ME16351-Unit 3-Unconventional machining

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UNIT III 
Non-Traditional machining methods (NTMM) 
3 outstanding needs of future manufacturing technology are 
i) Sustained productivity in face of rising strength barriers 
ii) Higher accuracy consistent with the increasing demand for higher tolerances and 
iii) Versatility of automation 
 
The strength of alloy steels has increased 5 fold due to continuous R&D effort (100-500 
BHN) 
In advanced industries like aerospace, nuclear power, requirement of high strength at elevated 
temperatures with light weight has led to the development and use of hard titanium alloys, 
nimonic alloys and high-strength-temperature-resistant (HSTR) alloys. 
With the development of new high-strength materials, it has become essential to develop 
improved cutting tool materials so that productivity is not hampered by the rising strength 
barrier. This is governed by the fact that tool material must be harder than the work piece 
material. In addition to carbon tool steels, High-speed steels (HSS), cemented carbides, 
ceramics and satellites are used as tool materials now-a-days. 
 In spite of rapid technological advancements in the field of conventional machining, the 
machining of carbides and hard – to – machine materials has been limited to the diamond 
wheel grinding for a long time. The process has become costly because of the scarcity and 
high cost of abrasives necessary for the diamond wheel. 
Besides, the processing of the parts of complicated shaped have been difficult, time 
consuming and uneconomical by conventional machining, looking forward to greater scope 
for further development. 
Consequently, some non-traditional techniques of machining (NTMM) have been invented in 
order to supplement effectively the metal cutting, pressure forming and casting methods, 
especially when a complicated shape is to be produced on any hard-to-machine and brittle 
material. These are now-a-days known as ‘New technologies’. 
 
Classification of new technology 
These processes are not affected by hardness, toughness or brittleness of materials and can 
produce any intricate shape on any work piece materials by suitable control over the physical 
parameters of the processes. The underlying principle is to apply some sort of energy to the 
workpiece directly and have the desired shape transformation or material removal from the 
work surface by using the known scientific principles. 
 
 
 
 
 
 
 
 
 
 
EDM (Electric Discharge Machining) or Spark erosion machining 
The machining process involves controlled erosion of electrically conducting materials by the 
initiation of rapid and repetitive electrical spark discharge between the tool (or cathode) and 
the workpiece (or anode) separated by a dielectric fluid medium. 
 
A suitable gap, known as spark gap, is maintained between the tool and the (0.01-0.5mm) 
workpiece to cause the spark discharge. 
Due to the presence of micro-irregularities on the surface of workpiece and electrode, the 
spark discharge is produced by the controlled pulsing of direct current at the shortest distance 
between the workpiece and tool. 
A conducting electrical path is developed for the spark discharge owing to the ionisation of 
the fluid medium in the spark gap. 
Billions of electrons are developed in each spark and thousands of sparks are normally 
initiated in each second to produce a true replica of the tool surface on the workpiece. 
The amount of energy contained in each spark is discrete and it can be controlled so that the 
material removal rate, surface finish and tolerance can be predicted. 
 
 
The temperature of the spot may rise upto 10000°C causing the work surface to melt and 
vapourize. 
A dielectric flushing system removes the debris and the machining is continued in some other 
place where the gap is the smallest. 
 
ELECTRODE MATERIAL 
It should have either a high melting point or vapourizing temperature like that of graphite or 
high thermal conducting like copper. Other materials used are brass, tungsten-copper, 
Tellurium copper, silver tungsten. 
Electrodes are manufactured by conventional machining techniques. Electroforming of 
copper electrode and moulding of graphite is also done. 
 
The functions of dielectric fluid are: 
1) It acts as a coolant between tool and workpiece and enables arcing to be prevented. 
2) It serves as a conducting medium when ionised and conveys the spark. 
3) It serves as a flushing medium in removing chips. 
 
Kerosene is the most common dielectric fluid. Others include silicon oils, white spirit, 
transformer oil and aqueous solution of ethylene glycol. 
 
Solution based upon 
1) High electric strength for proper insulation. 
2) Low viscosity and good wetting capacity. 
3) Chemical neutrality 
4) High flash and fire point to avoid fire hazards. 
5) Non-toxic fumes. 
6) Low decomposition rate. 
7) Low cost. 
 
Advantages 
1) The process can be applied to all electrically conducting metals and alloys irrespective of 
strength, hardness brittleness or toughness. 
2) It works without any cutting force (expect blasting pressure), hence it allows machining 
of thin, fragile complicated jobs. 
3) Machining time is less. 
4) Advantageous for tool maintenance and repair work. 
5) Dimensional repeatability and surface finish obtained are extremely good. 
6) Surface produced helps in better oil retention, thus improving the die life. 
7) Once set up, does not need constant operator’s attention. 
 
Disadvantages 
1) Power required is very high. 
2) Reproduction of sharp corners is the limitation of the process. 
3) Surface cracking may take place. 
4) Distortion of surface microstructure in some cases. 
 
Applications used for machining of 
1) Tools, dies, fixtures, cutting tools and gauges. 
2) Press tools, extrusion dies, sintering and press dies, injection moulds, mould insert, 
pressure roller dies, hammer moulds, repair and modification of mould inserts. 
3) Manufacture of forging dies, trimming dies, repair of damaged hot or cold forging dies, 
cutting dies, guides, stripper plate. 
4) Cutting and calibrating tools. 
5) Jet engine components, reactor components, electronic parts, production fixture. 
6) EDG of complicated tungsten carbide tools, templates, gauge axle, stamping tools. 
 
ELECTROCHEMICAL MACHINING (ECM) 
It is a process in which the metal removal is achieved by controlled anode dissolution in an 
electrolytic medium containing anode (workpiece) and cathode (tool). 
 
The metal removal is governed by Faraday’s Law of electrolysis. 
Fig. shows two electrodes which are placed closely with a gap (0.05 – 0.7mm) and immersed 
in an electrolyte which is Nacl solution. 
When an electrical potential of about 20V is applied between the electrodes, the ions existing 
in the electrolyte migrate towards the electrodes. Positively changed ions are attracted 
towards the cathode and negatively charged ions are attracted towards the anode. This 
initiates the flow of current in the electrolyte. 
 
The rate at which the ions arrive at their respective electrode determines the current density 
and varies in direct proportion to the applied voltage, the concentration of the electrolyte and 
the gap between the electrodes. 
The electrolysis process that takes place at the cathode liberates hydroxide ions and free 
hydrogen. The hydroxyl ions combine with the metal ions of anode to form insoluble metal 
hydroxide and the material is thus removed from the anode. This process continues and the 
tool reproduces its shape in the workpiece (anode) as shown in Fig. 
 
FARADAY I LAW: The amount of chemical change produced by current is proportional to 
the quantity of electricity that is passed through the electrolyte 
FARADAY II LAW: The amount of metal removed from an electrode by the flow of same 
quantity of electricity is equal to one gram equivalent weight of metal. 
 
 
 
 
 
 
Advantages1) There is virtually no wear of the metal. 
2) No burrs are produced 
3) The rate of metal removal is not dependent on the physical properties of the metal. All 
metals, regardless of hardness, are machined at nearly the same rate. 
4) Any complicated profile can be easily machined in a single step operation of the process. 
5) The machining time of conventional finish machining contain grinding, deburring, deep-
hole drilling, internal spline forming, honing has been reduced. 
6) No thermal damage to the workpiece. 
7) Bright and smooth finish can be obtained. 
8) The process can be easily automated, the important parameters controlled one voltage, 
current, feed rate, electrolyte pressure and electrolyte temperature. 
 
Limitations 
1) High electrical power is consumed. 
2) Post machining cleaning is a must to reduce the corrosion of the workpiece. 
3) Sharp internal corners cannot be produced. 
4) Stray etching and inter-granular attack needs modification of electrolyte and careful 
control of parameters. 
5) Electrical connections to the workpiece must be handled carefully to reduce the heating 
effect due to the large current flow. 
6) Maintenance of higher tolerances requires complicated controls. 
 
Applications 
ECM process can be used in applications where the quantity of parts required is high so that 
the process economy is justified. 
It is used to machine gear coupling, forging dies, complicated parts for textile industry, 
extrusion dies, turbine blades, parts in automotive industry etc. 
It is a versatile metal working process, the specific advantage in productivity can be in the 
application of fairly difficult shapes in fairly difficult-to-machine material like stainless steel, 
alloy steel etc. 
 
ULTRASONIC MACHINING (USM) 
Ultrasonic machining removes material through erosion by abrasive particles. The energy to 
these particles are imparted by a tool oscillating normal to the work surface at ultrasonic 
frequency of 20 – 30kHz. The tool is pressed against the workpiece with a few kgs of force 
and the abrasive slurry made of water and abrasive is pumped in at low pressure. The shape 
of the tool is copied on to the workpiece with a fair degree of accuracy. 
 
Analysis of the mechanism of material removal by USM process indicates that it may 
sometimes be called as Ultrasonic grinding or impact grinding but however there are some 
basic differences. 
 
 Ultrasonic machining Conventional grinding 
Motion Motion of the tool is normal to work 
surface. 
Motion of grinding wheel is 
tangential to workpiece. 
Basic process Material removal occurs by: 
Shear deformation, Brittle fracture 
through impact, Cavitation, Chemical 
action 
Material removal takes place by 
shear deformation. 
Abrasive grits Grits are externally supplied in a slurry. Wheel itself composed of grits. 
 
In USM process, ultrasonic waves or vibrations are transformed by means of a 
magnetostrictive transducer into mechanical vibrations of small amplitude and high 
frequency. 
A horn (stepped or exponential) is attached to the end of the transducer for mechanical 
amplification of the amplitude of vibration of the transducer and a tool of any desired shape is 
attached at the free end of the horn to serve the purpose of cutting. 
As the tool vibrates with a specific frequency, an abrasive slurry (usually a mixture of 
abrasive grains and water of definite proportion) is made to flow through the tool – 
workpiece interface at low pressure. The impact force arising out of the vibration of the tool 
 
end and the flow of slurry through the work-tool interface actually causes thousands of 
microscopic abrasive grains to remove the work material by abrasion. Material removal from 
hand and brittle materials will be in the form of sinking, engraving or any other precision 
shape. 
 
Various parameters which influence the M.R.R are 
1) Slurry temperature 
2) Amplitude of tool vibration 
3) Grit size and 
4) Work material condition 
 
The ultrasonic vibrations imparted to the fluid medium surrounding the tool have three fold 
action as follows: 
1) To bring about the ultrasonic dispersion effect rapidly in the machining fluid medium 
between the tool end and the machining surface of the workpiece. 
2) To cause violent circulation of the fluid as a result of micro – agitation. 
3) To causes the cavitation effect in the fluid medium arising out of the ultrasonic vibrations 
of the tool in the fluid medium. 
 
The abrasives used generally are: 
1) Boron carbide 
2) Silicon carbide and 
3) Aluminium oxide 
 
The liquid used in the slurry can be water, benzene, glycerol, oil, etc. Chemical additive may 
sometimes be added to aid the cutting action by chemical action. 
Steel is generally chosen to be the tool material. Material for horn are K-monel metal, bronze 
and mild steel. 
 
Magentostriction means a change in the dimensions occurring in ferromagnetic materials 
subject to an alternating magnetic field. When the transducer is magnetised, a change in 
length occurs. The connecting body attached to the transducer receives and transmits this 
change in length and is further amplified by a horn. 
(Eg) Alloys of nickel, Cr, iron, cobalt, Invar etc 
 
Advantages 
1) Hard – to – machine and brittle materials – whether conductive or non-conductive 
material (like gemstones, synthetic ruby, glass) can be machined. 
2) Since heat is not generated in this process, materials can be machined without any 
transformation of grain structure which would affect the physical properties of materials. 
3) Dimensional accuracy obtained is of the order of ±0.005mm 
 
Limitations 
1) Lower metal cutting rates. 
2) Depth to diameter ratio upto only 1:2.5 possible. 
3) High tool wear which introduces taper on the workpiece. 
 
Applications 
1) USM can perform machining operations like drilling, grinding, profiling and milling 
operations on all materials which can be treated suitably with abrasives. 
2) It has efficiently applied to machine glass, ceramics, precision mineral stones, sintered 
carbides, titanium and tungsten. 
3) It has been applied for piercing of dies and for parting off and blanking operations. 
4) Machining of semi-conductors, ferrites and steel parts can be done by USM. 
5) It enables a dentist to drill a hole of any shape on teeth without creating pain. 
6) USM can be applied in conjuction with EDM, ECM, ECG etc to obtain better efficiency. 
 
ABRASIVE JET MACHINING (AJM) 
A focussed stream of abrasive particles carried by a high pressure gas or air is made to 
impinge on the work surface through a nozzle and the work material is removed by erosion 
by the high velocity abrasive particles. 
 
It basically differs from sand blasting operation because 
1) The abrasive particles are of finer size in AJM than in the sand blasting operation. 
2) Process parameters of AJM can be made properly controlled and regulated in comparison 
with sand blasting operation. 
 
 
 
The filtered gas, supplied under pressure to the mixing chamber containing the abrasive 
powder and vibrating at 50Hz, entrains the abrasive particles and is then passed into a 
connecting hose. 
This abrasive feed rate is controlled by the amplitude of vibration of the mixing chamber. A 
pressure regulator controls the gas flow and pressure. 
The nozzle is mounted on a fixture. Either the workpiece on nozzle is moved by cams, 
pantographs or other suitable mechanisms to control the size and shape of the cut. 
Hand operation is sometimes adequate for removing surface contaminations or in cutting 
where accuracy is not critical. 
Dust removal equipment is necessary to protect the environment. 
 
 
The criteria used for evaluating the AJM process viz., M.R.R. geometry of cut, surface 
roughness and nozzle wear rate are influenced by 
a) Abrasive – composition, shape, size and flow rate of abrasives.b) Carrier gas - pressure, velocity, molecular weight and flow rate. 
c) Nozzle - geometry, material of construction, stand off distance, orientation with 
horizon. 
Principle: Abrasion by high-speed gas abrasive stream 
Abrasive: Al2O3, SiC, NaHCo3, dolomite, glass beads size 20-50 microns. 
Flow rate of abrasive : 3 – 20 gm/min 
Velocity (exit) : 200 – 400 m/s 
Pressure : 2 – 8.5 kgf/cm
2
 
Nozzle size : 0.07 – 0.4 mm 
Material of nozzle : Sapphire, Tungsten carbide 
Nozzle life : 12 – 300hrs 
Stand -off distance : 0.7 – 15 mm 
Carrier gas : Air, Co2, N2 
 
Advantages 
1) Ability to cut intricate hole shapes in materials of any hardness and toughness. 
2) Ability to cut fragile and heat sensitive materials without damage. 
3) Low capital cost. 
4) Depth of surface damage is low. 
5) High surface finish can be achieved. 
 
Disadvantages 
1) Material removal rate is low. 
2) Abrasive may get embedded in the work surface. 
3) Stray cutting is difficult to avoid. 
4) Tapering effect because of flaring of the jet. 
5) There must be a suitable dust collecting system. 
 
Applications 
1) For suitable machining super alloys and refractory materials. 
2) To machine thin sections of hard materials and for making intricate holes. 
3) Used in cutting, drilling, grooving, cleaning, finishing and deburring operations of hard 
and brittle materials like germanium, glass, ceramic and mica. 
4) To prepare surfaces for strain gauge applications. 
5) To create artificial flaws in materials for calibration of testing equipments. 
 
LASER BEAM MACHINING (LBM) 
It is a machining process in which the work material is melted and vaporized by means of an 
intense, narrow monochromatic beam of light called the laser. 
 
LASER – Light Amplification by Stimulated Emission of Radiation 
Specialities of laser rays are: 
i) Spectral purity. 
ii) Highly directive property 
iii) Highly focussed density. 
 
Two types of lasers are now in common use: 
1) Solid laser – short bursts of power 
2) Gas laser – continuous laser beam 
Solid lasers best suited to production work use a neodymium – doped glass rod or ruby as the 
lasing medium. The rod ends are finished as optical surfaces with reflective coatings. One 
end has a partially reflective coating to permit escape of the laser beam when it has reached 
the required intensity. The laser rod is initially excited by a high intensity flash lamp. 
Mirrors located inside the optical oscillators are used to reflect and to focus the light inside 
the discharge tube or optical oscillator. 
Co2 gas laser is the most efficient; it operates in basically the same manner as solid laser 
except that the gas serves as the lasing medium and is capable of producing a continuous 
laser beam and hence suited for cutting or welding. 
The principle on which a laser operates is that electrons in certain atoms oscillate when 
energy is supplied. 
 
Laser circuit consists of following parts: 
i) A pair of mirrors – one of them is perfect reflector and second is partially reflector. 
ii) A source of energy – flash lamp filled with xenon, argon or krypton. 
iii) An optical amplifier – laser 
iv) A control system, and 
v) A cooling system. 
 
 
The flash lamp is placed close to the laser inside a highly reflective cylinder so that as much 
energy as possible can be absorbed by the laser material. 
From the flash tube when energy is pumped into laser, light begins to bounce back and forth 
between two reflecting mirrors and light is amplified each time it oscillates and rapidly 
becomes very intense. At some point, light goes out through the partially reflecting mirror. 
This highly amplified light beam is focussed through a lens and made to fall at a selected spot 
on the workpiece by accomplishing the machining operations. 
 
 
 
Advantages 
1) Non-contact process with no workpiece distortion. 
2) Machining of any material including non-metal is possible, irrespective of their hardness 
and brittleness. 
3) Welding, drilling and cutting of areas not readily accessible are possible as long as the 
beam path is not obtained. 
4) Because the HAZ is small (0.1mm), it can weld or machine regions close to heat-sensitive 
components. 
5) Extremely small holes can be machined (precise operation). 
6) It can be weld or machine through glass or any optically transparent material. 
7) It can easily weld dissimilar materials. 
8) Process can be easily automated. 
9) Soft materials like rubber and plastics can be machined. 
 
Limitations 
1) High capital and operating cost. 
2) Its overall efficiency is extremely low (10 – 15%) 
3) Process is limited to thin sheets and low MRR 
4) Effective safety procedures are required. 
5) Certain materials like fibre-glass, reinforced materials, phenolics, vinyls etc cannot be 
worked by laser as these materials burn, char and bubble. 
6) Life of the flash lamp is short. 
 
Applications 
Laser drilling 
Holes with diameters ranging from 0.02mm to 0.5mm with a depth to diameter ratio as high 
as 20:1 can be economically drilled on metal. 
(Eg.) Drilling of fuel injection nozzle hole (0.02mm) at 30° angle – one hole per second. 
Drilling jet engine turbine vanes, Hole drilling on ceramic and alumina substrates, Drilling of 
PCB. 
 
Laser welding 
Gear box, wheel rims, steering jacket, torque converter, oil tanker, spark plug electrode 
welding. 
Soldering of beryllium, copper, lead. 
Soldering and wire stripping of electronic components. 
 
Laser heat treatment 
Suitable for selective heat treatment of materials. The quenching is by heat conduction to 
the bulk material, eliminating the need for external quenching. 
(Eg.) Cam shaft lobes, journals, fillets and pins of crankshaft, cast iron, valve seats, cylinder 
box and gear teeth. 
 
 
Laser cutting 
To cut titanium and its alloys in aircraft industry. 
 
Laser marking and engraving 
Writing speed upto 200mm/sec. 
Engraving of component members, name plates and trade marks in automobile industry. 
Marking and engraving of resistors, capacitors and ICs, ceramic scribing. 
 
Laser dynamic balancing 
Dynamic balancing of small rotating parts. 
Dynamic balancing of helicopter shafts. 
Other include drilling of baby milk bottle nipples, cigarette filter paper perforation, drilling 
and cutting of diamond. 
Resistor trimming, hermetic sealing of tantalum capacitors. 
 
PLASMA ARC MACHINING 
It is a process in which a high velocity jet of high temperature (11000 - 30000°C) ionised gas 
directed on the workpiece, melts, vaporises the material to the required shape. 
Plasma is a mixture of free electrons, positively charged ions and highly excited neutral 
atoms of a gas. It can be obtained by heating the gas at temperature above 5500°C, they are 
partially ionized and exist as plasma. 
Because of the high temperature involved, the process can be used on almost all material 
including those which are resistant to oxy-fuel gas cutting. 
A flowing volume of gas is subjected to the electron bombardment of an electric (pilot) are 
produced between a cathode electrode and anode nozzle as shown in Fig. 
The high velocity electrons generated by the arc collide with the gas molecules and produce 
dissociation of di-atomic molecules of gases like H2, N2, O2 etc., resulting in ionization of the 
atoms. 
A main arc is struck between the cathode electrode of the plasma arc generator and the 
workpiece when the plasma forming gas is made to flow through the constricted nozzle. 
Once the main (external) arc is generated, the pilot arc goes off. 
The flow of the gas should be such that the arc can be stabilized. 
Most of the heat transfer of the gas occurs at the constricted nozzle region resulting in high 
exit gas velocity with high core temperature of plasma column thus generated. 
 
 
The process of material removal is effected in 2 stages: 
1) Heating ofthe workpiece by electron bombardment and by convective heat transfer from 
the plasma column and, 
2) Blasting the molten metal away by fluid dynamic forces. 
 
The process parameters can be controlled by suitable adjustments of power, gas type, gas 
flow rate, traverse speed and flame angle, stand-off distance. 
 
GAS 
Carbon steels, alloy steels and cast iron – mixture of N2 - H2 or with compressed air. 
Stainless steel, aluminium and non-ferrous metals – Argon-H2 or N2 - H2 
 
Advantages 
1) It is almost equally effective on any metal, regardless of its hardness or refractory nature. 
2) Cutting rates in this process are high (5m/min) enough to facilitate this method to be used 
on almost all materials. 
3) As there is no direct contact of the tool and workpiece, only a simply supported 
workpiece structure is enough. 
4) Arc plasma torches give the highest temperature suitable for many practical purposes. 
The energy seems to be unlimited in this method. 
Disadvantages 
1) Heat affected zone which are high and needs secondary operation to ensure proper 
surfaces. 
2) Needs eye shielding and noise protection for the operator. 
3) High initial cost of the equipment. 
 
Applications 
1) It is used to cut stainless steel and aluminium alloys as it produces a smoother cut 
compared to oxyfuel cutting. Thickness upto 150mm can be cut effectively. 
2) Plasma arc is also used in conventional turning and milling machines to machine very 
hard materials successfully. 
3) It is used for removing gates and risers in foundry. 
4) Finds applications in many industries such as chemical, shipyard, nuclear and pressure 
vessel. 
 
Electron Beam machining (EBM) 
It is a process in which the material is removed with the help of a high velocity focussed 
stream of electrons (exceeding half the speed of light) which heats, melts and vapourises the 
work material at the point of bombardment, in vacuum. 
The production of free electrons is obtained by using a heated cathode emitting electrons. The 
acceleration of these electrons is carried out by an electric field while the focussing and 
concentration is done by controllable magnetic fields. The high momentum acquired by the 
electrons is lost through impingement with the atoms of the work material. 
The schematic diagram of EBM set up is shown in Fig. 
The electron gun emitting electron beam consists of a cathode, which is heated upto a high 
temperature and emitting electrode. 
 
The gun is supplied with electric current from a high voltage d.c source. 
At some distance from the cathode is the first anode with an aperture. The emitter is so 
designed as to ensure focussing of the electron beam through the anode aperture. 
The potential of the anode must be of very high order (50-150kV) so that emitted electrons 
from the cathode can acquire very high velocity. 
The electron beam is focussed by magnetic lens and strikes the workpiece with high kinetic 
energy which on impingement on the workpiece heats the workpiece material to a very high 
temperature which can melt or even vapourise the work material. 
The magnetic deflection system which controls the electron beam to be positioned accurately 
on the spot. 
This process takes place in a vacuum chamber (10
-5
 to 10
-6
 mm of Hg) to 
a) ensure the free movement of electrons from cathode to anode and onto the workpiece 
b) protect the cathode from chemical contamination and hence losses, and 
c) prevent the possibility of an arc discharge between the electrodes 
Equipments are available in capacities ranging from a few hundred watts to 25000 watts with 
vacuum chambers of standard or special shapes. The machines can be equipped with 
numerical control positioning tables. 
 
Advantages 
1. It is excellent for micro-machining. It can be used to drill micro holes or cut narrow slots 
which cannot be made otherwise 
2. EBM can cut any known material, metal or non-metal that would exist in vacuum 
3. There is no cutting tool pressure or wear having distortion free machining and resulting in 
precise dimensions 
4. No physical or metallurgical damage results in EBM. 
 
Limitations 
1. High cost of equipment 
2. High operator skill required for proper machining and welding 
3. Use of vacuum restricts the size of specimens and productivity of the process 
4. Only small cuts are possible with EBM. 
 
Applications 
1. To drill gas orifices for pressure differential devices (used in nuclear reactors, rotors and 
aircraft engines) 
2. To produce metering holes, either round or profile shaped to be used as flow holes on 
sleeve valves, rocket fuel injectors or injection nozzles on diesel engines 
3. To produce wire-drawing dies, light-ray orifices 
4. To perforate holes in glass fibre spinning head made from a heat-resistant super alloy 
5. Slotting and milling operations are economically practical with EBM