Manufacturing Process

202TA 202A
Introduction to Manufacturing Processes
2015‐16 (I Semester)
Instructor‐in‐Charge: Prof. Arvind Kumar
Li id M t l GLiquid Metals Group
Manufacturing Science Lab Building
Department of Mechanical Engineering
E‐mail: arvindkr@iitk.ac.in
Telephone: 7484
Webpage: http://home.iitk.ac.in/~arvindkr

Electric Discharge Machining (EDM)
The shape of the finished work surface is produced by a formed electrode tool The sparksThe shape of the finished work surface is produced by a formed electrode tool. The sparks
occur across a small gap between tool and work surface. The EDM process must take
place in the presence of a dielectric fluid, which creates a path for each discharge as the
fluid becomes ionized in the gap. The discharges are generated by a pulsating direct
Dr. Arvind Kumar Liquid Metals Group IIT Kanpur
current power supply connected to the work and the tool.

The discharge occurs at the location where the two surfaces are closest. The dielectric
fluid ionizes at this location to create a path for the discharge. The region in which p g g
discharge occurs is heated to extremely high temperatures, so that a small portion of the
work surface is suddenly melted and removed. The flowing dielectric then flushes away
the small particle (call it a ‘‘ chip ’’ ). Because the surface of the work at the location of
the previous discharge is now separated from the tool by a greater distance this locationthe previous discharge is now separated from the tool by a greater distance, this location
is less likely to be the site of another spark until the surrounding regions have been
reduced to the same level or below. Although the individual discharges remove metal at
very localized points, they occur hundreds or thousands of times per second so that a
gradual erosion of the entire surface occurs in the area of the gap.

ELECTRIC DISCHARGE MACHINING : HOW SPARKING TAKES PLACE?
PULSED D.C.
SOURCE
Asperity
Ion
PULSED
D.C.
SOURCE

ELECTRIC DISCHARGE MACHINING (EDM) : MACHINE ELEMENTS
Servo system
Control gap
IEG
DC
Pulse
G t
Ionized
fluid
Generator
REPLICA OF THE TOOL  WORKPIECE

• Tool: Usually graphite, Brass, Cu, Cu ‐ W;
Di t b l 0 1•   Diameter can be as low as 0.1 mm
•   Dielectric fluid (mineral oil, kerosene, distilled and de ‐ ionized
water) between tool and work piece
• Voltage: 50 – 380 V; Current: 0 1 – 500 A•   Voltage: 50 – 380 V; Current: 0.1 – 500 A
•   Discharge is repeated at rates between 50 and 500 kHz
Applications
• Tooling for many mechanical processes: molds for plastic injection molding• Tooling for many mechanical processes: molds for plastic injection molding,
extrusion dies, wire drawing dies, forging and heading dies, and sheetmetal
stamping dies
• Production parts: delicate parts not rigid enough to withstand conventional
cutting  forces, hole drilling where hole axis is at  an acute angle to surface,
and machining of hard and exotic metals g

Wire EDM
• Work is fed slowly past wire along desired
cutting path, like a bandsaw operation
• CNC used for motion control
• While cutting, wire is continuously
advanced between supply spool and
take‐up spool to maintain a constant
diameterdiameter
• Dielectric required, using nozzles directed
at tool‐work interface or submerging
workpart
ApplicationsApplications
• Production of die cavities for large
automotive–body components
• Deep small diameter holes
Deep small diameter holes
• Narrow slots in turbine blades

Laser Machining
• LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION (LASER)( )
• A laser converts electrical energy into a highly coherent  light beam with the
following properties:
– Monochromatic (theoretically, single wave length)
Highly collimated (light rays are almost perfectly parallel)– Highly collimated (light rays are almost perfectly parallel)
•  These properties allow laser light to be focused, using optical lenses, onto a very
small spot with resulting high power densities

Laser Beam Machining (LBM)
Uses the light energy from a laser to remove material by vaporization & ablation
* TWO TYPES OF LASERS: CONTINUOUS WAVE AND PULSED (WAVE)LASERSTWO TYPES OF LASERS: CONTINUOUS WAVE AND PULSED (WAVE)LASERS
* LONG PULSED LASES AND SHORT PULSED LASERS

TYPES  OF  LASERSTYPES  OF  LASERS
TIME SCALE
1*10‐3 secondMillisecond
12
1*10‐9 secondNano second
1*10‐6 secondMicro second
1 10 secondMillisecond
1*10‐15 secondFemto second
1*10‐12 secondPico second
LBM Applications
• Drilling, slitting, slotting, scribing, and marking operations

• Drilling small diameter holes ‐ down to 0.025 mm (0.001 in)
• Generally used on thin stock
• Work materials: metals with high hardness and strength, soft metals,
ceramics, glass and glass epoxy, plastics, rubber, cloth, and wood

LONG PULSE LASER MACHINING
DEMERITS OFDEMERITS OF
LONG PULSE
LASER

SHORT PULSE LASER MACHINING
MERITS OF SHORTMERITS OF SHORT
PULSE LASER

MICRO MACHINED LETTERS ON A SINGLE HUMAN HAIR
NOTE THE CLARITY OF THE LETTERS IN THE CLOSE-UP VIEW
16

ELECTRON BEAM MACHINING (EBM)
Uses high velocity stream of electrons focused on workpiece
surface to remove material by melting and vaporization
• EB gun accelerates a continuous
t f l t t b t 75%stream of electrons to about 75%
of light speed
•  Beam is focused through
electromagnetic lens,
reducing diameter to as small as
0.025 mm (0.001 in)
• On impinging work surface, kinetic
energy of electrons is converted toenergy of electrons is converted to
thermal energy of extremely high
density which melts or vaporizes
material in a very localized area

BASICS OF EBM
• IT WORKS IN MUCH THE SAME WAY AS A CATHODE RAY TUBE IN A
TELEVISION.
CATHODE SECTION(GENERATES BEAM)
ANODE SECTION(ACCELERATES THE BEAM)
LENS SYSTEM CONVERGES AND DEFLECTS THE
BEAM TO THE DESIRED POSITION
ELECTRON‐BEAM
ELECTRON MASS
ELECTRON V ELOCITY
MACHINING PROCESS

WHY VACCUM IS REQUIRED?
ELECTRON‐BEAM IN A
VACUUM
ELECTRON BEAM INELECTRON BEAM IN
AMBIENT AIR

EBM Applications
Id l f i hi iIdeal for micromachining
– Drilling small diameter holes ‐ down to 0.05 mm (0.002 in)
– Cutting slots only about 0.025 mm (0.001 in.) wide
Drilling holes with very high depth‐to‐diameter ratios
– Ratios greater than 100:1

MICRO MACHINING
Mi M hi iMicro Machining
Removal of material at micro levelRemoval of material at micro level
1.Macro components but material removal is at micro/nano
level
2.Micro/nano components and material removal is at micro/nano
level (Ex. MEMS, NEMS)
Unfortunately the presentUnfortunately , the present
day notion is
LEG OF A HOUSE FLY
Machining of highly miniature
components with miniature features.
LEG OF A HOUSE FLY
Literally it is NOT correct
SIZE : 2mm x 2mm
MORE CORRECT DEFINITION IS material removal is at micro/nano level
WITH NO CONSTRAINT ON THE SIZE OF THE COMPONENT

EXAMPLES OF EDMM
Holes as small as 6.5 microns in diameter
and an aspect ratio of 7.5
30‐micron shafts and 50‐micron
holes produced by micro‐EDM

EXAMPLES OF EDMM
MICROFLUIDICS MIXER
PIN OVER
MOULDINGMOULDING
JIG (655 m
HOLES)
520  m DIA
EXTRUSION DIE
MICRO GEARS
(DIA 520 m )LADDER WITH 100 m
GAP BETWEEN
TEETH

APPLICATIONS OF ECMM
MICRO‐HOLES PRODUCED ON A
Ti6Al4V CYLINDER USING JET‐EMM
PRODUCTION OF HIGH ACCURACY HOLES
6 4
CU STRUCTURE (SMALL PRISM, 5 µm( , µ
BY 10 µm BY 12 µm) MACHINED INTO
THE CU SHEET OF AN ELECTRONIC
CIRCUIT BOARD
3D MICROMACHINING

Manufacturing Process

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