ENGR 1120 Midterm

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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


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