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**Drafting – Product Design & Architecture**

Orthographic Projection

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**Sketching Multiview Drawings**

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Multiview Drawing A multiview drawing is one that shows two or more two-dimensional views of a three-dimensional object. Multiview drawings provide the shape description of an object. When combined with dimensions, multiview drawings serve as the main form of communication between designers and manufacturers.

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Multiview Drawing

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Width, Depth, and Height All three-dimensional objects have width, height, and depth. Width is associated with an object’s side-to-side dimension. Height is the measure of an object from top-to-bottom. Depth is associated with front-to-back distance.

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Width, Depth, and Height

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**Sketching Multiview Drawings**

Introduction to Engineering DesignTM Unit 1 – Lesson 1.2 – Intro to Technical Sketching Width, Depth, and Height 45° Tell students: Notice how all views line up and construction lines can be used to help project the views from the first view drawn. Project Lead The Way, Inc. Copyright 2007

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**Orthographic Projection**

Orthographic projection is a technique that is used to create multiview drawings. Orthographic projection is any projection of the features of an object onto an imaginary plane of projection. The projection of the features of the object is made by lines of sight that are perpendicular to the plane of projection.

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**Orthographic Projection**

The best way to understand orthographic projection is to imagine an object contained inside a glass box.

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**Sketching Multiview Drawings**

Introduction to Engineering DesignTM Unit 1 – Lesson 1.2 – Intro to Technical Sketching Orthographic Projection There is a total of six glass walls surrounding the object. Each wall represents a projection plane onto which a two- dimensional object view will be created. Tell Students: Notice the six glass walls that represent planes and six views can be projected from this view. Three views are typically used and they are top, front, and right side. The opposite of each view being bottom, back, and left side also exist. Project Lead The Way, Inc. Copyright 2007

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Projection Plane A projection plane, also referred to as a plane of projection or picture plane, is an imaginary surface that exists between the viewer and the object. The projection plane is the surface onto which a two-dimensional view of a three-dimensional object is projected and created.

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**Orthographic Projection**

Start by focusing only on the front projection plane. A person standing in front of the object would see only the five corners identified in black. 2 3 1 4 line of sight at 90° angle to projection plane 5

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**Orthographic Projection**

Projection lines are used to project each corner outward until they reach the projection plane.

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Projection Lines A projection line is an imaginary line that is used to locate or project the corners, edges, and features of a three-dimensional object onto an imaginary two-dimensional surface.

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**Orthographic Projection**

The visible edges of the object are then identified on the projection plane by connecting the projected corners with object lines.

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**Orthographic Projection**

The orthographic projection process is then repeated on the other projection planes.

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**Sketching Multiview Drawings**

Introduction to Engineering DesignTM Unit 1 – Lesson 1.2 – Intro to Technical Sketching Sketching a Multiview Drawing Given the overall dimensions of the object, a pencil, and a sheet of graph paper, a sketching multiview drawing can be easily done using points, construction lines, and object lines. There are several ways to sketch a multiview drawing. Feel free to use the best way that make since to you. Teachers may choose to explain from the board or overhead using an example and have students follow along. Project Lead The Way, Inc. Copyright 2007

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**Sketching a Multiview Drawing**

Step #1: Calculate the amount of space that the views will take up.

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**Calculating Required Space**

12 spaces Overall Multiview Sketch Height? Overall Multiview Sketch Width? 18 spaces

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**Sketching a Multiview Drawing**

Step #1: Calculate the amount of space that the views will take up. Step #2: Layout the boxes within which the individual views will occur using points and construction lines.

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**Construction Line Layout**

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**Sketching a Multiview Drawing**

Step #1: Calculate the amount of space that the views will take up. Step #2: Layout the boxes within which the individual views will occur using points and construction lines. Step #3: Identify the visible edges by drawing object lines on top of the construction lines.

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Object Line Layout

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**Sketching Multiview Drawings**

Introduction to Engineering DesignTM Unit 1 – Lesson 1.2 – Intro to Technical Sketching A Question… Each of the blocks at right has the same overall dimensions and color. What else do they have in common? You could have students practice sketching the multiview drawings of these objects individually or in groups to help determine the answer before revealing it. Project Lead The Way, Inc. Copyright 2007

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**They all have identical top views!**

A Question… Each of the blocks at right has the same overall dimensions and color. What else do they have in common? They all have identical top views!

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