UNIT 1 INTRODUCTIONBASIC PRINCIPLES OF DESIGNING FOR
PRODUCTION1.Simplicity2. Standard materials and
components3.Standardized design of the product itself4.Liberal
tolerances5.Avoidance of secondary operations6.Design appropriate
to the expected level of production7.Utilizing special process
characteristics8.Avoiding process restrictiveness9.Avialability of
raw materials10.Moderate design costGENERAL PRINCIPLES OF
MANUFACTURABILITY1.Reduce the number of parts 2.Use modular
design3.Design so assembly operations are in 1 direction4.Design so
it is only possible to assemble the components in single
process5.Minimize the use of fasteners6.Use popular standard /
preferred sizes7.Eliminate or simplify adjustments8.Avoid flexible
components9.Dimension in each direction should be from 1
datum10.Avoid sharp corners, use generous fillets11.Do not specify
tolerances tighter than necessary12.Do not specify surface
roughness than necessaryEVALUATION PURPOSE AND TYPESEvaluation
should be an on-going process. It provides an opportunity to modify
the 1.Programme when necessary. Evaluation helps to check
2.Programme effectiveness3.Programme response to change
needs4.Strengths and limitations of the programme5.Staff
development6.Reporting and follow-upTWO TYPES OF EVALUATION
1.Formative Evaluation2.Summative Evaluation TYPES OF EVALUATION:
1.Formative Evaluation : This types of evaluation is conducted
during the planning and designing of the programme. It provides
immediate feedback for programme and improvement. It is an on-going
process. It helps to determine the strength and
weaknesses.2.Summative Evaluation : This is concerned with the
evaluation of an already completed programme. It is used to
determine whether the programme has achieved its goals. It may help
programme leaders to determine whether the programme is worth
continuing. It helps to check the effectiveness of the programme.
It helps in early decisions of programme in order to eliminate the
waste of time and production cost. EVALUATION PROCEDURE:
1.Identification of goals to be assessed2.Development of an
Evaluation plan3.Application of the evaluation plan4.Utilization of
the findingsIt is important to consider the following, if
evaluation procedure are to be fruit:1.Deciding when to evaluate2.
Deciding whom the evaluation is intended to serve3. Deciding what
precisely to evaluate4. Deciding who should conduct the
evaluation5. Deciding what question the evaluation should
address6.Planning the evaluation study7.Deciding how to report the
evaluation study8.Dealing with the political, ethical and
interpersonal issues in evaluation.Process Capability: Process
capability is also defined as the capability of a process to meet
its purpose as managed by an organization's management and process
definition structures ISO 15504. The Process Capability is a
measurable property of a process to the specification, expressed as
a process capability index (e.g., Cpk or Cpm) Two parts of process
capability are: 1) Measure the variability of the output of a
process, and 2) Compare that variability with a proposed
specification or product tolerance.The process capability index or
process capability ratio is a statistical measure of process
capability: the ability of a process to produce output within
specification limits If the upper and lower specification limits of
the process are USL and LSL, the target process mean is T, the
estimated mean of the process is and the estimated variability of
the process (expressed as a standard deviation) is , then commonly
accepted process capability indices include: Process Capability
Index ( CP) = USL LSL/6 CP Lower = - LSL / 3 CP Upper = USL - /
3
GEOMETRIC TOLERANCES:Linear tolerance are specified to ensure
that actual size obtained after manufacturing lies within the
acceptable limits.Eg: A shaft may have its diameter well within the
specified limits of size, but may not be circularA hole may not
have its centre correctly locatedA square slot may not have its
surface exactly perpendicularHence it is necessary to specify
permitted deviations not for linear dimensions but also for
geometrical variations in the form of the surfaces and the
variation for their locations. The geometry variations are called
form variations and locations variations are called Position
variations.Hence the tolerance specified for variations for both
form and position using symbols, numerals and letters is called as
GEOMETRICAL TOLERANCESFORM VARIATION:It is the variation of the
actual condition of form feature (point, line, surface, median
plane) from the geometrically ideal formPOSITION VARIATION:It is
the permitted variation in the specified position of a features
(surface, line, medium plane or point) in relation to some other
feature or datumDATUM/DATUM FEATURE:Position tolerance is a
variation of actual position of the form feature (point line,
surface, medium plane) from the geometrically ideal position with
reference to another form feature called datum feature.Datum means
a place of reference . The datum feature is the particular feature
to which orientation of position and run out tolerances are
referredTYPES OF GEOMETRICAL TOLERANCES:1.Form Tolerance:
Straightness, Flatness, Roundness, Cylindricity, Profile of any
surface 2.Position Tolerance: Position of a line, concentricity,
symmetry, parallelism/ perpendicularity of a line3.Runout
Tolerance: Circular run out, Total Run outASSEMBLY LIMITS: DFA
(design for assembly) recognizes the need to analyze both the part
design and the whole product for any assembly problems early in the
design process. We may define DFA as "a process for improving
product design for easy and low-cost assembly, focusing on
functionality and on assemblability concurrently."Comparison of
Assembly Methods Assembly methods can be divided into three major
groups.In manual assembly, parts are transferred to workbenches
where workers manually assemble the product or components of a
product. Hand tools are generally used to aid the workers. Although
this is the most flexible and adaptable of assembly methods, there
is usually an upper limit to the production volume, and labour
costs (including benefits, cases of workers compensation due to
injury, overhead for maintaining a clean, healthy environment,
etc.) are higher.Fixed or hard automation is characterized by
custom-built machiner that assembles one and only one specific
product. Obviously, this type of machinery requires a large capital
investment. As production volume increases, the fraction of the
capital investment compared to the total manufacturing cost
decreases. Indexing tables, parts feeders, and automatic controls
typify this inherently rigid assembly method. Sometimes, this kind
of assembly is called "Detroit-type" assembly. Soft automation or
robotic assembly incorporates the use of robotic assembly systems.
This can take the form of a single robot, or a multi-station
robotic assembly cell with all activities simultaneously controlled
and coordinated by a PLC or computer. Although this type of
assembly method can also have large capital costs, its flexbility
often helps offset the expense across many different products.
Design Guidelines for Manual AssemblyObviously, the following
guidelines depend on the skill of the worker:1.Eliminate the need
for workers to make decisions or adjustments. ensure accessibility
and visibility. 2.Eliminate the need for assembly tools and gauges
(i.e. prefer self-locating parts). 3.Minimise the number of
different parts - use "standard" parts. 4.Minimise the number of
parts. 5.Avoid or minimise part orientation during assembly (i.e.
prefer symmetrical parts). 6.Prefer easily handled parts that do
not tangle or nest within one another. Note that many products do
not lend themselves to these guidelines. Many such products are
sold as "ready-to-assemble" kits or require that assembly be
shifted to cheaper labour markets. Tolerance stackups or tolerance
stacks are terms used to describe the problem-solving process in
mechanical engineering of calculating the effects of the
accumulated variation that is allowed by specified dimensions and
tolerances. Typically these dimensions and tolerances are specified
on an engineering drawing. Arithmetic tolerance stackups use the
worst-case maximum or minimum values of dimensions and tolerances
to calculate the maximum and minimum distance (clearance or
interference) between two features or parts. Statistical tolerance
stackups evaluate the maximum and minimum values based on the
absolute arithmetic calculation combined with some method for
establishing likelihood of obtaining the maximum and minimum
values, such as Root Sum Square (RSS) or Monte-Carlo methods.A
tolerance stack is a calculation to determine how tolerances
accumulate. Stacks help establish and optimize part tolerances, and
ensure that parts are designed to promote maximum function at
minimal cost.When used in the design stage, stacks provide an
opportunity to evaluate a part's manufacturability, which reduces
the need for costly prototypes.ASSEMBLY LIMITS:Evaluation Methods
for DFAIt is important to quantify the improvements and goals of
DFA. Two methods for DFA quantification considered here are the
boothroyd-dewhurst method and the Lucas method.Boothroyd-Dewhurst
MethodThis method is based on two principles:1.The application of
criteria to each part to determine if it should be separate from
all other parts. 2.Estimation of the handling and assembly costs
for each part using the appropriate assembly process. This method
relies on an existing design which is iteratively evaluated and
improved. Generally, the process follows these steps:Select an
assembly method for each part Generally, the process follows these
steps:1.Select an assembly method for each part 2.Analyse the parts
suitable for the given assembly methods 3.Refine the design in
response to shortcomings identified by the analysis 4.Loop to step
2 until the analysis yields a sufficient design The analysis is
generally performed using some kind of worksheet (example shown
below). Tables and charts are used to estimate the part handling
and part insertion time. These "lookup tables" are based on a
two-digit code that is in turn based on a part's size, weight, and
geometric characteristics.Non-assembly operations are also included
in the worksheet. For example, extra time is allocated for each
time the assembly is re-oriented.Next, parts are evaluated as to
whether it is really necessary (in the assembly) by asking three
questions:does the part move relative to another part? are the
material properties of the part necessary? does the part need to be
a separate entity for the sake of assembly? Minimum number of
theoretically needed parts, denoted by Nm. The method then assumes
that the assembly time for a part is 3 seconds. With that
assumption, the design efficiency can be calculated as:Design
efficiency = (3s x Nm) / Tm. (Tm. =Operation time)Basic DFA
GuidelinesHere are some basic guidelines for DFA. Generally, you
want to start with a concept design and then go through each of
these guidelines, decide whether or not it is applicable, and the
modify the concept to satisfy the guideline. There is no guarantee
that a given guideline will apply to a particular design problem.
Many of these guidelines are similar or the same as rules of
concurrent engineering.1.Minimise part count by incorporating
multiple functions into single parts 2.Modularise multiple parts
into single subassemblies 3.Assemble in open space, not in confined
spaces; never bury important components 4.Make parts such that it
is easy to identify how they should be oriented for insertion
5.Prefer self-locating parts 6.Standardise to reduce part variety
7.Maximise part symmetry 8.Design in geometric or weight polar
properties if nonsymmetrical 9.Eliminate tangly parts 10.Color code
parts that are different but shaped similarly 11.Prevent nesting of
parts; prefer stacked assemblies 12.Provide orienting features on
no symmetries 13.Design the mating features for easy insertion
14.Provide alignment features 15.Insert new parts into an assembly
from above 16.Eliminate re-orientation of both parts and assemblies
17.Eliminate fasteners 18.Place fasteners away from obstructions;
design in fastener access 19.Deep channels should be sufficiently
wide to provide access to fastening tools; eliminate channels if
possible 20.Provide flats for uniform fastening and fastening ease
21.Ensure sufficient space between fasteners and other features for
a fastening tool 22.Prefer easily handled parts PROCESS CAPABILITY:
It is the ability of the process to produce uniform products
inorder to meet the design specification. These specification or
tolerance limits are established by design engineer to meet a
particular function, whereas control limits are established as the
function of average. Process capability and the tolerance are
combined to form a capability index and it may be defined as
Process Capability Index ( CP) = USL LSL/6(process
capability)6(process capability) Only 105 loss due to poor quality
quality level If the capability index is greater than 1.00, the
process is capable of meeting the specifications, If the capability
index is less than 1.00 the process is not capable of meeting the
specifications.
UNIT 2 FACTORS INFLUENCING FORM DESIGNPrinciples of Design: The
principles of design help you to carefully plan and organize the
elements of art so that you will hold interest and command
attention. This is sometimes referred to as visual impact.Elements
of Design Line - is a mark on a surface that describes a shape or
outline. It can create texture and can be thick and thin. Types of
line can include actual, implied, vertical, horizontal, diagonal
and contour lines. (note: Ken does not list "psychic line" - that
was "new term"tome)
Color - refers to specific hues and has 3 properties, Chroma,
Intensity and Value. The color wheel is a way of showing the
chromatic scale in a circle using all the colors made with the
primary triad. Complimentary pairs can produce dull and neutral
color. Black and white can be added to produce tints (add white),
shades (add black) andtones(addgray).Texture - is about surface
quality either tactile or visual. Texture can be real or implied by
different uses of media. It is the degree of roughness or
smoothness in objects.
Shape - is a 2-dimensional line with no form or thickness.
Shapes are flat and can be grouped into two categories, geometric
and organic.
Form - is a 3-dimensional object having volume and thickness. It
is the illusion of a 3-D effect that can be implied with the use of
light and shading techniques. Form can be viewed from many
angles.
Value - is the degree of light and dark in a design. It is the
contrast between black and white and all the tones in between.
Value can be used with color as well as black and white. Contrast
is the extreme changes between values.
Size - refers to variations in the proportions of objects, lines
or shapes. There is a variation of sizes in objects either real or
imagined. (some sources list Proportion/Scale as a Principle of
Design)
These elements are used to create the Principles of Design.
Principles are the results of using the Elements. When you are
working in a particular format (size and shape of the work surface)
the principles are used to create interest, harmony and unity to
the elements that you are using. You can use the Principles of
design to check your composition to see if it has good
structure.Elements of Design:Color, Values, forms and Shapes, space
lines, and textures are called the elements of design. These
elements are known as the fundamentals for all works of art.
Without these elements art could not be created. All of these
elements exist in the world around us in nature and in the
environments we create for ourselves Design for manufacturability
(also sometimes known as design for manufacturing or DFM) is the
general engineering art of designing products in such a way that
they are easy to manufacture. The design of the component can have
an enormous effect on the cost of manufacturing. Other factors may
affect the manufacturability such as the type of raw material, the
form of the raw material, dimensional tolerances, and secondary
processing such as finishing. Factors influence in Form
Design:1.Fitness for Purpose2. Quantity to be manufactured3.
Product finish4.Durablity5. Safety6.ObsolescenceForging : Forging
may be defined as a metal working process by which metals and
alloys are plastically deformed(reduced) to desired shapes by
application of a compressive force. Forging can be done either by
hot or cold Hot forging and cold forging are two different metal
forming processes that deliver similar results. Forging is the
process of deforming metal into a predetermined shape using certain
tools and equipmentdeformation is accomplished using hot, cold, or
even warm forging processes. Ultimately, the manufacturer will look
at a number of criteria before choosing which type of forging is
best for a particular application.The Hot Forging Process When a
piece of metal is hot forged it must be heated significantly. The
average temperatures necessary for hot forging are:Up to 1150
degrees Celsius for Steel360 to 520 degrees Celsius for
Al-Alloys700 to 800 degrees Celsius for Cu-AlloysOther
considerations for hot forging include: 1. Production of discrete
parts 2. Low to medium accuracy 3. Scale Formation 4. Low stresses
or low work hardening 5. Homogenized grain structure 6. Increased
ductility 7. Elimination of chemical incongruities
Possible disadvantages of hot forging include:Less precise
tolerancesPossible warping of the material during the cooling
processVarying metal grain structurePossible reactions between the
surrounding atmosphere and the metal Cold Forging
Cold forging deforms metal while it is below its
recrystallization point. Cold forging is generally preferred when
the metal is already a soft metal, like aluminum. This process is
usually less expensive than hot forging and the end product
requires little, if any, finishing work. Sometimes, when aluminum
is cold forged into a desired shape, it is heat treated to
strengthen the piece. This is called "tempering.Other benefits of
cold forging include: Easier to impart directional
propertiesImproved interchangeability Improved reproducibility
Increased dimensional controlHandles high stress and high die
loadsProduces net shape or near-net shape partsSome possible
disadvantages of COLD FORGING include:1. Easier to impart
directional properties2. Improved interchangeability3. Improved
reproducibility4. Increased dimensional control5. Handles high
stress and high die loads6. Produces net shape or near-net shape
parts7. The metal surfaces must be clean and free of scale before
forging occurs8. The metal is less ductile9. Residual stress may
occur10. Heavier and more powerful equipment is needed11. Stronger
tooling is required12. Secondary process is required for finishing
the component.Forging and its typesForging is a manufacturing
process involving the shaping of metal using localized compressive
forces. Forging is often classified according to the temperature at
which it is performed: "cold", "warm", or "hot" forging. Forging is
the operation where the metal is heated and then a force is applied
to manipulates the metals in such a way that the required final
shape is obtained. Forging is generally a hot working process
through cold forging is used sometimes.Type of Forging 1. Smith
Forging2. Drop Forging 3. Press Forging 4. Machine Forging1: Smith
forging This is the traditional forging operation done openly or
in-openly dies by the village black smith or modern shop floor by
manual hammering or by the power hammer. The process involves
heating the stock in the black smith hearth and then beating it
over the anvil. To get the desire shape the operator has to
manipulate the component in between the blows.The types of
operation available are fullering, flattering, bending , upsetting
and swaging.2: Drop forging The drop forging die consists of two
halves. The lower halve of the die is fixed to the anvil of the
machine , while the upper halve is fixed to ram. The heated stock
is kept in the lower die, while the ram delivers 4-5 blows on the
metal spreads and completely fills in the die cavity. When the two
die of halves closed the complete is formed. The typical products
obtained in drop forging are cranks, crank shaft, connecting rods,
wrench, crane hooks etc. The types of operations are fullering,
edging, bending, blocking , finishing and trimming etc. Drop
forgingDrop forging is a forging process where a hammer is raised
and then "dropped" onto the work piece to deform it according to
the shape of the die. There are two types of drop forging: open-die
drop forging and closed-die drop forging. As the names imply, the
difference is in the shape of the die, with the former not fully
enclosing the work piece, while the latter doesVarious Stages /
Steps involved in Drop Forging:1.Fullering impression2.Edging
impression3.Bending impression4.Blocking impression5.Finishing
impression6.TrimmingPress forgingPress forging works by slowly
applying a continuous pressure or force, which differs from the
near-instantaneous impact of drop-hammer forging. The amount of
time the dies are in contact with the work piece is measured in
seconds (as compared to the milliseconds of drop-hammer forges).
The press forging operation can be done either cold or hot.The main
advantage of press forging, as compared to drop-hammer forging, is
its ability to deform the complete work piece. Drop-hammer forging
usually only deforms the surfaces of the work piece in contact with
the hammer and anvil; the interior of the work piece will stay
relatively unreformed. Another advantage to the process includes
the knowledge of the new part's strain rate. We specifically know
what kind of strain can be put on the part, because the compression
rate of the press forging operation is controlled.There are a few
disadvantages to this process, most stemming from the work piece
being in contact with the dies for such an extended period of time.
The operation is a time-consuming process due to the amount and
length of steps. The work piece will cool faster because the dies
are in contact with work piece; the dies facilitate drastically
more heat transfer than the surrounding atmosphere. As the work
piece cools it becomes stronger and less ductile, which may induce
cracking if deformation continues. Therefore heated dies are
usually used to reduce heat loss, promote surface flow, and enable
the production of finer details and closer tolerances. The
workpiece may also need to be reheated.3: Press Forging: Press
forging dies are similar to drop forging dies as also the process
in press forging, the metal is shaped not by means of a series of
blows as in drop forging , but by means of a single continuous
squeezing action. This squeezing is obtained by means of hydraulic
presses. Because of the continuous action of by hydraulic presses,
the material gets uniformly deform through out its entire depth
,the press forging dies with the various impression , such as
fuller, bender and finisher impression properly arranged .4:
Machine Forging / Upseting Forging: Unlike the press or drop
forging where the material is drawn out , in machine forging the
material is only upset to get the desire shape. As it involves the
upsetting operation some time it is simply called as upset forging.
Originally this was develop for making bolts head in a continuous
fashion, but now there are fairly large number of diverse.Forging
operations: 1: Drawing: This is the operation in which metal gets
elongated with a reduction in the cross section area. For this, a
force is to be applied in a direction perpendicular to the length
axis.
2:Up setting: This is applied to increase the cross sectional
area of the stock at the expanse of the length. To achieve the
length of upsetting force is applied in a direction parallel to the
length axis, For example forming of a bolt head. 3:Fullering: It a
similar to material cross-section is decreased and length
increased. To do this; the bottom fuller is kept in angle hole with
the heated stock over the fuller. The top fuller is then kept above
the stock and then with the sledge hammer, and the force is applied
on the top fuller. 4:Edging: It is a process in which the metal
piece is displaced to the desired shape by striking between two
dies edging is frequently as primary drop forging
operation.5:Bending: Bending is very common forging operation. It
is an operation to give a turn to metal rod or plate. This is
required for those which have bends shapes.6:Punching: It is a
process of producing holes in motel plate is placed over the hollow
cylindrical die. By pressing the punch over the plate the hole is
made.7:Forged welding: It is a process of joining two metal pieces
to increase the length. By the pressing or hammering then when they
are at forging temperature. It is performed in forging shop and
hence is called forged welding.8:Cutting: It is a process in which
a metal rod or plate cut out into two pieces, with the help of
chisel and hammer, when the metal is in red hot condition.9:Flating
and setting down: Fullering leaves a corrugated surface on the job.
Even after a job is forged into shape with a hammer, the marks of
the hammer remains on the upper surface of the job. To remove
hammer marks and corrugation and in order to obtain a smooth
surface on the job, a flatter or set hammer is used.10: Swaging:
Swaging is done to reduce and finish work for desire size and
shape, usually either round or hexagonal. For small jobs top and
bottom swage pair is employed, where as for large work swage block
can be used.
Drop forging diagram
Smith forging process diagramPress forging process diagram
Machine forging process diagram
Advantages of Machine Forging: 1. Quality of forging is better
than drop forging and press forging 2. Maintenance is very cheap in
compared with other forging type 3. Raw material wastage is reduced
and cost is also very less 4. Upsetting process can be automated 5.
Production rate is high in compare with other type of
forgingLimitations of Machine Forging: 1. It is not convenient to
forge heavier jobs due to material handling difficulties 2. Tooling
cost is high 3. Maximum diameter of the stock which can be upset is
25cmADVANTAGES OF MACHINE FORGING:Main advantages 100%
reproducibility during the manufacture of forged elements owing to
the presence of CNC (100 scrolls at the machine with will be always
made exactly the same).High productivity owing to the high rotation
speed of output shaft (up to 50 rpm in the industrial class, up to
20 rpm in the economy class).Convenience in work owing to smooth
adjustment of output shaft rotation speed (the adjustment for the
first detail can be made at a low speed and the batch can be
manufactured at maximum speed).2-year warranty for the
machines.Advantageous price offer: manufactured machines are
cheaper than German analogues by 50%.The machines are designed and
manufactured taking into account the newest developments of the
companies Mitsubishi, SEW-Eurodrive, PHILIPP Gruppe.The assembly of
the machines is carried out from the components of the leading
German manufacturers.ADVANTAGES OF FORGING PROCESS: 1.Impurities in
the metal in the form of inclusions are broken up, resulting in
structural homogeneity2.Forging are easily welded, greater strength
per unit of cross sectional area3. Forgings can be held to within
fairly close tolerances4.Relatively smooth surface of the
forging5.Minimum metal removal in machining6.Better mechanical
properties.7.Ability of the forging to withstand unpredictable
loads8. Superior machining qualities9.Porosity and blowholes in the
metal are largely eliminated10. Wide range of forgeable metals is
availableDIS ADVANTAGES OF FORGING PROCESS: 1.In hot forging due to
very high temperature of metal, there is a rapid oxidation or
scaling of the surface resulting in poor surface finish.2.Tooling
and handling cost is very high3.Many intricate and cored shapes
possible only by casting process cannot by forged4.Forging cost is
more than casting5. Absolute need for skilled labour6.Poor material
utilization7. Difficulty of maintaining moderately close
tolerances8.Restricted to simple shapes9. Less control in
determining grain flow, mechanical properties and
dimensions10.Restricted to short run production.
FORGING DEFECTS: 1.Unfilled Sections: Some sections of the die
cavity are not completely filled by flowing metal.2.Cold shut: This
appears as a small crack at the corners of the forging3.Scale pits:
This is seen as irregular depressions on the surface of the
forging4.Die shift: This is caused by the misalignment of the two
die halves5.Flakes : Basically internal ruptures caused by th
improper cooling6.Improper grain flow: This is caused due to
improper design of the dieThe advantages and disadvantages of hot
forging :Advantages Increase in ductile strength High temperature
helps in removal of homogeneous substances due to increased
diffusion Reduction in the pore sizeDisadvantages
Lesser tolerance Warping of material during the cooling process
Undesirable result due to reaction of metal with that of
surroundings Varied metal structureAdvantages of Cold Forging :
Finishing operation is not requiredIt has very less work during
processIn this Fabrication process it is very cost effective. Cold
forging has less impurities Cold forging Results into smooth shiny
surface. Disadvantages of Cold Forging: Less ductile metal Very
strong tools are needed Residual stress The surface of the metal is
to be cleaned before the process starts
RAW MATERIAL SELECTION:1.Organizational philosophy is to be
understood by the raw material supplier2.The supplier has a stable
management system working for quality and commitment. Check whether
the supplier is an ISO certified organization3.The supplier should
maintain high technical standards and have capabile to meet the
future technological innovation.4. Supplier should be in a position
to supply raw materials of quality & quantity as requested by
purchaser5.There should be no dangers of breaching the corporate
secrets6.Supplier should have a capable of meeting the delivery in
schedule and be easily accessible by road and through
communication7. Supplier should be sincere in fulfilling the
commitment according to contract provision8. Supplier should have
an effective quality updated system9. Supplier should have a track
record of customer satisfaction and organizational
credibilitySOURCING:Three types : 1. Sole sourcing 2. Multiple
sourcing 3. Single sourcingSole sourcing : It means the
organization is forced to use only one raw material supplier . This
is due to patents, technical specification, location of raw
materials.Multiple sourcing : It is the use of two or more supplier
for an item. This type of sourcing will be based on their quality,
price and delivery schedule. This type will create competition
among the supplier, so we get better raw materials and price will
be lower. It eliminate the disruption of supply due to strikes,
bundhs and etc.Single sourcing : It is a planned decision by the
organization to select one supplier for an item when several
sources are available. It results in long term contracts and a
partnering relationship. CASTING PROCESS: The solidified piece of
metal, which is taken out of the mould, is called as Casting.
Casting process is also called as Founding. The word foundry is
derived from latin word fundere meaning melting and pouring.
Casting is a manufacturing process by which a liquid material is
usually poured into a mold, which contains a hollow cavity of the
desired shape, and then allowed to solidify. The solidified part is
also known as a casting, which is ejected or broken out of the mold
to complete the process. Casting materials are usually metals or
various cold setting materials that cure after mixing two or more
components together; examples are epoxy, concrete, plaster and
clay. Casting is most often used for making complex shapes that
would be otherwise difficult or uneconomical to make by other
methodsDIFFERENT TYPES OF CASTING PROCESS:1)Investment casting
2)Permanent mold casting 3)Centrifugal casting 4)Continuous casting
5)Sand casting TYPES OF CASTING PROCESS:1)Investment Casting
:Investment casting (known as lost-wax casting in art) is a process
that has been practiced for thousands of years, with lost wax
process being one of the oldest known metal forming techniques.
Investment casting derives its name from the fact that the pattern
is invested, or surrounded, with a refractory material. The wax
patterns require extreme care for they are not strong enough to
withstand forces encountered during the mold making. One advantage
of investment casting it that the wax can be reused.
The process is suitable for repeatable production of net shape
components, from a variety of different metals and high performance
alloys. Although generally used for small castings, this process
has been used to produce complete aircraft door frames, with steel
castings of up to 300 kg and aluminum castings of up to 30 kg.
Compared to other casting processes such as die casting or sand
casting it can be an expensive process, however the components that
can be produced using investment casting can incorporate intricate
contours, and in most cases the components are cast near net shape,
so requiring little or no rework once cast.2 .Permanent Mold
Casting Permanent mold casting (typically for non-ferrous metals)
requires a set-up time on the order of weeks to prepare a steel
tool, after which production rates of 5-50 pieces/hr-mold are
achieved with an upper mass limit of 9 kg per iron alloy item (cf.,
up to 135 kg for many nonferrous metal parts) and a lower limit of
about 0.1 kg. Steel cavities are coated with a refractory wash of
acetylene soot before processing to allow easy removal of the work
piece and promote longer tool life. Permanent molds have a limited
life before wearing out. Worn molds require either refinishing or
replacement. Cast parts from a permanent mold generally show 20%
increase in tensile strength and 30% increase in elongation as
compared to the products of sand casting.
The only necessary input is the coating applied regularly.
Typically, permanent mold casting is used in forming iron,
aluminum, magnesium, and copper based alloys. The process is highly
automated.3 .Centrifugal casting
Centrifugal casting is both gravity- and pressure-independent
since it creates its own force feed using a temporary sand mold
held in a spinning chamber at up to 900 N (90 g). Lead time varies
with the application. Semi- and true-centrifugal processing permit
30-50 pieces/hr-mold to be produced, with a practical limit for
batch processing of approximately 9000 kg total mass with a typical
per-item limit of 2.3-4.5 kg.Industrially, the centrifugal casting
of railway wheels was an early application of the method developed
by German industrial company Krupp and this capability enabled the
rapid growth of the enterprise.4. Continuous casting
Continuous casting is a refinement of the casting process for
the continuous, high-volume production of metal sections with a
constant cross-section. Molten metal is poured into an open-ended,
water-cooled copper mold, which allows a 'skin' of solid metal to
form over the still-liquid centre. The strand, as it is now called,
is withdrawn from the mold and passed into a chamber of rollers and
water sprays; the rollers support the thin skin of the strand while
the sprays remove heat from the strand, gradually solidifying the
strand from the outside in. Continuous casting is used due to the
lower costs associated with continuous production of a standard
product, and also increases the quality of the final product.
Metals such as steel, copper and aluminum are continuously cast,
with steel being the metal with the greatest tonnages cast using
this method.
5 . Sand casting
Sand casting is one of the most popular and simplest types of
casting that has been used for centuries. Sand casting allows for
smaller batches to be made compared to permanent mold casting and a
very reasonable cost. Not only does this method allow for
manufacturers to create products for a good cost there are other
benefits to sand casting such as there are very little size
operations. From castings that fit in the palm of your hand to
train beds (one casting can create the entire bed for one rail car)
it can be done with sand casting. Sand casting also allows for most
metals to be cast depending in the type of sand used for the
molds.Sand casting requires a lead time of days for production at
high output rates (1-20 pieces/hr-mold), and is unsurpassed for
large-part production. Green (moist) sand has almost no part weight
limit, whereas dry sand has a practical part mass limit of
2300-2700 kg. Minimum part weight ranges from 0.075-0.1 kg. The
sand is bonded together using clays (as in green sand) or chemical
binders, or polymerized oils (such as motor oil.) Sand in most
operations can be recycled many times and requires little
additional input.ADVANTAGES OF CASTING PROCESS: 1- Low Cost 2- No
skilled operators needed 3- Equipments are cheap and easy to deal
with. 4- Suitable for few small production rates 5- Can produce
large (very large) castings (i.e. Pit casting in a very large whole
in the ground the molten metal is poured) Advantages of special
casting process over sand casting Greater dimensional accuracy.
Higher metallurgical quality. Lower production cost (in certain
cases). Ability to cast extremely thin sections. High production
rates. Better surface finish on the castings; therefore low labour
and finishing costs. Minimum need for further machining of
castings. Castings may possess a denser and finer grain structure.
Castings are slightly stronger and more ductile than solid mould
castingsADVANTAGES OF CASTING PROCESS:The reasons for the success
of the casting process are: Owing to physical properties, some
metals can only be cast since they cannot be re-modelled into bars,
rods, plates or other shapes. It's a process highly adaptable to
the requirements of mass production. Large numbers of a given
casting can be produced quickly. For example; in the automotive
industry there is massive production of cast engine blocks and
transmission cases. Certain light metal alloys because of their
respective strength and weakness, can be produced only as castings.
Shows excellent bearing qualities. Some of the key Advantages of
Casting over Forging can be with respect to the following:Design
flexibility High production rate Large and complex parts ADVANTAGES
OF CASTING PROCESS:
1. On Basis of Size of Object to be Manufactured: Size of cast
objects vary over large range. An object from 5gm to 200tonn,
anything can be cast. 2. On Basis of Complexity:
Casting can be effectively used for complex shaped objects. It
can work where general machining processes can not be used, as in
complicated inner and outer shapes of object. 3. Weight Saving:
Component made with casting process is lighter than the
component made with other machining processes 4. Control Over The
Process: Casting provides versatility. Wide range of properties can
be attained by adjusting percentage of alloying elements. 5.
Accuracy: Casting can be made with hair like precision provided
proper molding and casting technique is employed. 6. Fibrous
Structure: Only casting have this advantage. Casting leaves
component with its solid fibrous structure which inherit great
compressive strength. So, component subjected to compressive
strength are made with casting ex. IC engine cylinder. 7. Control
Over Grain Size: Grain size of cast component can be easily
controlled by controlling cooling rate which in turn can be used to
modify the properties. 8. Low Cost: Casing is one of cheapest
method for mass production.DIS ADVANTAGES OF CASTING PROCESS:1.
Weakness of CastingRequires close process control and monitoring
Shrinkage porosity may occur Metallic projections Cracks, hot
tearing, coldshuts Laps, oxides , Misruns, insufficient volume ,
Inclusions 2.Though casting is cheapest for MASS Production, it
becomes non economical in case of JOB production. 3.Sand casting
leaves rough surface which needs machining in most of cases. It
adds up the cost in production. 4.Again in sand casting, poor
dimensional accuracy is achieved. 5.Cast products are superior for
compressible loads but they are very poor in tensile or shock
loads.(They are brittle).1- Poor surface finish, due to sand
indentation and oxidizing medium ..etc.2- Many defects arise in the
casting (no good control on the process , die casting is much
better) 3- Not suitable for mass production, oftenly used to
produce few number of products compared with other casting
processes which produce thousands and millions. 4- Dangerous
operation , may cause harmful injuries ..etc.5.Only good for basic
shapes 6.Can usually only be used once 7.Accuracy of casting sizes
aren't great.Consequently, this process costs more than other forms
of casting
Another disadvantage of metal casting is that it is extremely
dangerous. People involved in this industrial process must be
highly trained, and even then, accidents happen. Molten metal can
reach temperatures of over 1,000 degrees Fahrenheit, so one small
mistake or equipment malfunction can lead to serious injury or
death. Sand casting is the cheapest process but also the least
accurate, thus making it unsuitable for precise work. In short,
metal casting requires a trade-off between quality and cost.DEFECTS
IN CASTING PROCESS: 1.BLOW HOLES :Gases and steam are formed when
molten metal is poured 2. SCAB: Erosion or breaking down a portion
of mould 3. SHIFT: Mismatching of casting sections4. SWELL:
Enlargement of casting5.SHRINKS: Shrinkage cavity on casting
surface6.HOT TEAR: Internal or external discontinuity in the
casting7.METAL PENETRATION: Molten metal penetrating the sand. so
casting will have rough external surface8.HONEY COMBING: Number of
small cavities present in the surface9.RUNOUT: Metal leaks out of
mould during pouring10.CRACKS OR WRAPAGE: Small cracks appear on
the sharp corners of the casting UNIT 3 COMPONENT DESIGN -
MACHININGPrinciples of DRILLS: A drill is a tool fitted with a
cutting tool attachment or driving tool attachment, usually a drill
bit or driver bit, used for boring holes in various materials or
fastening various materials together with the use of fasteners
Drills are commonly used in wood working, metal working,
construction and do-it-yourself projects. Specially designed drills
are also used in medicine, space missions and other applications.
Drills are available with a wide variety of performance
characteristics, such as power and capacity. A fastener is a
hardware device that mechanically joins or affixes two or more
objects together. It is a Devices that are used to join and
assemble parts togetherVarious type of DRILLS: There are many types
of drills: some are powered manually, others use electricity
(electric drill) or compressed air (pneumatic drill) as the motive
power, and a minority are driven by an internal combustion engine
(for example, earth drilling augers). Pistol-grip (corded)
drill
Hammer drill:The hammer drill is similar to a standard electric
drill, with the exception that it is provided with a hammer action
for drilling masonry. Rotary hammer drill: The rotoary hammer drill
(also known as a rotary hammer, roto hammer drill or masonry drill)
combines a primary dedicated hammer mechanism with a separate
rotation mechanism, and is used for more substantial material such
as masonry or concreteCordless drills: A cordless drill is an
electric drill which uses rechargeable batteriesDrill press: A
drill press consists of a base, column (or pillar), table,spindle
(or quill), and drill head, usually driven by an induction
motor.Radial arm drill press: Radial arm drill press controlsA
radial arm drill press is a large geared head drill press in which
the head can be moved along an arm that radiates from the machine's
column.Milling cutters: Milling cutters are cutting tools typically
used in milling machines or machining centres to perform milling
operations (and occasionally in other machine tools). They remove
material by their movement within the machine (e.g., a ball nose
mill) or directly from the cutter's shape (e.g., a form tool such
as a hobbing cutter).Various parameters of milling
cutters:1.Shape2.Teeth3.Helix angle4.Finishing5.Coatings 6. Shank
7. Centre cuttingTypes of Milling Cutters:1. End Mill2. Slot Mill3.
Roughing End Mill4. Ball Nose Cutter5. Slab Mill6. Side and Face
cutter7. In Volute Gear CutterFactors consider in Selecting a
Milling Cutter : 1. Material 2. Diameter 3. Flutes 4. Coating 5.
Helix angle Keyways: In mechanical engineering, a key is a machine
element used to connect a rotating machine element to a shaft. The
key prevents relative rotation between the two parts and enables
torque transmission. A key is used for temporary fastening. For a
key to function, the shaft and rotating machine element must have a
keyway, also known as a keyseat, which is a slot or pocket the key
fits in. The whole system is called a keyed joint Various types of
Keyways:1.Sunk keys2.Parallel keys3.Tapered keys4.Scotch key or
Dutch key5.Spline keyDoweling Procedure:A dowel is a solid
cylindrical rod, usually made of wood, plastic, or metal. In its
original manufactured form, a dowel is called a dowel rod. Dowel
rods are often cut into short lengths called dowel pins. Dowels are
employed in numerous, diverse applications including as axles in
toys, detents (e.g., in gymnastics grips), structural
reinforcements in cabinet making, and supports for tiered wedding
cakes.Dowel pins are used to hold two pieces of wood together. They
are often used as an alternative to glue or screws,... Other uses
include:As furniture shelf supportsAs moveable game pieces (i.e.,
pegs)As supports for hanging items such as clothing, key rings,
tools, toilet roll dispensers and picture framesTo precisely align
two objects in a dowel joint: a hole is bored in both objects and
the dowel pin is inserted into the aligned holesAs a core to wrap
cable or textiles aroundCounter Sunk Screws: A countersink (symbol:
) is a conical hole cut into a manufactured object, or the cutter
used to cut such a hole. A countersink may also be used to remove
the burr left from a drilling or tapping operation thereby
improving the finish of the product and removing any hazardous
sharp edges.Types: 1.Cross-hole Countersink Cutter 2.Form
Countersink Cutter 3. Fluted Countersink Cutter 4. Back Countersink
CutterAdvantage of Counter sunk screws in joints :1. Easy to fasten
and remove or replace 2. Different types of heads are
possible--straight cut, Allen, star, and many other 3. The pitch of
thread can be varied to ensure compatibility where only needed 4.
The thread could be very close ensuring tight fit or distanced to
be used on wood
Disadvantage Counter sunk screws in joints :1. Needs an external
too 2. Needs a cut on the head, special process 3. Needs threading,
special process 4. Wastage of material during manufacture Screws
are used to fit materials such as chipboard, MDF and natural woods
together although there is a type of screw called a self-tapping
screw that can be used for joining thin metal sheet. screws can be
used to join materials together permanently although as they can be
unused with relative ease they are also good as a way of fixing
materials temporarily. COUNTERSUNK - SLOT HEAD: This can be used
for general woodworking for example fitting hinges to doors.
Because the screw is countersunk it can be tightened 'flush' to the
surface of the material.SIMPLIFICATION BY AMALGATION:In general,
amalgamation is the process of combining or uniting multiple
entities into one form.Definition of 'AmalgamationThe combination
of one or more companies into a new entity. An amalgamation is
distinct from a merger because neither of the combining companies
survives as a legal entity. Rather, a completely new entity is
formed to house the combined assets and liabilities of both
companies. This sense of the term amalgamation has generally fallen
out of popular use and the terms "merger" or "consolidation" are
often used instead"Amalgamation is a union of two or more
companies, made with an intention to form a new company."In terms
of finance, the definition of amalgamation can be given as
under."Amalgamation is an agreement (deal) between two or more
companies to consolidate (strengthen) their business activities by
establishing a new company having a separate legal
existence."AMALGATION:A dowel is a solid cylindrical rod, usually
made of wood, plastic, or metal. In its original manufactured form,
a dowel is called a dowel rod. Dowel rods are often cut into short
lengths called dowel pins. Dowels are employed in numerous, diverse
applications including as axles in toys, detents (e.g., in
gymnastics grips), structural reinforcements in cabinet making, and
supports for tiered wedding cakes.Example of Amalgamation: Bank a
and Bank b proposed to be a BANK ab STEP BY STEP PROCEDURE OF
AMALGATION:1. Intimate the Stock Exchange about the Board Meeting
in which the proposal for amalgamation will be considered.2.
Conduct the Board Meeting for considering the proposal of
amalgamation. The Board has to inprincipally approve the
amalgamation and appoint Chartered Accountant as Valuer for
recommending the share exchange ratio and Advocates for
representing the matter on behalf of the Company before the Honble
High Court.3. Intimate Stock Exchange about the decision at the
Board and intimation about4. Hold the Board Meeting to approve the
Scheme of Amalgamation and the Share Exchange Ratio.5. Intimate
Stock Exchange about the result of the Board Meeting and the Share
Exchange Ratio.6. Apply to the Stock Exchange(s) where the Shares
of the Company are listed under Clause 24(f) of the Listing
Agreements.7. After 30 days of making the above application, apply
to the Honble High Court seeking directions for holding meeting of
Shareholders & Creditors.8. Obtain Order from the Honble High
Court convening the meeting of the Shareholders &Creditors
meeting and for publishing advertisements for the same. Creditors
meetings are not required in the Transferee Company.9. Publish the
Advertisements in Newspapers about meetings in accordance with the
schedule given by the Honble High Court.10. Send printed notices of
court convened meetings to the Shareholders & Creditors in
accordance with the instruction of the Honble High Court. The
notices have to be sent Under Postal Certification only (UPC). 11.
Send 3 copies to Stock Exchanges where the Company's Shares are
listed.12. Prepare the Affidavit for Dispatch of Notices and for
Publication of Advertisements and file them with the Honble High
Court alongwith original proof of dispatch and original proof of
publication of advertisements.13. Conduct the Court convened
Meetings of the shareholders and creditors in accordance with the
instructions of the Honble High Court. Please note that this
resolution has to be passed by Special Majority i.e. more than 50%
in number and more than 75% in value have to vote in favour of the
resolution. The result of the meeting has to be decided by Poll
only. 14. Inform the Stock Exchanges regarding the outcome of the
meeting and within reasonable time, submit Minutes of the
Meeting.15. After the resolution has been approved, File Form No.
23 with the Registrar of Companies (ROC) within 30 days from the
date of the meeting.16. Within 7 days of the Meeting, the
Chairman's Report for the meetings has to be filed with the Honble
High Court.17. Within 7 days of filing the Chairmans Report, the
Company Petition has to be filed with the Honble High Court for
approving the Scheme of Amalgamation.18. Obtain an Order of
admission of petition from Honble High Court. The Honble High Court
would order a copy of the Petition to be served to the office of
the Regional Director (RD) and the Official Liquidator (OL).19.
Submit a Certified Copy of the Petition with the office of the RD
and the OL. The RD would require a copy of the Petition to be
submitted to the office of the ROC and hence, it is advisable to be
proactive and file the copy of petition with the office of the ROC
as well.20. The ROC will investigate into the compliances by the
Companies and whether the scheme is prejudicial to the interest of
the shareholders or creditors. The ROC will submit its report to
the RD.21. The RD will require details from the Companies and make
a separate study of the Scheme of Amalgamation and whether the
scheme is prejudicial to the interest of the shareholders or
creditors. The RD will prepare its report and sent it to the ROC.
The ROC will forward the report to the Government Counsel.22. The
OL will recommend and appoint an auditor for verifying the details
of the Transferor Company and to investigate into the affairs of
the Company. The auditor appointed as per the instructions of the
OL will submit a report on the affairs of the Company. The Company
has to also submit some details to the office of the OL. The OL
shall prepare his report and submit to the Honble High Court /
Government Counsel.23. The matter would now be taken up for hearing
before the Honble High Court. The Honble High Court would consider
the arguments from both the sides and depending on the merits of
the case, would issue an order. I assume that the Honble High Court
has approved the Scheme of Amalgamation.24. File the Honble High
Court Order with ROC in Form No. 21. The merger becomes effective
once the Honble High Court Order is filed with the ROC.Advantages
of Amalgamations :1.Scale of economy2. Use of common resources3.
Increase of goodwill4.Avoidence of internal competitionThe main
benefits or advantages of amalgamation are as follows:1.Operating
Economics: Expenses associated with business and its allied
activities. 2.Diversification: It means to have presence
(establishment) in different business ventures, which are not
related to each other. 3.Financial Economics: It means expenses
associated with the acquisition of funds required to run the
business 4.Growth: amalgamated company grow faster than individual
companies. 5.Managerial Effectiveness: Manager's skill to attain
the desired outcome in the business operations. 6.Helps to Face
Competition: Business strategies that help to face market
competition with ease and confidence. 7.Revival of Sick Units:
Restarting the earlier shutdown companies. 8.Tax Advantages: When
one of the amalgamated companies enjoys a subsidized rate of
taxation. 9.Increase in Market Share: Increasing the combined sales
of the amalgamated companies 10.Increases GoodWill: Creates
goodwill in the market. 11.Miscellaneous Advantages: It helps to
increase the market price , It promotes the brand value
DisAdvantages of Amalgamations :1.Culture Clash :When two firms
merge, it is more than a coming together of two names or brands --
it is a real merger of people who bring along a specific corporate
culture2. Dis-economies of Scale:When businesses merge, it is often
to achieve economies of scale. Larger organizations are typically
able to produce goods and services more efficiently and at a lower
per-unit cost than smaller businesses because fixed costs are
spread out over a larger number of units3. Consumer Perceptions
:When two companies merge, they need to consider how consumers view
the two firms and whether or not they view them in a compatible
way4. Layoffs :Merging two businesses is often a good method for
reducing the labor force of the two organizations. For instance, a
company may combine its two offices into one and reduce the number
of staff performing the same duties5.Disclosing of competition:
Healthy competition may be eliminated6.Elemination of share holder:
reluctant shareholders may try to prevent an amalgamation - the
minority shareholders may have to be paid out in cash7. Adjustment
Period :Mergers require an adjustment period to combine the
operations of the two companies. 8. Stress :The uncertainty
surrounding mergers can create a high level of stress for
employees. Even before the merger becomes official, there can be
uncertainty about its impact on jobs, as mergers sometimes cause
the need for job elimination 9. Less Flexibility:Mergers can cause
two relatively small, nimble organizations to become one less
flexible large entity. Decisions that used to be made quickly may
now have to pass through several layers of management. Slower
decision-making may result in lost opportunities in the
marketplace.10.Possible Failure:There is no guarantee that a merger
will succeed. Mergers can fail for a number of reasons, such as a
poorly structured financial arrangement. Even if the merger deal is
financially sound, it is always possible that divergent corporate
cultures will not mesh or that workers will not be able to adapt to
the changes required of them.CLASSIFICATION OF AMALGAMATIONS /
MERGER :1. Horizontal amalgamation: It means combination two
companies dealing with same business inorder to increase the share
and also the business competition. Horizontal mergers take place
where the two merging companies both produce similar product in the
same industry2. Vertical amalgamation : It is an amalgamation takes
place between amalgamated companies with customer or with supplier.
Vertical mergers occur when two firms, each working at different
stages in the production of the same good. In this form, the
companies in merger decide to combine all the operations and
productions under one shelter3. Conglomerate amalgamation : Main
purpose is diversification of risk. Conglomerate mergers take place
when the two firms operate in different industries. Conglomerate
merger is a kind of venture in which two or more companies
belonging to different industrial sectors combine their
operations.4. Co - Generic Merger : Co-generic merger is a kind in
which two or more companies in association are some way or the
other related to the production processes, business markets, or
basic required technologies. It includes the extension of the
product line or acquiring components that are all the way required
in the daily operationsDESIGN FOR MACHINABILITY:Design Guidelines
for MachiningThe section below contains examples of some design
guidelines for machining. These guidelines may help companies to
avoid rejections and rework due to engineering errors leading to
higher cost of quality and delay in the delivery to customer.
1.Design for manufacturability (also sometimes known as design for
manufacturing or DFM) is the general engineering art of designing
products in such a way that they are easy to manufacture. The basic
idea exists in almost all engineering disciplines, but of course
the details differ widely depending on the manufacturing
technology. 2.This design practice not only focuses on the design
aspect of a part but also on the producibility. 3.In simple
language it means relative ease to manufacture a product, part or
assembly. 4.DFM describes the process of designing or engineering a
product in order to facilitate the manufacturing process in order
to reduce its manufacturing costs. The design stage is very
important in product design. Most of the product lifecycle costs
are committed at design stage. The product design is not just based
on good design but it should be possible to produce by
manufacturing as well. Often an otherwise good design is difficult
or impossible to produce. Typically a design engineer will create a
model or design and send it to manufacturing for review and invite
feedback. This process is called a design review. If this process
is not followed diligently, the product may fail at the
manufacturing stage.If these DFM guidelines are not followed, it
will result in iterative design, loss of manufacturing time and
overall resulting in longer time to market. Hence many
organizations have adopted concept of Design for
Manufacturing.Other factors may affect the manufacturability such
as 1. The type of raw material, 2.The form of the raw material, 3.
Dimensional tolerances 4. Secondary processing such as finishing.
DESIGN FOR MACHINABILITY:Design and shapeAs machining is a
subtractive process, the time to remove the material is a major
factor in determining the machining cost. The volume and shape of
the material to be removed as well as how fast the tools can be fed
will determine the machining time. When using milling cutters, the
strength and stiffness of the tool which is determined in part by
the length to diameter ratio of the tool will play the largest role
in determining that speed. The shorter the tool is relative to its
diameter the faster it can be fed through the material. A ratio of
3:1 (L:D) or under is optimum. If that ratio cannot be achieved, a
solution like this depicted here can be used. For holes, the length
to diameter ratio of the tools are less critical, but should still
be kept under 10:1.There are many other types of features which are
more or less expensive to machine. Generally chamfers cost less to
machine than radii on outer horizontal edges. Undercuts are more
expensive to machine. Features that require smaller tools,
regardless of L:D ratio, are more expensive.DESIGN PRINCIPLES FOR
ECONOMY :The top diagram gives the conventional picture (used
across the board by capitalists, socialists and communists alike)
of the major factors involved in economic activity. It begins with
the three "factors of production": land, labor, and manufactured
capital.Land was initially included in recognition of the
importance of agriculture, but as industrialization progressed it
has been broadened to represent all raw materials, like minerals
and timber.Labor covers all direct human inputs into economic
activity, although in practice it has been treated largely as a
simple head-count e.g., how big is the "labor-force" or how many
unemployed.Manufactured Capital refers to buildings, tools, and
equipment.The oval labeled Economic Activity stands for the process
by which Labor, with the aid of Manufactured Capital, converts Land
(as raw materials) into Goods & Services. Some of these Goods
& Services need to be Invested back into the factors of
production to either maintain or improve them. Whatever is left
over can then be Consumed to produce Utility or Welfare for
individuals and households.THE FIVE FORMS OF WEALTHEnvironmental
Capital (EC) expands beyond the idea of Land to include all natural
systems, such as the atmosphere, biological systems, and even the
sun.Human Capital (HC) expands beyond Labor to include quality as
well as quantity. According to Ekins "Human Capital has three
components: health, knowledge and skills, and motivation." Social
and Organizational Capital (SOC) recognizes a major form of wealth
that is ignored in the conventional diagram. It includes all of the
interpersonal "software" that enables societies and organizations
to function: habits, norms, roles, traditions, regulations,
policies, etcManufactured Capital (MC) includes, as in the
conventional picture, buildings, tools, and equipment. In this
picture, however, the idea of MC is broadened in two ways. First,
the conventional practice is usually to count as MC only equipment,
etc., used by businesses.Credit Capital (CC) is another reservoir
of wealth not included on the conventional diagram, nor in Ekins
work. It is defined here as a reservoir of credits and promises, so
it includes money and debt, but not stocks or deeds, which are
ownership rights tied to other forms of capital.Among the
advantages, we find the following:1.Competition between different
firms leads to increased efficiency.2. Most people work harder (the
threat of losing one's job is a great motivator).3. There is more
innovation as firms look for new products to sell and cheaper ways
to do their work;4. Foreign investment is attracted as word gets
out about the new opportunities for earning profit.5. The size,
power, and cost of the state bureaucracy is correspondingly reduced
as various activities that are usually associated with the public
sector are taken over by private enterprises.6. Many people quickly
acquire the technical and social skills and knowledge needed to
function in this new economy;7. A great variety of consumer goods
become available for those who have the money to buy them;
and8.Large parts of the society take on a bright, merry and
colorful air as everyone busies himself trying to sell something to
someone else. Free market responds quickly to the peoples wants:
Wide Variety of goods and services: Efficient use of resources
encouraged: DESIGN PRINCIPLES FOR ASSEMBLY :Design for assembly
(DFA) is a process by which products are designed with ease of
assembly in mind. If a product contains fewer parts it will take
less time to assemble, thereby reducing assembly costs. In
addition, if the parts are provided with features which make it
easier to grasp, move, orient and insert them, this will also
reduce assembly time and assembly costs. The reduction of the
number of parts in an assembly has the added benefit of generally
reducing the total cost of parts in the assembly1. Simplify the
design and reduce the number of parts2. Standardize and use common
parts and materials3. Design for ease of fabrication(i).For higher
volume parts, consider castings or stampings to reduce machining
(i)Use near net shapes for molded and forged parts to minimize
machining and processing effort. (iii)Design for ease of fixturing
by providing large solid mounting surface & parallel clamping
surfaces (iv)Avoid designs requiring sharp corners or points in
cutting tools - they break easier (v)Avoid thin walls, thin webs,
deep pockets or deep holes to withstand clamping & machining
without distortion vi)Avoid tapers & contours as much as
possible in favor of rectangular shapes (vii)Avoid undercuts which
require special operations & tools (viii)Avoid hardened or
difficult machined materials unless essential to requirements
(ix)Put machined surfaces on same plane or with same diameter to
minimize number of operations x)Design work pieces to use standard
cutters, drill bit sizes or other tools (xi)Avoid small holes
(drill bit breakage greater) & length to diameter ratio > 3
(chip clearance & straightness deviation)4. Design within
process capabilities and avoid unneeded surface finish
requirements5.Mistake proof product design and assembly6. Design
for parts orientation and handling7. Minimize flexible parts and
interconnections8. Design for ease of assembly9. Design for
efficient joining and fastening.10. Design modular products11.
Design for automated production.12. Design printed circuit boards
for assembly. DESIGN PRINCIPLES FOR ACCESSIBILITY :Accessibility is
the degree to which a product, device, service, or environment is
available to as many people as possible. Accessibility can be
viewed as the "ability to access" and benefit from some system or
entity. Accessibility is not to be confused with usability, which
is the extent to which a product (such as a device, service, or
environment) can be used by specified users to achieve specified
goals with effectiveness, efficiency and satisfaction in a
specified context of use.Principles of Accessibility : Perceivable
: Content should be consumable - Available through sight, hearing,
or touch.Operable: Interactions should be operable by everyone -
Compatible with keyboard or mouse.Understandable : Content should
be plain and clear to comprehend - User-friendly, easy to
comprehend.Robust - Works across browsers, assistive technologies,
mobile devices, old devices/browsers, etc. Follows
standards.Advantages and disadvantagesAdvantages Quick distribution
of scholarly research. There is no need to wait for months, for
example, for an article to fit with the theme of a journal before
it can be published.Free worldwide access for a large audience.
This way makes it possible for people without connections to a
scholarly institution to have access to results of scholarly
research.Greater visibility of scholarly output for both the
researcher and the research institution. This can have a
status-heightening effect.Research shows that open access
publications are cited more often on the average than closed
publications.Efficient archiving and availability.Guaranteed
sustainable storage and accessibility.Disadvantages Prestige.
Faculties and management teams often base their evaluation of a
scholar and the value of research on citation indices and the
Journal Impact Factor of the scholarly journal in which the
researcher published. This mentality must change before open access
can replace the traditional form of publishing.Quality control. In
contrast with the strictly regulated process of peer review,
quality control differs from one publication to the next in open
access. The quality control is especially low in repositories; some
repositories also contain dissertations as well as theses (RePub,
however, does not contain theses). The methods of quality control
in open access journals vary greatly.APCs (Article Processing
Charges). Open access journals often ask for APCs, which are meant
to be paid by the author or the scholarly institution.
Consequently, new scholars (primarily) are not in the financial
position to publish in open access journals.Fewer options among
journals with status/high impact factor.General PrinciplesAllow for
flexibilityProvide choices in features and ways that tasks can be
accomplishedAccommodate right- and left-handed useAllow the user to
customize settings whenever possibleKeep in mind that people may be
using adaptive technologiesBe simple and intuitiveDo not design
something differently from user expectations just to be
differentEliminate unnecessary complexity , Provide
feedbackMinimize errorsProvide warnings , Build fail-safe features
when possibleDo not establish patterns when you want people to pay
attentionInclude redundant modalitiesRedundancy provides
flexibility for different user preferences, system configurations,
or user abilities. This can be accomplished by using more than one
way to represent, display, and enter data, such as:using both a
beep and a menu bar flash to notify a user of an error using text
to label imagesredundantly allowing a user to issue commands by
typing or selecting something with a pointerAvoid side effectsSide
effects are actions that occur as the result of user actions that
do not seem to the user to be related to the primary goal of the
action. For instance, when starting a program that changes system
configurations (such as screen and sound settings) it should change
them back when the program is not being used.Side effects should be
avoided because they cause particular problems for novice users and
disabled users who may have difficulty detecting or correcting
certain types of side effects.DESIGN PRINCIPLES FOR ASSEMBLY :An
assembly line is a manufacturing process (most of the time called a
progressive assembly) in which parts (usually interchangeable
parts) are added as the semi-finished assembly moves from work
station to work station where the parts are added in sequence until
the final assembly is produced. By mechanically moving the parts to
the assembly work and moving the semi-finished assembly from work
station to work station, a finished product can be assembled much
faster and with much less labor than by having workers carry parts
to a stationary piece for assembly.Assembly lines are the common
method of assembling complex items such as automobiles and other
transportation equipment, household appliances and electronic
goods.The principles of assembly are these:(1) Place the tools and
the men in the sequence of the operation so that each component
part shall travel the least possible distance while in the process
of finishing.(2) Use work slides or some other form of carrier so
that when a workman completes his operation, he drops the part
always in the same placewhich place must always be the most
convenient place to his handand if possible have gravity carry the
part to the next workman for his operation.(3) Use sliding
assembling lines by which the parts to be assembled are delivered
at convenient distances.[ An assembly line is a manufacturing
process (most of the time called a progressive assembly) in which
parts (usually interchangeable parts) are added as the
semi-finished assembly moves from work station to work station
where the parts are added in sequence until the final assembly is
produced. By mechanically moving the parts to the assembly work and
moving the semi-finished assembly from work station to work
station, a finished product can be assembled much faster and with
much less labor than by having workers carry parts to a stationary
piece for assembly.Assembly lines are the common method of
assembling complex items such as automobiles and other
transportation equipment, household appliances and electronic
goods.