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4. Principles of Dimensioning

This week you will learn dimensioning . The steps to follow are:

Functional & Non-functional Dimensions Principles of Dimensioning Dimension Placement & Conventions Dimension Tolerances Geometric Dimensioning & Tolerancing Assignment #4

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4. Principles of Dimensioning

What is dimension ?Dimensions are defined as numerical values

expressed in appropriate units of measure and indicated on a drawing and in other documents.

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4. Principles of Dimensioning

FUNCTIONAL DIMENSIONS Functional dimensions directly affect the function or working

of a product and may be of the size or location types. A datum is a reference line on the drawing from which a

component is dimensioned. In practice, a datum is any functional surface or axis used for manufacture, inspection, location, or assembly purposes.

NON-FUNCTIONAL DIMENSIONS Non-functional dimensions, NF in Figure, are those

dimensions which are used for production purposes but which do not directly affect the function or working of a product. Non-functional dimensions usually are not inspected.

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4. Principles of Dimensioning

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4. Principles of Dimensioning

PRINCIPLES OF DIMENSIONING  Dimensions are normally expressed in millimeters. Dimensions of less than unity should be preceded by

zero Each dimension should appear only once It should not be repeated on other views. Dimensions relative to a particular feature should be

placed in one view, which shows the relevant features most clearly, rather than spread over several views.

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4. Principles of Dimensioning

AUTOMATIC DIMENSIONING Some more powerful CADD systems allow dimensions to

be added automatically to a drawing. In a drawing made by hand, there is no necessary or inherent correspondence between the dimensions of the drawn outline and the intended dimensions of the object, which it represents, until a scale has been specified.

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4. Principles of Dimensioning

Dimensioning Concept CADD software such as AutoCAD provides three basic

types of dimensioning: linear (horizontal, vertical, aligned, rotated, ordinate, baseline and continued), radial and angular.

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4. Principles of Dimensioning

Dimensioning System Variables The dimensioning system variables control the appearance of

dimensions. You may set these variables on the command line

Variable Value Explanation . Dimasz <2.5> Controls the size of the dimension arrowhead Dimgap <1.5> Sets the distance around the dimension text above its

line Dimexe <2.0> Determines how far to extend the extension line Dimexo <0> Determines how far extension lines offset from origin

point Dimdli <10> Sets the distance between adjacent dimension lines Dimrnd <0> Rounding dimension text value

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4. Principles of Dimensioning

Arrowheads

 

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Special Characters

Diameter %%C Ø %%C 50 Ø 50 Degree %%D ° 50 %%D 50 ° Plus/minus %%P ± 50 %%P 2 50 ±

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4. Principles of Dimensioning

Linear Dimensions

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Chain Dimensions

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4. Principles of Dimensioning

Radial Dimensioning

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4. Principles of Dimensioning

Angular Dimensioning

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4. Principles of Dimensioning

Text Justification

Centered Above Aligned & Centered

Above Outside

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4. Principles of Dimensioning

Text Fitting

Rounding off Dimensions

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4. Principles of Dimensioning

DIMENSION TOLERANCES 

Tolerance is the total amount that a specific dimension is permitted to vary; it is the difference between the maximum and minimum limits for the dimension. Tolerances can be applied directly to dimensioned features, using limit dimensioning.

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4. Principles of Dimensioning

Applying Dimension Tolerances in AutoCAD

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4. Principles of Dimensioning

Geometric Dimensioning & Tolerancing

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4. Principles of Dimensioning

Geometric Dimensioning & Tolerancing

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4. Principles of Dimensioning

Basic Dimensions 

Basic dimensions are the theoretical sizes from which limits of size are derived by the application of allowances and tolerances.

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4. Principles of Dimensioning

Next Week ;You will learn creating sectional views. The steps

to follow are: Cutting plane Types of sectional views (full, half, detailed etc) Hatching Assignment # 5

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4. Principles of Dimensioning

Assignment # 3You will sketch the three views for an objects in 1st

angle projection & give all necessary dimensions. Don’t forget to save it!

Submit the assignment on time by logging into

http://www.ninova.itu.edu.tr

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4. Principles of Dimensioning

Assignment ProcedureOpen ISO_A3 template fileFormat the drawing file (linetype etc)Sketch the front viewUse construction lineComplete the top view and the side viewFill in the title block (name, number, date etc)Save your file into Z disk (i.e.

YourNumber_YourNameSurname_A3.dwg) (i.e. YourNumber_YourNameSurname_A3.jpeg)