Experimental Investigation on Finishing of Inner Surfaces of Tubes Using Magnetic Abrasives

7/22/2019 Experimental Investigation on Finishing of Inner Surfaces of Tubes Using Magnetic Abrasives

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EXPERIMENTAL INVESTIGATION ON FINISHING OF INNER SURFACES OF

TUBES USING MAGNETIC ABRASIVES

CAPSTONE PROJECT-II

Submitted in partial fulfillment of the

Requirement for the award of the

Degree of

BACHELOR OF TECHNOLOGY

IN

MECHANICAL ENGINEERING

BY

ASHISH PANDAY Registration number: 10906000

RAHUL KUMAR Registration number: 10901641

KETAN KUMAR SINHA Registration number: 10907987

MOHAMMAD RAFI Registration number: 10902272

Under the guidance of

Jaiinderpreet singh, Astt. Professor

Discipline of mechanical engineering

Lovely professional university

Months and year of submissionApril 2013


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CERTIFICATE

This is to certify that the Capstone project titled INTERNAL FINISHING OF

CYLINDRICAL PIPES USING SINTERED MAGNETIC ABRASIVES that is

being submitted by Ashish panday , Rahul kumar , Ketan kumar sinha , Mohammad rafi is in partial

fulfillment of the requirements for the award of BECHOLER OF TECHNOLOGY DEGREE, is a record of

bonafide work done under my /our guidance. The contents of this Capstone project , in full or in parts, have

neither been taken from any other source nor have been submitted to any other Institute or University for award

of any degree or diploma and the same is certified.

Name:jaiinderpreet singh

U.ID:

Designation: Asst. Professor

(Name of the Organization)

(Organization stamp)


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ACKNOWLEDGEMENT

A research work owes its success from commencement to completion, to the people in love

with researchers at various stages. Let me in this page express my gratitude to all those who

helped me in various stage of this study. First of all, I would like to express my sincere

gratitude to Almighty GOD.

With immense pleasure, we wish to express our gratitude to our mentor Mr jaiinderpeet singh

for his excellent guidance, motivation, constant encouragement and co-operation during the

course of this work. It has been indeed an enriching scientific experience to work with him.

Last but not the least, the supporting staff of the institute assigned with the lab duties deserve

to be profusely thanked for helping me in carrying out my task.


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DECLARATION

We hereby declare that the project work entitled INTERNAL FINISHING OF

CYLINDRICAL PIPES USING SINTERED MAGNETIC ABRASIVES is an

authentic record of our own work carried out as requirements of Capstone Project (Part-II) for the award of

degree of B.Tech in Mechanical Engineering (152) from Lovely Professional University, Phagwara, under the

guidance of Mr. jaiinderpreet singh.

Project Group Number: G

Name of Student 1: Ashish pandayRegistration number: 10906000

Name of Student 2: Rahul KumarRegistration Number: 10901641

Name of Student 3: Ketan kumar sinhaRegistration Number: 10907987

Name of Student 4: Mohammad rafiRegistration Number: 10902272

(Signature of Student 1)





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Abstract

High purity gas and liquid piping system for critical applications, such as those required for

aerospace components and semiconductor plants, are required to provide smoothly finished

inner pipe surfaces to prevent the contamination of gas and liquid. This study presents the

application of one of emerging technique of finishing i.e. magnetic abrasive finishing (MAF)

for finishing the inner surfaces of brass tubes using Al2O3based sintered magnetic abrasives.

The Al2O3based sintered magnetic abrasives have been developed in sintering machine. The

experiments performed on brass tubes examine the effects of speed, magnetic flux density

(MFD), abrasive grit size and quantity of abrasives on the finishing characteristics. The

finished surface is highly dependent on the speed which increases number of cutting edges

takes part in machining; on MFD which affects strength as well as area of contact of the

magnetic brush with workpiece followed by abrasive grit size which controls the depth of cut

and the quantity of abrasives which increases the number of abrasive cutting edges. By

altering these conditions, this process will achieve surface finishes as fine as 0.05 m in

surface roughness (Ra). To understand the cutting mechanism of magnetic abrasive finishing

process, scanning electron microscopy (SEM) of the machined surfaces has been carried out.

An internal magnetic abrasive finishing (MAF) process will proposed to produce highly

finished inner surfaces of workpieces used in critical applications. The process principle and

the finishing characteristics of magnetic

abrasive finishing of cylindrical pipes using sintered magnetic abrasives are described in this

research work. The sintered magnetic abrasive is a mixture of Al2O3 abrasive and

ferromagnetic particles. The Al2O3 based sintered magnetic abrasives have been developed

in sintering machine. The surface roughness measurements resulting from finishing

experiments demonstrate the effects of the abrasive behavior on the surface modifications.

The surface finish will analysed in terms of percent improvement in surface finish (PISF).

Also surface finish will analysed using Response Surface Methodology (RSM). The obtained

minimum surface roughness was 0.05 m Ra. To further study the improvement in surface

finish, the surface was microscopically examined using X-Ray Diffraction (XRD).


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Abbreviations

Magnetic abrasive finishing (MAF).

Sintering, X-Ray diffraction (XRD).

Universal testing machine (UTM).

Magnetic flux density (MFD).


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Introduction

It is difficult to finish advanced engineering materials with high accuracy, and minimal

surface defects such as microcracks, by conventional grinding and polishing techniques. To

minimize the surface damage, gentle/flexible finishing conditions are required, namely, a low

level of controlled force. Magnetic field assisted manufacturing processes are becoming

effective in finishing, cleaning, deburring and burnishing of metal and advanced engineering

material parts. Magnetic Abrasive Finishing (MAF) is one of the non conventional machining

processes which came to the surface in 1938 in a patent by Harry P. Coats. The countries

which are involved in the study and development of this process are USA, CIS, France,

England, Bulgaria, Japan and Germany. In modern time, fine surface finish is in high demand

with the development of industry manufacturing technology, in a wide range of industrial

applications. A relatively new finishing advanced machining process in which cutting force is

primarily controlled by the magnetic field. A magnetic abrasive machining (MAF) process is

the one in which material is removed in such a way that surface finishing and deburring are

performed simultaneously with the applied magnetic field in the finishing zone and it can

achieve highly finished surfaces that conventional techniques never achieve.MAF is a fine

finishing technique

which can be employed to produce optical, mechanical, and electronic components with

micrometer or submicrometer form accuracy and surface roughness within nanometer range

with hardly any surface defects. Finishing of bearings, precision automotive components,

shafts, and artificial hip joints made of oxide ceramic and cobalt alloy are some of the

products for which this process can be applied. This process can be used to produce

efficiently good surface quality on at surfaces as well as internal and external surfaces of tube

type work pieces. The method can not only machine ferromagnetic materials such as steel,

but can also machine non ferromagnetic materials such as stainless steel, aluminium and

brass. The Abrasives generally rely upon a difference in hardness between the abrasive and

the material being worked upon, the abrasive being the harder of the two substances.

Shinmura studied the effects of different machining parameters like magnetic flux density,

vibration frequency and amplitude, machining time and pole-work gap on finishing

characteristics using sintered magnetic abrasives. They concluded that the two parameters

vibration and magnetic flux density remarkably affects the finishing efficiency. Shinmura


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prepared two types of magnetic abrasives by sintering. In first sample, diameter of iron

particle was varied and in second, diameter of abrasive particle varied. They reported that

diameter of iron particle effects both stock removal and surface finish. Influence of the

diameter of abrasive particle on stock removal was comparatively small while surface

roughness was remarkably affected. The diamond abrasives were mixed with iron to form

diamond magnetic abrasives by Shinmura and Aizawa . He concluded that finishing

efficiency increased with diamond magnetic abrasives with increase of speed of tool. He used

them for finishing of ceramics to get high surface finish. Results showed that machining

depth increases with increase of mixing weight percentage of iron particles. Khairy prepared

magnetic abrasives by blending of Al2O3(15%) and iron powders (85%), compacting them by

a bench press, sintering the mixture in a furnace at 1400 C in an inert environment, crushing

the compacts into small particles and then sieving to different ranges of sizes. The finishing

of silver steel bars was studied with these sintered magnetic abrasives for various

combinations of finishing parameters. Jain finished stainless steel workpiece material (non-

ferromagnetic) and observed that working gap and circumferential speed are the influential

parameters affecting the material removal and surface roughness value. Mori has studied the

process mechanism by using sintered magnetic abrasive particles. Kim has developed a new

type of magnetic abrasive composed of WC/Co sintered particles for cleaning the tubes, and

found the optimal finishing parameters. Yamaguchi and Shinmura studied the application of

MAF for finishing of the inner surfaces of alumina ceramic components using diamond based

magnetic abrasives. The experiments performed on alumina ceramic tubes examined the

effects of volume of lubricant, ferrous particle size, and abrasive grain size on the finishing

characteristics. Yamaguchi et al. proposed the finishing of SUS304 stainless steel bent tubes

using aluminium oxide composite magnetic abrasive with a mean diameter of 80 m. It

contains Al2O3with grain size less than 10 m sintered with iron in an inert gas atmosphere

with high pressure and temperature. A two phase finishing process controlling the size of the

ferrous particles was proposed to achieve efficient fine surface finishing. In particular, the use

of 150 m iron particles after 330 m iron particles was found to be effective. Wang and Hu

studied on the inner surface finishing of tubing by magnetic abrasive finishing. They used

three kinds of work materials i.e. Ly12 aluminium alloy, 316L stainless steel and H62 brass.

They concluded that material removal rate of brass is highest amongst all three materials. Lin

et al. prepared sintered magnetic abrasives by typically mixing iron powder and Al2O3

powder with composition of 60:40 of wt% and compressing mixture into the cylindrical

shape. These compacts were sintered into a vacuum furnace. After sintering process, these


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cylinders were crushed to produce magnetic abrasives. These abrasives were used for the

finishing of non-ferromagnetic material, SUS304. Khangura et al. highlighted major existing

technologies that are used to manufacture magnetic abrasives. Main performance

characteristics of magnetic abrasives have also been reviewed as regards to micromachining

of various surfaces. They stated that amongst all the available varieties of magnetic abrasives,

the sintered magnetic abrasives give highest surface finish on most of the work materials. The

best surface finish of 8 nm value is obtained on silver steel. They also stated that wet

abrasives give better finishing results as compared to dry abrasives.

Fine surface finish is in high demand in a wide spectrum of industrial applications. An

internal magnetic abrasive finishing process was proposed for producing highly finished

inner surfaces of work pieces used in critical such applications as aerospace components and

in semiconductor plants. It is difficult to finish advanced engineering materials with high

accuracy, and minimal surface defects such as microcracks, by conventional grinding and

polishing techniques. To minimize the surface damage, gentle/flexible finishing conditions

are required, namely, a low level of controlled force. Magnetic field assisted manufacturing

processes are becoming effective in finishing, cleaning, deburring and burnishing of metal

and advanced engineering material parts.

Magnetic abrasive finishing (MAF) is one of the non conventional machining processes

which came to the surface in 1938 in a patent by Harry P. Coats. The countries which are

involved in the study and development of this process are USA, CIS, France, England,

Bulgaria, Japan and Germany. In modern time, fine surface finish is in high demand with the

development of industry manufacturing technology, in a wide range of industrial

applications. A relatively new finishing advanced machining process in which cutting force is

primarily controlled by the magnetic field. A magnetic abrasive finishing (MAF) process is

the one in which material isremoved in such a way that surface finishing and deburring are

performed simultaneously with the applied magnetic field in the finishing zone and it can

achieve highly finished surfaces that conventional techniques never achieve. MAF is a fine

finishing technique which can be employed to produce optical, mechanical, and electronic

components with micrometer or submicrometer form accuracy and surface roughness within

nanometer range with hardly any surface defects. Finishing of bearings, precision automotive

components, shafts, and artificial hip joints made of oxide ceramic and cobalt alloy are some

of the products for which this process can be applied. This process can be used to produce

efficiently good surface quality on at surfaces aswell as internal and external surfaces of tube


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type work pieces The method can not only machineferromagnetic materials such as steel,

but can also machine non ferromagnetic materials such as stainless steel, aluminium and

brass. The Abrasives generally rely upon a difference in hardness between the abrasive and

the material being worked upon, the abrasive being the harder of the two substances.

Shinmura prepared two types of magnetic abrasives by sintering. In first sample, diameter of

iron particle was varied and in second, diameter of abrasive particle varied. They reported

that diameter of ironparticle effects both stock removal and surface finish. Influence of the

diameter of abrasive particle on stock removal was comparatively small while surface

roughness was remarkably affected. studiedthe effects of different machining parameters like

magnetic flux density, vibration frequency and amplitude,machining time and pole-work gap

on finishing characteristics using sintered magnetic abrasives. They concluded that the two

parameters vibration and magnetic flux density remarkably affects the finishing efficiency.

studied the application of MAF for finishing of the inner surfaces of alumina ceramic

components using diamond based magnetic abrasives. The experiments performed on

aluminaceramic tubes examined the effects of volume of lubricant, ferrous particle size, and

abrasive grain size on the finishing characteristics. concluded that with the increase in

rotational speed of magnetic pole,the metal removal rate increases. They almost keep a linear

relationship under given experimental conditions.The metal removal of brass work piece was

highest with the artificial abrasives (alloyed Titanium Carbide and Iron). The diamond

abrasives were mixed with iron to form diamond magnetic abrasives by He concluded that

finishing efficiency increased with diamond magnetic abrasives with increase of speed of

tool. He used them for finishing of ceramics to get high surface finish. Results showed that

machiningdepth increases with increase of mixing weight percentage of iron particles. has

developed a new type of magnetic abrasive composed of WC/Co sintered particles for

cleaning the tubes, and found the optimalfinishing parameters. prepared magnetic abrasives

by blending of Al2O3(15%) and iron powders (85%), compacting them by a bench press,

sintering the mixture in a furnace at 1400 C in an inert environment, crushing the compacts

into small particles and then sieving to different ranges of sizes. The finishing of silversteel

bars was studied with these sintered magnetic abrasives for various combinations of finishing

parameters.Yamaguchi et al. [15] proposed the finishing of SUS304 stainless steel bent tubes

using aluminium oxide composite magnetic abrasive with a mean diameter of 80 m. It

contains Al2O3 with grain size less than 10 m sintered with iron in an inert gas atmosphere

with high pressure and temperature. A two phase finishing processcontrolling the size of the

ferrous particles was proposed to achieve efficient fine surface finishing. In particular,the use


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of 150 m iron particles after 330 m iron particles was found to be effective. Jain et al

finished stainless steel workpiece material (non-ferromagnetic) and observed that working

gap and circumferential speedare the influential parameters affecting the material removal

and surface roughness value. has studiedthe process mechanism by using sintered magnetic

abrasive particles. Lin et al. prepared sintered magneticabrasives by typically mixing iron

powder and Al2O3 powder with composition of 60:40 of wt% andcompressing mixture into

the cylindrical shape. These compacts were sintered into a vacuum furnace. After sintering

process, these cylinders were crushed to produce magnetic abrasives. These abrasives were

used forthe finishing of non-ferromagnetic material, SUS304. Wang and Hu studied on the

inner surface finishing of tubing by magnetic abrasive finishing. They used three kinds of

work materials i.e. Ly12 aluminium alloy, 316L stainless steel and H62 brass. They

concluded that material removal rate of brass is highest amongst allthree materials. Khangura

highlighted major existing technologies that are used to manufacture magnetic abrasives.

They stated that amongst all the available varieties of magnetic abrasives, the

sinteredmagnetic abrasives give highest surface finish on most of the work materials.

The rapid development of the semiconductor, biotechnology, and optical electronic industries

has increased the importance of geometrical precision and part surface quality. Finishing is


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regularly applied to parts to obtain precise surfaces. Hence, numerous finishing techniques

have been applied for finishing parts to obtain parts with high quality. These techniques

include chemical mechanical polishing (CMP), electrical polishing (EP), and many others.

However, both CMP and EP suffer from the formation of pollutants during its operations, and

also yield surfaces with limited quality. Consequently, researchers in the industry and

academics have attempted to develop a better means of obtaining a high-precision surface,

with low cost, high efficiency, easy operations and low environmental pollution.

Following recent technological developments, stainless steel materials with characteristics of

anti-oxidizing, anti-corrosive, and shiny surface have been applied in electronic, biochemical

and medical instrumentation equipments. The surface of stainless steel parts must be

extremely smooth to prevent pollution. Optimally, the surface finish can reach a level in that

it looks like a mirror. A smooth stainless steel surface not only improves the parts quality but

it also prevents rusting and staining of the parts surface. Finished parts can prevent the

occurrence of the following situations: powder particles remaining on the part surfaces,

contact between parts and the stainless steel surface, rough surfaces residing with oil dusk or

food particles, and stainless steel burr of processed parts falling off when two parts contact

each other.

Stainless steel is a soft, tough, and a difficult finishing material. Thin plate stainless steel that

uses traditional processes is not easy to achieve a good surface finish. Hence, manual

finishing was usually applied to achieve a surface finish that looks like a mirror. However, it

is very time consuming to achieve a good surface finish using manual finishing techniques

for stainless container steel surfaces. To resolve the above problems, magnetic abrasive

finishing (MAF) was recently created. MAF involves using a permanent magnet or an

electronic magnet to generate a magnetic field, and the magnetic abrasives are formed as a

flexible magnetic brush for pressing the workpiece. Thus, the magnetic brush becomes a

finishing tool, and the magnetic abrasives of the magnetic brush stick to the workpiece during

the finishing. Moreover, the frictional force generated by the abrasive finishing can remove

particles of free-form surface. The procedure is repeated until a desired surface finish is

attained.

When a permanent magnet was installed on the topside of the workpiece, any uneven or

concave areas on the part could be finished. Moreover, when the magnetic pole was installed

inside or outside of the part, the internal and external pipes could also be finished . Therefore,


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MAF is a multi-function precise finishing method. Workpiece materials can be magnetic

(such as steel) or non-magnetic (such as ceramic), and the material removal weight can also

be adjusted based on the size of the magnetic abrasives. The finishing pressure is controlled

via the magnetic field, so MAF is used for micro-pressure finishing . Thus, the MAF method

achieved a highly efficient way of obtaining a good surface finish.

This study attempts to develop a surface finishing technique for stainless steel, with the aim

of analyzing the effects of different parameters and constructing the prediction system for the

development of a further adaptive control system. Secondly, this investigation seeks to

enhance surface finish of parts in order to meet the customer requirements

Fundamental principle

Magnetic abrasive finishing (MAF) of free-form surfaces involves filling the gap between thecircular magnetic pole and the workpiece with the magnetic abrasives. The magnetic

abrasives consist of sintered pure iron powder (99.9% Fe) and Al2O3. The end face of the

magnetic pole absorbs the magnetic abrasives and forms a closed-loop magnetic field with

the workpiece holder. The magnetic abrasives are generated in a non-uniformly magnetic

field; in which the abrasives will join each other and follow the direction of the magnetic

force to form a flexible magnetic brush. Refer to Figure 2-1 to see how the magnetic brush

acted on the free-form surface. The magnetic force lines generated power to apply pressure

from the magnetic abrasives to the workpiece, and the magnetic brush became a tool for

finishing the workpiece. Moreover, the magnetic abrasives in the magnetic brush stick to the

workpiece. When the magnetic pole rotates and moves with the workpiece relatively, the

frictional force generated from MAF cause the abrasives to finish the particles of uneven or

free-form surfaces until it becomes smooth. Moreover, the magnetic brush continues to move

on the x-y-z direction of the CNC machine, brushing the workpiece until it meets the

customers requirements.


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The basic principle of magnetic abrasive finishing is that magnetic abrasive particles

(MAPs) are attracted by magnetic field in the finishing zone. These particles join each other

along the lines of magnetic force due to dipoledipole interaction and form a flexible

magnetic abrasive brush (FMAB) which pushes against the work piece surface and develops

finishing pressure. This finishing pressure originates micro indentations in the workpiece

surface. The tangential force developed by FMAB is the major cutting force responsible for

micro chipping. Abrasives generally rely upon a difference in hardness between the abrasive

and the material being worked upon, the abrasive being the harder of the two substances.

In the configuration where magnetic poles N & S were placed face to face with their axes

crossing at right angle with a brass tubing shown in figure 1.In MAF operation, workpiece is

kept between the two magnets. The Magnetic field extends in the inner region of the tubing

without regard to presence and absence of the tubing to the machined and actuates magnetic

force to magnetic abrasive particles (MAPs) packed inside pipe. MAPs are made up of iron

powder and Al2O3 powder sintered at 1100C. MAPs can be used as unbonded, loosely

bonded or bonded. Bonded MAPs are prepared by sintering of ferromagnetic powder and

abrasive powder at a very high pressure and temperature in inert gas atmosphere. Loosely

bonded MAPs are prepared by mechanical mixing of ferromagnetic powder and abrasive

powder with a small amount of lubricant to give some holding strength between the abrasive

and ferromagnetic particles. Unbonded MAPs are mechanical mixture of ferromagnetic and

abrasive particles without any lubricant. The MAPs join each other along the lines of

magnetic force and form a flexible magnetic abrasive brush between each magnetic pole and

the workpiece. This brush behaves like a multipoint cutting tool for finishing operation. The

magnetic force on the abrasive particles provides the necessary machining force. This force is

responsible for the abrasion of the pipe by MAPs


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Magnetic abrasives introduced into the pipe are conglomerated at the finishing zone by a

magnetic field, generating the finishing force against the inner surface of the tube. In the

process, magnetic abrasive particles introduced into the workpiece are attracted by the

magnetic field and bear on the inner surface of the workpiece. These particles join each other

along the lines of magnetic force due to dipoledipole interaction and form a flexible

magnetic abrasive brush (FMAB) which pushes against the work piece surface and develops

finishing pressure. This finishing pressure originates micro indentations in the workpiece

surface. The tangential force developed by FMAB is the major cutting force responsible for

micro chipping. Abrasives generally rely upon a difference in hardness between the abrasive

and the material being worked upon, the abrasive being the harder of the two substances. In

MAF operation, work piece is kept between the two magnets. The magnetic poles N & S

were placed face to face with their axes crossing at right angle with a brass pipe in the

configuration. The Magnetic field extends in the inner region of the pipe without regard to

presence and absence of the pipe to the machined and actuates magnetic force to magnetic

abrasive particles packed inside pipe. Abrasive particles can be used as unbonded, loosely

bonded or bonded. Bonded magnetic abrasive particles areprepared by sintering of

ferromagnetic powder (iron) and abrasive powder (Al2O3) at a very high pressure andPalwinder Singh et al. / International Journal of Engineering Science and Technology


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(IJEST) temperature in H2 gas atmosphere. Loosely bonded MAPs are prepared by

mechanical mixing of ferromagnetic powder and abrasive powder with a small amount of

lubricant to give some holding strength between the abrasive and ferromagnetic particles.

Unbonded magnetic abrasive particles are mechanical mixture of ferromagnetic and abrasive

particles without any lubricant. The magnetic abrasive particles join each other along the

lines of magnetic force and form a flexible magnetic abrasive brush between each magnetic

pole and the workpiece. This brush behaves like a multipoint cutting tool for finishing

operation. The magnetic force on the abrasive particles provides the necessary machining

force. This force is responsible for the abrasion of the pipe by magnetic abrasive particles.


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Literature Review

The literature, which was reviewed for this project selection, was based upon various aspects

of abrasive mixtures prepared by various techniques. The abrasives are non magnetic and it is

required to attach these abrasives with any ferro magnetic material, so that the combination of

abrasives and ferro magnetic material can be attracted by magnetic field. The various mixing

techniques for this purpose were prepared by various researchers and tested for surface finish,

finishing time, wear of abrasives mixture Sakulevich et. al. (1980) developed a rotor type

machine for abrasive machining of parts with ferromagnetic abrasive powders in magnetic

field Kurobe (1983) used magnetic field to finish silicon wafer, glass and copper. In this

study the reasercher prepared magnetic fluid, which had the ability to move under magnetic

field. Kremen, Z., (1993) prepared diamond and non diamond carbon poly crystalline

composites particularly useful as abrasives are made by conventional sintering diamond

particles at temperature above about 1440 K but at pressures below which diamond is stable

or metastable with respect to its conversion to graphite. Tzong et al. (2003) in their study on

Electrolytic magnetic abrasive finishing, Electrolytic magnetic abrasive finishing (EMAF) is

a compound finishing process, involving traditional magnetic abrasive finishing (MAF) andan electrolytic process.

Dixit (2004) carried out experiments upon MAF having a slotted magnetic pole.


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Problem formulation

Earlier studies on Magnetic Abrasive Machining were only to utilize this machining process

in different operations. Only different types of material workparts are processed upon this

machine by various research personnel and organizations. But the cost can also be reduced by

maximizing the production rate and by making the best quality product in shortest time. This

can be achieved also by making an optimum abrasive grain-workpart combination, which

takes least processing time and the quality of the processed component will be best.

Therefore the present study was to develop a suitable combination of abrasives and workpart

materials by taking different material abrasive particles. By which the whole process will

become optimum.

Components used

Magnetic abrasives

DC Motor

Controller

Brass cylindrical pipe

Electromagnet


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Experimental setup

Figure shows an external view of the experimental setup, which embodies the processing

principle described in the previous section. The experimental setup has major components

like electromagnet (12 k Gauss), control unit, D.C. motor, variable D.C. supply. The main

elements of MAF equipment include the electro magnet (12 k Gauss), variable D.C. supply

and abrasive powder (Sintered Al2O3 + Fe). The work piece i.e. brass pipe was held in the

chuck attached to D.C. motor and abrasives were packed in the pipe. Magnetic field was

applied to the abrasives by electro magnet. Magnetic field strength is varied for

experimentation with the help of variable D.C. supply. Electromagnet plays an important rolein present experimentation. The space between workpiece and electromagnet is kept

constant. The magnetic field strength depends upon weight percentage of the magnetic

particles, present in the magnetic abrasive powder. Both the working gap and size of the

workpiece are taken into consideration, while designing. The objective of the design is to

measured at four points before and after finishing using a Mitutoyo surface roughness tester

(SJ-210P) having a least count of 0.001 m (cut off length = 0.8 mm) and averaged. The

material removal was measured on an electronic balance with 0.1 mg resolution. Therefore


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finishing characteristics in terms of PISF (Percentage Improvement in Surface Finish) and

MRR (Material Removal Rate) were analysed.

A schematic of experimental set up is shown in figure ., which embodies the principles of

internal finishing described in the previous section. The experimental setup has major

components like electromagnet (12 k Gauss), control unit, d.c. motor, variable D.C. supply.

The main elements of MAF equipment include the electro magnet (12 k Gauss), variable

D.C. supply and abrasive powder (Sintered Al2O3 + Fe). The cylindrical work piece i.e.

brass pipe was held in the chuck attached to D.C. motor and abrasives were packed in the

pipe. Magnetic field was applied to the abrasives by electro magnet. Magnetic field strengthis varied for experimentation with the help of variable D.C. supply. Electromagnet plays an

important role in present experimentation. The space between workpiece and electromagnet

is kept constant. The magnetic field strength depends upon weight percentage of the magnetic

particles, present in the magnetic abrasive powder. Both the working gap and size of the

workpiece are taken into consideration, while designing. The objective of the design is to

give rotational motion to the cylindrical workpiece. A DC motor is chosen for providing

rotational motion to the work piece. A schematic view of the setup is shown in the figure.


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Magnetic abrasive particles through magnetic pressure finish the workpiece. Al2O3 based

sintered magnetic abrasives are used as magnetic abrasives in this work.

In this study Al2O3 based sintered magnetic abrasives were used for internal finishing of brass

tubes. The Alumina (Al2O3) based sintered magnetic abrasives were prepared by blending of

Al2O3 (10%) of 200 mesh size (74 m) and iron powders (90%) of 300 mesh size (51.4m)),

compacting them by a universal testing machine (UTM), sintering the mixture in a sintering

set up at 1100C in H2 gas environment, crushing the compacts into small particles and then

sieving to different ranges of sizes. The obtained sizes are 120 m, 200 m, 300 m, 420 m.

The experimental conditions are shown in Table 1. Brass tubes (36mm 33mm 77mm)

were used for the experiments as workpieces. In this study, experimental variables such as

circumferential speed, magnetic flux density, abrasive grit size, and quantity of Abrasives

were considered. The finishing characteristics of magnetic abrasives were analysed by

measuring the surface roughness, which was blunt faster and need to be changed more

frequently. The machining performance decreases with the increase in circumferential speed

of workpiece beyond a certain value i.e. after 1000 rpm. The material removal rate (MRR)

goes on increasing with increase in circumferential speed. At low value of workpiece-pole

gap, magnetic abrasive brush is stronger and can take deeper cuts to remove more amount of

material from the workpiece. This effect will further escalate with the increase in

circumferential speed.

Effect of magnetic flux density (MFD) on finishing

characteristics

The MFD was varied between 0.4 to 1.2 T. Fig. 4 shows the variation of PISF and MRR with

MFD in the condition of 750 rpm speed, abrasive grit size 200 m, 12 gm quantity of

abrasives supplied. The magnetic field controls the abrasive configuration and the magnetic


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force on the abrasive, which determines the abrasive behavior and defines the finishing

characteristics. The Ra increases with increase in voltage because of the fact that higher

voltage to the electromagnet generates more number of lines of magnetic force, and therefore

higher flux density in a specified gap. Hence, strength as well as area of contact of the

magnetic brush with workpiece increases with increase in voltage, leading to a greater number

of indentations into the workpiece. Therefore, normal magnetic force increases leading to an

increase in cutting force due to increased rigidity of the FMAB. Hence, surface finish

increases. The PISF starts decreasing after 1.0 T of MFD. As the current/magnetic field

strength increases, the magnetization of iron particles increases hence they come closer to each

other. The material removal rate The quantity of abrasives was varied between 8 to 20 gm. the

variation of PISF and MRR with quantity of abrasives in the condition of 750 rpm speed, 0.6

T of MFD, abrasive grit size 200 m and 30 minutes time of finishing The percentage

improvement in the surface finish starts increasing as the quantity of abrasives increases to

certain extent and then PISF starts decreasing. The material removal rate increases with the

increase of the magnetic abrasive quantity up to certain extent beyond which it starts

decreasing. An increase of the supplied amount of magnetic abrasive mixture increases the

number of abrasive cutting edges and so the magnetic force acting on the abrasive increases

which results in more stock removal.

Effect of Speed on finishing characteristics

The speed was varied between 500 to 1250 rpm. Figure 3 shows the variation of PISF and

MRR with speed in the condition of 200 m abrasive grit size, 0.6 T MFD, 12 gm quantity of

abrasives supplied. The percent improvement in surface finish (PISF) starts increasing as the

circumferential speed of workpiece increases. As the circumferential speed of the workpiece

increases, the cutting velocity also increases. Therefore, larger number of cutting edges takes

part in machining, which results in more improvement in surface finish. But when the

circumferential speed increases by keeping the same frequency of cyclic power supply to the


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magnets, the accelerated wear takes place and the cutting edges (of abrasive powder) become

blunt faster and need to be changed more frequently. The machining performance decreases

with the increase in circumferential speed of workpiece beyond a certain value i.e. after 1000

rpm. The material removal rate (MRR) goes on increasing with increase in circumferential

speed. At low value of workpiece-pole gap, magnetic abrasive brush is stronger and can take

deeper cuts to remove more amount of material from the workpiece. This effect will further

escalate with the increase in circumferential speed.

Figure: Effect of speed on PISF and MRR

Effect of magnetic flux density (MFD) on finishing characteristics

The MFD was varied between 0.4 to 1.2 T. Fig. 4 shows the variation of PISF and MRR

with MFD in the condition of 750 rpm speed, abrasive grit size 200 m, 12 gm quantity of

abrasives supplied. The magnetic field controls the abrasive configuration and the magnetic

force on the abrasive, which determines the abrasive behavior and defines the finishing

characteristics. The Ra increases with increase in voltage because of the fact that higher

voltage to the electromagnet generates more number of lines of magnetic force, and therefore

higher flux density in a specified gap. Hence, strength as well as area of contact of the

magnetic brush with workpiece increases with increase in voltage, leading to a greater

number of indentations into the workpiece. Therefore, normal magnetic force increases


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leading to an increase in cutting force due to increased rigidity of the FMAB. Hence, surface

finish increases. The PISF starts decreasing after 1.0 T of MFD. As the current/magnetic field

strength increases, the magnetization of iron particles increases hence they come closer to

each other. The material removal rate increases as magnetic flux density increases up to

certain extent beyond which it becomes stable.

Figure: Effect of MFD on PISF and MRR

Effect of Grit Size on finishing characteristics

The experiments made use of four different grit sizes 120 m, 200 m, 300 m, 420 m.

Fig. 5 shows the variation of PISF and MRR with abrasive grit size in the condition of 750

rpm speed, 0.6 T of MFD, 12 gm quantity of abrasives supplied. The PISF increases with

increase in grit size up to certain extent, and then starts decreasing after size of 300 m. So

the percent improvement in surface finish decreases with higher grit size. The material

removal increases with increase of grit size. With increase of grit size, more cutting edges


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take part in material removal. Hence material removal rate increases with increase of grit

size.

Figure: Effect of Grit size on PISF and MRR

MICROSTRUCTURAL ANALYSIS

To further study the improvement in surface finish, the surface was microscopicallyexamined using scanning electron microscope (SEM). Fig. 7 shows the SEM micrographs of

inner surface of a tube before and after finishing for 30 min. The observations reveal that the

finishing of workpiece surface in this process is done by scratching or micro-cutting. The

SEM analysis shows that the finished surface has fine scratches/micro-cuts which are farther

distant apart resulting in smoothened surface. The initial surface profile has periodic peaks and

valleys generated by boring. Most of the peaks have been sheared off to much smaller height

by MAF resulting in improved surface finish.


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In this work Al2O3 based sintered magnetic abrasives were used for internal finishing of

cylindrical brass pipes. The Alumina (Al2O3) based sintered magnetic abrasives were

prepared by blending of Al2O3 (10%) of 200 mesh size (74 m) and iron powders (90%) of

300 mesh size (51.4 m)), compacting them by a universal testing machine (UTM), sintering

the mixture in a sinte ring set up at 1100C in H2 gas environment, crushing the compacts

into small particles and then sieving to different ranges of sizes. The obtained sizes are 120

m, 200 m, 300 m, 420 m. The experimental conditions are shown in table 1and coded

and real levels of independent variables are shown in table 2. Cylindrical Brass pipes

(36mm 33mm 77mm) were used for the experiments as workpieces. In this work,

experimental variables such as abrasive grit size, quantity of Abrasives, circumferential

speed, magnetic flux density were considered. The finishing characteristics of magnetic

abrasives were analysed by measuring the surface roughness, which was measured at four

points before and after finishing using a Mitutoyo surface roughness. Also surface finish

was analysed using Response Surface Methodology (RSM). Therefore finishing

characteristics in terms of PISF (Percentage Improvement in Surface Finish) were analysed.

Percentage Improvement In Surface Finishing

The effect of three input parameters (Proportion of Ferromagnetic / Abrasive Powder,

Condition of Application, Type of Magnetic Abrasive) on percentage improvement in surface

finish (Ra) has been discussed in the following points:

The developed magnetic abrasives (By adhesive bonding) are able to machine fine of

brass surface with reasonable percentage improvement in surface roughness of the

work piece .

Type of magnetic abrasive is a significant factor. On comparison of magnetic

abrasives made up by Adhesive bonding, sintering and with simply mixed iron

powder and abrasive powder, it is found that there is discernible improvement in


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surface roughness of workpiece by using developed magnetic abrasives, under all

other similar conditions.

In case of simply mixed magnetic abrasives and Silicon Carbide, the percentage

improvement in surface roughness is not very good. But in case of Adhesive bonded

iron-SiC, this value was upto the mark. In case of sintered iron-SiC, this value was

maximum.

The trend of variation of percentage improvement in surface roughness remains same

for the three type of iron-SiC i.e. simple mixed, glued and sintered.

Process Parameter Study

This section deals with identifying the basic process parameters and various steps involved in

process optimization. Figure 4.2 summarizes the important parameters useful for the

development of process. Some of the important process parameters of interest are the spring

loading compliance, abrasive size and type, polishing plate speed, spindle speed, liner joint,magnetic powder size, and viscosity of non-magnetic fluid. It should be noted that there are

large number of parameters and the account of their mutual influence on one another was

outside the scope of present study. For example, viscosity of non magnetic fluid was reported

as 0.17 [Childs and Moss, 2001], but on addition of magnetic particle the viscosity will

change. Such cross influencing parameters were not included. Childs [1995] and

Raghunandan [1997] classified MFP as 3-body polishing model because loose abrasives were

held between polishing pad and the worksurface. UMAP process works on the same principle

as MFP. Hence, UMAP can be categorized into 3-body polishing model. Material removal


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can be described in terms of 2-body or 3-body abrasion. Specifically, polishing falls into 3-

body abrasion category while grinding falls into 2-body abrasion. Further, researchers have

assumed that the material removal occurs due to indentation fracture, scratching, plastic

deformation, chemo-mechanical action, or combination of these mechanisms. Therefore, by

choosing process parameters similar to that of MFP; high material removal, good sphericity,

and surface finish can be achieved. The first step was to identify the polishing parameters

that can be closely linked to make meaningful descriptions. For example, magnetic field

analysis helps to define the dimensions of the magnets and their arrangement. Number of

balls in a batch can be determined by initial geometric analysis of the ball diameter and

chamber dimensions. Similarly, material removal behavior can be studied by knowing

physical and chemical properties of the workmaterials, and the abrasive particles. Interaction

of balls with various elements in contact accounts for the ball-motion study. Further, flash

temperatures during polishing facilitates for chemo-mechanical polishing.


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Results and discussions

The effects of interactions of different process parameters such as circumferential speed of

the work piece, magnetic flux density (MFD), abrasive grit size and quantity of abrasives on

percent improvement in surface finish (PISF) were analyzed using Response Surface

Methodology (RSM).


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Figure shows the effect of simultaneous variation of Speed (A) & Magnetic Flux Density

(B) on PISF. At lower level of speed, with increase in MFD, PISF increases but at higher

speeds when MFD increases surface finish decreases. At lower level of MFD with increase in

speed, PISF first decreases then starts increasing but at higher level of MFD, with increase in

speed PISF goes on decreasing. Figure shows the effect of simultaneous variation of Speed

(A) & Grit Size (C) on PISF. At lower level of grit size, with increase in speed PISF first

decreases then starts increasing but at higher level of grit size as the speed increases, PISF

goes on decreasing.


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Figure (a) shows the effects of Speed (A) and Quantity (D) on PISF. As quantity of abrasives

increases at lower level of speed PISF increases up to certain extent but after 12 gm, PISF

starts decreasing. At lower level of quantity with increase in speed, PISF first decreases then

starts increasing but at higher level of quantity, PISF goes on decreasing with increase in

speed. The PISF is better at lower level of quantity and higher level of speed.

Figure (b) shows that at all levels of Magnetic Flux Density, with increase in grit size PISF

decreases before it starts increasing. The %age surface finish improvement is better when

both the parameters are at higher level.


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Figure 5(a) shows the relationship between the Magnetic Flux Density (B) & Quantity (D),

keeping the value of speed & grit size of abrasives to a constant level. As the value of MFD

increases at lower level of quantity, the surface finish improves but decreases at higher levels

of quantity. The surface finish is better at lower values of quantity, as the quantity increases

the surface finish decreases. Figure 5(b) shows the relationship between the Grit size (C) &

quantity (D) of abrasives, keeping the value of speed & Magnetic Flux Density to a constant

level. The combined effect shows that surface finish is better at lower levels of grit size and

quantity. With increasing the value of grit size & quantity, the value of PISF goes on

increasing at different rates, reaches maximum value before it starts decreasing.


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CONCLUSIONS

The results of this study can be summarized as follows:

1) This study showed the feasibility of using a magnetic field assisted finishing process

with Al2O3 based sintered magnetic abrasive particles for the internal finishing of

brass tubes and gained an understanding of the mechanism involved.

2) The process removes material from the peaks of the uneven surface to generate a

smooth surface and achieves surface finishes as fine as 0.05 m in surface roughness

(Ra).

3) It is concluded from the results and discussions that Percent improvement in surface

finish (PISF) was significantly affected by magnetic flux density, quantity of

abrasives, interactions between rotational speed of workpiece & magnetic flux

density, rotational speed & grit size, rotational speed & quantity of abrasives,

magnetic flux density & grit size, magnetic flux density & quantity of abrasives.

References

[1] Jain, V.K., Prashant, K., Behra, P.K., and Jayswal, S.C. (2001) Effect of Working Gap

and Circumferential Speed on the Performance of Magnetic Abrasive Finishing

Process,Wear, pp. 250:384390.


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[2] Khairy A.B. (2001), Aspects of surface and edge finish by magnetoabrasive particles,

Journal of Materials Processing Technology, Vol. 116, pp.7783.

[3] Kim J-D. (2003) Polishing of ultra-clean inner surfaces using magnetic force,

International Journal of Advanced Manufacturing Technology, Vol. 21, pp.9197.

[4] Lin, C-T., Yang, L-D. and Chow, H-M. (2007) Study of magnetic abrasive finishing in

free-form surface operations using the Taguchi method, International Journal of Advance

Manufacturing Technology, Vol. 34, pp.122130.

[5] Mori, T., Hirota, K., and Kawashima, Y. (2003) Clarification of Magnetic Abrasive

Finishing Mechanism, Journal of Materials Possessing Technology, pp.143144.

[6] Shinmura T., Takazawa K., Hatano E. and Aizawa T. (1984) Study on Magnetic

Abrasive Process, Bull Japan Society of Prec. Engg. Vol. 18, No. 4 pp. 347348.

[7] Shinmura, T., Takajava, K., and Hatano, E. (1985) Study on Magnetic Abrasive Process

Application to Plane Finishing Bulletin of Japan Society of Precision Engineering , vol.

19(4), pp. 289291.

Experimental Investigation on Finishing of Inner Surfaces of Tubes Using Magnetic Abrasives

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Transcript of Experimental Investigation on Finishing of Inner Surfaces of Tubes Using Magnetic Abrasives