Dimensions

Dimensioning is to take measurements and then show them on the figure. AutoCAD offers the user to take dimensions in a variety of ways. One can dimension objects such as a line or polyline or between two points. Dimensions can be horizontal, vertical, aligned, rotated, ordinate, baseline or continued.

AutoCAD basically offers three types of dimensions, namely linear, radial and angular. Dimension when taken, have the same settings as that of the dimension style set. Hence they take on a particular arrowhead style, text location and lateral tolerances.

The following figure gives an example of the dimensions that can be taken. The dimensions have been taken of the jaw and are linear, radial and angular.

Coordinate Systems (UCS & WCS)

AutoCAD uses two coordinate systems:

• World Coordinate System (WCS)
  
  In this type of a coordinate system, the X axis is horizontal, the Y axis is vertical and the Z axis is at 90 degrees to the plane formed by the X and Y axis. The origin is the intersection point of the X and Y axis, i.e. (0,0), which is always at the left bottom side of the drawing.
  
• User Coordinate System (UCS)
  
  To facilitate changes in direction of the plane that one is working in, the UCS has been developed. The direction can be seen in the form of a grid by pressing F7. The UCS is defined in terms of the WCS

The UCS can be relocated in the following ways:

o By defining a new origin
o Rotating the UCS around any one of the axis. That is, the direction of one of the axis is fixed while the other two are interchanged.
o Loading a saved UCS
o Specifying the direction in the direction of the present view or by aligning it with an object

Once the UCS has been relocated, Snap, Grid, and Ortho modes all rotate in line with the new UCS.

Copy

In copy, images of the original objects are created at a specified distance from the original. Procedure similar to Move is applied here i.e. distance in the form of a point (base point) and the second point is specified. Direction is also given to place the object in the desired location.

Move

Objects can be moved without changing their size or orientation. When combined with object snaps, these objects can be relocated precisely where the requirement is.

There are basically two ways to move an object. Both of them however require that the Move command be chosen or it be typed in the command line.
· In the first one the object to be moved is selected. The base point of movement is then selected followed by the point of displacement.
· In the second method, the object that is to be move is again selected first. Coordinate values for the first point and second point of displacement are then given. Pressing ENTER then moves the object by using the relative displacement.

This command should not be confused with offset, which is also very similar.

Union Command

Union is a command that combines two or more objects to form one single object. The volume of the final object includes the volume of all the selected objects and its area encloses the area of all regions in a subset.

To apply this command, it must be written in the command line, after which the objects should be selected. Finally, ENTER is pressed for the result. The example explains this process. Two separate regions, 1 & 2, are to be unified. The procedure is followed and the end result is a single fused region

Subtract Command

Subtract command, as the name implies, subtracts one object from another. To be precise it subtracts the second selected objected from the first selected object. The result is that a new object is created.

One condition of subtraction is that both the

objects must be on the same plane. However, if the subtraction is performed simultaneously regions on different planes can also be subtracted.

Subtraction can be applied to both 2D and 3D figures.

The example shows that a cylinder has been subtracted from the object that was created in the Extrude Command topic

Extrude Command

Once a 2D region is obtained, it can easily be converted into a 3D object by the Extrude command. The height value, tapered angle and the planar face need to be specified.

For explanation purposes, work is continued on the region created in the Region Command topic and it is extended from a 2D region to a 3D object.

Region Command

Some parts of the robot required shapes that weren’t available directly in the Solids category. This meant separate line segments had to be joined to create a 2D shape and then extended to form a 3D object using the Extrude command.

This is where the region command comes in; it connects multiple line segments (which make a closed loop) to form one whole segment and fills the space inside them. An example diagrammatically is shown.

The 1st pic is the one before Region command is executed and the 2nd is after execution.

Line Command

LINE command, as the name suggests, creates a series of adjoining line segments. The procedure is fairly simple; the start point is initially specified by mentioning either the coordinate point or by using the pointing device. Then the length of the line is specified or the pointing device is used to confirm the endpoint. Result is a line segment of the desired length. Similarly, if the next endpoint is specified at this stage, another line segment is created. Or if it is required finish and not to create another line segment ENTER is pressed. Since most of the structure required that perpendicular lines be drawn, the Ortho command was mostly used in designing Badar when drawing the line segments.

Layers

Layers can be thought of as the overlays used in paper-based drafting. They are the tool used to group information by function and to enforce line type, color, and other standards.

Layer properties manager is a window in AUTOCAD that offers options to make layers current, add new layers, delete layers, and rename layers. Properties can be assigned to layers, layers can be turned off or on, locked or unlock, and plot styles can be set for layers. Layer names can also be filtered and the properties can be saved and restored.

14 layers were used to build the desired model of Badar. Each layer had its own individual color, which gave the robot an aesthetic look.

A copy of the layer properties manager is shown, along with the layers used

3D Orbit Command

The 3DORBIT command is a command that activates an interactive 3D view. It helps to view the entire model from different points around it. When active it displays an arcball (a circle divided into four quadrants) by smaller circles; the center of this arcball is the target point which stays stationary and the point of view moves around the target. Shown is the arcball.

Pan commands and zoom commands are also used for viewing purposes.

Pan commands allows the user to move the screen around without changing any attribute of the object or of the 3D view that is governed by the 3D orbit. The command can be activated by typing in the command line or by selecting a hand icon in the software window.

Zoom command allows the user to zoom in to better observe the model and to zoom out which gives the user an overall bigger picture.

Views

The first step when drawing any figure is always to switch to the front view. This helps to easily view and work on the figure from both the sides as well as from the top.

There are a total of 10 available views in AUTOCAD: Top view, bottom view, left view, right view, front view, back view, SW isometric view, SE isometric view, NE isometric view and NW isometric view. Three views of Badar have been shown here

AUTOCAD benefits

· It’s a comprehensive general purpose CAD program
· Contains a list of very useful functions for drawing purposes
· Provides option of electronic publishing and viewing
· Capability for 3D modeling and rendering
· Low system requirements and fast execution compared to other programs
. Contains a very useful help known as ‘user documentation’
· Latest versions are backward compatible