Engineering Design Graphics Exam 2

What is solid modeling?

It is a volumetric space representation of an object.

What information does solid modeling contain?

It contains information about the surface of an object.

What geometrical elements are included in solid modeling?

It includes wireframe and surface geometry necessary to describe the edges and faces of the model.

Manifold Model

Boundary that separate the spatial region into inside and the outside of the model

Non-Manifold model

It is the case that the a region isnot divided into inside and outside

Constructive Solid Geometry (CSG)

CSG modeling uses solid primitives that are related by Boolean operations

Types of booleans

Union, difference, and intersection

faceted surface

A faceted surface is a three-dimensional form composed of flat, polygonal faces with straight edges,

Exact surface

the total surface area of a 3D object, calculated using specific formulas based on its shape

What is Constraint-Based Modeling?

A modeling approach where the geometry of features is controlled through modifiable constraints.

What is a key benefit of Constraint-Based Modeling?

It allows for the creation of a dynamic model that can be updated as design requirements change.

Solid Modeling 3D Operations

Extrude, Revolve, Sweep, Loft

fully dimensioned part has three elements

Graphics, Dimensions, and Words

Lmc

least material condition

mmc

maximum material condition

Basic Dimension

numerical value defining the theoretically exact size, location, profile, or orientation of a feature relative to a coordinate system established by datums. Basic dimensions are identified on a drawing by enclosing them in a rectangular box. (See Chapter 10 .) Basic dimensions have no tolerance. They locate the perfect geometry of a part, while the acceptable variation or geometric tolerance is described in a feature control frame.

Reference Dimension

a numerical value enclosed in parentheses, provided for information only and not directly used in the fabrication of the part. A reference dimension is a calculated size without a tolerance used to show the intended design size of a part. Drawings made to older standards may have placed REF next to a reference dimension, instead of using parentheses.

Dimension Line

a thin, solid line that shows the extent and direction of a dimension. Dimension lines are broken for insertion of the dimension numbers.

Arrows

symbols placed at the ends of dimension lines to show the limits of the dimension, leaders, and cutting plane lines. Arrows are uniform in size and style, regardless of the size of the drawing. Arrows are usually about 3 mm (18") long and should be one-third as wide as they are long. Arrowheads on engineering drawings are represented by freehand curves and can be filled, closed, or open, as shown in the figure. While the size and proportion of arrowheads was critical when drawings were handmade, this concept is somewhat irrelevant in the modern digital enterprise.

Extension Line

a thin, solid line perpendicular to a dimension line, indicating which feature is associated with the dimension.

Visible Gap

there should be a visible gap of 1 mm (116") between the feature's corners and the end of the extension line.

Leader Line

a thin, solid line used to indicate the feature with which a dimension, note, or symbol is associated. A leader line is generally a straight line drawn at an angle that is neither horizontal nor vertical. Leader lines are terminated with an arrow touching the part or detail. On the end opposite the arrow, the leader line will have a short, horizontal shoulder. Text is extended from this shoulder such that the text height is centered with the shoulder line. Two or more adjacent leaders on a drawing should be drawn parallel to each other.

LMC/MMC

the largest acceptable size and the minimum acceptable size of a feature. The value for the largest acceptable size, expressed as the maximum material condition (MMC), is placed over the value for the minimum acceptable size, expressed as the least material condition (LMC), to denote the limit-dimension-based tolerance for the feature.

+/- dimension

the allowable positive and negative variance from the dimension specified. The plus and minus values may or may not be equal.

Tolerance

the amount that a particular dimension is allowed to vary. All dimensions (except reference dimensions) have an associated tolerance. A tolerance may be expressed either through limit dimensioning, plus and minus dimensioning, or a general note. The tolerance is the difference between the maximum and minimum limits.

Cordinate dimesioning

Tabular, on xy plane or datum, own plane

A symmetrical tolerance of (6)0.003 means that the dimension of the part can vary within the tolerance of

0.006

Interchangeability

The greatest impact oftolerance on parts is that the parts can beinterchange (Bolt and Nut)

Tolerances can be applied in

Direct limits, Geometric Tolerance, Notes referring to specific conditions, A general notes in title block

Nominal Size(tolerance)

General size in fraction ½

Basic Size(tolerance)

Theoretical size as a starting point

Actual Size(Tolerance)

Measure size of finished parts

Limits(tolerance)

Max and Min sizes shown by the tolerance

Allowance(tolerance)

he minimum clearance or maximuminterference between parts. Allowance of .001means that the parts do not interfere with eachother and that there is a minimum clearance of.001

Tolerance

the total allowable variation in adimension

Piece Tolerance

the difference between theupper and lower limits of a single part

System Tolerance

the sum of all piecetolerances

Clearance Fit

Mating parts always have clearancebetween them

Interference Fit

Mating parts always will interferewhen assembled

Transition Fit

Mating parts sometimes interfereand sometimes having a clearance between them

Functional Dimensioning

It is a practice thatthe parts that come in contact will getdimensioned and tolerance first!

Stack-Up Tolerance

Additive Rule fortolerance. This happen when we dimensionmating parts from different directions

Running and Sliding (RC) Fit

Loosest fit

Clearance Locational fit(LC)

Line-to-line fit

Transitional Fit: (LT)

transition between Clearance Locational fit(LC) and Interference Locational Fit (LN) fits

Interference Locational Fit(LN)

used for Alignment

Force and Shrink Fits (FN)

Force is required and usedfor transmitting power