Production Technology (MEE-S306) Lecture-1 Machining Advanced Machining Processesuietkanpur.com/Online_Course/AP_MEE_S306.pdf · 2020-04-07 · Advanced Machining Processes(AMPs)

Machining

Advanced Machining Processes

Arpit Srivastava

Asst. Professor

Mechanical Engg. Dept.

UIET CSJMU Kanpur

Production Technology (MEE-S306)

Lecture-1

Limitation of Traditional Machining

Processes

Machining of high strength temperature resistance alloys.

Example- titanium, stainless steel, nickel based alloys, ceramics

etc.

Production of complex shapes in such materials by traditional

methods is still more difficult.

Micro machining features by traditional method is still more

difficult.

Making holes (shallow entry angles, non circular, micro sized) in

difficult to machine material is another area where appropriate

processes are very much in demand.

4/6/2020Arpit Srivastava, Mechanical Engg. UIET

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Limitation of Traditional Machining

Processes

Requires much super quality of tool material to machine high

strength workpieces.


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Advanced Machining Processes(AMPs)

In AMPs, energy in its direct form is used to remove the materials from

the workpiece while in conventional machining, cutting tools are

employed for metal cutting.

Materials is removed in the form of atoms or molecules.

Macro Machining>= 1 mm

1μm=<Micro Machining<=999μm


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Classification of AMPs


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Hybrid Processes

To further enhance the capabilities of the machining processes, two

or more than two machining processes are combined to take

advantage of the worthiness of the constituent processes.

Example-

Electrochemical Grinding= Electrochemical Machining + Grinding

Electric discharge abrasive Grinding= Electric discharge Machining

+abrasive Grinding

Enhanced volumetric material removal rate and better

performance.


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Questions for Assignment

Q.1 How the developments in the area of materials are partly

responsible for evolution of AMPs ?

Q.2 Classify modern machining processes on the basis of the type

of energy employed. Also state the mechanism of material removal,

transfer media and energy source used.

Q.3 Enlist the requirements that demand the use of AMPs.


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Machining

Electric Discharge Machining

(EDM)

Arpit Srivastava

Asst. Professor


UIET CSJMU Kanpur


Lecture-2

Electric Discharge Machining (EDM)


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4/3/2020 Arpit Srivastava, Mechanical Engg. UIET CSJMU Kanpur

Working Principle of EDM


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When a discharge takes place between two points, instance heat is

generated near the zone having temperature range of 8000-12000C,

which evaporates the materials in the sparking zone.

Dielectric Fluid-

Drive away the debris of workpiece and tool from machining zone.

Provide spark between tool and workpiece.

Control temperature by providing coolant effect.

Example- kerosene oil, transformer oil, paraffin oil etc.

Tool Material-

Cu, Tungsten alloy, Cast iron, steel etc.

Workpiece-

All electric conductors of materials.


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Advantage-

Good surface finish, High MRR, Complex cavities can be cut.

Limitation-

High tool wear, workpiece and tool must be electrically conductive.

Application-

Blind, complex cavities, Hard material dies, making holes in dies.


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Questions for Assignment Q.1 Which of the following is/ are used as low wearing tool material inEDM

(a) Copper and brass, (b) aluminium and graphite

(c) Silver tungsten and copper tungsten, (d) cast iron

Q.2 Which statement is true for EDM

1. MRR increases with decreasing resistance

2. MRR increases with decreasing capacitance

3. MRR increases with increasing capacitance

4. MRR increases with optimum saprk gap then decreased withincreasing spark gap.

(a) 1,2,3 and 4 (b) 1,2 and 3 (c) 1,3 and 4, (d) 1,2 and 4

Q.3 Statement(I): In EDM process, tool is made cathode andworkpiece as anode.

Statement(II) In this process if both electrodes are made of samematerial, greatest erosion takes place upon anode.


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Questions for Assignment

Q.4 Metal removal in EDM takes place through

(a) Ion displacement, (b) melting and vaporization

(c) Corrosive reaction (d) plastic shear

Q.5 A circular hole of 25 mm diameter and depth of 20mm is

machined by EDM process. The material removal rate

(mm3/sec) is expressed as 4X 10^(4) I T^(-1.23) where I= 300

A and the melting point of the material, T=1600 C. Find the

time (in minutes) for machining this hole.

Questions for Assignment Q.6 Keeping all other parameters unchanged, the tool wear in

EDM would be less if the tool material has

(a) High thermal conductivity and high specific heat

(b) High thermal conductivity and low specific heat

(c) Low thermal conductivity and low specific heat

(d) Low thermal conductivity and high specific heat

Machining

Abrasive Jet Machining

(AJM)

Arpit Srivastava

Asst. Professor


UIET CSJMU Kanpur


Lecture-3

Abrasive Jet Machining (AJM)

A jet of inert gas consisting of very fine abrasive particles strikes

the workpiece at high velocity (usually between 200-400 m/s)

resulting in material removal through chipping / erosive action.

This erosive action has been employed for cutting , cleaning,

etching, polishing and deburring .

This method of material removal is quite effective on hard and /

or brittle materials (viz glass, silicon, tungsten, ceramics, etc ).

It can produce fine and complicated details on the parts made of

very brittle materials.


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Abrasive Jet Machining (AJM)


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Material Removal Mechanism of AJM


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Principle of AJM


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Process Parameters of AJM

The abrasive

composition, strength, size, mass flow rate.

The gas

composition, pressure, temperature and velocity.

The nozzle

Geometry, material, Stand-Off-Distance (SOD) or Nozzle-Tip-

Distance (NTD), feed rate, inclination angle to the normal to the

workpiece surface.


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Abrasive Particles Aluminium oxide (A1203), silicon carbide (SiC), glass beads,

crushed glass , and sodium bicarbonate are some of the abrasives

used in AJM.

Selection of abrasive(s) depends upon the type of work

material, material removal rate (MRR), and machining accuracy

desired.

The sizes of abrasive particles available in the market range

from 10 to 50 μm. Small abrasive particles are used for cleaning

and polishing while large particles perform better during cutting.

Re-use of the abrasives is not recommended.


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Abrasive Particles


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Carrier Gas


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Effect of Stand-off-Distance (SOD)


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Abrasive Flow Rate


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Effect of Nozzle Pressure on MRR


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Effect of Nozzle Pressure on MRR

Mixing ratio (M) also influences MRR.

Kinetic energy (K. E.) of the abrasive particles is responsible

for removal of material by erosion process. Abrasives must

impinge on the work surface with a certain minimum velocity so

that the erosion can take place. This minimum velocity for

machining glass by SiC particles is found to be around 150 m/s.


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Applications

AJM is useful in the manufacture of electronic devices,

deburring of plastics, making of nylon and teflon parts, marking

on electronic products, permanent marking on rubber stencils,

deflashing small castings, cutting titanium foil, and drilling glass

wafers.


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Documents

Production Technology (MEE-S306) Lecture-1 Machining Advanced Machining Processesuietkanpur.com/Online_Course/AP_MEE_S306.pdf · 2020-04-07 · Advanced Machining Processes(AMPs)