MIT2_007s09_lec04

MIT2_007s09_lec04 - MIT OpenCourseWare http/ocw.mit.edu...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: MIT OpenCourseWare http://ocw.mit.edu 2.007 Design and Manufacturing I Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. Sketching and Drawings 2.007 Spring 2009 Prof. David Gossard Lecture topics (tentative) Sketching & Drawings Modeling basic components 1 Modeling basic components 2 Making drawings Assemblies Case studies CAD Objectives Enable you to Communicate ideas about physical objects in isometric sketches Understand and create working drawings Create CAD models (parts, drawings, assemblies) Caveats: These lectures are only a start, i.e. the basics Mastery requires practice and time Reminder To those who've "seen it before": Bear with us Help those who haven't Terminology Sketch Rough, approximate Communicates general shape & proportion Quick, cheap Produced by hand or with simple tools Courtesy of Martin Culpepper. Used with permission. Terminology Drawing Precise, complete Sufficient to enable fabrication or assembly Not quick, not cheap Produced with tools, esp. computers Courtesy of Sang-Gook Kim and Jung-Hoon Kim. Used with permission. Isometric Sketching 3 axes 1 vertical 2 inclined 30o wrt to horizontal Lines parallel to axes are true length Used to establish scale Not true length Courtesy of Julie Arnold. Used with permission. Exercise 1 (signal when done...) done...) Make an isometric sketch (twice) of: a 6-inch long "2x4", half-scale, lying flat Long axis up & to the right Long axis up & to the left Sketching circles Normal: Circle Bounding square Tangency at midpoints Proportion at mid-arc Diagonals? (optional) Sketching isometric circles Isometric: Ellipse Bounding rhombus Tangency at midpoints Proportion at major & minor axes Sketching circles on principal planes Ellipses in different orientations Cube, tangent points, curves Sketching isometric cylinders Tangent lines normal to plane of ellipse leave from ellipse's major axis, NOT from tangency points ! Rookie error Exercise 2 Sketch a block letter "L" 1 x 1 base 1.5 height 0.25 thickness Sketch fillets on the 4 shortest edges (0.25 radius) Sketch a hole through the vertical face (0.5 diameter) PRACTICE !!! Drawings Are a special language for communicating about physical objects Reading Writing Can be a legal definition 3+ types of information: Shape Nominal dimensions Tolerances Other attributes (e.g. finish) Image from Wikimedia Commons, http://commons.wikimedia.org Orthographic Projection Outline of 3D object projected onto 2D plane Transparent plane in front of the 3D object Important points projected onto plane and connected normal to plane One "view" of the object (planar) Image from Wikimedia Commons, http://commons.wikimedia.org Principal Views "Glass Box" organization Multiple planes give multiple views Views are aligned Principal Views (2D) 6 principal views Views are aligned Image removed due to copyright restrictions. Please see http://commons.wikimedia.org/wiki/File:First_angle_projecting.png http://commons.wikimedia.org/wiki/File:First_angle_unfolding.png http://commons.wikimedia.org/wiki/File:First_angle_unfolded.png View Selection Non-symmetric parts: Front, side, top Front = largest Axially symmetric parts often need only 2 views Image from Wikimedia Commons, http://commons.wikimedia.org Courtesy of Sang-Gook Kim and Jung-Hoon Kim. Used with permission. Interpreting Lines Lines (solid or dashed) can mean Edge view of surface Intersection of two surfaces Surface limit Dashed lines means lines "hidden" in current view Centerlines are special, have their own symbol Image from Wikimedia Commons, http://commons.wikimedia.org Exercise 3 Make an isometric sketch of the object depicted in the following orthographic projections Courtesy of Martin Culpepper. Used with permission. Sections A cut-away view to reveal detail An imaginary plane (section plane) cuts the object Cut material is cross-hatched Section plane is identified Heavy dashed line Arrows Letters Image from Wikimedia Commons, http://commons.wikimedia.org Section Views ("Sections") ("Sections") Objectives: Eliminate confusion Aid "readability" Image from Wikimedia Commons, http://commons.wikimedia.org Sections Section plane may "jog" to show features of interest A B C Figure by MIT OpenCourseWare. Partial Sections Removed section Rotated section A A-A B-B C-C B C A B C Figure by MIT OpenCourseWare. Figure by MIT OpenCourseWare. Section View Conventions Show all visible edges Courtesy of Martin Culpepper. Used with permission. Don't cross-hatch ribs B is preferred A is correct Ribs in section. Ribs are treated as though the cutting plane were in front of them, to avoid misreading the section as a solid. Figure by MIT OpenCourseWare. Exercise 4 Sketch (the) three principal views of the following object END ...
View Full Document

This note was uploaded on 02/23/2012 for the course MECHANICAL 2.007 taught by Professor Fry during the Spring '11 term at MIT.

Ask a homework question - tutors are online