A Brief Introduction to Engineering Graphics

1 A Brief Introduction toEngineering GraphicsWill Durfee & Tim KowalewskiDepartment of Mechanical EngineeringUniversity of MinnesotaOpening comments Engineering Graphics is the method for documenting a design Mechanical Engineering students must be familiar with standards of Engineering Graphics as it is expected in industry This set of slides introduces some of the basics, but is not comprehensive For more, see Engineering Graphics section on the Resources page of the course ME2011 website Any Engineering Graphics a part drawings Universal language Conventions (drawing grammar) simplify communication; your drawing is at risk if you defy CAD packages make formal drawing you follow the conventions The machinist will laugh at you behind your back if you show up with a non-standard drawingMultiview drawingsFRONTRIGHT SIDETOP 3rdangle projection Multiview drawingsFRONTRIGHT SIDETOP 3rdangle projection Views MUST alignMultiview drawingsFRONTRIGHT SIDETOP 3rdangle projection You walk around part to the right (US)Rotate the part to the right (Europe)Views MUST alignThe Glass Box:Bertoline, Engineering GraphicsAlignment & Orientation are , Engineering GraphicsSix Principle views.

2 Obey layout Basic lines (the alphabet of lines )Object lineHidden lineCenter lineDimension lineHIDDEN LINESCENTER LINESI nterpreting Center LinesEnough Info?Enough Info?COULD BE THISC enterlines imply symmetry, NOT revolution per seHERE, ONLY 2 VIEWS NEEDED(Correct drawing)Find The Mistakes!Find The Mistakes!FRONTFIND THE MISTAKES!FRONTCORRECT DRAWINGSECTIONSAAYESNOW orking with person sitting next to you copy this and draw the TOP VIEWW orking with person sitting next to you copy this and draw the TOP VIEWP ossible GeometriesWorking with person sitting next to you, sketch the Section ViewCorrect Section ViewsOKOKW orking with person sitting next to you, Find the MISTAKESW rongWrongWorking with person sitting next to you, sketch the Section ViewREVOLVED SECTIONP referred True AND FINISHD imensioning5353 Conventions exist for choice and placement Not too many and not too few Never should measure off drawing with a rulerUnder/Over Dimensioning35535352 Dimensioning rules.

3 Find the mistakes. 35535352 Dimensioning guidelines355353521. Don t overdefineor underdefinethe object. [MOST IMPORTANT]2. Dimension to the visible contour or shape of the feature/ Don t dimension to hidden Don t dimension to object lines (model edges), use extension lines. 5. Don t overlap a dimension and the model. Place dimensions awayfrom the model s surface. 6. Don t cross extension lines if Group dimensions when possible unless it become difficult to Place dimensions on the side of the view were adjacent views exist (for easy referencing).Design Detail thick aluminum blockWhich is more expensive: A or B and why? Choices& Design Intent62266426 ABIf change width of block to 8, what happens to the hole location?

4 Placement gap letters about 1/8" tall dimension line extension line dimension arrow touches a little extended about 3/8" f rom part about 1/4" between dimensions : 1 or 2 directions gaps . break in lineAll on one dimension on view that shows the circleShow diameter rather than Matter because parts cannot be made to an exact dimension Must specify dimension tolerance so that every part A fits every part B Higher tolerance = higher cost A inch hole made on an ordinary drill press gives you a hole in the range to (+ ). For higher precision, drill undersize and use a it will cost you more and take longer to fabricate. inch drill bit: + inch reamer: +.0003, ! You can combine six 8-stud bricks of the same color 102,981,500 different ways 91% of all households with children in Denmark own LEGO products During the period 1949-1990, 110,000,000,000 (110 billion) LEGO elements were molded Bayer Corporation's Polymers Division is the official supplier of ABS plastic to the LEGO group.

5 Exact specifications of the Bayer resin supplied to the LEGO Group are a closely held secret. Dimension tolerance of mold is mm ( inch)! 5 Representing .. +. +..055 high stack? is min and max height of stack? Tolerance StackingWhat s the tolerance (+/-) on dimension x?Ans: + or Baseline Dimensioning?.. You ..1 Chain or Baseline ..1 Holes and all shafts fit into all holes? is maximum clearance? ANSI standards for shaft & smaller than hole for all shafts and holesInterferenceShaft larger than hole for all shafts and holesTransitionSmallest shaft fits in largest holeRunning/SlidingRC1 (fit together, no play) to RC9 (fit loosely)Force/shrinkFN1 (light drive and pressure) to FN5 (high stresses and pressures).

6 And othersLike Locational, etc. Basic holeUse nominal size of hole as starting pointBasic shaftUse nominal size of shaft as starting pointPreferred Fit Basic Hole + . shows 1 in. nominal, ANSI RC4 clearance fit Basic Hole means smallest possible hole = nominal, then size shaft for clearanceRC4 clearance = [ , ] = [smallest hole-largest shaft, largest hole -smallest shaft]Title block information for toleranceALL DIMENSIONS IN INCHESHOLD ALL DIMENSIONS TO UNLESS DetailBent aluminum sheet, 1/16 thickA or B: Which is more expensive and why? + { ..075$$$$$$$$Tolerance vs. CostManufacturing TolerancesGeometric Dimensioning and Tolerancing(GD&T)Traditional tolerancing is ..005?}

7 ? ..01++Square deviation Circular deviation Geometric Dimensioning and + Ideal position of hole..25, is marked with boxand no +/-notation. Feature control box shows how close hole is to exact; within circular tolerance zone with diameter .01 Geometric Dimensioning and website: Efundatutorial: FastenersWhat they are and how to indicate on a drawingThreaded Fasteners Holes Threads Threaded REF19 DRILL DEEPorO .166 . 75 Pix from notedThru holes19 DRILL THRUorO .166 Fasteners (screws, bolts) Specify diameter, thread, length, head1/4-20 x 1, RHMSROUND HEADMACHINE SCREW1" LONG20 THREADSPER INCH1/4" DIAC ommon screw thread sizesUnified Thread Standard 2-56 4-40 6-32 8-32 10-24 1/4-20 3/8-16 1/2-13 5/8-11 3/4-10 DIA.

8 = (N*.013) + .060 (inches)Alternate Thread CalloutHead shapesPanFlatRoundCap screwSocket head cap screw (SHCS)Set screwDriving a fastenerSlottedPhillipsTorxHex capHex head(Allen head) the Fastener: Name the Fastener: Socket Head Cap ScrewSocket Head Cap Screwwith counterboreSocket Head Cap Screw with counterborePhillips Flat Head Screw with countersinkCountersunk,Phillips Flat headSet ScrewConvention for screws SCHEMATIC SIMPLIFIED Convention for threaded holesFRONTTOPFRONTSECTION6-32 THRUB lind threaded holes1/2 13 x DEEPTHREAD DEPTHDRILL 13 82 OCSK, x 82O Counterbored holes19 DRILL 29 CBORE, 14 DEEPC-BORE DEPTH1929 14 Other Items for DrawingsLeaders & notesFINISH TOP SURFACE SMOOTHNOTE BTITLE BLOCKS Basic Title Name Date Units Optional Company name, sheet number, scale, tolerances, material, Follow your company standardsMY PARTW.

9 DURFEE 10/2/2014 ALL DIMENSIONS IN title block using a company templateProduction DrawingsMODELSKETCHESSKETCHESSKETCHESASS EMBLYDETAILDETAILDETAILDETAILDETAILBOMMA NUALSMFG PROCESSMany types of drawings can be produced fromthe CAD databas