NON-TRADITIONAL MACINING OF METAL MATRIX COMPOSITES

Dr. Babasaheb Ambedkar Technological University Lonere-Raigarh

HARESH S. MAHALAROLL NO:MT2015408

HARESH S. MAHALAROLL NO:MT2015408

OUTLINE

Background of MMCMMCProcessing of MMCWhy Non-Traditional Machining ?Non Traditional Machining ProcessesFuture Scope

BACKGROUND OF MMC

Composites:I. Composite materials are engineered or naturally

occurring materials made from two or more constituent materials.

II. Most composites have two constituent materials: a binder or matrix (polymers, metals, or ceramics) and reinforcement (fibers, particles, flakes, and/or fillers).

III. Classification of composites:(i) Natural, and (ii)Man-made

or synthetic

MMCA metal matrix composite (MMC) is composite material with at least two constituent parts, one being a metal.

Production Technologies in MMC: The most common manufacturing MMC technologies are divided into two main parts: the primary and the secondary.1. Primary processing: Composite fabrication by combining

ingredient materials but not necessarily to final shape or final microstructure.

2. Secondary processing: It follows primary processing, and its aim is to alter the shape or microstructure of the material & may change the constituents of the composite.

CONTINUED….

MMCs fabrication methods (primary processing):1. Liquid phase fabrication2. Solid phase fabrication3. Vapors state processing

MMCs machining methods (secondary processing):1. Conventional method2. Non-conventional method

WHY NON-TRADITIONAL MACHINING ?

The cutting tool and work-piece are always in physical contact, with a relative motion against each other, which results in friction and a significant tool wear.

In NTM processes, there is no physical contact between the tool and work-piece. Although in some non-traditional processes tool wear exists, it rarely is a significant problem.

MRR of the traditional processes is limited by the mechanical properties of the work material. NTM processes easily deal with such difficult-to-cut materials like ceramics and ceramic based tool materials, fiber reinforced materials, carbides, titanium-based alloys.

CONTINUED…..

Machining of small cavities, slits, blind or through holes is difficult with traditional processes, whereas it is a simple work for some NT processes.

Traditional processes are well established, use relatively simple and inexpensive machinery and readily available cutting tools. NTM processes require expensive equipment and tooling as well as skilled labor, which increases significantly the production cost.

TYPES OF NTMMechanical Processes

I. Abrasive Jet Machining (AJM) II. Ultrasonic Machining (USM) III.Water Jet Machining (WJM) IV.Abrasive Water Jet Machining (AWJM)

Electrochemical Processes I. Electrochemical Machining (ECM) II. Electro Chemical Grinding (ECG) III.Electro Jet Drilling (EJD)

Electro-Thermal Processes I. Electro-discharge machining (EDM) II. Laser Jet Machining (LJM) III.Electron Beam Machining (EBM)

Chemical Processes I. Chemical Milling (CHM) II. Photochemical Milling (PCM) etc.

ABRASIVE JET MACHINING (ABJ) Abrasive particles are made to

impinge on the work material at a high velocity.

The high velocity stream of abrasive is generated by converting the pressure energy of the carrier gas or air to its kinetic energy.

High velocity abrasive particles remove the material by micro-cutting action as well as brittle fracture of the work material.

The abrasive particles of around 50 μm grit size would impinge on the work material at velocity of 200 m/s from a nozzle of I.D. of 0.5 mm with a stand off distance of around 2 mm.

AJM SETUP

PROCESS PARAMETERS Abrasive

I. Material – Al2O3 / SiC / glass beads

II. Shape – irregular / spherical III. Size – 10 ~ 50 μm IV. Mass flow rate – 2 ~ 20 gm/min

Carrier gas

I. Composition – Air, CO2, N2

II. Density – Air ~ 1.3 kg/m3

III. Velocity – 500 ~ 700 m/s IV. Pressure – 2 ~ 10 bar V. Flow rate – 5 ~ 30 lpm

Abrasive Jet I. Velocity – 100 ~ 300 m/s II. Stand-off distance – 0.5 ~ 5 mm III. Impingement Angle – 600 ~ 900

Nozzle I. Material – WC / sapphireII. Diameter – (Internal) 0.2 ~ 0.8

mm III. Life – 10 ~ 300 hours

WATER JET MACHINING (WJM)Water is pumped at a sufficiently

high pressure, 200-400 MPa (2000-4000 bar) using intensifier technology.

The potential energy of water is converted into kinetic energy, yielding a high velocity jet (1000 m/s).

Stabilizers (long chain polymers) that hinder the fragmentation of water jet are added to the water.

The cutting ability of water jet machining can be improved drastically by adding hard and sharp abrasive particles into the water jet.

Commercial CNC water jet machining system and cutting heads

ABRASIVE WATER JET MACHINING (AWJM)

In AWJM, abrasive particles like sand (SiO2), glass beads are added to the water jet to enhance its cutting ability by many folds.

the abrasive particles are allowed to entrain in water jet to form abrasive water jet with significant velocity of 800 m/s.

Such high velocity abrasive jet can machine almost any material.

The domain of “harder and “difficult-to-machine” materials like thick plates of steels, aluminum and other commercial materials, metal matrix and ceramic matrix composites, reinforced plastics, layered composites etc are reserved for AWJM.

SCHEMATIC OF AWJM

Stainless steel plate (50 mm thick) machined

with AWJ

Different engineering components machined with AWJ

ULTRASONIC MACHINING (USM)A tool of desired shape vibrates at an

ultrasonic frequency (19 ~ 25 kHz) with an amplitude of around 15 – 50 μm over the work-piece.

Machining zone is flooded with hard abrasive particles generally in the form of a water based slurry.

The tool vibrates over the work-piece, the abrasive particles act as the indenters and indent both the work material and the tool.

Used for machining brittle materials.(cannot be processed by ECM & EDM)

USM SETUP

ELECTROCHEMICAL MACHINING (ECM)

ECM is opposite of electrochemical or galvanic coating or deposition process.

A controlled anodic dissolution at atomic level of the work piece.

Reactions occurring at the electrodes i.e. at the anode or work-piece and at the cathode or the tool along with within the electrolyte.

The potential difference is applied between the anode & cathode.

The material removal takes place due to atomic level dissociation, the machined surface is of excellent surface finish and stress free.

SETUP OF ECM

PROCESS PARAMETERS

Power Supply I. Type: direct current II. Voltage: 2 to 35 V III. Current: 50 to 40,000 A IV. Current density 0.1 A/mm2 to 5

A/mm2

Electrolyte I. Material: NaCl and NaNO3

II. Temperature: 20oC – 50oC III. Flow rate: 20 lpm per 100 A

current IV. Pressure: 0.5 to 20 bar V. Dilution: 100 g/l to 500 g/l

Working gap: 0.1 mm to 2 mm

Overcut: 0.2 mm to 3 mm

Feed rate: 0.5 mm/min to 15 mm/min

Electrode material: Copper, brass, bronze

Surface roughness, Ra :0.2 to 1.5 μm

ELECTROCHEMICAL GRINDINGProcess that combines

electrochemical machining with conventional grinding.

Electrolytic material-removal process involving a negatively charged abrasive grinding wheel, a conductive fluid (electrolyte), and a positively charged work piece.

Grinder wheel is embedded with abrasive particles of diamond or aluminum oxide.

ELECTRO DIELECTRIC MACHINING (EDM)

Electrical energy is used to generate electrical spark and material removal mainly occurs due to thermal energy of the spark.

The tool and the work material are immersed in a dielectric medium.

The electric field is established between the tool and the job, the free electrons on the tool are subjected to electrostatic forces.

The electrical energy is dissipated as the thermal energy of the spark.

The electrons strike the job leading to crater formation due to high temperature and melting and material removal.

WIRE EDM

EDM WIRE EDM

ELECTRON BEAM MACHINING (EBM)

Electron beam gun provides high velocity electrons over a very small spot size.

EBM is required to be carried out in vacuum.

High-energy focused electron beam is made to impinge on the work-piece with a spot size of 10 – 100 μm.

The gun in EBM is used in pulsed mode. Holes can be drilled in thin sheets using a single pulse. For thicker plates, multiple pulses would be required.

SETUP OF EBM

MECHANISM OF MRR IN EBM

Localized heating by focused electron beam

Gradual formation of hole

Penetration till the auxiliary support

Removal due to high vapors pressure

LASER BEAM MACHINING (LBM)Laser stands for light amplification by

stimulated emission of radiation.

Lasing process describes the basic operation of laser, i.e. generation of coherent (both temporal and spatial) beam of light by “light amplification” using “stimulated emission”.

The electron moves from a lower energy level to a higher energy level.

Electron reaches an unstable energy band. And it comes back to its ground state within a very small time by releasing a photon.

Population inversion.

APPLICATION OF LBM

Variation in energy density with spot diameter of thermal beam processes

Electrical discharge typically provides even higher power density with smaller spot size.

Laser beams can be focused over a spot size of 10 – 100 μm with a power density as high as 1 MW/mm2

Defocused electron beam, power density would be as low as 1 Watt/mm2.

In case of focused beam the same can be increased to tens of kW/mm2.

VIDEOS

Electrical Discharge Machining.webmHow Electrochemical Machining Works.webm

How Wire EDM Works.webm

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