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ANNAMACHARYA INSTITUTE
OF TECHNOLOGY &SCIENCES
(Approved by A.I.C.T.E, New Delhi, Affiliated to JNT University, Anantapur)
Tirupati, Chittoor Dist. (A.P)
EXPERIMENTAL INVESTIGATION ON
EFFECTS OF CUTTING PARAMETERS ON
MRR IN WIRE-EDM PROCESS
(INCONEL- 825)
Submitted by
P.CHAITANYA 12AK1A0309
P.LEELA SAGAR 12AK1A0326
K.KARTHEEK 12AK1A0322
K.BALAJI 12AK1A0305
S.RAHULSRINIVAS 12AK1A0343
Under the esteemed guidance of
Mr. M.MARUTHI RAO,
M .Tech, ( Ph. D)
Assistant professor,
Department of Mechanical Engineering
ABSTRACT
Wire Electrical Discharge Machining (WEDM) is one of the important
non- traditional machining processes. The Wire Electrical Discharge
Machining plays an important role in manufacturing sectors especially
industries like aerospace, automobile and general engineering etc. Intricate
profiles used in bio medical applications can also be done in WEDM .
INCONEL-825 is a nickel-based high-temperature strength super alloy
found applications in aerospace, missile, nuclear power, chemical and petro
chemical, heat treatment, marine and space shuttle components. The
characteristics such as higher strain hardening tendency, high dynamic
shear strength and poor thermal diffusivity are the major causes of
difficulty in machining of this alloy. These, in turn , produce higher cutting
forces, highly strain hardened and toughened chips and cause surface
damages extending to subsurface levels. All these effects, in general,
hamper the machinability of this alloy .owing to all these problems, it is
very difficult to machine INCONEL-825 by conventional machining
processes and moreover, by conventionally used tool materials.
• Hence the present work focused on optimization of process parameters in Wire Electrical Discharge Machining of Inconel-825 super alloy.In the present work, Taguchi's orthogonal array L27 .Each experiment was conducted under different conditions of input parameters is Pulse on Time, Pulse off Time, Flushing pressure Of Dielectric fluid, spark gap voltage, servo feed, Cutting speed.
• By using Minitab software by considering machining parameters: servo feed, servo voltage, cutting speed.
• The experiments were carried out on Inconel-825 Using ultra cut 843 CNC WEDM machine according to Taguchi experimental design . The experimental responses such as material removal rate(MRR) are recorded for experimental run. This experimental data is analysed using optimization methods : Taguchi method for process parameters optimization. The confirmation results of obtained optimum parameter combinations are evaluated and the best combination is selected. With this best combination , the goal of maximization of material removal rate (MRR) is achieved.
• W I R E E L E C T R I C A L D I S C H A R G E M A C H I N I N G ( W E D M ) I S O N E O F T H E M O S T I M P O RTA N T N O N - T R A D I T I O N A L M A C H I N I N G P R O C E S S E S .
• H E N C E , N O N - T R A D I T I O N A L M A C H I N I N G M E T H O D S I N C L U D I N G E L E C T R O C H E M I C A L M A C H I N I N G , U LT R A S O N I C M A C H I N I N G , E L E C T R I C A L D I S C H A R G I N G M A C H I N I N G ( E D M ) E T C . A R E A P P L I E D T O M A C H I N E S U C H D I F F I C U LT T O M A C H I N E M AT E R I A L S .
• W I R E E L E C T R I C A L D I S C H A R G E M A C H I N I N G ( W E D M ) P R O C E S S W I T H A T H I N W I R E A S A N E L E C T R O D E T R A N S F O R M S E L E C T R I C A L E N E R G Y T O T H E R M A L E N E R G Y F O R C U T T I N G M AT E R I A L S . W I T H T H I S P R O C E S S , A L L O Y S T E E L , C O N D U C T I V E C E R A M I C S A N D A E R O S PA C E M AT E R I A L S C A N B E M A C H I N E D I R R E S P E C T I V E O F T H E I R H A R D N E S S A N D T O U G H N E S S .
• F U RT H E R M O R E , W E D M I S A C A PA B L E O F P R O D U C I N G A F I N E , P R E C I S E , C O R R O S I O N A N D W E A R R E S I S TA N T S U R FA C E .
•. H O W E V E R , W E D M U T I L I Z E S A C O N T I N U O U S LY T R AV E L L I N G W I R E E L E C T R O D E M A D E O F T H I N C O P P E R , B R A S S O R T U N G S T E N O F D I A M E T E R 0 . 0 5 - 0 . 3 0 M M , W H I C H I S C A PA B L E O F A C H I E V I N G V E RY S M A L L C O R N E R R A D I I .
• T H E W I R E I S K E P T I N T E N S I O N U S I N G A M E C H A N I C A L T E N S I O N I N G D E V I C E R E D U C I N G T H E T E N D E N C Y O F P R O D U C I N G I N A C C U R AT E PA RT S . D U R I N G T H E W E D M P R O C E S S , T H E M AT E R I A L I S E R O D E D A H E A D O F T H E W I R E A N D T H E R E I S N O D I R E C T C O N TA C T B E T W E E N T H E W O R K P I E C E A N D T H E W I R E , E L I M I N AT I N G T H E M E C H A N I C A L S T R E S S E S D U R I N G M A C H I N I N G .
Introduction
Schematic diagram of the basic principle
of WEDM process
BASIC PRINCIPLE OF WEDM PROCESS
The main table moves along X and Y axes and it is driven
by the D. C servo motors.
The travelling wire is continuously fed from wire feed
spool and collected on take up spool which moves
through the work piece and is supported under tension
between a pair of wire guides located at the opposite sides
of the work piece.
The lower wire guide is stationary and moves according
to the upper wire guide.
BASIC PRINCIPLE OF WEDM PROCESS
A series of electrical pulses generated by the pulse
generator unit is applied between the work piece and the
travelling wire electrode, to cause the electro erosion of
the work piece material.
While the machining operation is continuous, the
machining zone is continuously flushed with water
passing through the nozzle on both sides of work piece.
Pictorial View of WEDM Machine Tool
History of WEDM
In 1969, the SWISS FIRM 'AGIE' produced the world's first WEDM, the process was fairly simple, not complicated and wire choices were limited to copper and brass only.
Early WEDM produced were extremely slow but as more and more research was done WEDM, cutting speed and overall capabilities of WEDM have been modified. In the early 70's a typical machine cut 2 square inches per hour (i. e. 21mm/min, in the early 80's, 6 square inches per hour (i. e.64mm2/min), however WEDM which are under operation today can cut 20 times faster than these earlier machines.
In recent years, the technology of WEDM has been improved significantly to meet the requirements in various manufacturing need, especially in the precision mold and die industry
. WEDM has greatly improved in terms of accuracy, quality, productivity and precision, thus immensely helped the tooling and manufacturing industry. WEDN=M operated in industry today are equipped with Computer Numerical Control (CNC) which helps in improving efficiency and accuracy[103]
WEDM Cutting gap
Importance of WEDM in industry
Wire Electrical Discharge Machining (WEDM) technology has grown tremendously since it was first applied more than 30 years ago. IN 1974, D.H. Dulebohnapplied the optical-line follower system to automatically control the shape of the components to be machined by the WEDM process.
By 1975,its popularity rapidly increased, as the process and its capabilities were better understood by the industry. It was only towards the end of the 1970s, when Computer Numerical Control (CNC) system was initiated into WEDM. which brought about a major evolution of the machining process (Ho et. al., 2004).
Features of WEDM
Multi pass facility (Up to 60-70mm height in punch and up to 100-120mm height in cavity)
Can cut a minimum radius of 0.08mm.
Total connected power of machine is 1.5KVA.
Low running cost.
Paper filter not required. Reusable fine mesh filtering system provided.
Can cut up to 500mm height.
Soft water and soap gel is mixed and used as a coolant, which gives a good surface finish, anti- corrosive protection to the components as well as machine.
Easy maintenance.
Can obtain a surface finish of 1.25µRa in multi pass machine (under appropriate parameter setting and standard test conditions).
New programs can be entered while cutting previous program.
Auto centre find, auto edge find, auto shift off at wire breakage and auto stop at the end of job.
Major components of WEDM
Work Table
Types Of Wires
1. Copper
2. Brass wires
3. Coated Wires
4. Fine wires (Molybdenum and Tungsten)
Electric Discharge power unit
Dielectric fluid
Filtration
INPUT PARAMETERS
Pulse ON Time
Pulse OFF Time
Flushing Pressure of Dielectric fluid
Servo Feed
Spark Gap
Cutting speed
INPUT PROCESS PARAMETERS
Pulse ON time
During This time the voltage is applied across the
electrode
Pulse OFF time
During this time the voltage is absent during the part of
the cycle.
INPUT PROCESS PARAMETERS
Spark gap set voltage
This sets the gap voltage between the wire and the work
piece. Lowering this setting makes this gap smaller.
Wire Feed
Wire feed is the rate at which the wire-electrode travels
along the wire guide path and is fed continuously for
sparking.
INPUT PROCESS PARAMETERS
Wire Tension
Wire tension is the amount of tension on the wire as it is
driven through its cutting motions.
It determines how much the wire is to be stretched
between upper and lower guides.
Servo Feed Set Voltage
Pulse peak voltage setting is for selection of open gap
votage.
INPUT PROCESS PARAMETERS
Flushing Water Pressure
This is because the small particles created by the EDM
process must be removed from the work area, otherwise
double burning of these particles will occur and the
insulation properties of the dielectric are eliminated
resulting in unstable cutting.
Servo Feed
It decides the servo speed, it can vary in proportion with
the gap voltage or can be held constant while machining.
OUTPUT PARAMETERS
MATERIAL REMOVAL RATE (MRR)
SURFACE ROUGHNESS
DIMENSIONAL DEVIATION
GAP CURRENT
OUTPUT PROCESS PARAMETERS
Material Removal Rate
Surface Roughness
Dimensional Deviation
Material Removal Rate
For WEDM, MRR is a desirable characteristic and it
should be as high as possible to give least machine cycle
time leading to increased productivity.
OUTPUT PROCESS PARAMETERS
Surface Roughness
Irregularities in the surface may form nucleation sites for
cracks or corrosion. Roughness is the measure of the
texture of a surface
Dimensional Deviation
It has been found that spark gap is an important response
decides the accuracy of the machined component in
WEDM.
Chemical composition of Inconel-825
Properties of Inconel-825
Advantages of WEDM Process
As continuously travelling wire is used as the negative electrode fabrication is no required as in EDM.
There is no direct contact between the work piece and the wire, eliminating mechanical stressed during machining.
WEDM process can be applied to all electrically conducting materials and alloys irrespective of their melting points, hardness, toughness or brittleness.
Users can run their work pieces over night or over the weekend unattended
Disadvantages of WEDM Process
High capital cost is required for WEDM process.
There is a problem regarding the formation of recast layer.
WEDM process exhibits very slow cutting rate.
It is not applicable to very large work piece.
Preparation of specimens
OPTIMIZATION METHODS Taguchi's Method
The objective of the robust design is to find the controllable process parameter settings for which noise or variation has a minimal effect on the products functional characteristics.
It is to be noted that the aim is noted that the aim is not to find the parameter settings for the un controllable noise variables, but the controllable design variables. To attain this objective, the control parameters, also known as inner array variables, are mathematically varied as stipulated by the inner orthogonal array.
For each experiment of the inner array, a series of new experiments are conducted by varying the level settings of the uncontrollable noise variables. The level combinations of noise variables are done using the outer orthogonal array.
The influence of noise on the performance characteristics can be found using the S/N ratio. Where S is the standard deviation of the performance parameters for each inner array experiment and N is the total number of experiment in the outer orthogonal array.
This ratio indicates the functional variation due to noise. Using this result, it is possible to predict which control parameter settings will make the process insensitive to noise. Taguchi method focuses on robust design
APPLICATIONS OF ORTHOGONAL ARRAY
Taguchi's OA analysis is used to produce the best parameters for the optimum design process, With the least number of experiments
OA is usually applied in the design of engineering products, test and quality development ,and process development.
ADVANTAGES AND DISADVANTAGES OF ORTHOGONAL ARRAY
Conclusions valid over the entire region spanned by the control factors and their settings.
Large saving in the experiment effort.
Analysis is easy.
OA techniques are not applicable , such as a process involving influencing factors that vary in time and cannot be quantified exactly
PROCESS PARAMETERS AND LEVELS FOR WEDM
Experimental data and results for the response parameters material removal rate
Surface roughness Tester
Applications of WEDM Process
Medical
Dental
Optical
Jewellery industries
Automobiles
Aerospace
RESULTS AND DISCUSSIONSANLAYSIS OF TAGUCHI
signal to noise ratio:
Calculation of the S/N ratio depends on the experimental objective .
Taguchiʼs emphasis on minimizing deviation from target lead him to develop measures of the process output that incorporate both the location of the output as well as the variation. These measures are called signal to noise ratios.
The signal to noise ratio provides a measure of the impact of noise factors on performance. The larger the S/N, the more robust the product is against noise
Response table for signal to noise ratios
Response Table for Means
Normal probability plotResponse is MRR
CONCLUSIONS
The results obtained in this study lead to conclusions for machining of INCONEL-825 After conducting the experiments and analyzing the resulting data.
1. From the results obtained by experiment, the influence on the response parameter Metal Removal Rate (MRR) by cutting parameters like servo voltage, servo feed and cutting speed of cut
a: The speed of cut has the variable effect on the Metal removal rate , servo voltage and servo feed an approximate decreasing trend.
2. The design of experiments (DOE), Taguchi method is applied for optimization of cutting parameters and analysis of variance (ANOVA) is done and found that
a: The optima combination of process parameters for minimum Metal removal rate is obtained cutting speed 40 m/min, servo feed 2100 mm/min and servo voltage 20 v voltage.
3. ANOVA shows that the cutting speed has great influence for the response Metal Removal rate (MRR) and its percentage contribution to the metal removal rate is determined to be
4. Using the experimental data, a multi linear regression model is developed and the values obtained for the response MRR is compared with measured values. A graph was plotted between Regression predicted values and experimentally measured values and shows that the models are adequate without any violation of independence or constant assumption
FUTURE SCOPE OF THE WORK
The effect of tool vibration, Work piece toughness, cutting fluid, tool material ,and work material can be considered as they have great influence on Metal removal rate and cutting forces. so , including all those along with cutting speed, servo feed, servo voltage and surface roughness may be calculated
ANY QUERIES?
THANK YOU