UNIT 7
Customization & CAD Drawing
DRAWING ENVIRONMENT
ACAD provides two drawing environments for creating and laying out the drawing.
i. Model Space
Ii. Layout Space.
ACAD allows creating drawing, called a model, in full scale in an area known as model space without regard to the final layout or size when the drawing is plotted on the paper.
In the space opened for the first time, it is possible to create floating viewports to contain different views of the model. In the paper space, floating viewports are treated as objects which can be moved and resized in order to create a suitable layout.
PRINTING
When you print or plot a drawing, you need to specify what region you would like
To print. From within Paper space you usually print the Layout. However, in Model space,
There are four different ways of selecting a region to print. The Model and Paper space
Will be discussed in “Drawing Orthographic Projections in AutoCAD®”.
1. Display: Prints everything that you can see, at the moment, in the drawing area.
2. Extents: Prints the minimum area which will include everything that is drawn.
3. Limits: Prints the area that you have defined as your drawing size.
4. Window: Prints the area that you select using a window.
Figure 2.11-1 and 2.11-2 show a drawing and the printing results using the first
Three region selection methods. The line around the drawing’s title block indicates the
Limits/drawing size.
SCALING OF DRAWING: Zoom command displays the object at a specified scale factor. The value entered is relative to the limits of the drawing .for example, entering 2 doubles the apparent display size of any objects from what it would be if it were zoomed to the limits of the drawing. If you enter a value followed by xp, auto CAD specifies the scale relative to paper scale units for example; entering 0.5xp displays model space at half the scale of paper space units. The following illustration shows a number of viewports arranged in paper space. The view in each view port is scaled relative to paper space .the first view is scaled 1=1 relative to paper space (1xp) ,the second is scaled 0.5=1 relative to paper space (0.5xp),and so on.
SCALE: This enlarges or reduces selected objects equally in X and Y directions
At the command prompt, enter scale
Select objects: use an object selection method
Base point: specify a point (1)
<Scale factor>/reference: specify a scale or enter r
Units: The format for display co – ordinates and measurement can be selected
According to the requirement. Several measurement styles are available in ACAD. The main methods are engineering and architectural, having specific base unit assigned to them.
i. Decimal: select to enter and display measurements in decimal notation
Ii. Engineering: Display measurements in feet and decimal inches.
Iii. Architectural: Display measurements in feet, inches and fractional inches
Iv. Fractional: Display measurements in mixed numbers notation
v. Scientific: Display measurements in scientific notation.
The precision that is specified controls the number of decimal places or fractional size to which we want linear measurements displayed.
LIMITS
This sets and controls the drawing boundaries.
At the command prompt, enter limits
ON/OFF/<LOWER LEFT CORNER> <current>: Specify a point, enter on or off, or
Press
Enter.
In order for the drawings to be dimensioned so that all people can understand them, we need to follow standards that every company in the world must follow. Standards are created by these organizations:
-ANSI -MIL
-ISO -DOD
-DIN -CEN
-JIS
- ANSI - American National Standards Institute - This institute creates the engineering standards for North America.
- ISO - International Organization for Standardization - This is a world wide organization that creates engineering standards with approximately 100 participating countries.
Geometric Dimensioning and Tolerancing (GD&T) is a system for defining and communicating engineering tolerances. It uses a symbolic language on engineering drawings and computer-generated three-dimensional solid models that explicitly describe nominal geometry and its allowable variation. It tells the manufacturing staff and machines what degree of accuracy and precision is needed on each controlled feature of the part. GD&T is used to define the nominal (theoretically perfect) geometry of parts and assemblies, to define the allowable variation in form and possible size of individual features, and to define the allowable variation between features.
Dimensioning specifications define the nominal, as-modeled or as-intended geometry. One example is a basic dimension.
Tolerancing specifications define the allowable variation for the form and possibly the size of individual features, and the allowable variation in orientation and location between features. Two examples are linear dimensions and feature control frames using a datum reference (both shown above).
When drawing a Line spline or Wall object, Ortho Snapping Mode constrains line creation to the horizontal or vertical directions relative to the active grid. That is, with Ortho on, you can draw only lines that are parallel to lines of the active grid.
- By default, Ortho Snapping Mode is not directly accessible in the 3ds Max user interface. To add it as a button on the Snaps toolbar, see the Procedures section, below.
Ortho is particularly useful for drawing plans where all lines must be at 90 degrees to each other, such as a house plan. To constrain line-drawing to other angle increments, use Polar Snapping Mode instead.
The following provisions apply to using Ortho:
- Use of Ortho is mutually exclusive of use of the Polar Snapping Mode; only one can be active at a time.
- Ortho Snapping applies primarily to the creation of line splines and wall objects. It can be used while creating other objects, but results are likely to be unsatisfactory.
Ortho mode displays a compass which gives a readout of the current angle of the input relative to the positive direction of the local X axis.
Note: If you hold down the Alt key in Ortho mode, the next point becomes doubly constrained by both the previous point and the first point of the current object. This allows you to close splines precisely. In this mode, two compasses are displayed; one each at the first and previous points.
Procedures
To add Ortho Snapping Mode to the Snaps toolbar:
- Open the Snaps toolbar, if necessary. To do so, right-click an empty part of the main toolbar, such as the area directly below one of the drop-down lists, and choose Snaps.
- Drag the right end of the toolbar to the right to make room for a new button.
- Choose Customize menu
Customize User Interface.
This opens the Customize User Interface dialog.
4. On the dialog, click the Toolbars tab.
5. Scroll down the Action list on the dialog to the Ortho Snapping Mode item. You can jump to the O section by clicking any item in the list and then pressing O on the keyboard.
6. Drag the Ortho Snapping Mode item from the list to the empty section of the Snaps toolbar. This adds the button to the toolbar.
7. Close the Customize User Interface dialog.
3ds Max automatically saves the toolbar in its revised state and makes the new button a permanent part of the user interface.
Object snaps provide a way to specify precise locations on objects whenever you are prompted for a point within a command.
For example, you can use object snaps to create a line from the center of a circle to the midpoint of another line.
Specify an Object Snap
To specify an object snap at a prompt for a point, you can do one of the following:
- Press Shift and right-click to display the Object Snap shortcut menu
- Right-click and choose an object snap from the Snap Overrides submenu
- Click an object snap button on the Object Snap toolbar
- Enter the name of an object snap
When you specify an object snap at a prompt for a point, the object snap stays in effect only for the next point that you specify. Object snaps work only when you are prompted for a point.
Drawing a rectangle using Cartesian coordinates
We will be drawing the rectangle shown using lines defined by absolute and
Relative Cartesian coordinates.
1) View the Coordinates video.
2) Open your set-inch.dwt drawing template.
Drawing using relative polar coordinates
1) Review section 2.8.3).
2) Erase all the previously drawn objects.
To draw the most basic lines in your LayOut document, you can use the orderly Line tool to draw straight lines or its freewheeling cousin, the Freehand tool, to draw loopy swerving lines any which way you like. You see an example of both in the following figure.
Drawing straight lines
Predictably, you draw lines with the Line tool (), which you find on the default toolbar or the Tools menu.
To draw a line or lines, follow these steps:
Select the Line tool.
To place the line’s starting point, click in the drawing area or set a precise location using the Measurements box. For details about using the Measurements box to draw lines, see the following table. To lock the line to the red or green axis, hold down the Shift key. (See Drawing Lines and Shapes for an introduction to Layout’s inference engine.)
To place the line’s end point, double-click in the drawing area. (Alternately, you can select a new tool.)
When you select the Line tool, the Measurement’s box is ready for you to type precise points, or coordinates, to define your line. Here’s how to use the Measurements box:
Click in the drawing area or type an absolute coordinate value to set the starting point. Absolute coordinates are measured from the upper-left corner of the drawing area. For example, to set the starting point shown in the following figure, type an absolute coordinate of [2“,3”] and press Enter (Microsoft Windows) or Return (Mac OS X).
After you define the first coordinate, you can define the second coordinate, or end point, with one of three coordinate types: absolute, relative, or polar. In the following figure, the end point was created with the absolute coordinates [5“,8”].
After you type the end point coordinates, press Enter or Return, and your line appears precisely as you indicated.
