Pictorials with AutoCAD

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Pictorials with AutoCAD
Thursday, October 21st 2004

• Class 8.2 Using AutoCAD to Create Pictorial
  Drawings

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Learning Objectives

• Use AutoCAD to draw an oblique of an object given
  orthographic views of the object
• Select the best orientation of an object in
  pictorial
• Define what makes a drawing a cavalier oblique,
  cabinet oblique, general oblique, isometric,
  axonometric, perspective, or orthographic views
• Use AutoCAD to generate Isometric Drawings of
  objects given the orthographic views of the
  object.

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Types

• Obliques
• Cavalier
• Cabinet
• General
• Axonometrics
• Isometrics
• Dimetric, Trimetric
• Perspectives
• 1,2,or 3 points

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Cavalier Oblique

• Front view true size
• Receding Axis Angle (Normally 30, 45
• or 60) is Variable
• Depth dimension (receding axis) true size

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Cabinet Oblique

• Front view true size
• Receding Axis Angle (Normally 30, 45 or 60) is
  Variable
• Depth dimension (receding axis) half size

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General Oblique

• Front view true size
• Receding Axis Angle (Normally 30, 45 or 60) is
  Variable
• Depth dimension (receding axis) between half
  (D/2) and full size (D)

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Angles in Oblique

• Angles in front view are drawn true size
• Other angles must be located using coordinates
• Appearance of angles may be distorted

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Obliques

• Obliques are theoretical drawings. In reality,
  you can not actually view an object as an Oblique
• Thin parts look very good as Obliques
• Parts with angular features on multiple planes
  are difficult to draw as Obliques

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Circles in Oblique

• Drawn true size in front view
• Drawn as ellipses on receding planes
• Layout using a Rhombus

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Todays AutoCAD commands

• Drawing setup
• Drawing Aids
• Display control
• ZOOM
• General Concepts
• Keyboard Coordinates

• Editing and inquiry
• MOVE
• COPY
• TRIM
• Review polar coordinates
• used with copy and move
• Example _at_1.2lt45
• Object Snap
• ENDPoint
• TANgent
• NEArest

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Display Control

• ZOOM -- scales the screen view to an area of the
  drawing surface
• Window will zoom down to a window
• All will zoom out to show the larger of the
  drawn entities or limits
• Realtime allows you to shrink or enlarge the
  display in real time.
• PAN -- moves around on the drawing surface

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Formats of Keyboard Coordinates

• Either absolute or relative
• Absolute -- references origin of drawing (0,0)
• Relative -- references previously selected point
  
• Absolute is the default
• Precede relative coordinates with an _at_ sign
• _at_10,20 or _at_ 10lt45
• Direct Distance
• Enter a distance in the direction of the cursor
  and return

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Grips

• Grips serve two purposes
• Basic editing of properties
• Modification of size/location
• Grips are the small hollow squares which appear
  when you select an object
• If you click on a hollow square grip, it will
  become active and you can drag the grip to a new
  location. The actual effect of this will vary
  depending on what object and which grip you
  select.

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Modifying Properties via Grips

• Once an object is selected and the grips are
  visible, you can change the Layer, Linetype,
  Color, and LineWeight by using the properties
  toolbar at the top of the screen.
• Anytime you have an object activated with grips,
  the properties toolbar modify the object
  properties, not the drawing settings.

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Drawing Obliques in AutoCAD

• Always make a rough pencil sketch of the object
  first to get an idea of what your drawing should
  look like.
• Draw the front view as a flat orthographic view
• Use the COPY command along with keyboard
  coordinates to place the front view along the
  receding axis to represent all frontal surfaces
  in the object
• Connect the copies with lines representing the
  depth of the object. Remember to use OSNAP to
  assist in this process
• Use ERASE and TRIM as appropriate to remove
  unwanted lines/arcs

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Example
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Example
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Construction of an oblique

• Draw the front view using normal AutoCAD commands
  and techniques

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Construction of an oblique

• Use the COPY command to replicate the front view
  to depict the depth
• Command COPYE
• Select objects Other corner 11 found
• Select objectsE
• ltBase point or displacementgt/Multiple mE
• Base point
• Second point of displacement _at_.8lt40E
• Second point of displacement _at_1.8lt40E
• Second point of displacementE

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Construction of an oblique

• ERASE the portions of the depth profiles which
  will not be seen.
• Command eraseE
• Select objects
• Select objects
• Select objects
• Select objects E

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Construction of an oblique

• Add receding lines using OSNAP and the LINE
  command.
• Command lineE
• From Point endpE of
• To Point endpE of
• To PointE

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Construction of an oblique

• TRIM and ERASE the remaining lines which would
  not be visible.
• Command TRIME
• Select cutting edges (Projmode UCS, Edgemode
  No extend)
• Select objects 1 found
• Select objectsE
• ltSelect object to Trimgt/Project/Edge/Undo
• ltSelect object to trimgt/Project/Edge/UndoE

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Exercise 8.2.1 Cavalier Oblique.
Use Template English1.dwt with a receding axis of
30º
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Isometrics

• Axes equally separated (120)
• H, W, and D measurements are true size along iso.
  axes
• Angles must be located by coordinates
• Circles appear as ellipses on all surfaces

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Drawing Isometrics in AutoCAD

• Initially you should do a rough sketch of the
  object by hand to get an idea of what your
  drawing should look like
• Switch the crosshairs to isometric mode (snap,
  style, iso)
• Draw the object using the LINE and ELLIPSE
  commands
• Use F5 to toggle the current isometric plane
• Use OTRHO and OSNAP to assist you in the drawing
• Copy face planes along isometric axes and connect
  corners similar to oblique method shown earlier
• TRIM or ERASE any portions which are not visible

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Using isometric snap

• If the crosshairs are not set in isometric mode,
  use the Drafting Settings dialog box.
• Right click on snap button and choose settings

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Drawing Ellipses

• In isometrics, circular features which lie on the
  principal planes are shown as ellipses
• These MUST be drawn using the ELLIPSE command
  with the Isocircle option

Command ellipse ENTER Arc/Center/Isocircle/ltAxi
s endpoint 1gt I ENTER Center of circle
ENTER ltCircle radiusgt/Diameter ENTER
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Individual Exercise

• Draw an Isometric pictorial of the object shown
  on the next slide using AutoCAD.
• The grid is a .2 grid
• Use template English1.dwt

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Isometric Example
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Individual Assignment

• 41 BC Cabinet oblique
• 43 BC Cavalier oblique
• 48 CD isometric
• 49 CD isometric
• Due Thursday 28 October 2004