Transcript Manufacturing Technology (ME461)

Introduction to Manufacturing
Technology
(Overview of Manufacturing technologies)
Instructors:
(1)Shantanu Bhattacharya, ME, IITK, email:
[email protected]
(2)Prof. Arvind Kumar, ME, IITK email:
[email protected]
Overview of the Lecture
• Manufacturing systems approaches.
• Basic manufacturing processes. (Casting, Forming process,
Fabrication process, Material removal process)
• Advanced Machining processes (ECM, EDM, EBM, LBM, AJM,
USM processes)
• Micro-manufacturing processes (Etching, Deposition,
Lithography, Replication and molding, Dip-pen lithography,
Compression molding, Nano-imprint lithography)
Manufacturing Systems Approach
Definition of Manufacturing Technology:
•Manufacturing technology provides the tools that enable production of all
manufactured goods. These master tools of industry magnify the effort of
individual workers and give an industrial nation the power to turn raw materials
into the affordable, quality goods essential to today’s society.
•Thus manufacturing process really represents adding value to a raw material and
creation of wealth.
Replenish
Sales
fluctuations
Output
Manufacturing
Facility Add
Value
Raw materials cost and
availability
Business
environment
Input
Social Pressure
Manufacturing
System
comprising of
manufacturing
processes
Production rate,
quality and
delivery
Profit
Reputation
Resources and
plans
Wealth
Manufacturing
Process is the key
to wealth
generation
Casting Processes
•
•
•
•
•
These are the only processes
where liquid metal in used.
Casting is the oldest known
manufacturing process.
It requires preparation of a cavity
usually in a refractory material to
resemble closely to the object to
be realized.
Molten metal is poured into this
refractory mould cavity and is
allowed to solidify.
The object after solidification is
removed from the mould.
Equilibrium Phase Diagrams
• A convenient way of describing the phase transformations is a diagram where the
phases at different combinations of temperatures and compositions are indicated.
•Such a diagram is called an equilibrium phase diagram. The word equilibrium is
indicative of the fact that at every temperature sufficient time is provided at every
temperature to complete all diffusion processes.
• The diagram in the left shows a phase
diagram of Ni-Cu alloy which forms a solid
solution without any restriction on %
composition.
•The diagram has been obtained by
study of the cooling curves for various
composition of the alloys.
Forming Processes
•
•
•
•
These are solid state manufacturing processes involving minimum amount of
material wastage and faster production.
Metal is heated to a temperature which is slightly below the solidus temperature
and then a large force is applied such that the material flows and take the desired
shape.
The desired shape is controlled by means of certain tools called dies which may be
completely or partially closed during manufacture.
These processes are normally used for large scale production rates.
Extrusion
Drop forging
Rolling Process
Wire Drawing
Fabrication processes
• These are secondary manufacturing processes where the starting raw
materials are processed by any of the previous methods.
•It essentially involves joining pieces either temporarily or permanently so
that they would perform the necessary function.
•The joining can be achieved by both heat and pressure and / or a joining
material.
Gas Welding
Resistance Welding
Arc Welding
Material Removal Processes
•
•
These are also secondary manufacturing processes where the additional unwanted
material is removed in the form of chips from the blank material by a harder tool
so that a final desired shape can be obtained.
Material removal is the most expensive manufacturing process because more
energy is consumed, and also a lot of waste material is generated in the process.
Turning
Milling
Shaping
Grinding
Drilling
Sawing
History of Machining
• Mankind used bones, sticks and stones as
hand tools since the earliest times
The most ancient Paleolithic stone tool
industry the Oldowan was developed by
the earliest members of the genus Homo
such as Homo habilis around 2.6 million
years ago. and contained tools such as
choppers, burins and awls.
During the Upper Paleolithic further
technological advances were made such
as the invention of Nets, bolas, the spear
thrower the bow and arrow.
History of Machining
Hand held tools from Bronze Age
developed around 1 million years back.
Upto almost the seventeenth century all
tools were either hand operated or done
so by other very elementary methods.
Introduction of water, steam and later
electricity as useful sources of energy
led to the concept of power driven
machine tools.
Ceremonial giant dirk of the
Plougrescant-Ommerschans type,
Plougrescant, France, 1500-1300BC.
Bronze Age weaponry
and ornaments
John Wilkinson in 1774 first constructed a precision
machine for boring engine cylinders, powered by steam.
History of Machining
• 23 years later, Henry Maudslay made a further advancement in machining
when he devised screw cutting engine lathes.
• James Nasmyth invented the second basic machining tool for shaping and
planing.
First Universal Milling machine was built by J.R. Brown in
1862.
In the late nineteenth century, the grinding machine was
introduced. An advanced form of this process is the lapping
process used to produce a high quality surface finish and a
very tight tolerance
History of Machining
• In the later part of 19th and 20th Centuries the machine tools became
increasingly electrically powered.
• The basic machine tools had further refinements; for instance multiple
point cutters for milling machines were introduced.
• The whole machining paradigm was however still related to an operators
judgment who by looking at a part and using his skills would set up an
operation sequence and use this for machining the work piece. Accuracy
of such a product would depend solely on the operator.
• The introduction of NC (numerical control) in 1953 lead to computer
numeric control and direct numeric control.
• Present capabilities of these tooling systems have enormously increased
due to development in electronic controls and computers and present
capabilities enable complex shapes to be produced with finishing accuracy
close to a + 1 Micron.
History of Machining
• In modern machining practices, harder, stronger, and
tougher materials that are more difficult to cut are used. So,
processes should be independent of material properties of
the work piece.
• Non conventional machining practices came very handy as
an alternative to the conventional domain which could
handle shape complexity, surface integrity and
miniaturization requirements.
• Hybrid machining made use of the combined enhanced
advantages of two or more participating processes.
• Micromachining had emerged because of this change of
capabilities.
• Recent applications of micromachining include silicon/ glass
micromachining, excimer lasers and photolithography.
History of Machining
• Machines such as precision grinders may be capable of
producing an accuracy level of + 1 microns that can be
measured using laser instruments and optical fibers.
• Future trends in micromachining include laser and electron
beam lithography and super high precision grinding, lapping
and polishing machines. For measurements high precision
laser beam based scanners are used for measuring surface
finish etc.
• Nano-machining is a very recent trend in these processes
wherein atoms and molecules can be removed instead of
chips in conventional machines.
• Nano-machining was introduced by Tanigushi to cover the
miniaturization of components and tolerances in the range
from submicron level to that of an individual atom or
molecule between 100nm and 0.1 nm.
Abrasive Machining Categories
• The Metal abrasion action is
adopted during grinding, honing
and super finishing processes that
employ either a solid grinding
wheel or sticks in the form of
bonded abrasive.
• Furthermore in lapping, polishing,
and buffing, loose abrasives are
used as tools in a liquid medium.
Machining Accuracies
100 -1 microns
1 -0.01 microns
Micro-turning and Micro-Milling M/C
0.1 -0.001 microns
Classification of all Material Removal
Processes
Area of
interest
Non Traditional Machining
• Traditional machining is mostly based on removal of materials
using tools that are harder than the materials themselves.
• New and novel materials because of their greatly improved
chemical, mechanical and thermal properties are sometimes
impossible to machine using traditional machining processes.
• Traditional machining methods are often ineffective in
machining hard materials like ceramics and composites or
machining under very tight tolerances as in micromachined
components.
• New processes and methods play a considerable role in
machining for aircraft manufacture, automobile industry, tool
and die industry mold making etc.
• They are classified under the domain of non traditional
processes.
Classification of Non Traditional Machining
Single action non traditional Machining processes:
For these processes only one machining action is used for material removal. These
can be classified according to the source of energy used to generate such a
machining action: mechanical, thermal, chemical and electrochemical.
Mechanical Machining
• Ultrasonic Machining (USM) and Waterjet Machining (WJM) are typical examples of
single action, mechanical non traditional machining processes.
• The machining medium is solid grains suspended in an abrasive slurry in the
former, while a fluid is employed in the WJM process.
• The introduction of abrasives to the fluid jet enhances the machining efficiency and
is known as abrasive water jet machining. Similar case happens when ice particles
are introduced as in Ice Jet Machining.
Thermal Machining
• Thermal machining removes
the machining allowance by
melting or vaporizing the
work piece material.
• Many secondary phenomena
occur during machining such
as microcracking, formation
of heat affected zones,
striations etc.
• The source of heat could be
plasma as during EDM and
PBM or photons as during
LBM, electrons in EBM, ions
in IBM etc.
Chemical and Electrochemical
Machining
• Chemical milling and
photochemical machining or
photochemical blanking all use a
chemical dissolution action to
remove the machining allowance
through ions in an etchant.
• Electrochemical machining uses
the electrochemical dissolution
phase to remove the machining
allowance using ion transfer in an
electrolytic cell.
Introduction to Abrasive Jet Machining
(AJM)
• In AJM, the material removal takes place due
to impingement of the fine abrasive particles.
• The abrasive particles are typically of
0.025mm diameter and the air discharges at a
pressure of several atmosphere.
Mechanics of AJM
• Abrasive particle impinges on the work
surface at a high velocity and this impact
causes a tiny brittle fracture and the following
air or gas carries away the dislodged small
work piece particle.
Basics of the USM process
• The basic USM process involves a tool ( made of a ductile and tough
material) vibrating with a very high frequency and a continuous flow of an
abrasive slurry in the small gap between the tool and the work piece.
• The tool is gradually fed with a uniform force.
• The impact of the hard abrasive grains fractures the hard and brittle work
surface, resulting in the removal of the work material in the form of small
wear particles.
• The tool material being tough and ductile wears out at a much slower rate.
Electrochemical Machining (ECM)
•Electrochemical machining is one of the most unconventional machining
processes.
•The process is actually the reverse of electroplating with some modifications.
•It is based on the principle of electrolysis.
•In a metal, electricity is conducted by free electrons but in a solution the
conduction of electricity is achieved through the movement of ions.
•Thus the flow of current through an electrolyte is always accompanied by the
movement of matter.
•In the ECM process the work-piece is connected to a positive electrode and the
tool to the negative terminal for metal removal.
•The figure below shows a suitable work-piece and a suitably shaped tool, the gap
between the tool and the work being full of a suitable electrolyte.
Electrochemical Machining
• With ECM the rate of metal
removal is independent of
the work-piece hardness.
•ECM becomes
advantageous when either
the work material possesses
a very low machinability or
the shape to be machined is
complex.
•Unlike most other conventional and unconventional processes, here there is
practically no tool wear.
•Though it appears that, since machining is done electrochemically, the tool
experiences no force, the fact is that the tool and work is subjected to large forces
exerted by the high pressure fluid in the gap.
Electric Discharge Machining
• EDM is the process of material removal by a controlled erosion
through a series of electric sparks.
• It was developed in USSR around 1943.
• The basic process is illustrated below.
• When a discharge takes place between two points of the anode
and cathode the intense heat generated near the zone melts
and evaporates the materials in the sparking zone.
• For improving the effectiveness the work-piece and the tool are
submerged in a dielectric fluid. (Mineral oils or hydrocarbons)
•Experiments indicate that in
case both electrodes are of
the same material there is a
prominently more erosion of
the electrode connected to
the positive terminal.
Schematic view of the e-beam
machine
•The figure below shows the basic schematic view of the electron beam machine.
•The electrons are emitted from the cathode (a hot tungsten filament), the beam is
shaped by the grid cup, and the electrons are accelerated due to a large potential
difference between the cathode and the anode.
•The beam is focussed with the help of the electromagnetic lenses.
•The deflecting coils are used to control the beam movement in any required manner.
•In case of drilling holes the hole diameter depends on the beam diameter and the energy
density.
•When the diameter of the
required hole is larger than the
beam diameter, the beam is
deflected in a circular path with
proper radius.
•Most holes drilled with e-beam
are characterized by a small crater
on the beam incident side of the
work.
Introduction to MEMS fabrication
NEMS/ MEMS silicon fabrication
•Formation of structures that could be used to form
sensors and actuators.
•Processing of electrical or non electrical signals.
•Conventional and new semiconductor manufacturing
techniques are used.
•Etching, Deposition, Photolithography, Oxidation,
Epitaxy etc.
•Deep RIE, Thick plating etc.
Bulk and surface micromachining.
Topics Covered
• Non-traditional Machining processes. (detailed
analysis based AJM, USM, ECM, EDM, LBM, PAM,
MRAFF, EDD, ECD, MEMS processes, RP processes,
rapid tooling techniques) [10-Lectures]
• Traditional Machining processes.(detailed analysis on
turning, milling, drilling, shaping ad planning
processes, orthogonal and oblique cutting).[06Lectures]
• Introduction to Metrology.(Limits, fits, tolerances,
Automated inspection and CMM), [01-Lecture]
Course Requirements
• (1) 35% of total grade on Mid Semester
• (2) 35% of total grade on Final Examination
• (3) 30% of total grade on Experiments.
(The rationale of the distribution of 30% is the
following: 5% will be on report making, 5%
will be based on feedback of supervisorial
support, 20% will be done on the basis of a lab
quiz that will be taken towards the end of the
semester at a mutually convenient date.)