Gongoleski,+Greg-chapter

The actual final project is at the following link:

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I used Wetpaint since it will give a little more flexability when it comes time to add the instructional videos.

=Topic: Sectional View in CADD Class: CADD II =

=I. Introduction – =

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This unit on sectional views will make the assumption that the reader has some working knowledge of technical drawings. The reader should already understand orthographic projections, dimensioning, multiview drawings and the language of and types of lines. =====

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A sectional view is a method of looking at an object, many times a mechanical part and seeing the internal workings of that part. The sectional view can look at both assembled parts and individual parts. However, many sectional views are of single parts. The sectional view also eliminates the need for hidden lines and thus will simply some complicated drawings. The actual sectional view is seen as if you have cut the object down a preset plane. (It is easier to think of it as a knife that cuts through the object in a very precise and clean manner.) The part that has been cut, or sectioned, is pulled apart and the needed side is then looked at. If you look at the example below you can see a basic section. The middle drawing shows a top down view of an object. The cutting plane, or section line is the magenta line delineated by arrowheads. ===== 

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The section view is show in the lower drawing. (__Mech Draw__) Sectional Views can also be called cross – sections or sections. =====

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Using a CADD system can greatly increase the speed and accuracy of these types of drawings. In many systems you may draw the mechanical part in 3D and use the 3D model to develop a sectional drawing. =====

=II. Full Sectionals / Sectioning Techniques – =

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The first sectional view that will be discussed is the Full Section. It is the most basic and because of that it will be used to discuss techniques and terminology that are used in other section views. =====

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 __Visible Edges__ – The visible edges of the object should be shown with a continuous solid line, otherwise known as a visible line. =====

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__Hidden Lines__ - The hidden line, typically a dashed line, is omitted from the sectional. This is due to the fact that the sectional view will show the inner workings that were previously shown by the hidden lines. =====

__Cutting Planes__ - Please see section on cutting planes below. Examples of basic line-types
 

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<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">Section lines, sometimes called cross hatch lines, are the same for all types of materials today. In the past, different lines and symbols were used to show the material. Since there are so many different types of materials, the section lines are displayed in the same manner for each material and the material is noted elsewhere. =====

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<span style="font-size: 12pt; font-family: 'Times New Roman'; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;"> <span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"> =====

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<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"><span style="font-size: 12pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;"> “To draw a section line the spacing is between 1/32 to 1/8, depending on the size of the drawing. If the section lines are ever parallel to a 45 degree component of an object, then it is OK to change the angle to 30 degrees” (Giesecke and Mitchell and Spencer 209). =====

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<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">A cutting plane is the exact plane, or line, is used to cut through and section an object. The plane is displayed as a line or plane. Some types of sectional views use planes that take multiple turns to show the important areas of an object. “The cutting plane is indicated in a view adjacent to the sectional view” (Giesecke and Mitchell and Spencer 209). The following example shows the section AA located adjacent to the main views. ===== <span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">

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<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"> What this means is that to be able to decipher what you are actually looking at in the section you must be able to see the original drawing as well. =====

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<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"> <span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">The cutting plane is displayed by one of two types of dashed lines. Those lines then turn 90 degrees at each end and are terminated by arrowheads. The arrowheads show the direction that you are viewing the drawing. =====

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<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">The cutting plane line is labeled by a letter on each end, typically starting with AA. The letters help to distinguish different sections of the same part. These letters will also be placed at the end of the arrowheads or next to them. =====

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<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"> The full section view is the most basic of the sectional views. The object in divided by the cutting plane line and the component facing away from the cutting plane line is “removed”. This allows the interior of the object to be view without any obstructions. The areas of the object that would have actually been cut through (where the knife would actually touch) are filled in with section lines. It is important to note that hidden lines are not displayed in the full sectional drawing. =====

<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">E. Full Sectional Problems
=<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">III. Half Sectionals =

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<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"> A. The half section called so because the view that is drawn will have half of the object shown in a section and the other half shown in the standard orthographic projection. The usefulness of a half section is “largely limited to symmetrical objects” (Giesecke and Mitchell and Spencer 214). “However, ASA, recommends that A visible or center line may be used to divide the sectioned half from the unsectioned half of a half section” (Giesecke and Mitchell and Spencer 214). Half section views, although not the most basic, can sometimes help people to understand how the full section works. This can be done by using a simple example, such as a pipe flange, that is completely symmetrical. This in turn allows the individual to view each side of the object in a mirror view that has the visible lines of the external workings and the internal workings of the object. =====

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<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"> As a rule of thumb hidden lines are still to be omitted from the half sectional drawing. However, if the hidden lines are needed for the purpose of dimensioning then they may still be used. C. Half Sectional Problems  =====

=<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">IV. Broken – Out Sections =

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<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">The break line is the line that divides the sectioned component of the drawing from the rest of the drawing. It is also an irregular wavy line that divides the drawing. =====

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<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"> The above example shows a broken out section. Be sure to note the break line displayed in the lower left hand drawing. C.  =====

C..Broken – Out Sectional Problems
=<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">V. Revolved Sections =

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<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"> A. Revolved sections are important because you are allowed to create a section, within a drawing, thus avoiding the creation of a brand new section. The cutting plane is inserted at the desired position. When the cutting plane is in place the section of the object is revolved so that you can see the sectioned area. This example will help to alleviate confusion. =====

<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"> B. Revolved Sectional Problems
=<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">VI. Offset Sections =

<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">
=<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"> =

<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"> A. Offset sections are used in cases when the object is not symmetrical in shape. Some non symmetrical objects can be complicated, but have important internal components that need to be viewed. To accomplish the offset section the cutting plane line does not go in a straight line. Instead the line curves at 90 degree angles throughout the object.

The two following examples are excellent and show the same part. The top one shows where the cutting plane will move through the object and the lower drawing shows the offset section as it will be drawn.

(__Offset Section of the Electrical Contact Plate Solid Model__)

(__Full Section Drawing of the Chuck Jaw__) <span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"><span style="font-family: 'Times New Roman', Times, serif;">It is important that the object, when viewed in section, makes no indication that the cutting plane line has changed direction in it’s course.

B. Offset Sectional Problems

=<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">VIII. Aligned Sections =

<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"> A. The aligned section is very similar to the Offset Section. One method allows for the cutting plane to change direction at the angle needed to view the components that are important. The difference between the Offset Section and the Aligned Section is that the Aligned Section does not move back and forth through the object. It will typically change direction in one spot and continue in that direction.

Another method allows for the cutting plane line to move around the object in a bend and a circular path. The examples will make this easier to understand.

The Aligned Section is also used on objects that have spokes and ribs. This allows for the cutting plane to be aligned with various features. When this is the done the view that is drawn will be done so in a manner that makes the object look as if certain section have been revolved into place.

(__Aligned Section Drawing of the Filter Cover__)

B. Aligned Sectional Problems

=<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;">IX. Follow Up / Peer Editing Review =

=<span style="font-size: 130%; font-family: 'Times New Roman', Times, serif;"> = __Works Cited__

__Aligned Section Drawing of the Filter Cover__. Digital image. __ME 210 Engineering__ __Design Graphics__. 2000. University of Texas at Austin. 20 Mar. 2009 []. __Broken-Out Section Drawing of the End Adapter__. Digital image. __ME 210 Engineering__ __Design Graphics__. 2000. University of Texas at Austin. 20 Mar. 2009 []. " Drawing Class Notes." __San Diego State University College of Engineering__. San Diego State University. 23 Mar 2009 < http://kahuna.sdsu.edu/~johnston/drawing_basics.html

__Full Section__. Digital image. __Drawing Class Notes__. San Diego State University. 10 Mar. 2009<http://web.archive.org/web/20040309130524/http://kahuna.sdsu.edu/~johnston/drawing_basic// __Full Section Drawing of the Chuck Jaw__. Digital image. __ME 210 Engineering__ __Design Graphics__. 2000. University of Texas at Austin. 20 Mar. 2009 []. Giesecke, Frederick, Alva Mitchell, and Henry Cecil Spencer. Technical Drawing. //4th. New York, New York, USA: The Macmillan Company, 1958.

__Half Section__. Digital image. __Drawing Class Notes__. San Diego State University. 10 Mar. 2009<http://web.archive.org/web/20040309130524/http: //kahuna.sdsu.edu/~johnston/drawing_basic __Line types__. Digital image. __Engineering Drawing__. 24 June 2008. Wikipedia: The Free Encyclopedia. 10 Mar. 2009 []>. __Mech Draw__. Digital image. __Engineering Drawing__. 24 June 2008. Wikipedia: The Free Encyclopedia. 10 Mar. 2009 []>. __Offset Section of the Electrical Contact Plate Solid Model__. Digital image. __ME 210__ __Engineering Design Graphics__. 2000. University of Texas at Austin. 20 Mar. 2009 <http://www.me.utexas.edu/~rbarr/draft/Section_Views/Broken-Out_Section.html>. __Revolved View__. Digital image. __Drawing Class Notes__. San Diego State University. 10 Mar.2009<http://web.archive.org/web/20040309130524/http://kahuna.sdsu.edu/~johnston/drawing_basic//