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E112 | W3L6: Isometric & Orthographic Projections - Coggle Diagram
E112 | W3L6: Isometric & Orthographic Projections
Isometric Projection
When we present a 3D design through the use of three-dimensional drawings, the drawings are also known as axonometric projection.
One of the more commonly used axonometric projections is isometric drawing. Isometric means equal measure. Therefore to produce an isometric drawing, the principal edges are equally inclined to the viewer and they are of the true length.
Isometric drawings are constructed on 3 axes that divide the circle equally. They are 120° from each other.
Orthographic Drawings
Orthographic Projections: A simple way of representing engineering design drawings is by using orthographic projections. Orthographic projections are a collection of 2D drawings used to define a 3D model.
Commonly, the Front + Top + Right Side View combination is used. The Back view may be omitted as it is an inverse of the Front other, just like the Top/Bottom views, and Left/Right views.
However, if a bottom view has more details than the top view, we can use the Front + Bottom + Right combination (instead of Front + Top + Right), for instance.
While there are six (6) possible projections - Front, Back, Top, Bottom, Left, and Right Views. Three of these views can give us a complete representation of a 3D model.
First and Third Angle Projections
In engineering drawings, first and third angle projections are methods used to represent three-dimensional objects in two dimensions. These projections are essential for accurately conveying the dimensions and geometry of a part or assembly.
First Angle Projection - The object is placed between the observer and the plane of projection, resulting in the views being projected onto the opposite side of the plane
Third Angle Projection - The plane of projection is between the observer and the object, causing the views to be projected onto the same side of the plane
Types of Lines in Orthographic Drawings
Hidden Lines
Hidden lines are used to represent features that are not visible in a particular view. These lines are usually drawn as dashed lines to differentiate them from visible lines.
Center Lines
Center lines are used to indicate the centers of holes, cylinders, and other symmetrical features. These lines are typically drawn as alternating long and short dashes.
Visible Lines
Visible lines are used to represent features of an object that are visible in a particular view. These lines are typically drawn as solid, thick lines to ensure they stand out clearly on the drawing.