ME CAPSTONE DESIGN II
ME CAPSTONE DESIGN II ME 412
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This 7 page Class Notes was uploaded by Vidal Goyette on Friday October 23, 2015. The Class Notes belongs to ME 412 at University of Kentucky taught by Staff in Fall. Since its upload, it has received 12 views. For similar materials see /class/228239/me-412-university-of-kentucky in Mechanical Engineering at University of Kentucky.
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Date Created: 10/23/15
ME m Memicalsngmemq quot unimm oYKenkay quot ME 412 Desi n for Senior Design 9 39 39 39 Fall 2004 Lecture 7 ME 112 Memamcalsngmeemg unitwry omenmcky Generic Development Process Designing for Specification No need to elaborate here really what you ve been trained to do Manufacturability Sure you can design it but can it be made Economy Who cares if it works if it costs too much Safety Products that results in lost digits and massive lawsuits have short shelf lives Others New in lpgguct NEW PRODUCT deve m 5am mm x 2mm 5 PmductDelVgizndbevel pment ME 112 Memamcalsngmeemq ME l1lMecnamcaIEn9meerm quot unimm oYKerchky quot unimm oYKenkay Detailed Design Phases Preliminary Design Functional Selected PrDbIErrf Requiremenis Concepts Identification stage Constraints i I I Determine exactly I List possible I what is needed I methods or motion or i I ener transrer ldeniiry all elements 0quot m39z a mquot 9y I or the design I i i I Optimization Illuslmte design and build I I modelsprototypes i I Explain advanlages and I Evamauon shortcomings or design gt7 S age Be prepared ror onlicisin Design Developmeni Make a linai iuogerneni on the design Production Stage Sysiem Performance Product Analysis Stage Intermediate Design SynthESIS Slage Tentative Deiail Design ME 4 1 2 Mechanical Engineering nl39versity of Kentucky Intermediate Design Phase Generally occurs after preliminary design but the two phases may overlap Intermediate design always involves iterations In this phase we deal with individual components ofthe machine Identify components Define component functions Identify constraints involving cost size etc rm Re limcmul Develop tentative conceptions of the components mechanismprocess combinations using good form synthesis principles Perform supporting analyses including analyses at each critical point in each component Select the best component designs Document component designs prepare a layout consr nemm A pillar component geomeiries Preliminary Design Phase Often the first step in which a designer becomes involved and may not involve intense iteration In this phase we deal with the entire machine Define function f tudirlal rilenlb Develop alternative conceptions of mechanismprocess combinations that can satisfy the constraints Identify constraints involving cost size etc Perform supporting analyses thermodynamic heat transfer uid mechanics kinematics force stress life cost compatibility with it SPeCIaI constralnts 0 Select the best mechanism Alternativedesignconceptsf r o cro s members in a light duty iruok rloorpan Document the design IIK ME 412 Mechanical Engineering u nlversity of Kentucky Detail Design Phase Subsequent to intermediate and In this phase we deal with individual components ofthe machine and the machine as a whole Select manufacturing and assembly processes Specify dimensions and tolerances Prepare component detail drawings Line rendering ora pickup box assembly 0 Prepare assem bly d raWIngS snowing geomeirio details such as wheel well openings cross members and bed corrugation Lecture material in most courses focus on the preliminary and intermediate design phases where the analysis of the design is paramount Your design projects obviously involve elements of detail design however drawing UK ME 4 1 2 Mechanical Engineering University of Kentucky UK ME 4 1 2 Mechanical Engineering University of Kentucky Design Considerations The design of a component or system is typically influenced by a number of requirements Any requirement a e 39ng design is a design consideration For example if the ability to carry large loads without failure is important we say that strength is a design consideration Most product development projects involve a number of design considerations Strengthstress Cost Thermal properties Distortionstiffness Processing requirements Surface nish ear Weight Lubrication Corrosion Life Marketability Safety oise Maintenance Reliability Aesthetic considerations Volume Fiction Sha e Liability Usabilityutility Size Scrappingrecyclability MEHLMecbamcalEnqmeerm UK WWWMW Standards and Codes Standards and codes represent a prescriptive approach to design that may be incorporated into a design process this aids in design manufacturability cost and safety Standards A set oftechnical de nitions and guidelines for designers and manufacturers Standards are written b p rtsquot rid are considered voluntary SME groups develops and maintains standards using committees Code A set of standards that has been adopted by one or more 39 ui39 39 F enliallv a code is a set of standards with the force of law behind it According to its web site ASME maintains and distributes 600 codes and standards used around the world for the design manufacturing and installation of mechanical devicesquot ME 112 Memamcalsngmeemg unimm omenmcky ASME Standards All2 Plumbing Materials and Equipment Threads Bl Screw B5 ools 7 components Elements Performance and Equipment Bl8 standardization of Pastene B2 cnains Attacnments and Sprockets for Power Transmission and Conveying 832 Metal and Metal Alloy Wrought Mill Product Nornlrla sizes standards ror Pressure and Temperature instruments and Accessories classirication and Designation of Surface Qualities ca e Blanks cnemical standard Pumps Dimensional Metrology cutting ools Drlvers and Busnings d Accessories cas Turblrle Procurement Ov e Ho s s tof Fluid Flow in closed conduits Pallets slip sneets and Otner Bases Por Unit Loads Slew Ping Bearing steel Stacks WA Practices ME m Mecnamcatsngmemq quot Univerle oYKenkay wwiinwwwwwww ADI Safgd quotwe dwa I g 1 A o 9 ASME Standards for Screw Threads Bl l4989 Uniried lncn Screw Threads UN and UNR Thread Porm Bl 24983 Pl99l cages and caging for United lncn Screw Threads Bl 499 Screw Thread caging Systems or Dimensional Acceptablllty e lncn and Metric Screw Threads UN UNR UMu M and Mu Bl 54997 Acme Screw Threads Bl M D riniti n aridL iii iiiu i i i i Threads 84988 Pl994 Stub Acme Screw Threads Bl M4958 Pl994 Microscope Oblectlve Thread Bl l24987 Pl998 class 5 lnterrerencePit Thread Bl l3M4995 Metric Screw aneadse M Proflle Bl l8M4984 Pl992 cages and caging for Metric M Screw Threads Bl 2o l4983tPl992 PlpeThleadS ceneral Purposetlncn e P g Screw Threads inch Bl 2lM ead roflle Bl 22M4985 l992 cages And caging Practice ForWiJ series Metric Screw Threads Bl 30M4992 Screw Threads 7 standard Practice for calculating and Pounding Dimensions ME m Mecnamcatsngmemq quot Univerle oYKenkay ri s ASME Standard 81311989 Bi 171989 Unified inch Screw Threads UN arid UNR Thread Forrn scope se and designation for unified screw threads in ordert threads are based oh inch modules they may be denoted unifiedi unified this Standard Covers only UN arid UNR thread forrns or easy reference a metric translation of this standard has been incorporated as ugh c Appendix c Appendices Athro Contain useful rhrorrhatroh that is supplementary to the Sections ofthis Standard Order No M020889 55 00 ries ciass ah o emphasizet hch r an i i ran hatunified screw screw threads ad however UK ME J12Mecnamca15ngmeemq ummsmr omenmcky ASME Standard 81 7M1984 R1992 Bi M 40 A D finiti n andi N r rnboisforScreWThreadS scope The purpose of this standard is to estaohsh ohrrorrh practices for standard screw threads with regard to the following a Screw thread nomenclature and o Letter symboisfor designatingfeatures of screw threads foruse oh drawings in taoies of drrhehsrohs which set forth drrhehsrohai standards and in other records and for expressing mathematical relationship This standard consists of a glossary of terms and illustrated taoie showing the application of symbols and atabie of thread series designations Many of the terms and symbols specified in this standard vary considerably from those of previous issues the same Order No LOOOM 32 00 UK ME J12Mecnamca15ngmeemg ummsmr omenmcky Code of Ethics Fundamental Principles Engineers uphold and advance the integrity honor and 39on by dignity ofthe Engineering professi using their knowledge and skill forthe enhancement of Ifare human we being honest and impartial and serving with delity the public their employers and clients an striving to increase the competence and prestige of the en gin eerin g profession The American Society of Mechanical Engineers ME J12Mecnamca15ngmeemq ummsmr omenmcky Code of Ethics Fundamental Canons 39 ty the public in the performance oftheir professional duties Engineers shall perform services only in the areas oftheir competence 39 uglIuLu 39 39 r 39 r mlu their careers and shall provide opportunities for the professional development ofthose engineers under their supervision Engineers shall act in professional matters for each employer or client as faithful agents or trustees and shall avoid con icts of interest 39 39 39 professional r 39 quot their services and shall not compete unfairly with others Engineers shall associate only with reputable persons or organizations 39 39 only in j quot quot truthful manner UK The American Society of Mechanical Engineers ME J12 MemamcalEnqmeerm ummsmr omenmcky ASME Code Example Boiler and Pressure Vessel Code The International Boiler and Pressure Vessel Code establishes rules of safety governing the des39 a LE experience are constantly being added by Addenda 15 sections on the design and manufacturing of boilers and pressure vessels The Complete 2004 lntemational Boiler and Pressure Vessel Code Order No B00230 1060000 ME m MechamcalEnqmeerm w unimm oiKenkay Standards Common standards ANSI American National Standards Institute NIST National Institute of Standards and Technology ASTM American Society for Testing and Materials ISO International Organization for Standardization IEEE Institute of Electrical and Electronics Engineers Others Design for ManufacturabilityAssembly Must be considered in the intermediate and detailed design phases rstprove the concept works then design it to be buidabe Some Guidelines Simplify the design and reduce the number of parts E h part has an opportunity for defects and assembly error Standardize Use common o theshelfparts when possible Design for ease offabrication see next slide 39 39 process capabilities and avoid unneeded Design Within surface nishes and tIg tto erances Mistakeproofand easy assem ly a s can be assembled in only one way Minimize exible parts and connect39ons Ef cient joining avoid screws snap t instead Design for automated production ME m MechamcalEnqmeerm quot unimm oYKenkay ME 112 MemamcaIEngineermq Linnerle amenmcky Designing for Ease of Fabrication Select compatible processes and materials For higher volume parts consider castings or stamping to reduce machlnln Use near net shapes for molded and forged parts to minimize machining and processing effort Design for ease of fixturing by providing large solid mounting surface amp parallel clamping surfaces Avoid designs requiring sharp corners or points in cutting tools they break easier Ayoid thin walls thin webs deep pockets or deep holes to Withstand clamping amp machining Without distortion Avoid tapers amp contours as much as possible in favor of rectangular sha es Avoid undercuts which require special operations amptools Avoid hardened or difficult machined materials unless essential to requirements Putmachined surfaces on same plane or with same diameter to minimize number of operations Defign workpieces to use standard cutters drill bit sizes or other 00 5 Avoid small holes drill bit breakage greater amp length to diameter ratio gt 3 chip clearance amp stralgh ness deviation ME 112 Mememalsngmwmq Linnerle amenmcky Design for Economy Strength safety reliability and cost are perhaps the most important design considerations In general the design alternative that satisfies other design considerations at the lowest costs is to be preferred Issues affecting the cost of a design include Hand screw machine 710 punsm Na setup lime r szomour labor Product development costs Material choice 12 Manufacturing processes involved mu Economies of scale Tolerances specified Use of standard sizes and components Breakeven pmnl 50 straws Aulamahc screw machine 25 panslmm r 3 hour sewn Irma r 20Ihuur labor Toal cost 3 Production run screws Ereakev en pointfor two dilferent screw manufacturing processes ME412 Mechanical Engineering 5 University of Kentucky Design for Safety Safety is paramount most importantly because it is an ethical issue Safety is also related to function Safe designs tend to function well and perform reliably The United States law recognizes the concept of strict reliability The manufacturer of a product is responsible for any damage or harm that arises due to a defect in the product It doesn t matter how long after manufacture the damage occurs or if the defect is due to a design flaw or manufacturing error Negligence does not have to be proven A plaintiff only has to establish that the product was defective and that the defect caused damage or harm ME412 Mechanical Engineering 0 University of Kentucky Most Expensive Item by Weight Commercial Aircraft 5000000050000 lbs 200kg Diamonds 1 000carat 50000000kg Electricity 007kW hr 1 7x1054kg ME412 Mechanical Engineering 0 University of Kentucky Inherent Uncertainty in Design Sources of Uncertainty Random variables associated with material processing result in strength distributions that vary from sample to sample Some samples will have strengths greater than the specified value Others hopefully a very few will have strengths lower than the specified value Statistical scatter in critical dimensions specified into the design during the detail design phase due to imperfections in manufacturing processes Approximations used in the analytical expressions used to perform design calculations Inexact knowledge of the magnitude and tie history of external loads Effect of corrosion and wear on strengths UK ME412 Mechanical Engineering University of Kentucky Dealing With Uncertal nty Permissible Stress Method Permissible stress in a design is based upon a fraction of 39 139 quot quot isbase 39 with successful designs Still used by civil engineers and for the design of weldments Design Factor Method There is a difference between a design goal which may be based upon experience often involving load and desi n realization which is based u on a speci c failure criterion often involving stress quanti ed by a strength value strengtn a 0 n e design factor punent in tne iuad te strengtn reiatiunship c stress ME 112 Memam39caIEnqmeerm Umvers mr amenmcky Last Assignment Due next week Develop a list of changes that would be required in your production design to increase it s manufacturability economy and safety Develop a list of safety guidelines to be used in the use of our your product refer to any codes necessary Both ofthese sections should be included in your nal report UK ME 112 MemamcaIEnqmeerm Umverslfy amenmcky Dealing with Uncertainty Stochastic Design Factor Method Stochastic means involving random variables and uncertainty in strength and stress can be statistically quanti ed The design factor equation can then be adapted to use to determine a mean design factor For a linear load stress relationship 0 a ean designfactur ean strengtn a rnean aiiuvvabie stress Stochastic Method Does not use a design factor Based upon the concept of reliability R 0 s R lt10 Murmur emamcalsnginwmq Umversinl amenmcky
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