Bruce Mayer, PELicensed Electrical Mechanical .ppt

1、Bruce Mayer, PE Licensed Electrical & Mechanical Engineer BMayerChabotCollege.edu,Engineering 22,OrthroGraphic View Dwgs-1,Learning Goals,How to Unfold the “Glass” Box to draw Perpendicular Projection (OrthoGraphic) Views Determine the Minimum No. of Views Needed to Fully Describe an Object Properly

2、 Place Views Relative to Each Other Which Views show Which Combination of the Objects H, W, & D,Learning Goals cont,Understand the Criteria for Selecting the CENTRAL View Apply the Guidelines for the Proper Use of Hidden Lines Determine When Lines/Shapes are in TRUE Length/Shape as opposed to FOREsh

3、ortened Construct MultiView Orthographic Projection Drawings,OrthoGraphic View Drawing,All Objects Are Three Dimensional (3-D) Height, Width, and Depth Drawings are done on a 2-D surface Multiview Sketching (Orthographic Projection) Represents A 3-D Object With A Series Of 2-D Views Best Understood

4、By Technical People In Contrast To “Pictorials” Which Show Three Dimensions In A Single View,Projection Planes Versus Views,Projection planes: Objects are Formed From Parallel “Sight Lines” Projected Perpendicularly Onto A Projection Plane Horizontal, Frontal, Profile Each Projection Plane Is Perpen

5、dicular To the Adjacent Projection Planes Lines/Features Parallel to Proj Plane are TRUE Length/Size,Principle Views,The Object Is Rotated 90 About The Horizontal Or Vertical Axis To Yield the Six Principle Views Top, Bottom, Front, Rear, Left & Right Side Common views: Top Front Right Side,View Sel

6、ection,Only Use The Views That Are Needed To Represent The Object One view drawings Stamped part: Specify uniform thickness with a note Two view drawings A Cylindrical Part Three view drawings Usually Sufficient For All Other Objects Top, Front, And Right-Side Views,General Guidelines,The Most DESCR

7、IPTIVE View Should Be The FRONT, or CENTRAL, View Views MUST Be ALIGNED Top View ABOVE Front View Right-Side View To The RIGHT Of Front View Hidden lines Represented With Dashed Lines Precedence of lines (Visible, Hidden, Center) Views Should Be Selected To MINIMIZE The Use Of HIDDEN LINES,Parallel

8、Projection,Preserves true relationship between features Parallel lines are drawn parallel The geometry is generally not distorted Parallel projectors Light from a point-source at an -distance,The Glass Box,Projection Planes Placed Parallel to the Principle Faces of an Object Form a Glass Box What An

9、 Observer Would See From the OUTSIDE Looking IN,Unfolding The Glass Box,Hinge the Four Intersections on The Frontal Plane And “Flatten Out” the Box Maintains the TRUE-Length Of Lines Parallel to the Viewing Planes The 5 Hinge Lines are Known as FOLDING Lines,The Unfolded Glass Box,Common Dimensions,

10、Every 3-D Object Can Be Described By its Height, Width, and Depth The Views from the Glass Box Share These Dimensions in This Form,Central View = Front View,Criteria for Selecting Central View Front View Shows The Shape Of The Object MOST Clearly Chose Front View So That It Has A Large Number Of Nor

11、mal () Surfaces Minimize Hidden Lines Show The Object In A Usual Or Operating Position i.e., Do NOT show the Object “UpSide Down”,The Primary Views,Producing a Multiview Drawing,Select Front View As Before Align View Bounding Boxes i.e., Block-In Views Approx. Center on Drawing Border Draw Features

12、Using Instruments/CAD True Shapes Remain Project Between Views Use 45 “Mitre” Lines to Xfer Depth Dims Label Vertices if Needed,Align Bounding Boxes,WIDTH,WIDTH,HEIGHT,HEIGHT,DEPTH,DEPTH,FRONT,TOP,RIGHT,Miter line at 45,Construction Lines to Xfer Dims,FRONT,TOP,RIGHT,Use 45 Miter Line to Transfer Di

13、ms Between Top & Side View,Label Vertices,An Intermediate Step to Aid Construction Only If needed to Clarify Positions For the Designer,Views FULLY Aligned,Very FEW Hidden Lines,True Length Vs. Foreshortened,Only Lines/Planes that Are PARALLEL to the Projection Plane are (LoS Plane) show in TRUE LEN

14、GTH/SHAPE Others are ForeShortened in the View,Hidden Line Usage,Hidden Lines can Greatly-CLARIFY or Greatly-CONFUSE a Drawing View Visible Lines are Usually Easy Exceptions = Fillets & Rounded Edges Creating Useful Hidden Lines Requires Judgment Adherence to Convention,Draw Hidden Lines,Dashes are

15、2X to 3X Longer Than Spaces .e.g.; Dashes 1/8” (3mm) Long, Spaces 1/16” (1.5mm) Long. Should Intersect Neatly Except Where A Line Of A Different Linetype Would Appear To Be Extended “Jump” Visible Lines That They Cross Closely Spaced Parallel Hidden Lines Are Drawn With The Dashes STAGGERED if Possi

16、ble,Conventions for Hidden Lines,Hidden lines should join neatly to form “T” or “L” shaped inter- sections.,Hidden lines should jump visible lines that they do not intersect. It is permissible for a hidden line to cross a visible line.,Hidden lines should join neatly with visible lines except when i

17、t causes a visible line to be extended. When two different lines join to form a single line, leave a gap on the less important line.,More Hidden Line Conventions,Stagger the dashes on closely spaced parallel hidden lines.,Hidden line dashes should intersect neatly to from clear corners, as in the bo

18、ttom of this drilled hole.,Intersecting hidden lines should form neat corners, as in this countersunk hole.,Curved Hidden Lines,Curved hidden lines should not extend a visible curve in the same direction. Leave a gap on the hidden line so that you can easily see where the visible line ends.,Curved h

19、idden lines dashes should extend to the point of tangency. Dont end with a gap at the point of tangency. It makes it hard to see the location.,Hidden Lines,Hidden Lines Can be Made A number of ways in AutoCAD Draw Line in a LAYER with Hidden Form Draw a SOLID Line, then CHANGE to a Hidden LAYER (Des

20、cribed Last Lecture) Draw a SOLID Line, then CHANGE to a Hidden LINETYPE using PROPERTIES ToolBar Draw a SOLID Line, then CHANGE to a Hidden LINETYPE using PROPERTIES Side-Menu,Chg Hidden-Line by ToolBar,Want,Select Line to Light-Up Handles Click on “Layer Control” Box to PullDown LineTypes Menu,Sel

21、ect HIDDEN,Deactivate Grips by Hitting Esc,Chg Hid-Ln by Properties Menu,Want,Select Line to Light-Up Handles Activate the Properties Side Menus by one of,Rt-Click Line or Grips to Activate the Context PullDown Menu Select properties Double-Click an END Grip,Chg Hid-Ln by Properties Menu,On Properti

22、es Side Menu Activate the LineType PullDown,Select Hidden and Deactivate Grip by Hitting Esc,NOTE The Prop-ToolBar or Prop-Menu Can also Change Line Color, and Thickness,Visualization: Ortho 3D,For a Practicing Engineer with Detail-Design Assistance, READING Projection Drawings Is as Important as MA

23、KING them The Practicing Engineer Must be Able to Think in 3-D Using 2-D Projections i.e., To Visualize a 3-D Object Given Front, Top and Side Views This is Inverse of Creating Views from the 3-D Object,Visualization Aids,Using Labels on Multiview Drawings,1,3,S,3,1,S,S,Label surfaces; e.g.,Label su

24、rfaces; e.g.,Label vertices; e.g., 1,3,Visualization Continued,Recognize Similar Shapes in Different Views Equal number of sides Parallel edges Best Way to “Read” Engineering Drawings is the “Writing” of Great Numbers of them,Eliminate Unnecessary Views,Show Only The Views Needed Drawing To Fully De

25、fine The Shape Of The Object Choose The Views Which Show The Shapes Of The Features Most Clearly The Right Side View Is Preferred To The Left Side View If They Show The Object Equally Well The Top View Is Preferred To The Bottom View If They Show The Object Equally Well Showing Only The Necessary Vi

26、ews Saves Time, Makes The Drawing Less Cluttered, And Makes It Easier To Interpret,All Done for Today,Try 0.7mm MechPencil w/ HB or B Lead,Bruce Mayer, PE Licensed Electrical & Mechanical Engineer BMayerChabotCollege.edu,Engr/Math/Physics 25,Appendix,Time For Live Demo,Recall Std Lines,Line Patterns

27、 Communicate What The Line Represents In The Drawing Line Patterns Tell You Information Such As Whether The Line Is Hidden, Visible, Or A Centerline Line Precedence: Visible Hidden Center,Visible line Hidden line Hatching Centerline Dimension Extension Leader Cutting Plane Viewing Plane Short break

28、Long break Phantom Stitch Chain,Hidden Line Example,2,4,6,2,2,3,11,1Hx2D Groove, Ctrd,3,4,3,3,3,4,8,11,Block-In sizes FView 15W x 7H TView 15W x 6D RView 7H x 6D,OrthoGraphic View Sketching,Block-In Views Using Approximately True-Length Dimensions Engr-Comp-Pad Grid is Useful for Scaling Block-In all Details Such as Corners, Notches, Circles, etc. Dim All Construction Lines with Eraser Darken All Final Lines to Emphasize Object in All Views,