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Chapter 4 CAD Commands and Functions. Section 1 Introduction to Drafting. Objectives. List several general categories of commands used in popular CAD programs. Explain how points and objects are located using a coordinate system. Explain the use of linear, angular, and leader dimensioning.
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Chapter 4 CAD Commands and Functions Section 1Introduction to Drafting
Objectives • List several general categories of commands used in popular CAD programs. • Explain how points and objects are located using a coordinate system. • Explain the use of linear, angular, and leader dimensioning. • Identify and describe drawing aids.
Objectives • Discuss the purposes of colors, linetypes, and layers. • Explain layer naming conventions as related to CAD drawings. • Describe 3D drawing. • Explain rendering. • Explain animation.
Types of CADCommands • File management • Drawing • Editing • Display control • Dimensioning
Command Entry Methods • Pull-down menus • Toolbars • Command line • Tablet
File Management Commands • Used to create, save, or open file. • Files may originate from scratch or template. • Drawings should be saved every 10 to 15 minutes.
Coordinate Systems • Used to specify point locations for objects. • Cartesian coordinate systemis most common.
Cartesian Coordinate System • X axisand Y axisused to locate points. • Points designated as (X,Y). • XY drawing plane sufficient for 2D work.
Types of Coordinate Entry • Absolute coordinates • Relative coordinates • Polar coordinates
Absolute Coordinates • Measured from origin (0,0). • Most basic way to locate points.
Relative Coordinates • Used to locate point from previous point. • Designated with @ symbol.
Polar Coordinates • Used to locate points at relative distance and angle. • Designated @distance<angle. • Angles typically measured from 0 horizontal.
Three-Dimensional Coordinates • Z axisused to define “vertical” measurement. • Points designated as (X,Y,Z).
User Coordinate System (UCS) • Used to establish different origin from world coordinate system. • Commonly used with 3D drawing functions. • Created with UCS command.
Line Double Line Point Circle Arc Spline Ellipse Rectangle Polygon Drawing Commands
Line Command • Used to draw straight lines. • Two points specified. • Coordinates entered or picked on screen.
Double Line Command • Used to create parallel lines. • Allows user to set distance between lines.
Point Command • Used to create point objects. • Helpful for construction purposes. • Visibility modes used to change display.
Circle Command • Used to create circles based on user input. • Center and radius • Center and diameter • Three points • Two points
Arc Command • Used to create arcs based on user input. • Three points • Start, center, end • Start, center, angle • Start, center, chord length • Start, end, radius
Spline Command • Provides several ways to create spline. • Picking points along curve. • Converting existing lines into spline.
Ellipse Command • Used to create ellipse. • Points specified for major and minor axes.
Rectangle Command • Provides several methods for drawing rectangles. • Width and height • Opposite corners
Polygon Command • Provides several options to create regular polygon. • Circumscribed • Inscribed • Side length
Text Command • Used to create text objects. • Allows text font to be set. • Provides justification and rotation options.
Hatch Command • Used to “hatch” areas in section views. • Provides selection of standard material patterns. • Internal areas typically picked for hatching.
Erase Undo Move Copy Mirror Rotate Scale Fillet Chamfer Trim Extend Array Editing Commands
Mirror Command • Used to “mirror” objects about mirror axis. • Useful for symmetrical features.
Fillet Command • Used to create fillet or round. • Creates radial curve between two selected objects.
Chamfer Command • Used to chamfer corners. • Operation similar to Fillet command.
Array Command • Used to copy objects in rectangular or polar pattern. • Rows, columns, and offset specified for rectangular array. • Number of objects, center point, and angle specified for polar array.
Inquiry Commands • List • Properties • Distance • Area
List and Properties Commands • Used to display object data. • Coordinates • Line lengths • Layer assignments • Linetype settings
Area Command • Used to make area and perimeter calculations. • Points picked to define enclosed area.
Display Control Commands • Zoom • Pan • View • Redraw • Regenerate
Zoom Command • Used to enlarge or reduce display of objects. • Does not change actual size of objects. • Allows “real time” zooming and specified magnification factor. • Useful for “zooming in” on object details.
Pan Command • Used to move drawing on screen. • Does not “zoom” drawing. • Helpful for large drawings with objects “off” screen.
View Command • Used to save current display of drawing. • Allows restoring certain display without zooming or panning.
CAD Dimensioning • Provides major advantage over manual drafting. • Permits flexibility for placement of text and dimension elements. • Types of commands relate to dimension method and content.
Dimensioning Commands • Linear • Angular • Diameter • Radius • Leader
Drawing Aids • Grid • Snap • Ortho
Grid • Used to show display gridon screen. • Composed of configuration of dots. • Provides visual cue for drawing size and spacing.
Snap • Permits alignment of cursor with specific points on screen. • Useful for “connecting” to endpoints, intersections, and centers. • Provides critical tool for ensuring accuracy of point locations.
Types of Snap • Grid snap • Object snap
Common Object Snaps • Endpoint • Center • Midpoint • Perpendicular • Tangent • Intersection
Ortho • Forces lines to be drawn horizontally or vertically. • Useful when lines must be drawn “square.” • Must be deactivated to draw inclined lines.
Layers • Similar to overlays in manual drafting. • Each object has assigned layer. • Used to control visibility of drawing content. • Usage typically regulated by company or industry standards. • Same naming conventions should be followed by everyone working on project.
Display Colors • Typically assigned to layers to identify content. • Useful for distinguishing dimensions and text from object lines. • Usage often dictated by layer standards.