上海交通大学：《现代机械工程图学》教学资源_教学课件_Lec02_Engdrawing1

Engineering Drawing ME 250:Design Manufacturing I School of Mechanical Engineering Shanghai Jiao Tong University 1

Shanghai Jiao Tong University 1 Engineering Drawing ME 250: Design & Manufacturing I School of Mechanical Engineering

Course Outline Descriptive Geometry Spatial Visualization Orthographic Projection -Auxiliary Views Engineering Drawing Shanghai Jiao Tong University 2

Shanghai Jiao Tong University 2 Course Outline n Descriptive Geometry n Spatial Visualization n Orthographic Projection n Auxiliary Views n Engineering Drawing

Descriptive Geometry What is Descriptive Geometry Descriptive geometry is the use of orthographic projections in order to solve for advanced technical data involving the spatial relationships of points,lines,planes and solid shapes. Shanghai Jiao Tong University 3

Shanghai Jiao Tong University 3 Descriptive Geometry n What is Descriptive Geometry ? n Descriptive geometry is the use of orthographic projections in order to solve for advanced technical data involving the spatial relationships of points, lines, planes and solid shapes

Descriptive Geometry Why do I need to understand it With the advent of CAD software,computers are routinely being used to design and illustrate many projects which were formerly hand drawn.This (relatively)new technology eliminates the need for hand completed drawings but still requires the engineer(or artist)to be well versed in the theory and practice of multiview(or orthographic projection) 3-D Spatial visualization is a very powerful tool Shanghai Jiao Tong University 4

Shanghai Jiao Tong University 4 Descriptive Geometry n Why do I need to understand it ? n With the advent of CAD software, computers are routinely being used to design and illustrate many projects which were formerly hand drawn. This (relatively) new technology eliminates the need for hand completed drawings but still requires the engineer (or artist) to be well versed in the theory and practice of multiview (or orthographic projection) n 3-D Spatial visualization is a very powerful tool

Descriptive Geometry Engineers (and others)often use two- dimensional pictures to communicate three-dimensional shapes.The most common way to represent a three- dimensional object in a two-dimensional plane is by orthogonal projection. Shanghai Jiao Tong University 5

Shanghai Jiao Tong University 5 Descriptive Geometry n Engineers (and others) often use two- dimensional pictures to communicate three-dimensional shapes. The most common way to represent a three- dimensional object in a two-dimensional plane is by orthogonal projection

Descriptive Geometry ■ One can easily visualize the corresponding situation in 3D.However,it is also necessary to be able to go back and forth between 2D and 3D.That is,be able to: represent a given three dimensional situation by a series of 2D views (i.e.,orthographic views- principal and auxiliary) visualize (and derive pertinent geometric information about)the three dimensional situation from a given set of orthographic views. Shanghai Jiao Tong University 6

Shanghai Jiao Tong University 6 Descriptive Geometry n One can easily visualize the corresponding situation in 3D. However, it is also necessary to be able to go back and forth between 2D and 3D. That is, be able to: n represent a given three dimensional situation by a series of 2D views (i.e., orthographic views— principal and auxiliary) n visualize (and derive pertinent geometric information about) the three dimensional situation from a given set of orthographic views

Spatial Visualization There are two types of projections to communicate engineering and technical illustration work pictorial projections multiview projections Shanghai Jiao Tong University 7

Shanghai Jiao Tong University 7 Spatial Visualization n There are two types of projections to communicate engineering and technical illustration work n pictorial projections n multiview projections

Pictorial projections Pictorial projections consist of single view drawings that are suitable for representing preliminary ideas or sketches,but are not appropriate for communicating technical data. Examples of pictorial projections are the oblique,isometric or perspective projections (or views) Shanghai Jiao Tong University 8

Shanghai Jiao Tong University 8 Pictorial projections n Pictorial projections consist of single view drawings that are suitable for representing preliminary ideas or sketches, but are not appropriate for communicating technical data. Examples of pictorial projections are the oblique, isometric or perspective projections (or views)

Examples PICTORIAL OBLIQUE PROJECTION PERSPECTIVE PROJECTION ISOMETRIC PROJECTION Shanghai Jiao Tong University 9

Shanghai Jiao Tong University 9 Examples

multiview projections Multiview drawings present multiple different views of the same object.This method presents projections of the same object on three planes simultaneously,namely the top, front and side (or profile)planes,providing three views known as the principal views.All dimensions are drawn to scale and the three principal views can be used to form additional views known as auxiliary views. Shanghai Jiao Tong University 10

Shanghai Jiao Tong University 10 multiview projections n Multiview drawings present multiple different views of the same object. This method presents projections of the same object on three planes simultaneously, namely the top, front and side (or profile) planes, providing three views known as the principal views. All dimensions are drawn to scale and the three principal views can be used to form additional views known as auxiliary views