Menggambar Teknik

Slide 01By Taharuddin

Development of Engineering Graphics

Multiview DrawingsFrancesca (1420-92)

Cartesian CoordinatesDescartes (1596-1650).

Engineering Design Process is (92%) graphically based.

Engineering Drawing

What you will learn

Visualization Graphics Theory Standards Conventions Tools Applications

Lines may be defined as…….

1. The shortest distance between two points

2. The geometry created by the intersection of two planes or surfaces

3. A set of points organized that have length and direction, but no thickness

The “Language”

Lines come in all types and shapes:

Parallel lines will always maintain the same distance from each other throughout their entire length, and NEVER touch!

Lines come in all types and shapes:

Non-parallel lines do not maintain the same distance from each other throughout their entire length, and may either touch, or eventually cross each other.

Lines come in all types and shapes:

Perpendicular lines are at 90 degrees to one another.

Lines come in all types and shapes:

Intersecting lines cross each other at any angle.

Lines come in all types and shapes:

Tangent lines are created when:

1. A curved and straight line meet, and….

2. The two lines intersect at only one point, and….

3. A smooth transition into one line can be generated.

Lines come in all types and shapes:

Lines will appear as edges when there is an intersection of two planes or surfaces.

Lines come in all types and shapes:

Tangent conditions may appear in both 2D and 3D geometry….

Figure A shows a tangent being created at Point C

Figure B shows Tangent F being identified as the intersection point between the 2 circles.

Lines come in all types and shapes:

Here we can see that Line VT is lying tangent to the cone.

Lines come in all types and shapes:

Can you explain why Example A is tangent, but Example B is not??

Circles are considered the most perfect form geometric shape. All circles are made up of many parts…

A parabola’s shape can be generated from a 3D cone and 2D plane….

Notice that the parabola’s shape is symmetrical (mirror image of itself), and that it has a focus point inside the arc of the line. The cutting plane is always parallel to the slope of the cone.

Parabolas have many engineering uses and shapes….

As the shape of the curve of the parabola changes, it allows for more diverse applications.

The ellipse is generated in much the same way as the parabola….

Notice that the ellipse’s shape is symmetrical (mirror image of itself), like the parabola.

However, the ellipse has no focus point identified inside the arc of the line, and the cutting plane is NOT parallel to the slope of the cone.

A circle may appear as an ellipse when the object is not perpendicular to the line of sight.

While the circle’s geometry remains true shape and size, our view of its shape appears more oval as the object is rotated from its 90 degree position.

Lines can be set at angles to points or other lines…

Lines set at angles help us understand the relationship of other lines, or the geometry’s position in space.

Quadrilaterals have two main characteristics:

1. They are CLOSED entities,

2. They have 4 sides.

Polygon means “many sided”:

Most polygons have names based on the number of sides they have.

2D and 3D Space:

Let’s take a few minutes to see how lines and points are used to organize space…..

If we take the centre of the universe as our home position (X=0 and Y=0) , we are able to map out the coordinate vertices of any object from that point and assign them addresses so they may be easily located.

However, as the universe is not 2-dimensional, we must take into consideration a 3rd axis (Z) that represents its volume.

Since the computer ALWAYS remembers that its home is (0,0,0), we may locate any point in space, or on a 3D model, by referencing home.

Example: (4, 3, 0)

Each point on a 3D model has its own address in space that is designated by an X, Y, & Z value.

Here we can see the address of each vertex.

Standard Sheet Sizes

Technical Sketch:

Pictorial Sketch

Examples of Sketches:

Examples of Sketches:

Multiview Sketch

Sketching used Throughout Design Process:

Classification of Sketches:

Each classification of sketch has a particular purpose from production use…to technical illustration.

(ISOmetric, Dimetric & TRImetric)(Orthographic)

Sketching Grids:

A. Orthographic grid

B. Isometric grid

C. Perspective grid

Perspective:

The line of sight is cone-shaped - which makes objects far away appear smaller to our view. Objects are not “true shape and size”.

Parallel:

The line of sight is always parallel regardless of how far away the object is from our view. This allows surfaces to be drawn “true shape and size”.

Multiview Drawings:Only two of the three dimensions(Height, Width & Depth)can be seen in a single view

Most Descriptive View:

Visualizing a Multiview Drawing:

Six Principle Views:

Ortho means “at 90 degrees”, and is a form of parallel projection.

Orthographic projections are used to show several views of the same object in one drawing set.

Extracting “Orthographic” Views of an Object:

Orthographic:

The “principle views “ should be chosen to show the most detail of the object with the least number of hidden lines.

Here, the TOP, FRONT, and RIGHT SIDE were chosen.

Understanding what Center Lines do…

Center lines show the theoretical perfect center of arcs, holes, and cylinders. They can be used to show symmetry, or used to aid in dimensioning an object.

Center lines NEVER start or stop on another line!

The “Alphabet of Lines”…

Lines have both style and precedence.

Object (visible) lines are the MOST important … then hidden lines…then center lines…etc.

Multiviews of Common Objects:

Question!

How do you know when a sketch or CAD drawing is complete?

ANSWER: When the production people can make the part without having to ask you any questions!

Most drawings not only have views of the object, but also I include written notes and dimensions to aid in its production.

Types of Lettering:

Simple gothic is used for engineering design. Notice that it is “san serif” (no hats or shoes!)

Tips on creating a multi-view drawing:

1. Lightly sketch all the information that you know first.

2. Use reverse construction to locate lines that may be

unknown such as compound angles.

3. Darken all arcs and circles first.

4. Then darken straight lines.

Practice Problem:

Practice Problem:

Practice Problem:

Sketching Practices

End of slide 1