Lesson (Week) #1,
EGR-110-40, Burgener, Monday August 21, 2000
Handouts:
Pages D-1 and D-2, Orthographic surfaces labeling, due next class
(2nd week).
Page 27, Orthographic "complete the views puzzles", due 3rd week
(most likely).
LESSON WK3 (2-pages) clock-ish looking AutoCAD assignment,
due 4th week (most likely).
SMILEY.DWG stick-figure AutoCAD modify practice assignment,
maybe due at a later time.
Page 26, Orthographic "complete the views puzzles" maybe due at a later
time.
Page 30, Orthographic "complete the views puzzles" maybe due at a later
time.
Page 31, Orthographic "complete the views puzzles" maybe due at a later
time.
Page 36, Orthographic "complete the views puzzles" maybe due at a later
time.
Page 1B, Orthographic "complete the views puzzles" maybe due at a later
time.
Topics covered in class:
Textbook Page 92. Orthographic views. US standard "3rd Angle Projection"
style of Top, Front, and Right Side views. The views
line-up so that two views help find (locate) missing lines in the third.
A 45 degree line between the Top and Right Side views is
helpful.
p93. "Third Angle Projection" is common in the US, Canada,
and Britain.
p99. More orthographic views.
p100. Hidden and Centerlines: How and when to use dashed lines to indicate
lines that are hidden from view, but are necessary to fully explain the
object. Centerlines, which are drawn along the
"cylindrical center" of holes and arcs.
p103 More orthographic views.
p105 More orthographic views.
p106 Centerlines
p?? Precedence of lines: When various linetypes (visible, hidden, and
center) are drawn "on top of each other" the object (visible) lines
are always shown. Hidden lines have the next highest "priority", and
centerlines are only drawn (shown) if they are not obstructed by object
or hidden
lines (though the centerline "tail" may extend past the conflicting line). Note: Your textbook page 100 says differently. Page 100 section 5-4, 2nd paragraph says "... if either a centerline or a solid line is coincident, both would take precidence over a hidden line." However, other textbooks (Giesecke's Engineering Graphics, 2nd ed, page 148) says "A hidden line always takes precidence over a centerline." Let's table this topic for a while. I need to check the ANSI specs for clearification.
p101 AutoCAD Object Snaps. Object Snaps are used to "home in" on specific
points, such as the ENDpoint of a line, CENter of a circle, TANgent of
a circle or arc, MIDpoint of a line or arc, etc. For the time being,
use the Object Snaps individually, that is, leave "turned off"
the "OSNAP" button on the status bar (at the bottom) of your AutoCAD
screen. We'll learn "running osnaps" later.
There are several ways to "invoke" object snaps. Typing the first three
letters is one way, if you're quick with the keyboard. Using the icons
on the Object Snap "flyout" of the standard toolbar (top of the screen)
is another way. The middle mouse button (if equiped) is another
very convenient way. (NOTE: The system variable MBUTTONPAN must be set to 0 for this to work.) - Right click is another way, and you
can alway leave open the Object Snap toolbar, etc.
Object snaps must be "invoked" immediately BEFORE you click for (on) the
point with your left mouse button. They only last (work) for the ONE
point, with the OSNAP status bar button turned off, as I'd like you
to have set, for now.
AutoCAD Status bar settings:
SNAP (leave OFF for today, using status bar, or ) SNAP limits your points
to only be on a specified matrix, as if magnets attracted you cursor.
GRID (though not important, suggest leave OFF for today, using status bar, or )
The GRID is a matrix of dots, and CAN be helpful in judging distances. SNAP is usually
a finer spacing than the GRID dots.
ORTHO (learn to toggle on and off today, using status bar, or ) ORTHO limits your
lines to vertical and horizontal, like an electronic T-square
POLAR (leave OFF for today, using status bar) Note: for POLAR to work, OSNAP must be on, for some reason.
OSNAP (leave OFF for today, using status bar, or )
OTRACK (leave OFF for today, using status bar, or ...)
LWT - shows the line lineweights (width, sort of), that will take affect
during plotting. Although not necessary, suggest leave OFF for today, using
status bar, or ...)
MODEL/PAPER- leave this set for MODEL for today. PAPER involves an advanced
concept we'll learn later.
p113 Classwork practice: Although it WON'T be turned in, stay long
enough to complete a problem on page 113 (I'll suggest which). Use the
commands or icons (which I'll demonstrate):
Zoom-All Shows you all there is to see, even the area filled by the
GRID dots, even if GRID is turned off.
RTPAN and RTZOOM: Realtime ZOOM and PAN. Click the icon, and "click and
drag" your mouse up and down, or right or left.
LINE Remember to hit Enter when finished drawing the zig-zag line.
ORTHO On and Off with button at status bar (bottom of your screen) or .
Makes like an elctronic T-square for straight lines vertical or horizontal.
Direct Distance feature- To continue a line (or displacement) in a direction
at a distance,
move your cursor in the direction (with or without ORTHO on) type the
length or distance you want, and hit .
ERASE
Object Snaps: ENDpoint, NEArest, PERpendicular, see above discussion.
Drawing 45 degree lines: I appoligized in class for suggesting you draw 45 degree lines to help the orthographic views, when you didn't yet know how. It occurred to me later that you know enough to draw 45 degree lines, after all. Just use Direct Distance in BOTH the horizontal and vertical directions the SAME ammount, forming an L shape. Then use ENDpoint object snaps to draw the 45 degree line from end to end of the L.
At the end of class, I crashed and burned by not getting POLAR to work. Later I realised that OSNP must be turned on for POLAR to work, possibly because it uses OSNAPs internally.
GRIPS: When you see the blue squares on your lines or other object, just hit the Esc key twice to remove them. They have some special uses, but they just get in the way this early in the class.
When drawing lines, you can keep drawing line after line, forming zig-zagging lines, until you hit Enter to finish the line.
Due next week:Handouts D1 and D2, described above, at the
START of class.
Heads up for next week: See the downloadable old Fall 1999 word file.
I HOPE to follow the old Fall 1999 lessons, but change some of the
assignments. We WON'T, however, learn solid modeling and 3D
AutoCAD commands until much later in the semester. I taught that stuff
way too early in Fall '99.
