Assignment # 2

3D CAD Software:-

CAD (computer-aided design):-

 CAD (computer-aided design) software is used by architects, engineers, drafters, artists, and others to create precision drawings or technical illustrations. CAD software can be used to create two-dimensional (2-D) drawings or three-dimensional (3-D) models. Computer-aided design (CAD) is the use of computer systems to aid in the creation, modification, analysis, or optimization of a design. CAD software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, and to create a database for manufacturing. CAD output is often in the form of electronic files for print, machining, or other manufacturing operations.

3D CAD Software

Since introducing AutoCAD software in 1982, Autodesk has developed a broad portfolio of 3D CAD software programs to help users explore design ideas, visualize concepts, and simulate how designs will perform in the real world.

Autodesk’s Digital Prototyping tools help engineers and designers experience their 3D CAD designs virtually, before they’re built. By connecting every phase of your design process through a single digital model, our Digital Prototyping solutions let your teams test and optimize 3D CAD designs, helping to drive innovation, achieve higher quality, and speed time to market.

INTRODUCTION - WHY 3-D?

You may have already figured out why CAD has many advantages over manual drafting. One big advantage is that once you've drawn something, you shouldn't have to draw it again. If you manually drew a house plan, you would have to draw a front elevation, side elevations, and possibly a perspective view. With one 3-D CAD model, you can generate views from any angle either inside or outside the house and animations. Afterwards, if your client needs something changed, you can then make the changes once and re-render your views. If you're drawing mechanical parts, you can generate virtual prototypes or even create rapid prototypes. In this manner Boeing was able to design and prototype the 777 jetliner. This level of engineering would be impossible without CAD.

Your company may not do a lot of 3D work, but it is still a good skill to have and it's also more fun than 2D.

3-D concepts in the following order:

·       Isometric Drawings (not true 3D)

·       Wire-frame (very basic 3D)

·       Surfaces / Regions (primitive 3D)

·       Solid Objects (advanced 3D)

Will have a chance to draw the same object different ways to see the differences between the various methods.

Before entering the exciting world of 3-D, you'll have to learn some more CAD terminology.

3-D CAD TERMINOLOGY

2-D: A concept of displaying real-world objects on a flat surface showing only height and width. This system uses only the X and Y axes.

3-D: A way of displaying real-world object in a more natural way by adding depth to the height and width. This system uses the X Y and Z axes.

Boolean operations: Commands that allow you to add, subtract or intersect solid objects in AutoCAD.

Complex surface: Generally a curved surface. Examples: car fender, landscape contour.

Elevation: The difference between an object being at zero on the Z-axis and the height that it is above zero.

Extrude: The extrude command raises the shape of a 2D outline into a 3D solid. For example, a circle would be extruded into a cylinder.

Face: The simplest true 3-D surface.

Facet: A three or four sided polygon that represents a piece (or section) of a 3-D surface.

Hidden line removal: A way of hiding lines that would not be visible if you were viewing the actual object you have drawn in AutoCAD.

Isometric Drawing: A simple way of achieving a '3-D' appearance using 2-D drawing methods.

Plan View: Also known as the top view, a plan view looks directly down the WCS Z-axis to the X-Y axis.

Primitive: A basic solid building block. Examples would be boxes, cones, cylinders.

Region: A 2-D area consisting of lines, arcs, etc.

Rendering: A complex way of adding photo-realistic qualities to a 3-D model you have created.

Shading: A quick way of adding color to a 3-D object you have drawn. (Command: SHADE)

Solid Model: A 3-D model creating using solid 'building blocks'. This is the most accurate way of representing real-world objects in CAD.

Surface Model: A 3-D model defined by surfaces. The surface consists of polygons. (See facets.)

Thickness: A property of lines and other objects that gives them a 3-D like appearance.

UCS: The user co-ordinate system. This is defined by the person drawing to have easier access to portions of a 3-D model.

View: A particular view of the object you have created.

Viewport: A window into your drawing showing a particular view. You can have several viewports on your screen. Different from the viewports used in plotting.

Wire-frame Model: A 3-D shape that is defined by lines and curves. A skeletal representation. Hidden line removal is not possible with this model.

Z-Axis: The third axis that defines the depth.

Isometric Drawing

Using Isometric commands is one of the simplest ways to give a 3-D representation while using only 2-D commands. This has been the usual way of doing things before CAD allowed true 3-D work to be done. Many times an isometric drawing is used to compliment or give more information to a 3 view orthographic drawing. See the sample below.

You can see that it is a very simple drawing. This basic isometric drawing of the object gives a very good idea of what it looks like. If this is all that is needed then isometric works well. Unfortunately, as soon as you change anything, like the block's height, you'll need to redraw all four views. AutoCAD has a command called ISOPLANE which allows you to easily draw at a 30 degree angle as needed for an isometric drawing. You can switch between the three 'isoplanes' (top, right, left) by using this command or by pressing the F5 key.

Command: ISOPLANE <ENTER> 
Current isoplane: Right
Enter isometric plane setting [Left/Top/Right] <Left>: T <ENTER>
Current isoplane: Top

The 3-D Co-ordinate system

By now you should be very comfortable working your way around the X-Y coordinate system. Anyway, here is a quick review. Looking from the plan view, this is what you see to figure out where is positive X and positive Y.

If you were to look at the same picture, but at a slight angle, you would see the third axis. This new axis is called the Z-axis. Imagine that the positive Z-axis is coming towards you out of the monitor.

3D Rotation

Now for the confusing part. You already know how to rotate 2D objects, but you also have to know how AutoCAD measures angles of rotation in 3-D. There is a somewhat simple rule for this called "The Right Hand Rule". To figure out which is the positive rotation angle, imagine that you are wrapping your right hand around the axis with your thumb pointing towards the positive end. The direction that your fingers are wrapped is the positive direction of rotation. This applies to all three axes.

Direction of positive rotation using the right hand rule

The main point of this lesson is to tell you that objects can trick you in 3D space. Shortcuts don't always work, you have to be careful with Osnaps and your drawing can turn into a mess very quickly if you're not paying attention. Trust me, I've seen enough students take the easy route and have to start over. If you want to learn 3D, review each lesson before progressing. Make sure you know the concepts inside and out. This is just an introduction to the concepts, you will learn more in the following lessons. You may still want to refer back to this tutorial, though.