BMayer@ChabotCollege.edu ENGR-22_Lec-0_2D_Construction-1.ppt 1 Bruce Mayer, PE Engineering 22 –...

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BMayer@ChabotCollege.edu • ENGR-22_Lec-0_2D_Construction-1.ppt1

Bruce Mayer, PE Engineering 22 – Engineering Design Graphics

Bruce Mayer, PELicensed Electrical & Mechanical Engineer

BMayer@ChabotCollege.edu

Engineering 22

AutoCADAutoCAD©© 2D 2D

Construction-1Construction-1

Learning GoalsLearning Goals

Become Proficient with invocation of AutoCAD Drawing Commands

Create Basic AutoCAD 2-Dimensional Drawing Elements • e.g.; Lines, Circles, Ellipses and PolyGons

Use a Combination of ACAD 2D Elements to construct more Complex 2D Shapes

Initiating AutoCAD CommandsInitiating AutoCAD Commands Generally There are

Three Ways to Invoke AutoCAD commands

Example – Draw a Circle

1. By PullDown Menu

If you get “Stuck” in ACAD

Try the ESCAPE Key

Invoke Commands Invoke Commands contcont

2. By Typing the Command into the Command line

The Typed Commands often have ShortCuts Instead of typing

circle, type only c

3. Using a Tool from a ToolBAR

Drawing LinesDrawing Lines To Random Points

• Type in line (or l), or click the Line Tool

• Pick PointsUsing the Mouse – The Line follows the mouse.

• Click at each vertex

• Terminate Line by Hitting Enter or Esc

Many times these “Assisters” Help with Line Drawing• SNAP

• GRID

• ORTHO

• OSNAP

Random Pts LineRandom Pts Line

• This Example uses SNAP and GRID, but NOT Ortho

Mouse Click Sets Vertex

Closed LineClosed Line To Make a

CLOSED figure of an arbitrary shape1. Invoke line and set

at least 3 Vertices

2. With Line still ACTIVE type in the command-line one of:– close

Line Ready to Close

Closed Line

ErasingErasing To delete drawing

elements use the Erase command

Invoke Erase by• PullDown Menu

• Click the Erase Icon on the Modify ToolBar

• Type in Command line erase or e

To Erase:

• Start Erase• Select Element(s)

with Mouse• Hit Enter or RIGHT

Line by CoordsLine by Coords Type in the

Command Line the CoOrds, one at a time

Be Sure That “Dynamic Input” is Turned OFF

Make a Box

Line by Relative CoOrdLine by Relative CoOrd To Draw a Line

RELATIVE to a Given point

Invoke the line command

ID a Starting point with the Mouse or by CoOrds

In the command Line Type Either

• @ x, y– x & y are CoOrds

RELATIVE to the Current Point

• @ dist, <angle– The distance and

angle (in Degrees, thakfully) Relative to Current Point

Relative LinesRelative Lines By X & Y By Distance &

Construction LinesConstruction Lines Construction Lines

are Very Useful for “Blocking In” or “Aligning” Drawing Objects

They are lines of Infinite (h) Length that may be trimmed later

Invoke Construction Line by• Construction Line

Tool on Drawing Tool Bar

• Command line → xline or xl

Some Construction LinesSome Construction Lines

Construction Line Options

Construction Line OffsetConstruction Line Offset

Lets• Make a Layer; Green

in Color

• Draw some Lines

• Offset a Construction Line

Hit ENTER twice to ReInvoke ConstrLn

Drawing CirclesDrawing Circles To Draw a circle

Invoke the Command• Click the Circle Tool

• Use the PullDown Menu: Draw → Circle → option

• Type in the Command Line one of– Circle or c Command Line Text

Command: circleSpecify center point for circle or [3P/2P/Ttr (tan tan radius)]: 2p

Drawing Circles Drawing Circles contcont

To Draw a Simple Circle1. Click the Circle Tool

2. Use the Mouse to Pick a Center Point

3. Do one of – DRAG with the

mouse to Set the Radius

– Type in a Number for the radius

Circle by• Pick Center Point

• Drag Radius

The Circle Command has Many useful options

Default → Center, Radius

Center, Diameter

2 Points Tan, Tan, Tan

Start Pt

Tan, Tan Radius

Circle Center Marks/LinesCircle Center Marks/Lines Technical Drawing

Practice Calls for Marks and Lines to ID Circle Centers

CenterMark Sizing

Center MarkOnly

Center Mark & CenterLines

ACAD has many Commands and Parameters that Can ONLY be accessed thru the Command Line

SETVAR commandSETVAR command Typing SetVar in the

Command Gives access to 480 AutoCAD System Variables

Partial Listing bySetvar → ? → *

For Example, The acad.dwt has a Center mark Size of 0.09”

Use Variable DIMCEN to Change to 5X this Value

Note: Can type DIMCEN w/o SetVar

CenterLines by Dim StyleCenterLines by Dim Style The acad.dwt

default for Circle Center is a MARK only; NO Lines

To Change, use Dimension Styles

Invoke the Dim Style Dialog by one of

• Dim Style Tool on the Dimension ToolBar

• PullDown Menus: Dimension → Dimension Style...

• Command Line → DIMSTYLE

Any of these actions Activates the Dim Style Dialog Box

CenterLines by Dim Style CenterLines by Dim Style contcont

The DimStyle Dialog Box

Select Modify... To activate next dialog

• Select the Symbols and Arrows Tab

Check this Button to Produce CntrLns

Can Use Instead of DIMCEN

CenterLines by Dim Style CenterLines by Dim Style contcont

After the change A new Circle

POLYLINE CommandPOLYLINE Command The PLINE

command allows you to create "grouped" objects that can be extruded, given line width on the screen, and can contain arc segments.

To Invoke the PolyLine Command• PullDown Menu:

Draw → Polyline

• The Tool on the Drawing ToolBar

• Command Line: pline or pl

Polyline ConstructionPolyline Construction

PolyLines Are Constructed using the same methods as “Regular” Lines, but the WIDTH of the Line is VARIABLE

PLINE also has a List of OPTIONS

[Arc/Halfwidth/Length/Undo/Width]• Width and Halfwidth Set the Starting & Ending PolyLine width(s)

• Arc Helps Fine Tune PLine Arcs

• Length allows typing of the Next Segment Length

Some PolyLinesSome PolyLines

Command: plineSpecify start point:Current line-width is 0.2000Specify next point or [Arc/Halfwidth/Length/Undo/Width]: hSpecify starting half-width <0.1000>: .05Specify ending half-width <0.0500>:Specify next point or [Arc/Halfwidth/Length/Undo/Width]:Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]:Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]:Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: *Cancel*

Some PolyLines Some PolyLines contcont

PLINESpecify start point:Current line-width is 0.1000Specify next point or [Arc/Halfwidth/Length/Undo/Width]: wSpecify starting width <0.1000>: 0Specify ending width <0.0000>: 1.2Specify next point or [Arc/Halfwidth/Length/Undo/Width]:Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: *Cancel*

Some PolyLines Some PolyLines contcont

Command: plPLINESpecify start point:Current line-width is 1.2000Specify next point or [Arc/Halfwidth/Length/Undo/Width]: hSpecify starting half-width <0.6000>: .05Specify ending half-width <0.0500>:Specify next point or [Arc/Halfwidth/Length/Undo/Width]: aSpecify endpoint of arc or[Angle/CEnter/CLose/Direction/Halfwidth/Line/Radius/Second pt/Undo/Width]: *Cancel*

SPLINE commandSPLINE command A spline is a smooth

curve that is fitted along a number of control points

The ACAD Spline command creates a type of spline known as a NonUniform Rational B-Spline, NURBS for short

To Invoke the Spline Command• PullDown Menu:

Draw → Spline

• The Spline Tool on the Drawing ToolBar

• Command Line: spline or spl

SPLINE ConstructionSPLINE Construction

Splines Are Constructed using the same methods as “Regular” Lines, but the segments are splined arcs

Command: splineSpecify first point or [Object]:Specify next point:Specify next point or [Close/Fit tolerance] <start tangent>:Specify next point or [Close/Fit tolerance] <start tangent>:Specify next point or [Close/Fit tolerance] <start tangent>:Specify next point or [Close/Fit tolerance] <start tangent>:

Specify start tangent: *Cancel*

• Constructing a Spline

ELLIPSE commandELLIPSE command The Ellipse

command includes a number of different creation options. • The default option is

to pick the two end points of an axis and then a third point to define the eccentricity of the ellipse.

To Invoke the Ellipse Command• PullDown Menu:

Draw → Ellipse

• The Ellipse Tool on the Drawing ToolBar

• Command Line: eLLipsE or EL

ELLIPSE ConstructionELLIPSE Construction

Command: elELLIPSESpecify axis endpoint of ellipse or [Arc/Center]:Specify other endpoint of axis:Specify distance to other axis or [Rotation]: *Cancel*

ELLIPSESpecify axis endpoint of ellipse or [Arc/Center]: aSpecify axis endpoint of elliptical arc or [Center]:Specify other endpoint of axis:Specify distance to other axis or [Rotation]:Specify start angle or [Parameter]:Specify end angle or [Parameter/Included angle]:

ELLIPSESpecify axis endpoint of ellipse or [Arc/Center]: cSpecify center of ellipse:Specify endpoint of axis:Specify distance to other axis or [Rotation]: <Ortho on> <Ortho off>

PolyLines & EllipsesPolyLines & Ellipses

Let’s Draw some of the Elements that have many Options• PolyLines

• Ellipses

All Done for TodayAll Done for Today

Not a CAD Circle But aBoat Circle

Bruce Mayer, PELicensed Electrical & Mechanical Engineer

BMayer@ChabotCollege.edu

Engr/Math/Physics 25

AppendiAppendixx

6972 23 xxxxf

BMayer@ChabotCollege.edu ENGR-22_Lec-0_2D_Construction-1.ppt 1 Bruce Mayer, PE Engineering 22 –...

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