micro mach

RECENT TRENDS OF“NON-CONVENTIONAL MICROMACHINING”

Taha Ali El-TaweelProduction Engineering and Mechanical Design

Faculty of Engineering, Shebin El-Kom, Menoufiya University

By

INTRODUCTION Electrochemical micro-machining (EMM)

Through-maskless - Through-mask Micro-electrodischarge machining (MEDM) Laser micro-machining (LMM)

Mask projection techniques - Direct writing techniques Micro-ultrasonic machining (MUSM) Chemical- micro machining (CMM)

Dry chemical etching - Wet chemical etching FUTURE POTENTIAL

LAYOUT OF THE PRESENTATION

Thermal Action- EDM- LBM- IBM

Mechanical Action- USM- WJM- AJM

INTRODUCTION

The need for fabricating parts from hardened high-strength and heat-resistant metals and alloys has created difficult machining problems for industry. To meet these problems, non-conventional machining methods have been developed. (no mechanical force)

Chemical ActionChemical Milling

Electrochemical Action- ECM

Non-conventional Machining

Micro-machining

The term micro-machining refers to material removal of small dimensions that range from several microns to one millimeter.

NON-CONVENTIONAL MICROMACHINING

• Electrochemical micro-machining (EMM)• Micro-electrodischarge machining (MEDM) • Laser micro-machining (LMM) • Ultrasonic micro-machining (USMM) • Chemical micro-machining (CMM)

The unit of removal can be of the order of atomic quantities through;

Electrochemical machining (ECM)Electrochemical machining (ECM) Ion exchange is the metal removal mechanism.- Reverse of electroplating- Workpiece must be electrically conductive- Electrolyte acts as a current carrier

- High rate of electrolyte movement; washes metal ions. - ECM for the production of gas turbine compressor blades

Principle of ECM machining

EMM through-maskless EMM through-mask

Electrochemical micro-machining

- Capillary drilling- MEJM

- One-sided EMM- Two-sided EMM

Electrochemical micro-machining (EMM)

Requires highly localized material removal induced by the impingement of a fine electrolytic jet.


EMM through-maskless Micro electrochemical jet machining (MEJM)

Capillary drilling workpiece(anode)

nozzle diameter

electrolyte jet (cathode)

Insulation

glass tubeplatinum (cathode)

workpiece (anode)

electrolyte

MEJM Capillary drilling

Removes material by using an electrolyte jet from a small nozzle, which works as cathode without advancement of the jet.

Fine cathode tool in the form of a capillary that is advanced at constant rate towards the workpiece.

EMM through-mask

Involves selective metal dissolution from unprotected areas of a one- or two-sided photoresist-patterned workpiece.

The sample is held in a stationary holder while the multi-nozzle cathode, which is attached to the table, moves at a constant speed facing the sample

One-sided

Localized dissolution induced by scanning two cathode assemblies over a vertically held work-piece providing movement of the electrolyte

Two-sided

One-sided EMM Two-sided EMM


Fabrication of micro-electronic components

Ink-jet nozzle plates Metal masks Micro-hole drilling Micro-surface production

Ink-jet nozzle

Photograph of micro holes Cylindrical micropin DC current

Pulse current

EMM applications

Micro gear pattern

Machining with ultra-short voltage

pulses

EMM applications

Micro grooves by wire ECM

Electrodischarge machining (EDM)

Electrical Discharge Machining (EDM) is a non-conventional machining technique in which the material is removed by the erosive action of electrical discharges (sparks) provided by a generator.

Benefits Widely accepted production technology -

2% of worldwide machining. High surface finishes Hardness of material not a concern Odd/Delicate shapes easier to produce Small holes easy to produce Heat treatment usually unnecessary

Drawbacks Slower machining time Surface integrity effects

Electrodischarge machining (EDM)

EDM Process Mechanism

Different Types of EDMDie-sinking EDM Wire EDM Machinable material » electrically conductive » semiconductor materials

Schematic illustration of EDM system Principle of WEDG

Can be made » micro shafts » micro holes » other complex shapes

Micro-electrodischarge machining (MEDM)

It is required for micro-machining to maintain the energy of a single discharge in the order of 10-6J to10-7J

E =1/2 (C + C') V 2

Reducing the discharge energy: » By reducing the discharge voltage » By reducing the total capacitance (C + C') Effective discharge control can be achieved,by Controlling parameters:» Discharge current» Open circuit voltage » Off-time» Polarity of electrode

Description of eroding pattern and overlapping pattern of discharge

MEDM applications

. MEDM of ceramics

Cross-sectional shape on the TiN coating and the EDMed surface

Micro-electrodes for and micro-pins

Fabrication of Micronozzle

Micro-hole drilling

positive polarity negative polarity

MEDM applications

Pagoda machined by micro wire EDM

Laser machining (LM)

– Heat treatment– Welding– Ablation– Deposition– Etching– Focused beam milling

Laser applications

Setup of the laser micro-machining

Highly focused optical energy of Laser is used to melt and evaporate workpiece portions in a controlled manner.- Refectivity and thermal conductivity of workpiece are important

- Widely used in automotive and electronics industries due to its accuracy, reproducibility, flexibility, ease of automation.

LMM applications

» Micro-machining of electrostatic electron lenses» Ink-jet printer nozzles» Micro-hole drilling » Micro-channels produced by mask projection» Manufacturing of 3D structures

Example geometries in WC/Co

Ink-jet printer nozzles

Micro-channelsMicro-holes

Ultrasonic machining (USM)Ultrasound - above 20 kHz, can be generated using peizoelectric or magnetostictive effects

- A formed tool, with the shape of the cavity to be machined is made to vibrate against the workpiece surface and between the two are placed abrasive particles (slurry).

- The material is removed in the form of grains by shear deformation, brittle fracture of work material; and by impact, cavitation and chemical reaction

Principle of USM

Micro-ultrasonic machining (MUSM)

Micro USM procedure

MUSM tools

The WEDG/EDM combination is used to generate co-axial micro-tool first, which MUSM of brittle materials carried out

Non-thermal, non-chemical and thus can produce a high-quality surface finish

The machining procedure of microtool

MUSM applications

» Micro-hole drilling

The entrance The exit

Micro air turbine.Center pin diameter 70 µm; rotor diameter 350 µm

Finishing

» Manufacturing of 3D s tructures

» Finishing EDMed parts

Chemical machining (CM))

# Chemical milling# Chemical blanking# Photochemical blankingUsed to make precise, microscopic holes microscopic grooves

Material removal from the surface by controlled chemical dissolution using reagents, etchants- acids/alkalies

» Dry chemical etching » Wet chemical etching

» Photoetching (lithography and isotropic etching)

Chemical-micro machining (CMM)

CMM applications

Surface etching Electrochemical etching

Chemical milling (surgical knife tool)

FUTURE POTENTIAL The use of ultra-short pulses

in EMM, MEDM & Laser to machine the widest choice of materials with very high quality.

Studying the effect of machining parameters on surface integrity of micro component.

Newest hybrid processes are suggested for micro-machining.

EMM with Laser Assistance (EMML)

EMM with MEDM MUSM with EMM & MEDM

Nanomachinery

Nanofabrication as another way to get into the nano domain

Nanomachinery

Aerospace: Gyroscopes, transducersBiomedical: DNA detection/separation devicesMolecular: sieves for protein sortingElectronics: Flexible (paper like) displays,nanowiresAutomotive: Accelerometers, pressure sensorsHealthcare: Nanotherapeutic devices, catheters,infusion pumps, intrauterine products

Industry Application Examples

Nanomachinery

Scanning probe microscopes have been used for the machining of nanofeatures ranging from ~100 nm down to atomic dimensions

Various approaches used are based on lithography, atomic and molecular level manipulation and material transfer, material modification by tip induced oxidation desorption hydrogenation or decomposition mechanical scratching of metals semiconductors and polymers.

Nano Machining Using SPM

Nanomachinery

Bottom-up processes Top-down processesContact printing, ImprintingTemplate growth Spinoidal wetting/dewettingLaser trapping/tweezerAssembly and joining (Self- and directed assembly)Electrostatic (coatings and fibres)Colloidal aggregation.

Lithography (E-beam, ion beam, Scanning probe, optical near field)

Energy beam machining (Laser, electron beam, ion beam)

Erosive processes (electrical, chemical, mechanical and ultrasonic)

Typical nanomachining processes

Nanomachinery

Nano groove (1000 × 150 × 2.4 nm )machinedin copper using atomic force microscope

Nanomachinery applications

5 μm deep spiral machined in Ni sheet Nanomachining by ECM

(a) Tungsten Tool(b) Structure in

Ni

Nanomachinery applications