ENGINEERING STUDY

EDM

Electro discharge machining process is an electro thermal non traditional machining process, in which electrical energy is used to generate spark and occur material removal due to electric spark. EDM process is also called as spark erossion machining process where the metal is removed by the erossion of repeated path . It is high voltage and low current process . EDM is mainly used to machine difficult to machining the material and high strength temperature resistante alloy. EDM used to machining difficult geometry in small batches .

WORKING PRINCIPLES.

A high voltage is applied on EDM , a potential difference is applied between the tool and the workpiece . Here both the tool and workpiece are electrical conductor . The tool and workpiece are immersed in a dielectric medium . A small gap is maintained between the tool and workpiece , depending upon applied voltage . An electronic field would extablished between the tool and workpiece . Generally the tool is connected to the negative terminal and workpiece is connected to the positive terminal of the generator. If the work function or binding energy of electron is less, electron is called cold emission of electron is called cold emission. The cold emitted electron are accelerate towards the workpiece through dielectric medium. The cyclic process would increase the concentration of electrons in the dielectric medium between the tool and the workpiece at the spark gap .Thus the large of electron will flow from the tool to the workpiece and ions from the workpiece to the tool . The electrical energy is dissipated as that thermal energy of the spark. High speed of electron impinges on the workpiece and ions to the tools , the kinetic energy of electron impact on the surface of the workpiece and converted in to thermal energy ( Heat flux) . Such head flux rises the temperature and leads the metal to remove (10,000•c ) .

Advantages:-

1:- +- 0.005mm tolerance can be achieved in EDM.

2:- Material hardness doesn't effect in this process.

3:- Cutting complex shape will be done in EDM.

4:- EDM is indirect contact and no forces is required for the machining.

Disadvantages :-

1:- EDM process only able to machining conductive material.

2:- more expensive process than conventional machining .

INTRODUCTION .

A thermo dynamic process with in dentical end state is called thermo dynamic cycle .

The thermo dynamic cycle are two types
(1) Power cycle
(2) Refrigeration cycle

Power cycle

Power Cycle are that thermodynamic cycle which can generate net power output

Refrigeration

Refrigeration cycle is that type of thermodynamic cycle which can produce a cooling effect .

Power cycle are two types .

(1) Vapour power cycle .
(2) Gas power cycle .

∆. Vapour Power cycle uses high pressure vapour to produce mechanical work . It is used to in steam power plant

∆. Gas power cycle utilises high pressure gas to convert highest in to mechanical work . It is used in aeroplane .

STEAM POWER PLANT CYCLE .

In this cycle water is the working fluid . It under goes a change of phase during cycle . Heat is produce by burning the Cole in side the burner which produces heat . Heat is utilises to convert water in to steam in side the boiler . This steam then passes through the super heater to the turbine . High pressure high temperature steam expand in side the turbine to produce mechanical work . Exhaust steam from the turbine enter in to the condenser . Where it is cooled by the cooling water and converted into water . The feed water again enter in to the boiler through the feed pump and economiser . In this cycle heat energy of the coal is converted in to mechanical energy .

STEAM POWER PLANT CAN BE RUN IN THE FLOWING CYCLE .

(1) Carnot cycle .

(2) Rankine cycle .

(3) Reheat cycle .

(4) Regenerative Cycle .

(5) Reheat regenerative cycle .

(6) Binery Vapour cycle .

CARNOT CYCLE :

The Carnot cycle is a theoretical ideal thermodynamic cycle proposed by French physicist Sadi Carnot at in 1824 and expanded upon by others in the 1830s and 1840s. It provides an upper limit on the efficiency that any classical thermodynamic engine can achieve during the conversion of heat into work, or conversely, the efficiency of a refrigeration system in creating a temperature difference by the application of work to the system. It is not an actual thermodynamic cycle but is a theoretical construct. practically not possible .

Steam power plant Carnot cycle consist of

(1) Two isothermal process

(2) Two adiabatic process

Carnot limitations

∆ It Is extremely difficult to operate in practice becubec of following reasons :-

(1) It is difficult to comparess a wet Vapour isentropically to the saturated state as required by process 3-4
(2) It is difficult to control the quality of condensate coming out of the condenser so that state 3 is exactly obtained .
(3) The size of the pump has to be large to handle the condensate steam vapour minture corresponding to state 3 .
(4) The compression work is large resulting in a low cycle efficiency .
(5) The steam at the turbine in let is just dry saturated during its expansion over the turbine blades . It's be coming progressively wetter causing erosion damage of the turbine blades .

RANKINE VAPOUR CYCLE

The Rankine cycle is a model used to predict the performance of steam turbine systems. It was also used to study the performance of reciprocating steam engines. The Rankine cycle is an idealized thermodynamic cycle of a heat engine that converts heat into mechanical work while undergoing phase change. It is an idealized cycle in which friction losses in each of the four components are neglected. The heat is supplied externally to a closed loop, which usually uses water as the working fluid. It is named after William John Macquorn Rankine, a Scottish polymathand Glasgow University professor.

Rankine cycle consist of following processes

Process (1-2) :- Isentropic expansion inside

the turbine .

Process (2-3) :- Constant pressure heat

resection inside.

Process (3-4) :- Isentropic compression inside

the pump.

Process (4-1) :- constant pressure heat a adelition inside the boiler.

REGENERATIVE CYCLE

Regeneration in thermodynamics process refers to a method where the certain quantity of heat abstracted from the steam is utilized to heat the water. The regeneration process occurs between the stages of turbine and pump respectively. Using regeneration, the efficiencies of thermodynamic cycles can be improved.

The overall efficiency of both the Rankine cycle and the Carnot cycle will be identical, when there is a complete accomplishment of heat regeneration.With the steam regeneration, the efficiency of Rankine cycle can be improved more equivalent to that of Carnot cycle when both the cycles are operated between the same intervals of time.

BINARY VAPOUR CYCLE.

A binary vapour cycle comprises two different cycle working with two different fluid so that the condenser one cycle becomes boiler of another cycle .
This cycle is used to increase the overall efficiency of the plant.
The must important binary comprise of the mercury cycle and steam cycle .

MILLING MACHINE .

Milling machine are employed for maching flat surface contour surface , external ,internal threads & helical surface of various cross section .

PRINCIPLE OF MILLING MACHINE .

A milling machine is a power driven machine

The metal is cut by mines of multy tooth rotating cutter .

For cutting operation the work piece is feed against the rotating cutter .

As the work piece moves against the cutting edge of the rotating cutter .

The work to be machined is held in a vice a three jaw chuck , An index head , A rotating table between the centres bolted to a machine table .

The speed of the cutting tool and the rate at which the work piece travel is dependent upon the kind of material beinged .

TYPES OF MILLING MACHINE .

According to design the different types of milling machine such as :-

(1) Column and knee type milling machine .

(a) Hand Miller

(b) Plane milling machine

(C) Universal milling machine

(d) Vertical milling machine .

(2) Planer milling machine .

(3) Fixed bed type ar manufacturing type milling machine .

(a) Simplex milling machine .

(b) Duplex milling machine .

(c) Triplex milling machine .

(4) Maching centre machine .

(5) Special purpose milling machine .

(a) Rotating type milling machine

(b) Planetary type milling machine
(c) Profile milling machine
(d) Duplicating milling machine
(e) Pontograph milling machine
(f) Continuous milling machine.

MILLING MACHINE WORKPIECE HOLDING DEVICE .

The work piece is can be milled on a milling machine veary in size from smaller to larger .

The mejority of the work piece are in the 2.5 kg to 225kg range .

The proper method holding the work piece for milling is governed by the work .

(1) Size of the work
(2) Shape the work
(3) The nature of the milling operation
(4) The number of parts to be produce

The work piece mounted on the milling machine table because the greter thrust produce by the rotating milling cutter can damage the work piece on the machine .

There are various methods of mounting the work piece on the milling machine for maching.

(1) Holding in vice
(2) Fixed to angle plate
(3) In a chuck
(4) In a milling fixtures
(5) Between centres on the rotating ar tilting table

WHAT IS PLANER MACHINE ?

(1) The planer machine is similar to the shaper machine . Primarily used to produce flat surface by a single point cutting tool

(2) Planer machine is capable of machine large and heavy workpiece which can not be machined by shaper machine .

(3) The planer is very large and heavy compare to shaper machine .

DIFFERENT PARTS OF THE PLANER MACHINE ?

The different parts of the planer are mentioned below :-

(1) Bed

(2) work table

(3) column

(4) crossrail

(5) saddle

(6) Tool head

FUNCTION OF THE DIFFERENT PART'S OF THE PLANER MACHINE ?

BED :

The bed of a planer must be a casting twice as long as the table .

The bed acts as a foundation of the machine .

The bed has accurately finished way on which the work table is slides .

WORK TABLE .

The work table is a heavy rectangular casting which carriages the heavy and long workpiece .

It travels on the flat ways of the bed .

The upper surface of the table has T slots in it to facilitates the clamping of the vices and fixture with the belt .

COLUMN

The frame of the planer has heavy column fastened at the top .

This creates very strong rigid structure which will handle heavy loads .

CROSSRAIL .

The Crossrail is a heavy box like structure .

It slides up and down on the flat ways controld by hand

The purpose of Crossrail is to carry the vertical tool head .

TOOL HEAD .

The tool head of the planer is similar to that of a shaper both in construction and operation .

The tool head is attached to the Shaddle which contains the tool post which holds the cutting tool .

WORKING OF TOOLS & TOOL SUPPORTS .

The cutting tool used in planer machine are single point cutting tool .

The planer tool are made heavyer & large cross section to take up heavy load during body .

Planer tools may be solides forged are bit type .

The materials is are used for planer tools are HHS , cemented carbides .

The tools used in a planer machine are mention below

(1) straight roughing tool .

(2) Round nose tool .

(3) Square nose finishing tool .

(4) Gooseneck finishing tool .

(5) Left hand dovetail end cutting roughing tool for cast iron.

(6) For Conner .

(7) Roughing flat surface rool

(8) Finishing .

(9) slide cutting tool .

CLAMPING OF WORK THROUGH SKETCH .

A Planer table is used to hold very large and heavy workpiece may be held on a planer table by flowing methods by standard clamping by spacial fixture .

Standard clamping are used for holding most of the workpiece on a planer table.

The standard clamping device are
(1) Heavy duty vices
(2) T - Bolt & clamp
(3) Stet blocks
(4) poppets & to edogs
(5) Angle plates
(6) Planer jacks
(7) Planer centers
(8) Stop
(9) V - blocks

Heavy duty vices .

A planer vice is much more heavier in construction the a shaper vice.

The workpiece clamp between the fixed movebul jaw .

The vice me be plane are swivelled base type .

T - Bolt & clamp .

Most of the work piece are clamped directly on the table by T bolt & clamped

Different types of clamped are used for different types work.

Stet block .

Stet block are used to give support other and of the clamped .

Work piece of different hight me be supported by using different Stet blocks .

Poppets & to edogs

These are used for holding very thin pieces of work on a planer table.

Angle plates .

These are used for holding L shaped work piece.

Planer jacks .

These are used for supporting the over hanging parts of a work to prevent it from bending .

Planer centres .

The planer centres these are used for holding the work piece between two centres .

Stops .

These are used prevent the work piece from moving end wise & sideways under thrust of the cut .

V - blocks .

These are used for holding the round workpiece .

WHAT IS THE TURRET LATHE

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WORKING PRINCIPLES.

Advantages:-

Disadvantages :-

TURRET LATHE :

MAIN PARTS OF TURRET LATHE :

BED

HEAD STOCK

CARRIAGE

TURRET