ME 123
in first angle, you _______ the object
"roll"
in third angle, you _________ the object
"unfold"
when going from an oblique pictorial to a multi-view, what does a scale of .7071 mean?
1 diagonal on the oblique = 2 units on the pictorial (only for receding axis)
what is the order of line precedence?
1) visible 2) hidden 3) center
how do you select the front view of a multi-view?
1. best shape 2. best operating position 3. least hidden lines 4. longest dimension
what is the scale going back in cabinet oblique projections?
1/2 scale
types of CAD
2D Wireframe Surface modeling Solid modeling
user-defined features
2D sketches that are pulled through space
what angles can oblique projections have?
30, 45, or 60
additive manufacturing
3D printing; software generates thin slices of a model and system creates and fuses them together
who makes drawing standards
ASME
How can you tell a pictorial is a perspective?
All parallel lines converge
Which 2 kinds of projection are orthographic?
Axonometric and multi-views
How can you tell if a pictorial is an axonometric or not?
Axonometric if 3 mutually perpendicular planes have a horizontal that creates two 30 degree angles or if all ellipses have the same amount of foreshortening or "squishiness"
What are three negative features of wireframes?
Can't render Ambiguous No volume information, which limits analysis capabilities
scale
DRAWING = OBJECT or DO!
True or false: Centerlines take precedent over hidden lines in multi-view drawings
False
True or false: Isometric axes all have different foreshortening factors
False
True or false: The receding axis of an oblique must be drawn at a 45-degree angle
False
Are pictorials more or less ambiguous than multi-views?
More
Can you determine when edges are hidden from a wireframe?
No
In what kind of pictorial can you measure a true angle on the front?
Oblique
What kind of pictorial has parallel lines converge to a vanishing point?
Perspective
Rapid prototyping
Solid physical model is made directly from 3D CAD model data without any special tooling
What does controlling design intent look like with using geometric relations?
Tangent, horizontal, concentric Ex: if you want holes to remain equal you can set up that relation
What does controlling design intent look like by placing certain dimensions?
The choice depends on how you want the part to update after changes. For example, you could place a hole position with respect to an edge or respect to a different hole
What does controlling design intent look like from a modeling approach?
What your base feature is What features you add If you take away or add material Ex: how to place holes, individually or a pattern Ex: which edges to fillet first
Can hidden lines be shown in a pictorial?
Yes
What does controlling design intent look like by using equations?
You can set a length equal to a fraction of a different length
where is the viewer in perspective projection?
a finite distance
what is characteristic of an oblique pictorial?
a parallel front face (90 degree angles)
2 kinds of CAD that evolved
additive manufacturing and numerical control machining
what kinds of drawings should always have centerlines?
all 2D drawings
pre-defined features
already defined features such as fillets or chamfers
what is the scale going back in general oblique projections?
anywhere between 1/2 and 1
why do we have fillets/chamfers?
appearance protection safety easier to coat harder to break
where is the viewer with oblique projections?
at infinity
what are the two kinds of orthographic projection?
axonometric and multi views
what are the three kinds of oblique projections?
cabinet, general and cavalier
what is the best way to figure out if views are in first or third angle?
choose one, then prove or disprove it
what do title blocks need?
company name drawing title scale drawing number
CAD
creating, changing, optimizing a design through using computerized tools
milter lines are a graphical way of keeping the _______ the same
depth
working drawings
describe shape, size and more specifications to construct an object
What kind of modeling software would you use to make late stage design changes?
direct
What kind of modeling software would you use when working with legacy data?
direct
What kind of modeling software would you use with ideation?
direct
direct modeling
direct manipulation of geometry by pushing, pulling and twisting
solid modeling
easy to visualize and manipulate lots of information can analyze and optimize can put into CAM, add. manufacturing and # control machining
detailed assembly drawings
enough info to manufacture and assemble the part
True or false: proportion controls the size of the drawing
false
true or false: construction lines are thick, light lines
false
true or false: lines that are parallel on an object are not always parallel on an axonometric view
false
true or false: selecting a surface before entering the Hole Wizard command allows you to create holes on multiple faces
false
true or false: when creating a diameter dimension for a revolve sketch, you want to select the end point of the centerline
false
True or false: proportion is stipulated y the ratio of the drawing size to the actual object size
false, that is scale
what are the two kinds of multi-views?
first angle and third angle
how do oblique planes look in all three views?
foreshortened but seen in all three principal views
how do inclined planes look in all three views?
foreshortened in two views and shown as an inclined line in the third
How can you tell a pictorial is an oblique?
front face is dead on right angles on front face are 90 degrees circles on front face are totally circular and not ellipse-like
what is the scale going back in cavalier oblique projections?
full scale
2 types of parameters
geometric constraints and dimensions
what four things affect design intent?
geometric relations dimensions (which and placement) equations method of modeling (extrude vs rotate)
surface modeling
good for rendering like putting a sheet over the wireframe
parametric modeling is good for ______ and bad because _________
good: multiple configurations and design intent bad: show performance and large file size
direct modeling is good for ___________ and bad because ________
good: speed and objects with a short life cycle bad: it is less design controlled
detail drawings
have enough detail to manufacture the part has title block
to draw non-isometric lines, you must...
have two corners to draw a line in between
multi-views must have...
hidden lines and center lines
design intent
how we want a model to behave
what is a good way to tell between an isometric and a trimetric?
if circles are foreshortened differently or "different squishyness"
what is the difference between isometric views and trimetric views?
in isometric, all angles are equal, but in trimetric, no angles are equal
in axonometric projection, the viewer is at...
infinity
in multi-views, the viewer is at...
infinity
In what kind of pictorial is the angle of the receding axis set by definition?
isometric
What's larger, isometric projections to isometric drawings?
isometric drawings
What is the difference between an isometric drawing and an isometric projection?
isometric projections are projected on a plane (scaled about 80%). Drawings use full measurements
what are the three kinds of axonometric projection?
isometric, dimetric and trimetric
what is the difference between a multi-view and an isometric pictorial?
isometrics are tilted and rotated to see all 3 dimensions instead of just 2
what is the first thing to look for when deciding what kind of pictorial an object is?
look for parallel lines, if they converge then it's a perspective drawing
wireframe modeling
makes 2D objects 3D using wires good for animation and rendering can be ambiguous no surface/volume information
2D modeling
more exact than drawing freehand less expensive if you don't need a 3D model hard to visualize, analyze and optimize ex: detail drawing, floor plan
Are dimensions along width, depth and height true length in a cavalier oblique drawing?
no
Is a multiview a pictorial sketch?
no
Should you re-use dimensions when modeling?
no
can two adjacent areas in a multi-view lie in the same plane?
no
do assembly drawings have dimensions or hidden lines?
no
In what kind of pictorial are distances foreshortened along two of the three principal axes?
none
What kinds of objects have detailed assembly drawings?
objects that will probably never be pulled apart
if front face angles are 90 degrees, what kind of pictorial is it?
oblique
if front face circles are circular, what kind of pictorial is it?
oblique
what are the two kinds of parallel projection?
oblique projection and orthographic projection
what are the three main types of pictorials
oblique, perspective and axonometric
how would you describe oblique projection?
one face parallel to the projection plane, then a receding axis going back
isometric lines are...
parallel to on axis and change in one direction
What kind of modeling software would you use for multiple configurations?
parametric
What kind of modeling software would you use to preserve design intent?
parametric
Solidworks is a...
parametric, feature-based model
in axonometric projection, the projectors are _______ to the projection plane
perpendicular
in multi-view projections, projectors are _______ to the plane of projection
perpendicular
What is the most realistic type of drawing?
perspective
what kind of projection is closest to what humans see?
perspective
what are the two types of projection?
perspective and parallel
rendering
photo realism
working drawings can be...
pictorials or multi-views *usually bad to use pictures as technical drawings because they are unclear*
assembly drawings
show how parts fit together has "exploded" views has parts list and notes for manufacturing (like cleaning and assembly)
how do normal planes look in all three views?
shown as true size in one view and shown as edges in the other two
numerical control machining/conventional manufacturing
subtractive process in which the CAD model is made into a code that drives machine tools
parametric modeling
system that models using parameters
what is the front view of a multi-view called?
the "common" or "central view"
features are...
the building blocks and are subject to parent/child dependancies (history-based) can be user-defined or predefined
how should you decide which face should be the front of an oblique projection? why?
the face with the most detail or curve (or longest dimension) features so they aren't foreshortened
if we don't know the operating position of an object, what should we go by?
the most stable position
what is the relationship between the object, viewer, and plane in first angle projection?
the object is between the viewer and the plane
what is the relationship between the object, viewer, and plane in third angle projections?
the plane is between the object and the viewer
what happens to the projectors in perspective projection?
they converge
what do converging projectors do?
they make things farther away look smaller
True or false: a child can be suppressed without suppressing its parent
true
True or false: it is possible to change the order in which a feature was created
true
True or false: oblique and axonometric projections use parallel projection
true
True or false: proportion is considered key to freehand sketching
true
True or false: proportion is helpful when creating sketches in SolidWorks
true
True or false: proportion maintains the size of one part of the sketch relative to the entire sketch
true
true or false: a center line may sometimes be short unbroken lines
true
true or false: a tangent line touches an arc/circle at one point
true
true or false: fillets and chamfers will affect the model differently depending on whether they are added before or after a shell
true
true or false: hidden lines show areas not visible in the current view
true
true or false: only two principal views are necessary to show the length, width and height of an object
true
true or false: the receding axes on an isometric sketch are drawn at an angle of 30 degrees to the horizontal
true
when do we show lines at tangent points?
when when the tangent surfaces are perpendicular
Can a plane still be oblique or incline if it is hidden from a view?
yes
what is bi-directional associativity?
you can go between any files associated with a part, when you update one file the others will update as well
what do you do to an object in axonometric projection? why?
you tilt and rotate the object so that you can see all three dimensions