To find your current grade, look on the "home page" of the class, below the
link for the Final.
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Show and tell:
I showed an AutoCAD drawing we received from the Port of Anchorage,
that includes a rotated UCS, an inserted title block into paper space,
and 3 floating viewports.
Returned and Reviewed Midterm:
I returned the midterms, and asked if anyone had questions.
One student had a perfect midterm score.
Show and tell (again):
I showed the class the old sample drawing "solar.dwg" and demonstrated
how widespread the range of views is with AutoCAD. We zoomed in so far
we could see single words on the lunar lander plaque. Then we
zoomed out so far that the entire
solar system appeared to be a small dot.
Textbook Significant Facts:
I went over several
areas of the textbook, highlighting pages, some of which should have
already been covered when we did the section view work. Other pages
cover machine part features, or dimensioning. In the table below, the
letters "ul", "lr", "c", mean "upper left", "lower right", and "center",
P64, lr, no gap should exist between a centerline and the
connecting extension line. Other books say the exact opposite. Just be
consistent one way or the other. P67, ul, Centerlines shouldnít terminate
at object lines p106, ul, same as p64 above. P153, breaks in long
simple parts, tubular shapes, "general" break lines p154, ur, "lie" a
little to simplify section views. P185, c, counterbore, spotface p186
and p285, countersink p187, ur, repetitive features and dimensions,
"2XÖ" "(TYP)" p209-211, surface finish marks. High number means rough
surface, low number means smooth, and expensive. P233, section
views p235, top show centerlines, but not hidden lines p235, ll,
"full section" looks like Ĺ is removed p235, lr, patterns for general
pupose or cast iron (ANSI31), and steel (ANSI32) p236, ll, crosshatching
lines should be neither parallel nor perpendicular to edges p237, ll,
thin items, such as gaskets can be drawn solid, and probably should be
for economy. P238, "half section" looks like ľ of the object is removed.
P240, cr, nuts, bolts, pins, rivets, shafts, etc are not crosshatched
in section views p240, gaskets shown as solid p241, offset section
view. Donít show where section line "bends" p242, ribs arenít crosshatched
(typically) p242, "lie" a bit for section views of symmetric items.
Show as if itís got even number of holes, even iif itís really an odd number.
Rely on the "front" view to show the truth. P244, "revolved" sections
for long parts or "ring" parts easily show the shape. P246, ur, "broken
out" sections show sectioning just for area of importance Someplace I also
covered the machining terms "chamfer", "fillet" (concave), "round" (convex),
and "boss" (elevated island-looking area).
Intro to Dimensioning:
I showed a typical dimension on the board, and pointed out several
parts, such as "extension line",
"dimension line", "dimension text", "terminator" (arrow head),
"leader", gaps here and there, and "extension". I pointed out that old
AutoCAD (Release 9 or 10?) required knowledge of "dimension variables",
which controlled all
these features, and their sizes. The operator had to type or select
(off menus) the 6 to 8
character "dimvars", and enter the desired settings. Nearly all
dimvars begin with "DIM". The only one (or maybe the first one)
worth memorizing is "DIMSCALE" which scales up the SIZE of everything.
The text still is honest, but is enlarged or reduced depending on the
DIMSCALE value. All the gaps, extensions, and terminators also change size.
Since R11 or so, AutoCAD has had dialog boxes to alter
the dimvars indirectly. Itís still a good idea, however, to learn the 6 to 8
character dimvars, though, in case you ever continue into programming or
"script" file (macro) writing.
AutoCAD Dimensioning Demo:
I quickly sketched a plate in
AutoCAD and began demonstrating the dimensioning icons. I showed how
to alter the number of decimals from the default 4 to only 2
(Annotation>Units>Precision). I showed how to force the text to go between
the extension lines, for small values (Format>Fit>text only), I showed how
to truncate the leading zero, for dimensions under 1.00
(Annotation>Units>Supress leading zero). I showed how to allow the operator
to control placing the text for diameter dimensions (Format>User
Defined) (I think). What else? Oh, I showed how to enlarge the size
of all the dimension geometry with Geometry>Overall scale, and warned
about the danger of using "Linear scale" (cheating factor) on the
Annotation dialog box. I briefly showed how to change the terminators from
arrow heads to dots or architectural ticks (on Geometry dialog box).
I demonstrated for the class the icons: Linear, Aligned, Radial, Diameter,
Angular, Dim Styles, and Dim Update. I advised the class to turn on a
running osnap, starting with ENDpoint.
Advice for the UCS and Viewport Homework:
I demonstrated to the class (again): UCS control, starting
paper space (by double clicking on "Model" at the bottom of the screen),
inserting a title
block drawing (asize.dwg), and creating, moving, and stretching floating
viewports. Using a studentís completed solid
model, I showed the steps to complete the UCS and viewports project
(page 416 FIG 12-3-B, Connecting Bar), which is due next class. Each
viewport can get the same "zoom scale" with Z(enter) .025xp (enter). Aligning the
views can be easily done by moving the viewports, using construction
lines and osnaps.
I also made available an optional magazine article explaining
paper space and floating viewports. It walks the students through
a paper space tutorial, but doesn't teach UCSes.
Just the optional paperspace article mentioned above.
Due next class:
The UCS and viewports project
(page 416 FIG 12-3-B, Connecting Bar), discussed above.
Next class we'll continue into dimensioning. I'll show you
how to save the dimvar settings (once you've got them all adjusted)
as "Dimensioni Styles". We'll have another CAD assignment where
at least two separate Dim Styles are required. Maybe it'll be a
tiny object requiring fractions for the dimensions, and
another huge part requiring dots for the terminators, and 2 decimals.
You'd then need a dim style for each, and show them both in
separate floating viewports, with asize.dwg surrounding them. Maybe.
Either next week or the week after, we'll get into various
types of tolerances. You might care to read (skim) ahead
Chapter 7, beginning on page 171, and chapter 26,
beginning on page 529. We'll likley learn "limits", "deviation",
and geometric tolerances with AutoCAD. Be aware we'll only
have a day or two of tolerancing. We really can't
cover it well in such little time.