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 GroupManufacturing Science Lab Building

Department of Mechanical Engineering

E‐mail: [email protected] 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 sparksoccur across a small gap between tool and work surface. The EDM process must takeplace in the presence of a dielectric fluid, which creates a path for each discharge as thefluid 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 gdischarge 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 systemControl gap

IEG

DC PulseG 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 sheetmetalstamping 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)LASERS TWO TYPES OF LASERS: CONTINUOUS WAVE AND PULSED (WAVE)LASERS

* LONG PULSED LASES AND SHORT PULSED LASERS


TYPES OF LASERSTYPES OF LASERSTIME SCALE

1*10‐3 secondMillisecond

12

1*10‐9 secondNano second1*10‐6 secondMicro second1 10 secondMillisecond

1*10‐15 secondFemto second1*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

16Dr. Arvind Kumar Liquid Metals Group IIT Kanpur

ELECTRON BEAM MACHINING (EBM)

Uses high velocity stream of electrons focused on workpiecesurface 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


21

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/nanolevel

2.Micro/nano components and material removal is at micro/nanolevel (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 2mmMORE CORRECT DEFINITION IS material removal is at micro/nano levelWITH 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 MOULDING MOULDING 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 ( , µBY 10 µm BY 12 µm) MACHINED INTO THE CU SHEET OF AN ELECTRONIC CIRCUIT BOARD

3D MICROMACHINING

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