Introduction to CAD - Basic parts 1 -Product Development Cycle CostsMotivationHistory of New CAD/CAM FunctionalityKey ConceptPhilosophy of CAD LecturesReminderFeaturesSketched Feature TypesSketched FeaturesApplied FeaturesThe Drill…Demonstrations / ExercisesMake a simple partDimensions & Sketch RelationsLinkages & BlocksSymmetryCase Study – RampGeometryENDMIT OpenCourseWare http://ocw.mit.edu 2.007 Design and Manufacturing ISpring 2009For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms.Introduction to CAD - Basic parts 1 -Introduction to CAD Introduction to CAD --Basic parts 1 Basic parts 1 --2.007 Spring 2009Prof. David Gossard2.007 Spring 2009Prof. David GossardProduct Development Cycle CostsProduct Development Cycle CostsProduct Development Cycle CostsCostCostTimeTimeEarly decisions have large leverageEarly decisions have large leverageLate changes are very costlyLate changes are very costlyDesignDesignReleasedReleasedForForproductionproductionMfg docs produced:Mfg docs produced:purchase specs,purchase specs,assyassyinstructions,instructions,design drawings for design drawings for tool/fixtures, tool/fixtures, instruction manuals, instruction manuals, etc.etc.DesignDesignManufacturing, Manufacturing, Assembly, Assembly, TestingTestingHard tooling Hard tooling produced: produced: dies, molds, dies, molds, fixtures, etc.fixtures, etc.Ramifications:Ramifications:MotivationMotivationMotivation Computer-based models permit designers to better understand how their products will look and function beforephysical models are made Computer-based models permit designers to better understand how their products will look and function beforephysical models are madeMake better early decisionsMake better early decisionsEliminate late changesEliminate late changes(Enables you to work on your machine(Enables you to work on your machineeven when the shop is closedeven when the shop is closed……))History of New CAD/CAM FunctionalityHistory of New CAD/CAM FunctionalityHistory of New CAD/CAM Functionality 1960’s - Design of complex surfaces, programming of NC machine tools 1970’s - Automation of Drawings 1980’s – Solids 1990’s - Parametric Feature-based Solids 1960’s - Design of complex surfaces, programming of NC machine tools 1970’s - Automation of Drawings 1980’s – Solids 1990’s - Parametric Feature-based SolidsKey ConceptKey ConceptKey Concept “Parametric”, “Associativity”y Changes in dimensions propagate between parts, drawings, assemblies Movie “Parametric”, “Associativity”y Changes in dimensions propagate between parts, drawings, assemblies MoviePhilosophy of CAD LecturesPhilosophy of CAD LecturesPhilosophy of CAD Lectures Demonstrate small fraction of available functionality Ideally the most useful fraction… Accelerate your learning process Get you up-to-speed as quickly as possible… Promote self-discovery Motivate you to learn more on your own… Demonstrate use as a design tool Not (just) a detailing/documentation tool Demonstrate small fraction of available functionality Ideally the most useful fraction… Accelerate your learning process Get you up-to-speed as quickly as possible… Promote self-discovery Motivate you to learn more on your own… Demonstrate use as a design tool Not (just) a detailing/documentation toolReminderReminderReminder To those who have “seen it before”: bear with us help those who haven’t To those who have “seen it before”: bear with us help those who haven’tFeaturesFeaturesFeatures Sketchedy 2D geometry (sketch) swept along a 3D path Appliedy Attached to existing geometry Sketchedy 2D geometry (sketch) swept along a 3D path Appliedy Attached to existing geometrySketched Feature TypesSketched Feature TypesSketched Feature Types Extrudey Constant cross-sectiony along a straight line Revolvey Constant cross-sectiony around an axis of revolution Sweepy Constant cross-sectiony along a space curve Lofty Multiple cross-sectionsy along a space curve Extrudey Constant cross-sectiony along a straight line Revolvey Constant cross-sectiony around an axis of revolution Sweepy Constant cross-sectiony along a space curve Lofty Multiple cross-sectionsy along a space curveSketched FeaturesSketched FeaturesSketched Features May add or subtract material ! Sketched (add) (subtract)y Extrude boss/base cut Hole Wizardy Revolve boss/base cuty Sweep boss/base cuty Loft boss/base cut May add or subtract material ! Sketched (add) (subtract)y Extrude boss/base cut Hole Wizardy Revolve boss/base cuty Sweep boss/base cuty Loft boss/base cutRequireRequiremore more complex complex mfg mfg methodsmethodsApplied FeaturesApplied FeaturesApplied Features Attached to existing geometryy e.g. edges, faces Typesy Fillety Patterny Shelly Drafty Rib Attached to existing geometryy e.g. edges, faces Typesy Fillety Patterny Shelly Drafty RibInjectionInjection--molded partsmolded partsThe Drill…The DrillThe Drill…… Series of demonstrations/exercises Demonstration: You watch it done Exercise: You do it Series of demonstrations/exercises Demonstration: You watch it done Exercise: You do itDemonstrations / ExercisesDemonstrations / ExercisesDemonstrations / Exercises Screen/window layout View control Make a simple part Dimensions & sketch relations Linkages & Blocks Symmetry Screen/window layout View control Make a simple part Dimensions & sketch relations Linkages & Blocks SymmetryMake a simple partMake a simple partMake a simple partDimensions & Sketch RelationsDimensions & Sketch RelationsDimensions & Sketch RelationsLinkages & BlocksLinkages & BlocksLinkages & BlocksSymmetrySymmetrySymmetryCase Study – RampCase Study Case Study ––RampRamp Drop-down ramp (see geometry) Companion robot drives onto ramp Companion robot (150 lb)y is lifted off the groundy Powered by pneumatic cylinder(s) Drop-down ramp (see geometry) Companion robot drives onto ramp Companion robot (150 lb)y is lifted off the groundy Powered by pneumatic cylinder(s)GeometryGeometryGeometryF1 dx1F2dx2Virtual Work Principle:F1 dx1 = F2