Dept of Mechanical Engineering and Mechanics, Drexel University

Sectional Orthographic Views

MEM 201

Fundamentals of Computer Aided Design

Dept of Mechanical Engineering and Mechanics, Drexel University

Today’s Learning Objectives…

• Need for Sectional View

• Contents of Sectional view

• Identifying different kinds of sectional views.

• Sectional View Guidelines and good practices.

• Cross Hatching in AutoCAD.

Dept of Mechanical Engineering and Mechanics, Drexel University

Sectional Views

• These are views that show internal features such as cuts, holes, step cuts as orthographic views.

Dept of Mechanical Engineering and Mechanics, Drexel University

Sectional Views

Dept of Mechanical Engineering and Mechanics, Drexel University

Purpose of Sectional Drawings

• Depict assembly of parts.

• Show internal detail.

• Replace complex orthographic views.

• Describe materials in an assembly.

Dept of Mechanical Engineering and Mechanics, Drexel University

Contents of a Sectional View

• Sectional views have: – Cutting plane shown as edge view: cutting plane line.– Cutting plane arrow representing the direction of line of sight.– Section lines (hatch) shows where areas of solid material are

present.

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Dept of Mechanical Engineering and Mechanics, Drexel University

Different Kinds of Sectional Views

• Full Section• Half Section• Offset Section• Aligned Section

Dept of Mechanical Engineering and Mechanics, Drexel University

Full Sectional View

• Cutting plane cuts fully through object.• No Hidden Lines are shown.• Visible Lines behind the cutting plane must be shown.

Dept of Mechanical Engineering and Mechanics, Drexel University

Half Sectional View

• Cutting plane passes halfway through object. • Used for symmetric parts. • Omit hidden lines.

Dept of Mechanical Engineering and Mechanics, Drexel University

Offset Sectional View

• Cutting plane line not straight but offset to pass through important features.

• Don’t show cut formed by offset.

Dept of Mechanical Engineering and Mechanics, Drexel University

Aligned Sectional View

• Align sections cut at an angle (for circular shapes).

• Features may be projected onto plane for clarity.

Dept of Mechanical Engineering and Mechanics, Drexel University

Good Sectional View Drawing Practices

• Different parts at different angles or patterns• Hatch spacing of about 1/16”-1/8”• Cutting plane line .020” wide (bold)• Section or hatch lines -- thin .007”• Visible lines -- width .015”• Do not show Hidden lines.• Direction 45° – not parallel or perpendicular to boundary• Name them on the side.

Section A-A

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Dept of Mechanical Engineering and Mechanics, Drexel University

Position of Sectional Drawings

Dept of Mechanical Engineering and Mechanics, Drexel University

Sectioning of Holes

Dept of Mechanical Engineering and Mechanics, Drexel University

Cross Hatching in AutoCAD

• AutoCAD can apply a given pattern to fill an area.• The area must be a closed area.• To fill the area use the BHATCH command.

Dept of Mechanical Engineering and Mechanics, Drexel University

In AutoCAD….

Dept of Mechanical Engineering and Mechanics, Drexel University

Standard Material Patterns

• The ANSI patterns represent the more standard engineering materials.

• ANSI31 is the generic material which can be used in no material is specified.

Dept of Mechanical Engineering and Mechanics, Drexel University

Predefined Pattern Library

Dept of Mechanical Engineering and Mechanics, Drexel University

Questions

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Note: A 20min quiz of Orthographic Views, Sectional Views will follow next week.