Lecture notes Computer Aided design

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ME 6501 - CAD III/ V MECHANICAL ENGINEERING An e-Course Material on ME 6501 – COMPUTER AIDED DESIGN ME 6501 – COMPUTER AIDED DESIGN By Mr. A. MAHENDRAN, M.E., PGDPC., MISTE., ASSISTANT PROFESSOR DEPARTMENT OF MECHANICAL ENGINEERING SASURIE COLLEGE OF ENGINEERING VIJAYAMANGALAM – 638 056 1 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V M ME EC CH HA AN NI IC CA AL L E EN NG GI IN NE EE ER RI IN NG G UNIT - I F F FU U UN N ND D DA A AM M ME E EN N NT T TA A AL L LS S S O O OF F F C C CO O OM M MP P PU U UT T TE E ER R R G G GR R RA A AP P PH H HI I IC C CS S S 1. PRE-R RE EQ QU UI IS SI IT TE E D DI IS SC CU US SS SI IO ON N 1.1. P PR RO OD DU UC CT T L LI IF FE E C CY YC CL LE E ( (P PL LC C) ) E E Ev v ve e er r ry y y p p pr r ro o od d du u uc c ct t t g g go o oe e es s s t t th h hr r ro o ou u ug g gh h h a a a c c cy y yc c cl l le e e f f fr r ro o om m m b b bi i ir r rt t th h h,,, f f fo o ol l ll l lo o ow w we e ed d d b b by y y a a an n n i i in n ni i it t ti i ia a al l l g g gr r ro o ow w wt t th h h s s st t ta a ag g ge e e,,, a a a r r re e el l la a at t ti i iv v ve e el l ly y y s s st t ta a ab b bl l le e e m m ma a at t tu u ur r re e ed d d p p pe e er r ri i io o od d d,,, a a an n nd d d f f fi i in n na a al l ll l ly y y i i in n nt t to o o a a a d d de e ec c cl l li i in n ni i in n ng g g s s st t ta a ag g ge e e t t th h ha a at t t e e ev v ve e en n nt t tu u ua a al l ll l ly y y e e en n nd d ds s s i i in n n t th he e d de ea at th h o of f t th he e p pr ro od du uc ct t a as s s sh ho ow wn n s sc ch he em ma at ti ic ca al ll ly y i in n Figure. Figure.1.1. Product Life Cycle (1) Introduction stage: : I In n t th hi is s s st ta ag ge e t th he e p pr ro od du uc ct t i is s n ne ew w a an nd d t th he e c cu us st to om me er r a ac cc ce ep pt ta an nc ce e i is s l lo ow w a an nd d hence the sales are low. (2) Growth stage: : : K K Kn n no o ow w wl l le e ed d dg g ge e e o o of f f t t th h he e e p p pr r ro o od d du u uc c ct t t a a an n nd d d i i it t ts s s c c ca a ap p pa a ab b bi i il l li i it t ti i ie e es s s r r re e ea a ac c ch h he e es s s t t to o o a a a g g gr r ro o ow w wi i in n ng g g n n nu u um m mb b be e er r r o o of f f customers. (3) Maturity stage: : : T T Th h he e e p p pr r ro o od d du u uc c ct t t i i is s s w w wi i id d de e el l ly y y a a ac c cc c ce e ep p pt t ta a ab b bl l le e e a a an n nd d d s s sa a al l le e es s s a a ar r re e e n n no o ow w w s s st t ta a ab b bl l le e e,,, a a an n nd d d i i it t t g g gr r ro o ow w ws s s w w wi i it t th h h t th he e s sa am me e r ra at te e a as s t th he e e ec co on no om my y a as s a a w wh ho ol le e g gr ro ow ws s.. (4) Decline stage: : : A A At t t s s so o om m me e e p p po o oi i in n nt t t o o of f f t t ti i im m me e e t t th h he e e p p pr r ro o od d du u uc c ct t t e e en n nt t te e er r rs s s t t th h he e e d d de e ec c cl l li i in n ne e e s s st t ta a ag g ge e e... I I It t ts s s s s sa a al l le e es s s s s st t ta a ar r rt t t d d de e ec c cr r re e ea a as s si i in n ng g g b b be e ec c ca a au u us s se e e o o of f f a a a n n ne e ew w w a a an n nd d d a a a b b be e et t tt t te e er r r p p pr r ro o od d du u uc c ct t t h h ha a as s s e e en n nt t te e er r re e ed d d t t th h he e e m m ma a ar r rk k ke e et t t t t to o o f f fu u ul l lf f fi i il l ll l l t t th h he e e s s sa a am m me e e customer requirements. 8 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V M ME EC CH HA AN NI IC CA AL L E EN NG GI IN NE EE ER RI IN NG G 1.2. P P PR R RO O OD D DU U UC C CT T T L L LI I IF F FE E E C C CY Y YC C CL L LE E E ( ( (P P PL L LC C C) ) ) F F FO O OR R R C C CO O ON N NT T TI I IN N NU U UO O OU U US S S I I IM M MP P PR R RO O OV V VE E EM M ME E EN N NT T T F F Fi i ig g gu u ur r re e e...1 1 1...2 2 2... P P Pr r ro o od d du u uc c ct t t L L Li i if f fe e e C C Cy y yc c cl l le e e f f fo o or r r c c co o on n nt t ti i in n nu u uo o ou u us s s I I Im m mp p pr r ro o ov v ve e em m me e en n nt t t ( ( (B B Ba a as s si i ic c c) ) ) F F Fi i ig g gu u ur r re e e...1 1 1...3 3 3... P P Pr r ro o od d du u uc c ct t t L L Li i if f fe e e C C Cy y yc c cl l le e e f f fo o or r r c c co o on n nt t ti i in n nu u uo o ou u us s s I I Im m mp p pr r ro o ov v ve e em m me e en n nt t t ( ( (D D De e et t ta a ai i il l le e ed d d) ) ) 9 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V MECHANICAL ENGINEERING 1.3. TECHNOLOGY DEVELOPMENT CYCLE The development of a new technology follows a typical S-shaped curve. In its early stage, the progress is limited by the lack of ideas. A single good idea can make several other god ideas possible, and the rate of progress is exponential. Gradually the growth becomes linear when the fundamental ideas are in place and the progress is concerned with filling the gaps between, the key ideas. It is during this time when the commercial exploitation flourishes. But with time the technology begins to run dry and increased improvements come with greater difficulty. This matured technology grows slowly and approaches a limit asymptotically. The success of a technology based company lies in its capabilities of recognizing when the core technology on which the company’s products are based begin to mature and through an active R&D program, transfer to another technology growth curve which offers greater possibilities. Figure.1.4. Schematic outline of Technology Development Curve 10 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V MECHANICAL ENGINEERING Figure.1.5. Improved program to develop new technology before the complete extinct of existing technology 1.4. THE DESIGN PROCESS - INTRODUCTION The Engineering Design Process is the formulation of a plan to help an engineer build a product with a specified performance goal. This process involves a number of steps, and parts of the process may need to be repeated many times before production of a final product can begin. It is a decision making process (often iterative) in which the basic sciences, mathematics, and engineering sciences are applied to convert resources optimally to meet a stated objective. Among the fundamental elements of the design process are the establishment of objectives and criteria, synthesis, analysis, construction, testing and evaluation. The Engineering Design process is a multi-step process including the research, conceptualization, feasibility assessment, establishing design requirements, preliminary design, detailed design, production planning and tool design, and finally production. 11 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V M ME EC CH HA AN NI IC CA AL L E EN NG GI IN NE EE ER RI IN NG G 1 1..4 4..1 1.. S St te ep ps s i in nv vo ol lv ve ed d i in n E En ng gi in ne ee er ri in ng g D De es si ig gn n p pr ro oc ce es ss F Fi ig gu ur re e..1 1..6 6.. E En ng gi in ne ee er ri in ng g D De es si ig gn n P Pr ro oc ce es ss s Conceptual Design I I It t t i i is s s a a a p p pr r ro o oc c ce e es s ss s s i i in n n w w wh h hi i ic c ch h h w w we e e i i in n ni i it t ti i ia a at t te e e t t th h he e e d d de e es s si i ig g gn n n a a an n nd d d c c co o om m me e e u u up p p w w wi i it t th h h a a a n n nu u um m mb b be e er r r o o of f f d d de e es s si i ig g gn n n c c co o on n nc c ce e ep p pt t ts s s a a an n nd d d t t th h he e en n n n n na a ar r rr r ro o ow w w d d do o ow w wn n n t t to o o t t th h he e e s s si i in n ng g gl l le e e b b be e es s st t t c c co o on n nc c ce e ep p pt t t... T T Th h hi i is s s i i in n nv v vo o ol l lv v ve e ed d d t t th h he e e f f fo o ol l ll l lo o ow w wi i in n ng g g s s st t te e ep p ps s s... (1) Identification o of f c cu us st to om me er r n ne ee ed ds s: : T Th he e m ma ai il l o ob bj je ec ct ti iv ve e o of f t th hi is s i is s t to o c co om mp pl le et te el ly y u un nd de er rs st ta an nd d t th he e c cu us st to om me er rs s’ ’ n ne ee ed ds s a an nd d t to o c co om mm mu un ni ic ca at te e t th he em m t to o t th he e d de es si ig gn n t te ea am m (2) Problem definition: : : T T Th h he e e m m ma a ai i il l l g g go o oa a al l l o o of f f t t th h hi i is s s a a ac c ct t ti i iv v vi i it t ty y y i i is s s t t to o o c c cr r re e ea a at t te e e a a a s s st t ta a at t te e em m me e en n nt t t t t th h ha a at t t d d de e es s sc c cr r ri i ib b be e es s s w w wh h ha a at t t all needs to be ac c cc c co o om m mp p pl l li i is s sh h he e ed d d t t to o o m m me e ee e et t t t t th h he e e n n ne e ee e ed d ds s s o o of f f t t th h he e e c c cu u us s st t to o om m me e er r rs s s’ ’ ’ r r re e eq q qu u ui i ir r re e em m me e en n nt t ts s s... (3) Gathering Information: : : I I In n n t t th h hi i is s s s s st t te e ep p p,,, w w we e e c c co o ol l ll l le e ec c ct t t a a al l ll l l t t th h he e e i i in n nf f fo o or r rm m ma a at t ti i io o on n n t t th h ha a at t t c c ca a an n n b b be e e h h he e el l lp p pf f fu u ul l l f f fo o or r r d de ev ve el lo op pi in ng g a an nd d t tr ra an ns sl la at ti in ng g t th he e c cu us st to om me er rs s’ ’ n ne ee ed ds s i in nt to o e en ng gi in ne ee er ri in ng g d de es si ig gn n.. (4) Conceptualization: I I In n n t t th h hi i is s s s s st t te e ep p p,,, b b br r ro o oa a ad d d s s se e et t ts s s o o of f f c c co o on n nc c ce e ep p pt t ts s s a a ar r re e e g g ge e en n ne e er r ra a at t te e ed d d t t th h ha a at t t c c ca a an n n p p po o ot t te e en n nt t ti i ia a al l ll l ly y y s sa at ti is sf fy y t th he e p pr ro ob bl le em m s st ta at te em me en nt t (5) Concept selection: : : T T Th h he e e m m ma a ai i in n n o o ob b bj j je e ec c ct t ti i iv v ve e e o o of f f t t th h hi i is s s s s st t te e ep p p i i is s s t t to o o e e ev v va a al l lu u ua a at t te e e t t th h he e e v v va a ar r ri i io o ou u us s s d d de e es s si i ig g gn n n c co on nc ce ep pt ts s,, m mo od di if fy yi in ng g a an nd d e ev vo ol lv vi in ng g i in nt to o a a s si in ng gl le e p pr re ef fe er rr re ed d c co on nc ce ept. 12 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V MECHANICAL ENGINEERING Embodiment Design It is a process where the structured development of the design concepts takes place. It is in this phase that decisions are made on strength, material selection, size shape and spatial compatibility. Embodiment design is concerned with three major tasks – product architecture, configuration design, and parametric design. (1) Product architecture: It is concerned with dividing the overall design system into small subsystems and modules. It is in this step we decide how the physical components of the design are to be arranged in order to combine them to carry out the functional duties of the design. (2) Configuration design: In this process we determine what all features are required in the various parts / components and how these features are to be arranged in space relative to each other. (3) Parametric design: It starts with information from the configuration design process and aims to establish the exact dimensions and tolerances of the product. Also, final decisions on the material and manufacturing processes are done if it has not been fixed in the previous process. One of the important aspects of parametric designs is to examine if the design is robust or not. Detail Design It is in this phase the design is brought to a state where it has the complete engineering description of a tested and a producible product. Any missing information about the arrangement, form, material, manufacturing process, dimensions, tolerances etc of each part is added and detailed engineering drawing suitable for manufacturing are prepared. 1.4.2. Models of the Design Process Designers have to: Explore - the problem ‘territory’ Generate - solution concepts Evaluate - alternative solution concepts Communicate - a final proposal 13 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V MECHANICAL ENGINEERING A simple model of the design process, derived from what designers have to do French’s model VDI model Cross’s basic model 1.4.3. New Design Procedures 14 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V M ME EC CH HA AN NI IC CA AL L E EN NG GI IN NE EE ER RI IN NG G 1 1..4 4..4 4.. N Ne ee ed d f fo or r A Ap pp pl ly yi in ng g T Te ec ch hn no ol lo og gy y i in n t th he e D De es si ig gn n P Pr ro oc ce es ss s D De es si ig gn n i is s t th he e e es ss se en nc ce e o of f e en ng gi in ne eering S St ta ar rt ts s w wi it th h r re ec co og gn ni it ti io on n o of f s so om me e n ne ee ed d P Pr ro og gr re es ss se es s t to o p ph hy ys si ic ca al l i im mp pl le em me en nt ta at ti io on n R Re es su ul lt ts s m ma ay y b be e s si im mp pl le e o or r c co om mp pl le ex x D De es si ig gn n c ca an n b be e o of f t tw wo o k ki in nd d: : o S So om me et th hi in ng g c co om mp pl le et te el ly y n ne ew w ,, o or r o A An n i im mp pr ro ov ve ed d f fo or rm m o of f s so om me et th hi in ng g a al lr re ea ad dy y i in n e ex xi is st te en nc ce e 1.5. M MO OR RP PH HO OL LO OG GY Y O OF F D DE ES SI IG GN N The consider r ra a at t ti i io o on n n o o of f f t t th h he e e p p pr r ro o od d du u uc c ct t t l l li i if f fe e e f f fr r ro o om m m i i it t ts s s c c co o on n nc c ce e ep p pt t ti i io o on n n t t to o o r r re e et t ti i ir r re e em m me e en n nt t t............... 15 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V M ME EC CH HA AN NI IC CA AL L E EN NG GI IN NE EE ER RI IN NG G Anatomy of Design D D De e et t ta a ai i il l le e ed d d e e ex x xa a am m mi i in n na a at t ti i io o on n n o o of f f t t th h he e e e e en n ng g gi i in n ne e ee e er r r’ ’ ’s s s a a ac c ct t ti i io o on n ns s s a a as s s h h he e e/ / /s s sh h he e e i i id d de e en n nt t ti i if f fi i ie e es s s a a an n nd d d s s so o ol l lv v ve e es s s t t th h he e e p p pr r ro o ob b bl l le e em m m: : : 1.5.1. Needs Analysis C Cr re ea at ti io on n b be eg gi in ns s b by y r re ec co og gn ni iz zi in ng g a a n ne ee ed d o A Ap pp pa ar re en nt t f fr ro om m o ob bs se ervation o R Re es su ul lt ts s o of f a a d de et ta ai il le ed d s st tu ud dy y o A A s sp pe ec ci if fi ic c s se et t o of f c ci ir rc cu um ms st ta an nc ce es s R Re es su ul lt ts s i in n a a p pr ri im mi it ti iv ve e s st ta at te em me en nt t o F Fa ac ct t o or r o op pi in ni io on n o D Do oe es s t th he e n ne ee ed d e ex xi is st t a an nd d i is s i it t r re ea al li is st ti ic c? ? o D Do oe es s i it t e ex xi is st t n no ow w o or r w wi il ll l i it t e ex xi is st t i in n t th he e f fu ut tu ur re e? ? o I Is s i it t a a n ne ew w n ne ee ed d? ? ( (n ne ew w m ma at te er ri ia al l o or r p ph hy ys si ic ca al l p pr ri inciple) O Of ft te en n d de ep pe en nd ds s o on n c ci ir rc cu um ms st ta an nc ce es s N N Ne e ee e ed d ds s s a a an n na a al l ly y ys s si i is s s o o on n nc c ce e e t t th h hr r ro o ou u ug g gh h h t t th h he e e A A An n na a at t to o om m my y y p p pr r ro o ov v vi i id d de e es s s a a a g g go o oo o od d d s s st t ta a ar r rt t ti i in n ng g g p p po o oi i in n nt t t f f fo o or r r t t th h he e e Feasibility Study 16 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V MECHANICAL ENGINEERING 1.5.2. Feasibility Study Designs can be futile unless satisfying the original need is feasible At this stage, the product appears in abstract forms, but is they feasible??? Alternative solutions must be subjected to physical and economic analyses and be realizable from both The Feasibility Study using analysis of several alternatives establishes the design concept as something which can be realised and accepted Some examples..... (i) A building must be comfortable to live in: Heating, ventilation and air conditioning are required. Specify limits of temperature, humidity, velocity and fresh air constituency. (ii) National fossil fuel supplies are low: Alternative forms of energy supply are required. Specify amount and where they are needed, and any restrictions of space, time or pollution levels. 1.5.3. Preliminary Design Main purpose is selection of the best possible solution from a choice of alternatives Make comparisons against given criteria & constraints Must maintain an open mind; use your judgement. 1.5.4. Detailed design Aim is to produce a complete set of working drawings which are then transmitted to the manufacturer This stage of design is far less flexible than those previous Design should now reflect all of the planning both for manufacture and consumption stages Construction/testing of various components may be required Prototype building ....is it what was expected? 1.5.5. Production Here, the device or system is actually constructed, and planning for this should have been incorporated into the design Knowledge of the capability of the machines is required, since it must be possible to build and assemble the components as specified Special jigs, fixtures and even machines may be required Planning is vital; including quality control hold points, methods of inspection, standards for comparison etc... Timing of construction may be important eg. Climatics 17 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V M ME EC CH HA AN NI IC CA AL L E EN NG GI IN NE EE ER RI IN NG G 1.5.6. Distribution Transport t ta a at t ti i io o on n n o o of f f t t th h he e e m m ma a an n nu u uf f fa a ac c ct t tu u ur r re e ed d d a a ar r rt t ti i ic c cl l le e e,,, c c co o om m mp p pl l le e et t te e e o o or r r i i in n n s s su u ub b ba a as s ss s se e em m mb b bl l ly y y f f fo o or r rm m m m m mu u us s st t t b b be e e anticipated in the design P P Pa a ac c ck k ka a ag g gi i in n ng g g,,, a a av v va a ai i il l la a ab b bi i il l li i it t ty y y o o of f f v v ve e eh h hi i ic c cl l le e es s s,,, r r re e eg g gu u ul l la a at t ti i io o on n ns s s f f fo o or r r u u us s se e e o o of f f t t th h ho o or r ro o ou u ug g gh h hf f fa a ar r re e es s s,,, s s sh h he e el l lf f f/ / /c c co o om m mp p po o on n ne e en n nt t t l li if fe e,, w wa ar re eh ho ou us se e s st to or ra ag ge e f fa ac ci il li it ti ie es s,, s sp pe ec ci ia al l h ha an nd dl li in ng g,, e en nv vi ir ro on nm me en nt ta al l c co on nt tr ro ol l o of f t te em mp pe er ra at tu ur re e a an nd d h hu um mi id di it ty y m ma ay y n ne ee ed d t to o b be e a ad dd dr re es ss se ed d 1.5.7. Consumption T Th he e p pr ro od du uc ct t i is s n no ow w u us se ed d b by y t th he e c co on ns su um me er r I If f t th he e d de es si ig gn n i is s e ef ff fe ec ct t,, i it t w wi il ll l h ha av ve e m me et t t th he e n ne ee ed d T T Th h he e e d d de e es s si i ig g gn n n m m ma a ay y y y y ye e et t t n n no o ot t t b b be e e c c co o om m mp p pl l le e et t te e e; ; ; r r re e ed d de e es s si i ig g gn n ns s s a a an n nd d d m m mo o od d di i if f fi i ic c ca a at t ti i io o on n ns s s m m ma a ay y y b b be e e r r re e eq q qu u ui i ir r re e ed d d depend di in ng g o on n f fi ie el ld d t tr ri ia al ls s o or r c co on ns su um me er r f fe ee ed db ba ac ck k M M Ma a ay y y n n ne e ee e ed d d t t to o o c c co o on n ns s si i id d de e er r r m m ma a ai i in n nt t te e en n na a an n nc c ce e e o o of f f c c co o om m mp p po o on n ne e en n nt t ts s s a a an n nd d d s s su u up p pp p pl l ly y y o o of f f s s sp p pa a ar r re e e p p pa a ar r rt t ts s s o o or r r subassemblies 1.5.8. Retirement T Th he e p pr ro od du uc ct t w wi il ll l b be e d di is sc ca ar rd de ed d a as s i it ts s l li if fe e c cy yc cl le e t te er rm mi in na at te es s I It t m ma ay y h ha av ve e b be ec co om me e o ob bs so ol le et te e w wh hi il ls st t s st ti il ll l s se er rv vi ic ce ea ab bl le e a an nd d t th he er re ef fo or re e t th he e d de es si ig gn n m ma ay y n no ot t h ha av ve e been fully economical D D Di i is s sp p po o os s sa a al l l a a an n nd d d r r re e ec c co o ov v ve e er r ry y y o o of f f u u us s se e ef f fu u ul l l m m ma a at t te e er r ri i ia a al l ls s s s s sh h ho o ou u ul l ld d d h h ha a av v ve e e b b be e ee e en n n i i in n nc c cl l lu u ud d de e ed d d i i in n n t t th h he e e d d de e es s si i ig g gn n n T Th hr re ea at ts s t to o s sa af fe et ty y s sh ho ou ul ld d b be e g gu ua ar rd de ed d a ag ga ai in ns st t 1.6. D DE ES SI IG GN N P PR RO OC CE ES SS S M MO OD DE EL LS S 1.6.1. Shigley Model 18 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V M ME EC CH HA AN NI IC CA AL L E EN NG GI IN NE EE ER RI IN NG G 1.6.2. Ohsuga Model 1.6.3. Earle Model 19 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V M ME EC CH HA AN NI IC CA AL L E EN NG GI IN NE EE ER RI IN NG G 1.7. S SE EQ QU UE EN NT TI IA AL L E EN NG GI IN NE EE ER RI IN NG G D DE ES SI IG GN N 1.8. C CO ON NC CU UR RR RE EN NT T E EN NG GI IN NE EE ER RI IN NG G D DE ES SI IG GN N 20 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V MECHANICAL ENGINEERING SEQUENTIAL AND CONCURRENT ENGINEERING With today's marketplace becoming more and more competitive, there is an ever-increasing pressure on companies to respond quickly to market needs, be cost effective, reduce lead-times to market and deliver superior quality products. Traditionally, design has been carried out as a sequential set of activities with distinct non- overlapping phases. In such an approach, the life-cycle of a product starts with the identification of the need for that product. These needs are converted into product requirements which are passed on to the design department. The designers design the product's form, fit, and function to meet all the requirements, and pass on the design to the manufacturing department. After the product is manufactured it goes through the phases of assembly, testing, and installation. This type of approach to life-cycle development is also known as `over the wall' approach, because the different life-cycle phases are hidden or isolated from each other. Each phase receives the output of the preceding phase as if the output had been thrown over the wall. In such an approach, the manufacturing department, for example, does not know what it will actually be manufacturing until the detailed design of the product is over. Figure.1.8.Over the Wall Engineering (Sequential Engineering) There are a lot of disadvantages of the sequential engineering process. The designers are responsible for creating a design that meets all the specified requirements. They are usually not concerned with how the product will be manufactured or assembled. Problems and inconsistencies in the designs are therefore, detected when the product reaches into the later phases of its life-cycle. At this stage, the only possible option is to send the product back for a re-design. The whole process becomes iterative and it not until after a lot of re-designs has taken place that the product is finally manufactured. Because of the large number of changes, and hence iterations, the product's introduction to market gets delayed. In addition, each re-design, re-work, re-assembly etc. incurs cost, and therefore the resulting product is costlier than what it was originally thought to be. The market share is lost because of the delay in product's introduction to market, and customer faith is lost. All this is undesirable. 21 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V MECHANICAL ENGINEERING Concurrent Engineering is a dramatically different approach to product development in which various life-cycle aspects are considered simultaneously right from the early stages of design. These life-cycle aspects include product's functionality, manufacturability, testability, assimilability, maintainability, and everything else that could be affected by the design. In addition, various life-cycle phases overlap each other, and there in no "wall" between these phases. The completion of a previous life-cycle phase is not a pre-requisite for the start of the next life-cycle phase. In addition, there is a continuous feedback between these life-cycle phases so that the conflicts are detected as soon as possible. Figure.1.9. Concurrent Engineering The concurrent approach results in less number of changes during the later phases of product life-cycle, because of the fact that the life-cycle aspects are being considered all through the design. The benefits achieved are reduced lead times to market, reduced cost, higher quality, greater customer satisfaction, increased market share etc. Sequential engineering is the term used to describe the method of production in a linear format. The different steps are done one after another, with all attention and resources focused on that one task. After it is completed it is left alone and everything is concentrated on the next task. 22 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V MECHANICAL ENGINEERING In concurrent engineering, different tasks are tackled at the same time, and not necessarily in the usual order. This means that info found out later in the process can be added to earlier parts, improving them, and also saving a lot of time. Concurrent engineering is a method by which several teams within an organization work simultaneously to develop new products and services and allows a more stream lined approach. The concurrent engineering is a non-linear product or project design approach during which all phases of manufacturing operate at the same time - simultaneously. Both product and process design run in parallel and occur in the same time frame. Product and process are closely coordinated to achieve optimal matching of requirements for effective cost, quality, and delivery. Decision making involves full team participation and involvement. The team often consists of product design engineers, manufacturing engineers, marketing personnel, purchasing, finance, and suppliers. Figure.1.9. Sequential and Concurrent Engineering 23 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V M ME EC CH HA AN NI IC CA AL L E EN NG GI IN NE EE ER RI IN NG G 1.9. R RO OL LE E O OF F C CO OM MP PU UT TE ER RS S I IN N D DE ES SI IG GN N 1.10. C CA AD D S SY YS ST TE EM M A AR RC CH HI IT TE EC CT TU UR RE E 24 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V M ME EC CH HA AN NI IC CA AL L E EN NG GI IN NE EE ER RI IN NG G 1.11. C CO OM MP PU UT TE ER R A AI ID DE ED D E EN NG GI IN NE EE ER RI IN NG G – CAD/CAM 1.12. A AP PP PL LI IC CA AT TI IO ON N O OF F C CO OM MP PU UT TE ER RS S T TO O D DE ES SI IG GN N • M Mo od de el li in ng g o of f t th he e D De es si ig gn n • E En ng gi in ne ee er ri in ng g d de es si ig gn n a an nd d a an na al ly ys si is s • E Ev va al lu ua at ti io on n o of f P Pr ro ot to ot ty yp pe e t th hr ro ou ug gh h S Si im mu ul la at ti io on n a an nd d Testing • D Dr ra af ft ti in ng g a an nd d D De es si ig gn n D Do oc cu um me en nt ta at ti io on n 1.13. BENEFITS OF CAD 1. P Pr ro od du uc ct ti iv vi it ty y I Im mp pr ro ov ve em me en nt t i in n D De es si ig gn n D De ep pe en nd ds s o on n C Co om mp pl le ex xi it ty y o of f d dr ra aw wi in ng g,, D De eg gr re ee e o of f r re ep pe et ti it ti iv ve en ne es ss s o of f f fe ea at tu ur re es s i in n t th he e d de es si ig gn ne ed d p pa ar rt ts s,, D De eg gr re ee e o of f s sy ym mm me et tr ry y i in n t th he e p pa ar rt ts s,, E Ex xt te en ns si iv ve e u us se e o of f l li ib br ra ar ry y o of f u us se er r d de ef fi in ne ed d s sh ha ap pe es s a an nd d c co om mm mo on nl ly y u us se ed d e en nt ti it ti ie es s 2. Shorter Lead Times 3. Flexibility in Design 4. Design Analysis 5. Fewer Design Error 6. S St ta an nd da ar rd di iz za at ti io on n o of f D De es si ig gn n,, D Dr ra af ft ti in ng g a an nd d D Do oc cu um me en nt ta at ti io on n 25 A.MAHENDRAN - AP/MECH 2015-16 ME 6501 - CAD III/ V MECHANICAL ENGINEERING 7. Drawings are more understandable 8. Improved Procedures of Engineering Changes 9. Benefits in Manufacturing : a. Tool and fixture design for manufacturing b. Computer Aided process planning c. Preparation of assembly lists and bill of materials d. Computer aided inspection e. Coding and classification of components f. Production planning and control g. Preparation of numerical control programs for manufacturing the parts on CNC machines h. Assembly sequence planning 1.14. REASONS FOR IMPLEMENTING CAD • To increase the productivity of the designer • To improve the Quality of Design • To improve Documentation • To create a Database for manufacturing 1.15. COMPUTER GRAPHICS or INTERACTIVE COMPUTER GRAPHICS Computer Graphics is defined as creation, storage, and manipulation of pictures and drawings by means of a digital computer It is an extremely effective medium for communication between people and computers Computer graphics studies the manipulation of visual and geometric information using computational techniques It focuses on the mathematical and computational foundations of image generation and processing rather than purely aesthetic issues Concept of Interactive computer Graphics In Interactive Computer Graphics (ICG) the user interacts with the compute and comprises the following important functions: 26 A.MAHENDRAN - AP/MECH 2015-16

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