Computer-Aided Drafting and Design

2. 7 Computer-Aided Drafting and Design

3. Explain how computer technology is revolutionizing drafting, design, and engineering. • Describe the basic features and operation of a computer-aided drafting program. • Explain the various commands used to create objects in CAD.

4. Describe the tools used to modify CAD drawings. • Identify the various display functions used in CAD programs. • Describe the typical components in a CAD program Help system.

5. Explain the importance of CAD file management and identify common storage techniques. • List different types of CAD software and their applications.

6. Benefits of CAD • Simplifies traditional drafting tasks • Drawing basic shapes • Lettering • Creating views • Maximizes accuracy and proficiency • Setup tools • Drawing and editing commands • Customization methods

7. Computer Graphics and CAD • First used for aerospace design in 1950s • Prior to emergence of CAD, design work consisted of 2D drawing production and modelmaking • CAD introduces many benefits • Eliminates repetitive tasks • Allows more time for creative work • Simplifies process of making 2D and 3D designs

8. Traditional Drafting and CAD • Principles of drafting are fundamental to both methods • Knowledge of standards, techniques, and procedures is essential to using CAD effectively

9. Computer Graphics Programs • Classified according to types of images created • Vector objects • Raster objects

10. Vector Objects • Created in CAD drawings • Made up of lines and arcs • Defined with point coordinates in space • Hard copy images may be converted to raster format with a scanner

11. Raster Objects • Also calledbitmap graphics • Number of pixels definesresolution • Modified using an image editing program

12. Vector and Raster Images

13. How CAD Works • Create CAD model in 2D or 3D form • Use commands to give program instructions • Modify objects with editing and modifying commands • Add dimensions and text • Output drawing to plotter or printer

14. CAD Drawing Display

15. File Management Commands • New • Open • Close • Save • Save as

16. Exporting Files • Typically done with the Export command • Used to create files in a different format • Windows Metafile (WMF) • Bitmap (BMP) • Stereolithography (STL) • Portable Document Format (PDF)

17. Plotting and Distribution Commands • Page setup • Used to specify plot device and layout settings • Plot • Used to configure plot device and select type of media • Publish • Used to “publish” multiple-sheet drawing sets

18. Basic CAD System Functions • Coordinate systems • Drawing aids • Layers and linetypes • Blocks

19. Coordinate Systems • Used to definecoordinates • World coordinate systemis most basic system • Based onCartesian coordinate system

20. 2D Cartesian Coordinates

21. Coordinate Entry Methods • Absolute coordinates • Relative coordinates • Polar coordinates

22. Absolute Coordinates

23. Relative Coordinates

24. Polar Coordinates

25. User Coordinate System • Useful for creating drawings in 3D • Orients drawing plane to specific surface • Coordinates are located on drawing plane relative to fixed origin (point on object) • Simplifies 3D drawing process

26. Drawing Aids • Grid • Snap • Object snap • Orthogonal mode

27. Layers • Used to organize drawing content • Named to reflect content • Layer naming conventions observe company or school standards • Similar to overlays used in manual drafting • Assigned colors • Assigned linetypes • Specified in a drawing template

28. Blocks • Typically created for commonly used symbols • Windows and doors on architectural plans • Used to save drafting time • Inserted into drawings as needed • Typically stored in asymbol library • May be saved with attributesfor use in creating aschedule

29. Drawing Setup Functions • Specify drawing unit format • Determine drawing scale and sheet size • Create layers • Save common user settings in a template

30. Object Drawing Commands • Line • Circle • Arc • Ellipse • Polygon

31. Drawing Lines • Line command typically used • Requires two coordinates • More coordinates may be added within single command sequence • Use proper linetype • Set appropriate layer current before drawing

32. Drawing Circles • Circle command typically used • Use appropriate method • Specify center point and radius or diameter • Specify points along perimeter of circle • Enter radius and select two lines or two circles to which circle should be tangent

33. Drawing Arcs • Arc command typically used • Use appropriate method • Specify center point, radius, and endpoint • Specify three points along arc • Specify start point, center point, and chord length

34. Drawing Ellipses • Ellipse command typically used • Specify center point, major axis, and minor axis • Elliptical arcs drawn in similar fashion • Specify axis endpoints and start and end angles

35. Drawing Polygons • Polygon command typically used • Enter number of sides • Specify center point • Inscribe or circumscribe the polygon • Enter radius

36. Editing and Modifying Commands • Move • Copy • Rotate • Scale • Undo • Erase • Array • Mirror • Fillet • Trim • Extend

37. Moving Objects • Move command typically used • Select object or objects to move • Specify base point for selection set • Specify displacement point

38. Copying Objects • Copy command typically used • Select object or objects to copy • Select base point • Specify displacement point • Multiple option copies same selection to more than one location

39. Rotating Objects • Rotate command typically used • Used to change angular position of object • Select object or objects to rotate • Specify base point • Specify angle (clockwise or counterclockwise)

40. Scaling Objects • Scale command typically used • Used to reduce or enlarge objects by specified scale factor • Select object to scale • Select base point • Specify scale factor

41. Undoing Operations • Undo command typically used • Used to “undo” previous action • Allows for undoing multiple actions in reverse sequence

42. Erasing Objects • Erase command typically used • Used to remove unwanted objects quickly • Select objects to erase • Use Undo command to restore erased object

43. Arraying Objects • Array command typically used • Used to copy and orient multiple objects in a pattern • Use rectangular array for rectangular orientation • Enter base point, number of rows, number of columns, and spacing • Use polar array for polar orientation • Specify center point, number of objects, and angular value determining amount of rotation

44. Mirroring Objects • Mirror command typically used • Used to create symmetrical objects by creating mirrored copy of object • Select object to mirror • Specify mirror axis • Keep or delete original object

45. Creating Rounded Corners • Fillet command typically used • Used to create round or fillet • Set radius • Select entities forming intersection

46. Creating Angled Corners • Chamfer command typically used • Used to create chamfer • Set chamfer distance • Select two lines

47. Trimming Lines • Trim command typically used • Used to clean up line overlaps • Specify cutting edge • Select object to trim

48. Extending Lines • Extend command typically used • Used to lengthen object to meet edge • Specify boundary • Select object to extend

49. Display Commands • Zoom command • Used to zoom in (to view drawing details) or zoom out (to reduce the view) • Pan command • Used to adjust view in real time without changing magnification • More advanced commands available in 3D drawing programs

50. Making Measurements • Measure Geometry command typically used to calculate common measurements • Linear distances • Select two points • Area and perimeter calculations • Select object or pick points defining the area