage Gap and Flushing Pressure have
significant effect on the surface roughness.

Abrasive waterjet cutting is one of the unconventional cutting processes capable of cutting extensive range of difficult-to-cut materials. This paper assesses the impact of process parameters on surface roughness which is a significant machining performance measure in abrasive waterjet cutting of hastelloy. The experimental parameters were selected based on Taguch's design of experiments. Experiments were conducted in varying nozzle traverse speed, abrasive mass flow rate and standoff distance for cutting hastelloy using abrasive waterjet cutting process. The effects of these parameters on surface roughness have been discussed.

Nickel-based superalloy Inconel 718 is one of the hardest materials owing to its high hardness and additional physical properties. It is the most commonly used superalloy in gas turbine, aerospace, and automobile sectors. Micro-milling is generally employed for precision manufacturing of tiny structures, but it is difficult to obtain good surface quality with micro-milling Inconel 718 because of its excellent mechanical properties like high strength and hardness. Atmospheric pressure cold plasma jet can effectively improve surface wettability without changing surface micromorphology, which is expected to have positive lubricating effects in micro-machining of difficult-to-cut materials. In addition, minimum quantity lubrication can induce coolants into the machining area more efficiently, and is especially appropriate for micro-machining. In this paper, we propose a composite micro-milling method combining plasma jet and minimum quantity lubrication to machine Inconel 718. The effect of plasma jet on machinability is investigated by performing micro-milling experiments under different atmospheres (dry, nitrogen jet, plasma jet, minimum quantity lubrication, and plasma + minimum quantity lubrication). Surface roughness, cutting forces, and residual stress are the measures using corresponding techniques. The results indicate that the atmospheric pressure cold plasma jet can efficiently improve surface quality and reduce cutting forces of Inconel 718.

In this paper, the effect of chromium powder mixed dielectric fluid on machining characteristics of AISI D2 die steel has been studied. Peak current, pulse on time, pulse off time, concentration of powder are the process parameters. The process performance is measured in terms of material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR). The research outcome will identify the important process parameters that maximize MRR, minimize TWR and SR. The design of experiment has been undertaken using Taguchi method. ANOVA analysis has been used to investigate the percentage contribution of each process parameter for optimizing the performance. The study indicates that all the selected parameters except pulse off time have a significant effect on MRR. Current is found to be the most significant factor for MRR and TWR. With increase in current, TWR increases. Also, surface roughness increases with increase in pulse off time.

The present study focuses on optimizing the process parameters during machining of NiTi (Nickel-Titanium) shape memory alloy by wire electric discharge machining (Wire EDM) for simultaneously maximizing material removal rate and minimizing tool wear rate u sing brass wire as electrode. Taguchi's design with utility and modified utility optimization techniques have been used for simultaneous multi-response optimization. Different analyses were performed to determine the optimal settings in both utility and mo dified utility concepts. The optimal results of both methods disclose that the pulse on time of 115µsec and pulse off time of 40µsec with spark gap set voltage of 20V are useful for maximizing material removal rate and minimizing tool wear rate. The optimization results indicate that the spark gap set voltage is the majority significant parameter that affects the tool wear rate and material removal rate.

Nickel alloys possess the excellent potential at high temperature and resistance to oxidation/corrosion owing to its high nickel content. These materials necessitate non-traditional machining methods. The rotary ultrasonic machining (RUM) process comes into existence as a superior alternative to the conventional machining of nickel alloys. The processing of these alloys using RUM needs attention. This article details the multi-response optimization in RUM of nickel alloy using the desirability concept. The present work is carried out with two shapes of the tool: (i) Plain tool and (ii) lateral slotted tool. During RUM, the process parameters-power rating tool rotation, abrasive diamond grit size and feed rate are varied. Compared with the plain tool, the lateral slotted tool shows the more efficient machining rate (MR) with less tool wear (TW). The micro-graphs disclose the mechanism of MR and TW during RUM.