ENGR 1120 Midterm
limiting element on a 3d model
"edge" seen on the side of a cylindrical feature
limiting element
"edge: seen on the side of a cylindrical feature
edge on a 3d model
intersection between two faces
what is the key to drawing a successful schematic
knowing the audience and communicating information to that audience in a clear manner
isometric lines
lines parallel to a principal axis
What are dimensions
numerical values that convey the size, shape, location, surface, texture, or geometric characteristic of a design
what are dimensions
numerical values that convey the size, shape,location, surface of a design -in this class dimensions are reported typically in inches feet (') inches (") diameter is a circle with line through it
engineering layouts vs schematics
oftern used interchangeably but engineering layouts focus more on defined physical or spatial arrangement of the features rather than flow through a system and functional relationship
multi view projection
one object face and two principal axes are parallel to the projection plane
tolerance fit: line
one of the limits on both the inner member and outer member are equal
primary auxiliary view
one that is projected onto a plane perpendicular to one of the principal planes and inclined to the other two
what are the different tolerance fits?
clearance , interference, transition, line, allowance
title block contains
company name, drawing title, drawing number, names,dates,designer,etc
working drawings
complete sets of standardized drawings specifying the manufacture and assembly of a product based on its design -blueprints used for manufacturing, creating the product
Schematics are...
concise, graphical symbolism that communicates to others the FUNCTIONAL RELATIONSHIP of the components in a system -represents the elements of a system (mechanical, electrical, process) that is designed to be easily interpreted by the viewer
what is the most commonly used parallel projection technique used by engineers and most CAD programs employ
orthographic projection
Orthographic Projection
parallel projection technique; differs from oblique projection in that parallel projetions are perpendicular (normal) to the projection plane -most commonly used parallel projection technique by engineers
what is the difference between the parallel and perspective projections? why are parallel projections used more often in engineering applications?
parallel projections are more often used in engineering vs. perspective projection because parallel projection minimizes the amount of foreshortening and allows for more visibility of the faces of the object and the dimensiosn
projectors are________ and used when it is important to preserve______properties of an object
parallel to one another & dimensional
DMFA stands for
design for manufacture and assembly
glass box theory
each of the three orthographic views shows two dimensions of the object in question.
vertex
end point of an edge
vertex on 3d model
end point of an edge (like the corner of a box)
t/f a standard three view multiview contains top,bottom and left view
f
t/f aligned views that share a common dimension are said to be related
f
t/f dimensions should be drawn to hidden lines whenever possible
f
t/f engineering layouts are not typically drawn to scale, b/c they contain no specfic details
f
t/f in multiview drawings, features should be dimensioned in every view in which they appear
f
t/f schematic diagrams use realistic pictures to represent components
f
t/f schematics are typically drawn to scale
f
t/f the 2 types of orthograhic projection are oblique and multiview
f
t/f the diameter of cylindrical parts should be dimensioned in their circular view
f
what are the orthographic views of the glass box theory called?
faces
what are nonstandard parts
parts that you design, must be manufactured according to your specifications
parallel projectors are
perpendicular to the projection plane in all orthographic projections
Projection
process of reproducing a spatial object on a plane, curved surface, or line by projecting its points
What are planar projections
projection is a way to represent spatial object on either a plane, curved surface, or line by projecting its points
tolerance fit: transition fit
ranges between a true clearance fit and a true interference fit
specifications
serve to further clarify the details for manufacturing the product
calculating tolerance: lower limit on the shaft?
shaft min=shaft max-shaft tolerance
foreshorten
shorten by proportionally contracting in the direction of depth so that an illusion of projection or extension in space is obtained
Hidden lines
show edges which cannot be seen from certain viewing angles in multi view drawings. they represent such hidden features as hidden extents or limiting edges of holes
what are hidden lines used for
show edges which cant be seen from certain viewing angles in multi view drawings
visible lines/ continuous lines
show lines visible from the line of sight for each view, edges of faces, edges between two intersecting faces
understanding multiviews and what each side shows: right view
shows height and depth
understanding multiviews and what each side shows: front view:
shows height and width
understanding multiviews and what each side shows: top view :
shows the width and depth
t/f engineering design follows a well documented cookbook approach
false
t/f recognizing principal competitors is not important when identifying the market segment of a product
false
t/f views that share a common dimension, but are not aligned are said to be adjacent
false
name the principal views
front-standard multiview back top-standard multiview bottom right-standard multiview left
orthographic projection technique
glass box theory-used to visualize multiview drawings
describe what "hidden lines" look like and what they represent in multiview drawings
hidden lines look like dashed lines and represent edges and lines that are not visible from that view in the multi view drawing
calculating tolerance: upper limit on the hole?
hole max=hole min+hole tolerance
detail drawings
includes all non standard parts
t/f benchmarking is a comparitive analysis of a product against its competitors
true
t/f product innovation is associated with mature products
true
t/f the glass box theory is used to describe the arrangement of the different multiviews with respect to one another
true
auxiliary views
type of orthographic projection used to determine the true size and shape of features whose true dimensions are not represented by one of the 6 principal views.
constraints
undeniable limitations to a design, can be physical (location of physical features of a site)
isometric projections
used in engineering because all three "sides" of an object are foreshortened equally along the three principal axes which allows objects to be scaled if desired
center lines
used to show the axes of cylinders and drilled holes. They are also used to show a path of motion, symmetry of an objects, etc.
projectors converge into a ....
vanishing point
differnt object features may sometimes coincide in a multiview drawing. when this occurs the order (precedene) in which center, visible, and hidden lines are shown is...
visible, hidden,center
partial auxiliary views
which is just the inclined surface, not the hidden lines etc, that may be present in a true auxiliary view
do isometric models distort the model?
yes- there is forshortening alond teh axes, distorition of circular features and angles
ex tolerance problem: a tolerance of 10.25 (+/_) 0.03 what are the limits of the size? what is the allowable variation or tolerance? what is the basic (nominal size) what is the actual size of a part?
-Limits: max: 10.28/ min: 10.22 -allowable variation or tolerance: 0.06 -basic/nominal size: 10.25 -actual size of parts is measured size of a finished part.. in this case somewhere between 10.22 and 10.28 (assuming its within tolerance)
what increases the cost of a product with regards to tolerance
-close tolerances generally increase cost b/c requires -additional processing steps -additional inspection -machines with lower production rates
what do working drawing show
-completely describe the parts both visually and dimensionally -show parts in functional assembly -identify the designed parts -identify standard parts
what are the 6 principal views? which ones are in a standard multiview?
-front,back,top,bottom, right, left -standard multi view: front,top,right
Planar Projections... for our purposes a projections
-mapping of a 3 dimensional (3D) space onto a two dimensional subspace
characteristics of a schematic
-may not provide all details -typically involve symbols may add unrealistic elements to aid comprehension -typically not drawn to scale since most are not drawn using actual measurements and don't include dimension
what do a set of working drawings include
-show how the different components fit together to form the product -shows all components in their operating position but not in assembled form (pulled apart) -bill of materials/ list of parts (provides info about indivdual parts of the assembly -detailed drawing of all non standard parts specifications (other instructions to serve for clarification)
perspective projection
-type of planar projection projectors converage to a single viewpoint called the center of the projection (CP) -typically used when its important to presenve dimensional properties of an object
what do schematics show/ what are they
1. dont have to be to sale and there is no scale written and features are not representative of true size 2. show functional relationship and figure shows how things flow from one part to the net 3. show process and are done to explain to audience so not all the details are given in the figure use symbols and abbreviations to convey ideas
how many principal views are there
6
principal enclosing box
PEB: contains the object and its dimensons are the maximum width, depth, and height of the object (principal dimensions of the object)
t/f in an isometric drawing, each principal axis is foreshortened by 75% of its true length
T
t/f projection is the process of reproducing a spatial object on a plane =, curved surface, or line by projecting its points
T
Face on a 3d model
bounding surface (flat space)
what are the benefits of tolerance
allow for interchangeable parts, allows for replacement of individual parts rather than replacing the entire system
calculating tolerance: upper limit on the shaft
allowance= hole minimum- shaft maximum shaft maximum=hole minimum-allowance
product dissection
approach to learning about engineering concepts and design principles by exploring engineered prodcuts
tolerance: maximum shaft size=
basic size
tolerance: minimum hole size=
basic size
why are the views in a multiview aligned?
because the feature project from one view to the next and some edges are shared between views
What are orthographic multiviews and why are they important
standard method for representing engineering designs in one, two, three (or more) view drawings primarily. -help manage distortion that happens (foreshortening) as an object is rotated and tilted create the ullusion of 3D
t/f an objects principal enclosing box represents its maximum width, depth,height
t
t/f center lines play a role in dimensioning, because they are used to locate the center of cylindrical parts and holes
t
t/f communicating information to the intended audience in a clear manner is the key to a successful schematic and layout drawing
t
t/f dimensions are used to specify size and location of features
t
t/f engineering layouts are typically used in the preliminary stages in a system
t
t/f engineering layouts focus more on defined physical arrangement of features
t
t/f parallel projection is typically used when it is important to preserve dimensional properties of objects
t
t/f schematics show the functional relationship of components in a system
t
t/f schematics typically omit details not relevant to the information they intend to convey
t
t/f smaller linear and aligned dimensions should be drawn inside of larger dimensions
t
t/f the abbreviations of TYP and the times (X) symbol may be used for features of the same type or size
t
t/f the overriding guidline of good dimensioning is clarity
t
t/f the purpose of multiview is to fully represent the size and shape of an object using one or more views
t
t/f the radius of circular arcs should be shown in the view where the true shape is seen
t
t/f the radius of cylindrical holes should be shown in their circular view
t
what is tolereance
the allowed range a size or location dimension may vary on an individual part -used to control the variation that exists on manufactured parts
what does the front view in a multiview drawing show?
the front view shows the height and width
tolerance fit: interference
the internal member is always larger than the external member
tolerance fit: clearance
the internal member is always smaller than the external member
what does the right view in a multiview drawing show?
the right view shows depth and height
tolerance fit: allowance how do you calculate allowance?
the tightest possible fit between two parts -it is the difference between the smallest hole size and largest shaft size allowance= hole minimum- shaft maximum shaft maximum=hole minimum-allowance
what does the top view in a multiview drawing show?
the top view shows the width and depth
what is a standard part
those that are already designed -not designed for one specific product -can be bought from an outside company or produced within a company
what are center lines used for
to show axes of cylinders and drilled holes
what are usually the most descriptive views of the 6 principal views
top, front, right therefore part of the standard multiview
