Ajeet Kumar Hard Copy

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A

Seminar Report on

sand casting

Submitted for partial fulfilment of the requirements for the degree of Bachelor of

technology in manufacturing technology

By

RAJ KUMAR

1018941030

Guided by

Ms. priti singh

Central Institute of Plastics Engineering & Technology

Lucknow, Uttar Pradesh

Affiliated to

GAUTAM BUDDHA TECHNICAL UNIVERSITY, LUCKNOW, U.P


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ACKNOWLEDGEMENT

It gives me a gre at pleasure to tender my deep sense of gratitude to

respected Ms PRITI SINGH for invaluable encouragement,

inspirations and continuous support. We are very much indebted to him

for the generously, expertise and guidance we have received from him

while working on this project. I will remain ever thankful to for precious

support, guidance and co operation. Without his support and timely

guidance the completion of seminar report would have seemed a far-

fetched dream. In this respect I find myself lucky to have him as our

guide. He guided us not only with subject matter, but also taught us the

proper style and techniques of documentation and presentation.

RAJ KUMAR


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CERTIFICATE

This is to certify that the Seminar entitled, SAND CASTING, which is being

submitted here with for the award of B.Tech,

is the result of the work completed by RAJ KUMAR under my

supervision and guidance within the four walls of the institute.

Guide:- Examiner

Ms. PRITI SINGH


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TABLE OF CONTENT

Acknowledgement

Certificate

Abstract

Introduction 1

History 2

What is EDM 3

Principle of EDM 4

Working principle of EDM 6

Types of EDM 5

Equipment 8

Process parameter 9

Characteristics of EDM 10

Application of EDM 11

Advantages and Disadvantage 14

Conclusion 15

References 16


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ABSTRACT

The traditional method of casting metals is sand casting; it is used to make large parts. There are six basic steps in

making sand casting patternmaking, core making, molding melting and pouring cooling and solidification, cleaning.

Pattern making a cavity in sand is formed by using a pattern which is typically made out of wood, sometimes metal.

The pattern is physically model of casting used to make the mould.

In core making core is a sand shape inserted in to mould to produce the internal features of the part such s holes or

internal passages. Cores are placed in cavity to form holes of desired shape.

Molding consists of all operations necessary to prepare a mould for receiving molten metal. It usually involves placing

a molding aggregate around a pattern held with supporting frame, withdrawing the pattern to leave mould cavity,

setting the core in mould cavity and finishing and closing mould.

In melting and pouring the preparation of molten metal for casting is done. It is usually dine in specific area of foundry

Molten motel is poured in poring cup, which is part of gating system that supplies the molten metal to the mould cavity

the vertical part of gating system connected to the pouting cup is sprue.

like nearly all materials, metal is less dense than a liquid than as a solid and so casting shrinks as it cools-mostly as it

solidifies but also as a temperature of solid material drops.

Cleaning refers to all operation necessary to the removal of sand, scale and excess metal from the casting. The casting

is separated from mould and transported to cleaning department. Burned on sand and scale are removed to increase

surface appearance of casting. Excess metal in the form of fins, wires and parting lines, gates is removed. Casting may beupgraded by welding or other procedures. Inspection of casting for defects and general quality.


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INTRODUCTION

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 work piece 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 tool-electrode, or simply the tool or electrode, while the other is called

the workpiece.When the distance between the two electrodes is reduced, the intensity of theelectric field in the

Volume between the electrodes becomes greater than the strength of the dielectric (at least in

Some point(s)), which breaks, allowing current to flow between the two electrodes. This

Phenomenon is the same as the breakdown of a capacitor (condenser) (see also breakdown voltage).

As a result, material is removed from both the electrodes. Once the current flow stops

(Or it is stoppeddepending on the type of generator), new liquid dielectric is usually conveyed

Into the inter-electrode volume enabling the solid particles (debris) to be carried away and the

Insulating proprieties of the dielectric to be restored. Adding new liquid dielectric in the inter-

electrode volume is commonly referred to as flushing. Also, after a current flow, a

difference of potential between the two electrodes is restored to what it was before the

breakdown, so that a new liquid dielectric breakdown can occur.

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http://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Capacitor#Breakdown_voltagehttp://en.wikipedia.org/wiki/Breakdown_voltagehttp://en.wikipedia.org/wiki/Difference_of_potentialhttp://en.wikipedia.org/wiki/Difference_of_potentialhttp://en.wikipedia.org/wiki/Breakdown_voltagehttp://en.wikipedia.org/wiki/Capacitor#Breakdown_voltagehttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Dielectric


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HISTORY

In 1770, English physicist Joseph Priestley studied the erosive effect of electrical discharges.

Furthering Priestley's research, the EDM process was invented by two Russian scientists, Dr. B.

R. Lazarenko and Dr. N. I. Lazarenko, in 1943. In their efforts to exploit the destructive effects

of an electrical discharge, they developed a controlled process for machining of metals. Their

initial process used a spark machining process, named after the succession of sparks (electrical

discharges) that took place between two electrical conductors immersed in a dielectric fluid.

The discharge generator effect used by this machine, known as the Lazarenko circuit, was

used for many years in the construction of generators for electrical discharge.

Additional researchers entered the field and contributed many fundamental characteristics of the

machining method we know today. In 1952, the manufacturer Charmilles created the first

machine using the spark machining process and was presented for the first time at the European

Machine Tool Exhibition in 1955.

In 1969 Agie launched the world's first numerically controlled wire-cut EDM machine. Seibu

developed the first CNC wire EDM machine 1972 and the first system manufactured in

Japan.

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http://en.wikipedia.org/wiki/Joseph_Priestleyhttp://en.wikipedia.org/w/index.php?title=Lazarenko_circuit&action=edit&redlink=1http://en.wikipedia.org/wiki/Agiehttp://en.wikipedia.org/wiki/Numerical_controlhttp://en.wikipedia.org/wiki/Numerical_controlhttp://en.wikipedia.org/wiki/Agiehttp://en.wikipedia.org/w/index.php?title=Lazarenko_circuit&action=edit&redlink=1http://en.wikipedia.org/wiki/Joseph_Priestley


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WHAT IS EDM

Electrical discharge machining is a machining method primarily used for hard metals or those

that would be very difficult to machine with traditional techniques. EDM typically works with

materials that are electrically conductive, although methods for machining insulating

ceramics with EDM have also been proposed. EDM can cut intricate contours or cavities in

pre-hardened steel without the need for heat treatment to soften and re-harden them. This method

can be used with any other metal or metal alloy such as titanium, hastelloy, kovar, and inconel.

Also, applications of this process to shape polycrystalline diamond tools have been reported.

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http://en.wikipedia.org/wiki/Ceramicshttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Hastelloyhttp://en.wikipedia.org/wiki/Kovarhttp://en.wikipedia.org/wiki/Inconelhttp://en.wikipedia.org/wiki/Inconelhttp://en.wikipedia.org/wiki/Kovarhttp://en.wikipedia.org/wiki/Hastelloyhttp://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Ceramics


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PRINCIPLE OF EDM

Electrical Discharge Machining (EDM) is a controlled metal-removal process that is used

to remove metal by means of electric spark erosion.

In this process an electric spark is used asthe cutting tool to cut (erode) the workpiece to produce

the finished part to the desired shape.

The metal-removal process is performed by applying a pulsating (ON/OFF) electrical charge of

high-frequency current through the electrode to the workpiece. This removes (erodes) very tiny

pieces of metal from the workpiece at a controlled rate.

fig.1

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TYPES OF EDM

WIRE EDM- is used primarily for shape cut out of a flat sheet or plate of metal. With

a wire EDM machine, if a hole needs to be machined, an initial hole must first be drilled

in the material. Then the wire can be cut and fed through the hole to complete the machining.

FIG2

SINKER EDMs- are generally used for very small piece where conventional milling is

not practical or very difficult due to hardness of material, such as die cast tooling .

For example, they can cut a hole in to the work piece without having a hole pre-drilled

for the electrode.

FIG3

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http://en.wikipedia.org/wiki/File:Robofil-300-WireCut.jpghttp://en.wikipedia.org/wiki/File:Robofil-300-WireCut.jpg


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WORKING PRINCIPLE OF EDMEDM, a potential difference is applied between the tool and workpiece. Both the tool and the work material areto be conductors of electricity. The tool and the work material are immersed in a dielectric medium. Generallykerosene or deionised water is used as the dielectric medium. A gap is maintained between the tool and theworkpiece. Depending upon the applied potential difference and the gap between the tool and workpiece, anelectric field would be established. Generally the tool is connected to the negative terminal of the generatorand the workpiece is connected to positive terminal. As the electric field is established between the tool andthe job, the free electrons on the tool are subjected to electrostatic forces. If the work function or the bonding

energy of the electrons is less, electrons would be emitted from the tool (assuming it to be connected to thenegative terminal). Such emission of electrons are called or termed as cold emission. The cold emittedelectrons are then accelerated towards the job through the dielectric medium. As they gain velocity andenergy, and start moving towards the job, there would be collisions between the electrons and dielectricmolecules. Such collision may result in ionisation of the dielectric molecule depending upon the work functionor ionisation energy of the dielectric molecule and the energy of the electron. Thus, as the electrons getaccelerated.


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Fig. shows schematically the basic working principle of EDM process.

the high speed

electrons then impinge on the job and ions on the tool. The kinetic energy of the electrons and ions on impact with the

surface of the job and tool respectively would be converted into thermal energy or heat flux. Such intense localised heat

flux leads to extreme instantaneous confined rise in temperature which would be in excess of 10,000o

C.

Such localised extreme rise in temperature leads to material removal. Material removal occurs due to instant

vapourisation of the material as well as due to melting. The molten metal is not removed completely but onlypartially.As the potential difference is withdrawn as shown in Fig. 1, the plasma channel is no longersustained. As the plasma channel collapse, it generates pressure or shock waves, which

evacuates the molten material forming a crater of removed material around the site of the spark.

Thus to summarise, the material removal in EDM mainly occurs due to formation of shock

waves as the plasma channel collapse owing to discontinuation of applied potential difference.

Generally the workpiece is made positive and the tool negative. Hence, the electrons strike the

job leading to crater formation due to high temperature and melting and material removal.

Similarly, the positive ions impinge on the tool leading to tool wear.

In EDM, the generator is used to apply voltage pulses between the tool and the job. A constant voltage is not

applied. Only sparking is desired in EDM rather than arcing. Arcing leads to localised material

removal at a particular point whereas sparks get distributed all over the tool surface leading to

uniformly distributed material removal under the tool.

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EQUIPMENT

EDM machine has the following major modules

Dielectric reservoir, pump and circulation system

Power generator and control unit

Working tank with work holding device

X-y table accommodating the working table

The tool holder

The servo system to feed the tool

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PROCESS PARAMETER

The process parameters in EDM are mainly related to the waveform characteristics. Fig. shows a generalwaveform used in EDM/

.

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the waveform is characterised by the The open circuit voltage - V

o

The working voltage - Vw

The maximum current - Io

The pulse on time the duration for which the voltage pulse is applied - ton

The pulse off time - toff

The gap between the workpiece and the tool spark gap -

The polarity straight polarity tool (-ve) The dielectric medium External flushing through the spark gap.

CHARACTERISTICS OF EDM

(a) The process can be used to machine any work material if it is electrically conductive

(b) Material removal depends on mainly thermal properties of the work material rather than its strength,hardness etc

(c) In EDM there is a physical tool and geometry of the tool is the positive impression of the hole orgeometric feature machined

(d) The tool has to be electrically conductive as well. The tool wear once again depends on the thermaproperties of the tool material

(e) Though the local temperature rise is rather high, still due to very small pulse on time, there is notenough time for the heat to diffuse and thus almost no increase in bulk temperature takes place. Thus theheat affected zone is limited to 24 m of the spark crater

(f) However rapid heating and cooling and local high temperature leads to surface hardening which may be

desirable in some applications

(g) Though there is a possibility of taper cut and overcut in EDM, they can be controlled and compensated.

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APPLICATION OF EDM

Prototype production

The EDM process is most widely used by the mold-making tool and die industries, but is becoming a common

method of making prototype and production parts, especially in the

aerospace, automobile and electronics industries in which production quantities are relatively

low. In Sinker EDM, a graphite, copper tungsten or pure copper electrode is machined into the desired

(negative) shape and fed into the workpiece on the end of a vertical ram.

Coinage die making

For the creation of dies for producing jewelry and badges by the coinage (stamping) process, the positive mastermay be made from sterling silver, since (with appropriate machine settings) the master is significantly erodedand is used only once. The resultant negative die is then hardened and used in a drop hammer to produce

stamped flats from cutout sheet blanks of bronze, silver, or low proof gold alloy. For badges these flats may be

further shaped to a curved surface by another die. This type of EDM is usually performed submerged in an oil-based dielectric. The finished object may be further refined by hard (glass) or soft (paint) enameling and/orelectroplated with pure gold or nickel. Softer materials such as silver may be hand engraved as a refinement.

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EDM control panel (Hansvedt machine). Machine may be adjusted for a refined surface (electropolish) at end of process

Master at top, badge die workpiece at bottom, oil jets at left (oil has been drained). Initial flat stamping will be "dapped"

to give a curved surface.

Small hole drilling

A turbine blade with internal cooling as applied in the high-pressure turbine.

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Small hole drilling EDM machines.Small hole drilling EDM is used in a variety of applications.

On wire-cut EDM machines, small hole drilling EDM is used to make a

through hole in a workpiece in through which to thread the wire for the wire-cut EDM operation. A separate EDM head

specifically for small hole drilling is mounted on a wire-cut machine and allows large hardened plates to have finished

parts eroded from them as needed and without pre-drilling.

Small hole EDM is used to drill rows of holes into the leading and trailing edges of turbine blades used in jetengines. Gas flow through these small holes allows the engines to use higher temperatures than otherwise

possible. The high-temperature, very hard, single crystal alloys employed in these blades makes conventionalmachining of these holes with high aspect ratio extremely difficult, if not impossible.

Small hole EDM is also used to create microscopic orifices for fuel system components, spinnerets for synthetic

fibers such as rayon, and other applications.

There are also stand-alone small hole drilling EDM machines with an xy axis also known as a super drill or

hole popperthat can machine blind or through holes. EDM drills bore holes with a long brass or copper tube

electrode that rotates in a chuck with a constant flow of distilled or deionized water flowing through the

electrode as a flushing agent and dielectric. The electrode tubes operate like the wire in wire-cut EDMmachines, having a spark gap and wear rate. Some small-hole drilling EDMs are able to drill through 100 mm

of soft or through hardened steel in less than 10 seconds, averaging 50% to 80% wear rate. Holes of 0.3 mm to

6.1 mm can be achieved in this drilling operation. Brass electrodes are easier to machine but are notrecommended for wire-cut operations due to eroded brass particles causing "brass on brass" wire breakage,therefore copper is recommended.

Metal disintegration machining

Several manufacturers produce EDM machines for the specific purpose of removing broken tools (drill bits ortaps) from work pieces. In this application, the process is termed "metal disintegration machining".

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http://en.wikipedia.org/wiki/Deionized_waterhttp://en.wikipedia.org/wiki/File:Small_hole_drilling_EDM_machines.jpghttp://en.wikipedia.org/wiki/Deionized_waterhttp://en.wikipedia.org/wiki/File:Small_hole_drilling_EDM_machines.jpg


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ADVANTAGES AND DISADVANTAGES

Some of the advantages of EDM include machining of:

Complex shapes that would otherwise be difficult to produce with conventional cutting tools

Extremely hard material to very close tolerances

Very small work pieces where conventional cutting tools may damage the part from excess cutting toolpressure.

There is no direct contact between tool and work piece. Therefore delicate sections and weak materialscan be machined without any distort.

A good surface finish can be obtained.

Very fine holes can be easily drilled.

Some of the disadvantages of EDM include:

The slow rate of material removal.

The additional time and cost used for creating electrodes for ram/sinker EDM.

Reproducing sharp corners on the workpiece is difficult due to electrode wear.

Specific power consumption is very high.

Power consumption is high.

"Overcut" is formed.

Excessive tool wear occurs during machining.

Electrically non-conductive materials can be machined only with specific set-up of the process.

Current Research Trends in EDM Development

There are two kinds of EDM research trends: the modeling technique and the novel technique.2

1. The modeling technique deals with mathematical modeling, artificial intelligence and optimization techniques

like regression analysis, artificial neural network and the genetic algorithm. They are used to validate the efforts

of input parameters on output parameters, because EDM is a complicated process. It has controlled input

parameters like machining depth, tool radius, pulse on time, pulse off time, discharge current, orbital radius,

radial step, offset depth and output parameters. It is similar to the MRR and SQ.2

2. Novel techniques deal with other (unconventional) machining principles (such as ultrasonic) that can be

incorporated into EDM to improve efficiency of the process by offering better MMR and SQ

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http://www.triz-journal.com/archives/2009/06/02/#Ref2http://www.triz-journal.com/archives/2009/06/02/#Ref2http://www.triz-journal.com/archives/2009/06/02/#Ref2http://www.triz-journal.com/archives/2009/06/02/#Ref2http://www.triz-journal.com/archives/2009/06/02/#Ref2http://www.triz-journal.com/archives/2009/06/02/#Ref2http://www.triz-journal.com/archives/2009/06/02/#Ref2http://www.triz-journal.com/archives/2009/06/02/#Ref2


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CONCLUSION

electric discharge machining is useful un-conventional machining techniques by which

we can machine hard metal or those that would be impossible to machine with traditional

techniques .

wire EDM is very useful for shape cut of a flat sheet or plate of metal.

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REFRENCES

^Elman C. Jameson, Electrical Discharge Machining, page 1, Society of Manufacturing Engineers, 2001ISBN

087263521X.

^The History of EDM, http://www.atlantaedm.com/articles/a8-history-of-edm.php, retrieved 2010-08-05

K. M. Moeed

Electro Discharge Machining

Version 2 ME, IIT Kharagpur

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THANK YOU


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