UNIT 1: DESIGN PHILOSOPHY
INTRODUCTION: Machine Design is defined as the use of scientific principles, technical information and imagination in the description of a machine or a mechanical system to perform specific functions with maimum economy and efficiency!
"#$IC %ROC&DUR& O' M#C(IN& D&$I)N: The *asic procedure of machine design consists of a step+*y+step approach +++++ from gien specifications a*out the functional re-uirements of a product, to the complete description in the form of drawings of the final product!
Market f config Survey
Defne
Specifcations Product
o
Study Alternative Mechanisms or Product & select proper mechanism
Prepare general layout o confguration& select joining methods
Design individual components
Prepare Assembly & detail drawings & modiy drawings ater testing prototype
"#$IC R&.UIR&M&NT$ O' M#C(IN& &/&M&NT$: The *road o*0ectie of designing a machine element is to ensure that it preseres it1s operating capacity during the stipulated serice life with minimum manufacturing and operating costs! In order to achiee this o*0ectie, the machine element should satisfy following *asic re-uirements: •
$trength
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Rigidity
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2ear resistance
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Minimum dimensions and weight
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Manufactura*ility
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$afety
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Conformance to standards
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Relia*ility
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Maintaina*ility
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Minimum life cycle cost
D&$I)N O' M#C(IN& &/&M&NT$: The design of machine elements is the most important step in the complete procedure of machine design! In order to ensure the *asic re-uirements of machine elements, calculations are carried out to find out the dimensions of the machine elements! These calculations form an integral part of the designing of machine elements! Speciy unctions o element
Determine orces acting on element
Select suitable material or element
Determine ailure mode o element
Determine geometric dimensions o element
Modiy dimensions or assembly & manuacture
Prepare working modeldrawing o element
'ig!:+ "asic procedure of design of machine element
'&#$I"I/T3 $TUD3: Once the pro*lems need has *een esta*lished and the specifications hae *een prepared, accepted and su*mitted, the feasi*ility study is done! The purpose of this study is to chec4 the possi*ility of success or failure of the proposed pro0ect *oth from technical and economic standpoint! In this study, arious -uestions are to *e answered:+ 5! Is any natural law *eing defied6 7! #re some of the specifications *eyond what is technically aaila*le at present6 8! Is there any dependence on scarce materials6 9! 2ill the cost of the end product *e too high6 The person doing the feasi*ility study will *e the engineers with strong design *ac4ground, 4nowledge of engineering sciences, a good 4nowledge of material usage, 4nowledge of production methods and re-uirements of the sales department! In fact, it is li4ely that the men responsi*le for the feasi*ility study will *e same engineers who will ultimately hae the design responsi*ility for the oerall pro0ect! .uite often, as a result of feasi*ility study, some changes are to *e made in the specifications and re-uirements in order to proide a greater li4elihood of pro0ect success!
D&$I)N $3NT(&$I$:
The design synthesis is defined as the process of creating or selecting configurations, materials, shapes and dimensions for a product! It is a decision ma4ing process with the main o*0ectie of optimiation! •
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In design analysis, the designer assumes a particular mechanism, a particular material etc and with the help of this information, he determines the dimension of the product! In design synthesis, the designer has to fi the o*0ectie! The o*0ectie can *e cost, minimum weight or olume, maimum relia*ility or maimum life! The second step is mathematical formulation of these o*0ecties and re-uirements! The final step is mathematical analysis for optimiation and interpretation of the results!
U$& O' $T#ND#RD$ IN D&$I)N: $tandardiation is defined as o*ligatory norms, to which arious characteristics of a product should conform! The characteristics include materials, dimensions and shape of the component, method of testing and method of mar4ing, pac4ing and storing of the product! •
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# standard is defined as a set of specifications for parts, materials or processes! The o*0ectie of a standard is to reduce the ariety and limit the num*er of items to a reasona*le leel! # code is defined as a set of specifications for the analysis, design, manufacture, testing and erection of the product! The purpose of code is to achiee a specified leel of safety!
There are three types of standards+++++++++++++++++ 5! Company standards ; used in a particular company or a group of sister concerns! 7! National standards ; eg!+ "!I!$, D!I!N < )ermany= 8! International standards ; eg! ; I!$!O $tandardiation offers following adantages:+ 5! The reduction in types and dimensions of identical components, ma4es it possi*le to manufacture the standard component on mass scale in a centralied process! 7! #aila*ility of standard components hae considera*ly reduced the manufacturing facilities re-uired *y an indiidual organisation! 8! $tandard parts are easy to replace when worn out due to interchangea*ility! 9! The application of standard machine element reduces the time and effort needed to design a new machine! >! The standards of specifications and testing procedures of machine elements improe their -uality and relia*ility!
$&/&CTION O' %R&'&RR&D $I?&$:
The @sieA of the product is a general term, which includes different parameters li4e powe r transmitting capacity, load carrying capacity, speed and dimensions of the component such as height, length and width of the product! %referred num*ers are used to specify the @siesA of the product! There are two terms namely:+ 5! "asic series < R>, R5B, R7B, R9B, RB= !" Deried series
#&$T(&TIC CON$ID&R#TION$ IN D&$I)N: &ach product has a definite purpose! It has to perform specific functions to the satisfaction of customer! The contact *etween the product and the people arises due to the sheer necessity of the functional re-uirement! The eternal appearance is an important feature, which not gies grace and lustre to the product *ut also dominates the sale in mar4et! This is particularly true for consumer dura*les li4e automo*iles, household appliances and audio isual e-uipment! The growing realiation of the need of aesthetic considerations in product design has gien rise to a separate discipline, 4nown as @industrial designA! The 0o* of an industrial designer is to create new forms and shapes, which are aesthetically pleasing! The outward appearance of the product has undergone many changes oer the years! There are fie *asic forms:+ 5! $tep form ; eg! ; multi+storeyed *uildings 7! $treamstreamline ; eg! ; automo*ile 8! Taper ; eg! ; tapered *loc4s 9! $hear ; eg! ; free standing engineering products >! $culpture ; eg! ; ellipsoids, para*oloids $election of proper colour is an important consideration in product aesthetics! The choice of colour should *e compati*le with the conentional ideas of the operator!
Colour
Meaning
Red
Danger ; (aard ; (ot
Orange
%ossi*le danger
Yellow
Caution
Green
$afety
Blue
Caution ; Cold
Grey
Dull
The eternal appearance of the product is a cumulatie effect of a num*er of factors such as rigidity and resilience, tolerances and surface finish, motion of indiidual components, materials, manufacturing methods and noise!
&R)ONOMIC CON$ID&R#TION$ IN D&$I)N: &rgonomics is defined as the relationship *etween man and machine and the application of anatomical, physiological and psychological principles to sole the pro*lems arising from man ; machine relationship! &rgonomics
ergon E nomos
wor4
Information reception
natural laws
Information display
M#N
M#C(IN&
Correctie action
Machine controls
'ig!:+ Man ; machine closed loop system
'rom design considerations, the topics of ergonomic studies are as follows: •
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#natomical factors in design of drier1s seat /ayout of instrument dials and display panels for accurate perception *y the operators
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Design of hand leers and hand wheels
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&nergy ependiture in hand and foot operationsF and
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/ighting, noise and climatic conditions in machine enironment!
