OLAUTOCAD2 - CHAPTER 1.pdf

CHAPTER 1 An introduction to drafting in 3 Dimensions Learning Objective: Upon completion of this lesson, you will be able to: ✓ Define 3 dimensional and identify 3D objects ✓ Explain different terminologies u...

CHAPTER 1 An introduction to drafting in 3 Dimensions Learning Objective: Upon completion of this lesson, you will be able to: ✓ Define 3 dimensional and identify 3D objects ✓ Explain different terminologies used in 3D-Drawing ✓ Create your first 3D drawing 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. You'll be learning the 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) You 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. This level presumes that you have a good understanding of 2D commands. 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. (Command: HIDE) 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. As computers and software get more powerful, working in 3D becomes more popular. You have more power in desktop machine today, than was dreamed of when CAD first appeared. Be prepared that you will likely need to learn 3D at some point in your career. Once you are comfortable working in 3D, you'll find that you will rarely want to draw in 2D again. Autodesk (the makers of AutoCAD) make other products designed specifically for certain disciplines - Revit, AutoCAD Architecture, AutoCAD Civil 3D, 3ds Max and more. Depending upon your budget and needs, you may need to look into programs like these. The concepts taught in these lessons will aid you when you work in any 3D program. Isometric Drafting Techniques Isometic 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 Current isoplane: Right Enter isometric plane setting [Left/Top/Right] : T Current isoplane: Top Newer versions of AutoCAD have an Isoplane icon on the status bar. You can click this to enter Isometric Drafting Mode as shown below. You can also change your Isoplanes here (but F5 is faster). By invoking this command, AutoCAD is now set to draw on the top isoplane by default. Your other choices would be Left or Right. Your first exercise will be to draw the object shown above using isometric methods. REFERENCE: https://www.mycadsite.com/tutorials/level_3/introduction-to-3d-autocad-3-1.html https://www.mycadsite.com/tutorials/level_3/isometric-drawing-in-autocad-3-2.html VIDEO: https://youtu.be/mgifL80Dbvw https://youtu.be/6reJsWxvGyM