Ch.4 Engineering Geometry & Construction

Ch.4 Engineering Geometry & Construction

Geometric construction and engineering geometry (4.1)

Coordinate spaces (4.3) Geometric elements (4.4) Points, lines, surfaces & solids (4.5) Conic curves (4.6)

We cannot cover all materials in this chapter in one lecture. Some of the definitions and concepts have been covered in your education up to this point (from elementary school). We place emphasis on quickly constructing necessary geometric elements. Terms you learn from this chapter have direct relevance to CAD.

Geometric construction and engineering geometry

Geometric construction Act of constructing a geometry, especially using hand tools.

Dividing a line Cylinder

Engineering geometry Basic geometric elements and forms used in engineering design.

Engineering geometry classified Manual

drafting AutoCAD

Coordinate space 2-D Cartesian coordinate system

Coordinate space (cont.) 3-D coordinate system

Coordinate space (cont.)

Right-hand rule for axes direction & positive direction of rotation on each axis Note that counter clockwise is positive (default positive rotation of ACAD)

Coordinate space (cont.) Polar coordinates, Cylindrical coordinates, & Spherical

coordinates

Points, lines, circles, and arcs In this lecture we focus on geometric

construction techniques that are needed to do manual drafting assignments.

Dividing a line into equal parts (4.5.2)

Points, lines, circles, and arcs (cont.)

Constructing arcs tangent to two lines (4.5.3)

Points, lines, circles, and arcs (cont.)

Constructing an arc tangent to a line and another arc

Points, lines, circles, and arcs (cont.) Constructing an arc tangent to two given arcs or circles

Points, lines, circles, and arcs (cont.)

Constructing an arc tangent to two given arcs

Points, lines, circles, and arcs (cont.)

Constructing an arc tangent to a given arc

Points, lines, circles, and arcs (cont.)

Constructing lines tangent to two circles o arcs, using a straightedge (a trial and error method)

Conic curves : parabolas

Focus

Conic curves : Ellipses

Conic curves : Ellipses (cont.)

Conic curves : Ellipses (cont.)