section 1 introduction to drafting

Section 1Introduction to

Drafting

Chapter 4CAD Commands and Functions

Permission granted to reproduce for educational use only.3© Goodheart-Willcox Co., Inc.

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 CAD Commands

• 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 system is most

common.


Cartesian Coordinate System

• X axis and Y axis used 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 axis used 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.


Drawing Commands

• Line• Double Line• Point• Circle• Arc

• Spline• Ellipse• Rectangle• Polygon


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.


Editing Commands

• Erase• Undo• Move• Copy• Mirror• Rotate

• Scale• Fillet• Chamfer• Trim• Extend• Array


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.


Arrays


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 grid on 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.


Linetypes

• Used to follow conventions in Alphabet of Lines.

• Scale settings used to control appearance.• Assigned by layer or by object type

depending on standard practice.


Blocks

• Provide way to store drawing symbols for repeated use.

• Typically saved to symbol library.• May include attribute definitions to indicate

different sizes and types.• Used to generate schedules when created

with attributes.


Block and Attributes


3D Drawing Functions

• Used for creating realistic representations of objects.

• Available in more advanced programs.• Include analysis tools in some

manufacturing applications.


Isometric Drawing

• Shows object in 3D, but it is actually two-dimensional.

• Typically made using isometric grid and snap.


Types of 3D Modeling

• Surface modeling• Solid modeling


Surface Modeling

• Creates 3D objects by giving wireframe “skin.”

• Used for rendering and animation.• Not typically used in manufacturing

applications.


Solid Modeling

• Most realistic form of 3D modeling.• Permits testing for manufacturing purposes.• Rendering and animation functions

typically supported.


3D Viewing Functions

• Hide command• Preset isometric views• Dynamic rotation


User Coordinate Systems

• Used to establish 3D drawing planes for modeling.

• Particularly useful for models with many surfaces.

• Icon used to identify system origin and orientation of XYZ drawing axes.


User Coordinate Systems (Cont.)


3D Animation and Rendering Commands

• Material• Used to define and apply surface textures to

objects• Render

• Used to “color” the drawing• Animate

• Used to add movement to objects


Rendered Model

(Bucyrus International)


Review Questions

1. Distances, areas, and perimeters can be calculated using _____ commands.

A. editingB. drawingC. inquiryD. file management

C. inquiry


Review Questions

2. The _____ command is used to create a smooth curve through a series of points.

A. LineB. EllipseC. SplineD. Hatch

C. Spline


Review Questions

3. The _____ command is used to reverse the last command operation.

A. UndoB. EraseC. MoveD. Copy

A. Undo


Review Questions

4. The _____ command is used to create multiple copies of objects in rectangular or circular patterns.

A. ScaleB. RotateC. LayerD. Array

D. Array


Review Questions

5. The _____ command is used to enlarge or reduce the drawing display by changing the magnification factor.

A. ScaleB. ZoomC. PanD. Hatch

B. Zoom


Review Questions

6. _____ coordinates define point locations at a given distance and angle from a fixed point.

Polar


Review Questions

7. A(n) _____ dimension measures the distance from the center of an arc to a point on that arc.

radius


Review Questions

8. The _____ function allows you to align the cursor with points on screen.

A. snapB. orthoC. gridD. redraw

A. snap


Review Questions

9. A _____ is a virtual piece of paper on which objects are placed.

A. gridB. hatchC. layerD. block

C. layer


Review Questions

10. A(n) _____ is text information saved with a block.

A. layerB. hatchC. gridD. attribute

D. attribute


Review Questions

11. The _____ command is used to “color” a drawing for presentation purposes.

A. RenderB. LayerC. UCSD. Hatch

A. Render


Review Questions

12. A(n) _____ drawing is a 2D drawing that shows a 3D representation of an object.

isometric


Review Questions

13. A(n) _____ is a series of still images played sequentially at a fast rate.

animation

section 1 introduction to drafting

Documents

educational use

coordinate systemsused

z axisthe coordinate

drawing file

threedimensional drawing

previous point

xy drawing plane sufficient

relative distance