Technical Drawing

1
Technical Drawing Week I
2008-Fall
2

• Overview

• Instructor Yavuz Keçeli
• Time Wed. 9301230
• Place Sim. Center, CBT LAB
• Evaluation
• Midterm Exam 30
• Homeworks 20
• Final Exam 50

3

• Course Outline

1. Introduction to AutoCAD and drawing
settings 2. Drawing objects 3. Modifying
objects 4. Object snapping 5. Dimensioning 6. Proj
ections/ Isometric drawing 7. Orthographic
drawing 8. Sectioning 9. 3D drawing
4

• Using the Drawing Editor

5

• Using the Drawing Editor

• Beginning a new drawing

• File menu
• New ?
• Command line
• new ?

• Saving a document file

• File menu
• Save ?
• Save as ?
• Command line
• save ? Save as ?
• qsave ? Save ?

6

• Using the Drawing Editor

• Undoing operations

• Simply CtrlZ
• Command line
• undo ?
• Enter the number of operations to undo or
  Auto/Control/BEgin/End/Mark/Back ltNumbergt
• Mark and Back
• The mark subcommand makes a special mark in the
  undo information, to which you can back up with
  the Back subcommand. This makes it easy to try an
  experiment and drop the whole thing if it does
  not work.
• The Back subcommand will take the drawing back to
  the state it was when the most recent Mark
  subcommand is entered. Back will take you back
  one mark each time, and removes the Mark when it
  finds it. If there is no preceding Mark, the Back
  subcommand will ask if you want to undo
  everything. If you answer Yes, everything you did
  since entering AutoCAD will be undone. If you
  answer No, the Back subcommand will be ignored. A
  mark stops multiple UNDO operations if the number
  entered is greater than the number of operations
  since the mark.

7

• Using the Drawing Editor

• Undoing operations

• Begin and End
• The BEgin and End subcommands cause a group of
  commands to be treated as a single command for
  the purposes of U and UNDO. This feature is
  mainly intended for use with menus, especially
  through the Auto feature.
• Auto
• The Auto subcommand issues the prompt
• Enter UNDO Auto mode ON/OFF ltcurrentgt
• Current is the present setting which is retained
  if you give a null reply. If Auto is ON, any item
  selected from a menu, no matter how complicated
  it is, will be treated as a single command, and
  will be completely undone by a single U. For
  instance the insertion of a door by using a menu
  macro, which could involve many commands, will be
  completely undone by a single U. UNDO Auto
  operates by inserting an UNDO BEgin at the start
  of each menu item, if a menu item is not already
  active, and an UNDO End upon exit from the menu
  item.
• UNDO Auto is not available if the Control option
  has turned off or limited the UNDO feature.

8

• Using the Drawing Editor

• Undoing operations

• Control
• The UNDO Control subcommand allows the user to
  limit the UNDO feature or to disable it
  completely. It gives the prompt
• Enter an UNDO control option All/None/One
  ltAllgt
• Enter an option or press ENTER
• The options are described below.
• All Turns on the full UNDO command.
• None Turns off the U and UNDO commands entirely
  and discards any UNDO command information saved
  earlier in the editing session. An attempt to use
  UNDO while the None option is in effect causes
  AutoCAD to immediately display the prompt for the
  Control option
• Enter an UNDO control option All/None/One
  ltAllgt
• One Limits UNDO to a single operation. The Auto,
  Group, and Mark options are not available when
  None or One is in effect. The prompt shows that
  only a Control option or a single step of the.
  The prompt shows that only a Control option or a
  single step of the UNDO command is available when
  the One option is in effect.
• Control / lt1gt

9

• Using the Drawing Editor

• Undoing operations

• UNDO displays the command (or system variable
  name) in the command line to indicate that you
  have stepped past the point where the command was
  used.
• Some commands (LINE, DIM, TRIM, and EXTEND, for
  example) have their own UNDO subcommands. These
  step back one operation at a time. However, once
  you exit the command, U will undo the entire
  command.
• The U command
• U Reverses the most recent operation. The U
  command is therefore equivalent to entering undo
  1. You can enter u as many times as you wish,
  backing up one step at a time, until the drawing
  is in its original state (as it was when you
  began the current editing session).
• REDO
• REDO reverses the effects of the previous UNDO or
  U command. REDO reverses the effects of a single
  UNDO or U command. REDO must immediately follow
  the U or UNDO command.

10

• Using the Drawing Editor

• Erase and Oops

• You can remove an entity by using the ERASE
  command, and then you can redraw the entity. When
  you use ERASE the, the crosshair change to a pick
  box, to select the entity that you want to
  remove. In the following exercise you will erase
  the last line segment on your screen. ERASE
  command is in the Modify menu.
• If you enter ERASE at the command prompt or
  use the Select menu choice, ERASE lets you select
  many entities and then erases them at the same
  time. You can write OOPS to bring back the last
  entity group erased. In the Screen menu, ERASE
  command is under the MODIFY1 group.

11

• Using the Drawing Editor

• Getting Help

• Help is almost always available online in
  AutoCAD. As in other Windows programs, the Help
  pull-down menu gives you the choices Contents,
  Search for Help on, and How to use Help. Another
  way to use help is to issue it while using the
  command about which you want to learn more. After
  issuing the relevant command, you press F1 to get
  the transparent Help where a description of how
  to use the command is given, and the command
  continues. This is called context-sensitive help.
  Once you get more accomplished in AutoCAD you may
  want to consult the manual set for a thorough
  explanation of some of the commands.
• When you access help from a Windows compatible
  release of AutoCAD, the Help Topics dialog box
  appears. Click the Contents tab to browse through
  topics by category. Click the Index tab to see a
  list of index entries either type the word
  you're looking for or scroll through the list.
  Click the Find tab to search for words or phrases
  that may be contained in a Help topic.

12

• Using the Drawing Editor

• Command Shortcuts

• If you use AutoCAD's command alias feature,
  keyboard command entry can be just as fast if not
  faster than menus. A command alias is an
  abbreviation that you can use instead of typing
  the entire command name. To execute the Circle
  command, for example, you can just type a C, and
  press Enter. Some of AutoCAD's standard
  abbreviations are shown in table
• These command aliases are defined in the ACAD.PGP
  file in the Support subdirectory. Each alias uses
  a small amount of memory. It should be mentioned
  that you could edit acad.pgp, for example with
  Windows Notepad.
• AutoCAD offers a similar keyboard shortcut for
  command options. You need only type the
  characters that are shown as uppercase in AutoCAD
  prompts to execute an option. For example the
  prompt after issuing the ZOOM command
• All/Center/Dynamic/Extents/Previous/Scale/Window
  ltreal timegt P?
• If you respond the prompt with merely a P,
  instead of typing the entire word Previous, the
  ZOOM Previous command starts.

Alias A C CP DV E L LA M P PL R Z
Command ARC CIRCLE COPY DVIEW ERASE LINE LAYER MOVE PAN POLYLINE REDRAW ZOOM
13

• Setting up an Electronic Drawing

• Drawing Setup

• Organizing an electronic drawing is a little
  different than the preparation of manual
  drafting. Before preparing an electronic drawing
  sheet, it is necessary to understand and be
  familiar with scale, layers and drawing entities
  of an electronic drawing and their difference
  from manual drawing.
• Setting your drawing scale
• Layers
• Entities and Properties
• Setting Up a Drawing
• Setting Units
• Determining Scale Factor
• Calculating a Sheet Size for a Known Scale and
  Object Size
• Setting Drawing Limits
• Limit check
• Working on several sheets simultaneously
• Linetypes
• Linetype Scale
• Other Settings

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• Setting up an Electronic Drawing

• Setting your drawing scale

• In AutoCAD, drawing elements are stored in real
  world units. Your measurement units can be in
  fractions or decimals, in meters, millimeters,
  feet, inches, or any measure that you want to
  use.
• In manual drafting, you usually create the
  drawing to fit a specific sheet size or scale.
  The text, symbols and line widths are generally
  about the same size from one drawing to another.
  In AutoCAD, however, you always draw the image at
  actual size (full scale) in real world units. At
  plot time, you can scale your full- size
  electronic drawings to fit the plot sheet. You
  must therefore plan ahead for scaling a full-size
  AutoCAD drawing and make settings that adjust the
  scale of the text, symbols, and line widths so
  that they plot at an appropriate size.

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• Setting up an Electronic Drawing

• Layers

• In manual drafting, transparent overlays may be
  used to separate a drawing into physical layers.
  In AutoCAD, virtually unlimited electronic layers
  are available. This gives more flexibility and
  control in organizing a CAD drawing than in
  manual drafting.
• A single sheet may be pulled out to examine or
  modify, or you can work with all layers at once.
• Any layer can contain any group of objects, which
  may be superimposed in space to co-exist with
  other objects on other layers. You should think
  of each layer as containing unique class of
  objects. You can look at all layer groups
  together, or you can look at any combination by
  specifying the layers you want to use.
• You can associate any color and linetype to a
  layer. When you setup your AutoCAD layers, you
  need to determine which parts of the drawing you
  are going to place on each layer and what color
  and linetype you are going to use with each
  layer. You can preset each layer's color and
  linetype, but your layering conventions should
  work compatibly with those used by any
  consultants with whom you exchange drawings. You
  can make as many as, or as few layers as you
  need.

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• Setting up an Electronic Drawing

• Layers

• If your drawing is too complicated, you can turn
  off selected layers and work on the layers you
  want. Each layer has a name, a default color, and
  a linetype. You can work on any layer. Although
  editing commands such as ERASE works on any
  number of layers at once, you can draw on only
  one layer at a time. The layer you currently are
  using is called the current layer. When you start
  a new drawing, layer 0 is the current layer,
  which is the default layer from the ACAD.DWT /
  ACADISO.DWT scratch drawings.
• The Layer Properties Manager dialog box contains
  every available tool for defining and setting up
  new layers. You can access this dialog box from
  the Format pull-down menu by selecting the Layer
  option by entering DDLMODES or LAYER command at
  the Command prompt, or by clicking on the LAYER
  button from the object properties toolbar.

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• Setting up an Electronic Drawing

• Layers

• Once created, you can set the current layer by
  choosing from the layer drop-down list in the
  object properties tool bar area.
• Keeping a good layer organisation is very
  important for efficient work. Keep entity colours
  BYLAYER and one linetype per layer whenever
  possible. For example, keep one layer for
  dimensioning only, one layer for construction
  lines (help lines), one layer for hatching and so
  on.
• Layers can be used to draw efficiently by
  reducing duplicate work. For example, architects
  commonly use the same floor plan for several
  different applications, one for dimensions, one
  for furniture arrangement, one for electrical
  details, and so forth. The same basic plan is
  used for all these applications by turning on the
  needed layers and turning off others. A
  disadvantage of this method is that the drawing
  file will increase greatly in size.
• NOTE AutoCAD add-on programs may structure
  layers specifically for the program
  functionality. A proposal exists for an
  international standard for structuring layers in
  computer aided Building Design, the ISO DIS
  13567, which may become an ISO standard similar
  to linewidths and paper sizes. This will make it
  easier for different parties to exchange drawings.

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• Setting up an Electronic Drawing

• Linetypes

• AutoCAD linetypes, continuos, dashed, dot and so
  on, are stored in linetype library files with the
  extension .LIN.
• By default, only the linetype CONTINUOUS is
  available. To be able to SET different linetypes
  you must first load them from a library file.
• You set, load, and list linetypes with the
  LINETYPE Manager Dialog Box.
• Command LINETYPE ? (Opens the Linetype Manager
  Dialog Box)
• If you have not created your own library file,
  you can choose only ACAD.LIN / ACADISO.LIN

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• Setting up an Electronic Drawing

• Linetype Scale

• The length of dashes in AutoCAD linetypes is in
  drawing units. Since drawing units mean
  millimetres in some drawing and kilometres (or
  whatever) in others, a method is provided for
  adjusting the linetypes to a meaningful scale for
  your drawing with the system variable LTSCALE. In
  civil engineering the drawing unit is normally
  meters. The default value of LTSCALE is 1.0.
• The LTSCALE command governs the global scale
  factor for dash lengths, ie. It affects all
  non-continuous lines in your drawing.
• Adjust your LTSCALE according to your drawing
  scale (plotting scale) factor and limits.
  Guideline values for LTSCALE could be

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• Setting up an Electronic Drawing

• Setting Units

• You can choose your system of units by using the
  Units option from the Format pull-down menu or by
  writing UNITS at the command promy. Both Units
  selection from the Format pull-down menu and
  writing DDUNITS or UNITS at the Command Promt
  displays the Drawing Units dialog box which gives
  you control over the unit options. Setting up
  units sets up the input format for entering
  distances and angles from the keyboard, and
  output format that AutoCAD uses when displaying
  and dimensioning distances and angles.
• In Turkey, SI (Systeme International dUnites)
  units are used, ie. Length in meters and decimal
  fractions. We will only be using SI in CE-101,
  but AutoCAD accepts other notations such as
  scientific, fractional and the special
  Engineering /Architectural systems which are used
  in the United States.
• Normal angle measurement in engineering is in
  decimal degrees. Other notations available in
  AutoCAD are radians, grads (surveying) and
  degrees/minutes/seconds, which should not be
  confused with decimal degrees, for example
• 30.125 307'30"
• You can also change the angle direction which
  controls the point from which AutoCAD measures
  angles and the direction in which they are
  measured. The default is 0 degrees on the right
  side of the figure, measured counterclockwise. To
  specify a new angle direction choose Direction
  from the drawing units dialog box.

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• Setting up an Electronic Drawing

• Determining Scale Factor

• First, you must determine a drawing scale factor,
  and then you use it to calculate the
• sheet size
• text heights (see chapter 6 for Text)
• symbol size
• linetype scale
• The limits setting is the AutoCAD equivalent of
  sheet size. You set the drawing's limits during
  the initial drawing setup. Linewidth is
  determined when you are setting up for plotting.
  AutoCAD line entities have zero width. Standard
  line widths are 0.7mm, 0.5mm, 0.35mm, 0.25mm,
  0.15mm. On screen all lines have the same width,
  but different colours.
• Sheet size is calculated in the same way as in
  manual drafting, except that you use the
  resulting scale ratio to scale up the sheet size
  to fit around the full scale size of your
  drawing. Then when you plot the drawing, you
  scale everything back down by the same factor. In
  Europe paper sheet sizes are predominantly
  according to DIN (Deutsche Institut für Normung)
• A4 297 x 210 mm
• A3 420 x 297 mm
• A2 594 x 420 mm
• A1 841 x 594 mm
• A0 1189 x 841 mm
• For mapping purposes or large civil engineering
  projects, such as a road construction, larger
  sizes are used. If you are working on a floor
  plan that is 31.5 meters by 20 meters, you may
  want the drawing to be scaled at 1m 100m. What
  is your scale factor and what size electronic
  sheet you are going to use? The size of your
  electronic sheet is set by the limits that you
  choose. The limits are determined by the X,Y
  values of the lower left and upper right corners
  of your electronic sheet.

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• Setting up an Electronic Drawing

• Calculating a Sheet Size for a Known Scale and
  Object Size

• You set the limits by multiplying the sheet size
  by your scale factor
• Size of floor plan 6.3 x 4.0 meters
• Scale 1 20
• Scale factor 20
• Now test a 21 by 29.7 cm sheet (A4)
• 21 x 20 420cm or 4.20 m
• 29.7 x 20 594 cm or 5.94 m
• This sheet size is not sufficient, because the
  6.3 x 4.0 meters drawing does not fit on the
  sheet.
• Now test a 29.7 by 42cm sheet (A3)
• 29.7 x 20 594 cm or 5.94 m
• 42 x 20 840 cm or 8.4 m
• This should work with plenty of room for
  dimensions, notes and a border.
• In the previous example, you determined your
  limits by the number of units that fit across a
  standard sheet. If you have to fit the drawing to
  a predetermined sheet size, start with that size
  and the size of what you are drawing, and then
  calculate the scale factor from them
• 42 x 29.7 cm sheet and 6.3 x 4.0 m object
• 6.3 m equals 630 cm, 42 cm 630 cm (ratio of
  sheet size to object size) equals a ratio of 1
  15
• To draw a borderline, a title block, text and to
  show dimensions we need an extra space around the
  sheet so we should increase the scale factor. If
  we accept a scale factor of 20
• 42 cm x 20 840 cm or 8.4 m
• 29.7 cm x 20 594 cm or 5.94 m
• These limits of 840 cm by 594 cm should work.

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• Setting up an Electronic Drawing

• Setting Drawing Limits

• After you establish your drawing's units, use the
  Drawing Limits option from the Format pull-down
  menu to set sheet boundaries for your drawing. By
  default, AutoCAD specifies the lower left
  boundary of your intended drawing area is X0 and
  Y0. You can enter a new lower left corner by
  assigning new X,Y coordinates. Then, you can
  accept the upper right corner default values or
  assign new X,Y coordinates. You can also issue
  the LIMITS command by entering LIMITS at the
  Command prompt. AutoCAD does not insert a
  border around the drawing area when you set the
  limits. You can solve this problem by setting a
  drawing grid. A grid is also useful for
  estimating coordinate values and distances.
• File ? New ? Save as ? SET (Begins a new drawing
  named SET.)
• Format ? Units (Drawing Units dialog box)
• Choose the Decimal radio button in the Units
  area.
• Format ? Drawing Limits (Starts the LIMITS
  command.)
• Specify lower left corner or ON/OFF
  lt0.0000,0.0000gt Press Enter (Accepts the default
  location for the lower left corner)
• Specify upper right corner lt420.0000,297.0000gt
  840,594 (Sets the limits for the upper right
  corner)
• Tools ? Drafting Settings... (Displays the
  Drafting Settings dialog box)
• Snap and Grid ? Grid On check box (Turns on the
  Grid)
• Enter 10 in the Grid X Spacing box (Sets the
  grid spacing to 10 cm)
• Snap On check box ? Enter 10 in the Snap X
  Spacing box
• View ? Zoom ? AllZooms (limits and the grid cover
  the drawing area)
• Press Enter (Repeats the ZOOM command)
• Choose File, then SaveSaves the drawing as
  SET.DWG.
• The area covered by the grid is the defined
  limits, representing an 42.0 by 29.7 cm plotting
  sheet at 1/20 cm 1 cm scale. If you draw
  outside the grid, you are drawing outside the
  area that represents the intended plot area.

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• Setting up an Electronic Drawing

• Limit check

• LIMITS command has an ON/OFF prompt, for limits
  checking. When you turn on limits checking,
  AutoCAD does not allow you to draw outside the
  limits.
• Settings ? Drawing Limits (Starts the LIMITS
  command)
• Command '_limitsReset Model space limitsSpecify
  lower left corner or ON/OFF lt0.00,0.00gt
• Enter ON (Turns on limits checking)
• While limits checking is enabled, AutoCAD rejects
  attempts to enter points outside the drawing
  limits, although an entity, such as a circle,
  might start within the limits and extend outside
  them. The LIMITS command affects the LIMCHECK
  (warning or not), LIMMIN (lower-left drawing
  limits for the current space, expressed in world
  coordinates), and LIMMAX (upper right limit)
  system variables in the current space.

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• Drawing Accurately

• Grid (F7) and Snap (F9)
• Object Snaps
• Coordinates

To be continued next week