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CADD PRIMER
Chapter 8: Printing and Plotting

 Contents 
About this Chapter
Key Terms in this Chapter
The Printing and Plotting Process
  • Selecting a Scale for Drawings
  • Composing a Drawing Layout
  • Selecting Text and Dimension Heights
  • Choosing Pens, Colors and Line weights
Steps to Plotting
Plotting and Printing Machines
  • Pen Plotters
  • Ink-Jet Printers/Plotters
  • Laser Printers
  • Electrostatic Printers/Plotters
AutoCAD, MicroStation and Cadkey Terms
About this Chapter This chapter introduces you to the printing and plotting process. It describes how the drawings are printed on a specific scale. It looks at a number of issues associated with scale. You will learn how a scale is applied to drawings, how to select a sheet size and how big or small diagrams can be drawn, how to compose a drawing layout for plotting and what height text should be used based on a scale. Join AutoCAD Training online - Learn more...

This chapter describes basic steps for plotting and how colors and line-weights are created in the drawings.

It also includes a discussion on common printing and plotting machines. You will learn about pen plotters, ink-jet printers/plotters, laser printers and electrostatic printers/plotters.

Key Terms in this Chapter
 
Term
Description
Configure A process by which a program, such as CADD, is made to recognize and work with a hardware component, such as a plotter.
Dpi Dots per inch; used to measure the accuracy of printing. 
Plot To print a drawing with a plotter.
Plotting reference An imaginary point on the screen that is used to align screen image with the paper in the plotter.
Plotting scale To proportionally reduce or enlarge diagrams for plotting.
Plotting scale factor A degree to which drawings are proportionally reduced or enlarged.

The Printing and Plotting Process AutoCAD Forum

CADD drawings are printed using a printer or a plotter. The process of printing is as simple as selecting the print or plot function from the menu. This action sends data from the computer to a printer or plotter, which produces the final drawing. The drawings are neat, clean and, depending on the quality of the printer, highly accurate.

You can specify a number of parameters to control the size and the quality of a plot. You can plot a drawing to any size by applying an appropriate scale factor. You can specify line thickness and colors for different drawing objects. You can make a number of other adjustments as well, including rotating a plot, printing only selected areas of a drawing, or using specific fonts for text and dimensions. The following are the important considerations for plotting:

    • Selecting a scale for drawings
    • Composing a drawing layout
    • Selecting text and dimension heights
    • Choosing pens colors and line weights
    Selecting a Scale for Drawings  
    When working on a drawing board, you use a specific scale to draw diagrams. For example, when you need to draw a plan of a building or a township, you reduce the size of the diagrams to 1/100 or 1/1000 of its actual size, that is, you use a 1:100 or 1:1000 scale. When you need to draw a small machine part, you draw it many times larger than its actual size. CADD uses the same principle to scale the drawings; however, a different approach is taken.

    All CADD drawings are created on a full scale (1:1). Even if you have to draw the map of a township, you will draw it using 1:1 scale! You can draw as big or small on the screen as you like and adjust the image using view-display functions. The magnification of the image has no relevance to the actual scale of the drawing. The actual scale of the drawing is determined when the drawings are plotted. If you drew a 36'-0" x 24'-0" rectangle and you want to fit it on a 36" x 24" paper, you need to scale it down to 1/12th, that is, you need to apply 1" = 1'-0" scale.

    The dimensions you enter on-screen are called "drawing units" (or master units); the actual size that is printed on paper is measured with "plotter units". When you enter the plot function, the plot dialog box opens to allow you to specify the ratio between drawing units and plotter units. The ratio between the plotting units and drawing units is called "scale factor". The scale factor determines how big or small the drawing will be printed. The following table shows some of the common scales used in architectural and engineering drawings and the scale factors associated with them:

Common scales in feet-inch format
Scale factor
1" = 1" (full size)
1
1" = 1’-0" (reduced 12 times)
12
1/2" = 1’-0" (reduced 24 times)
24
1/4" = 1’-0" (reduced 48 times)
48
1/8" = 1’-0" (reduced 96 times)
96
Common scales in metric format
Scale factor
10:1 (enlarged ten times)
0.1
1:1 (full size)
1
1:10 (reduced 10 times)
10
1:20 (reduced 20 times)
20
1:50 (reduced 50 times)
50
1:100 (reduced 100 times)
100
When starting a drawing, one of the first steps is to determine the plotting scale and sheet size. This is calculated the same way as it is when working on a drawing board. You choose a scale and a sheet size based on the size of the diagrams. You can calculate the maximum size diagram that can fit on a sheet by multiplying the scale factor with the sheet size.

The following example illustrates how to calculate the maximum size of a diagram that can fit on a sheet:

Let’s say the sheet size is 36"x24".

Actual drawing area leaving 1" border = 34"x22"

Maximum size diagram = (Sheet length x scale factor) x (sheet width x scale factor)

The following table shows the calculations to determine the size of diagrams:

Scale
Calculation
Max. size diagram
1" = 1" (34 x 1) x (22 x 1) 1'-10" x 2'-10"
1" = 1'-0" (34 x 12) x (22 x 12) 22'-0" x 34'-0"
1/2" = 1'-0" (34 x 24) x (22 x 24) 44'-0" x 64'-0"
1/4" = 1'-0" (34 x 48) x (22 x 48) 88'-0" x 128'-0"
1/8" = 1'-0" (34 x 96) x (22 x 96) 176'-0" x 256'-0"
Important Tip:

Once the plotting scale and sheet size are determined, you can draw a border representing the maximum drawing area. The border reminds you that this is the maximum size diagram you can draw on that size sheet. All drawing objects must be contained within this border; otherwise they will fall outside the plotting area.

Composing a Drawing Layout CADD provides a number of special functions to compose a drawing layout. You can arrange diagrams on a sheet and apply different scales to each diagram. Different programs use different protocols to accomplish this task.

One protocol used is a special mode of working called page layout or paper space. The paper space represents the actual sheet size. You can project an image of the diagram on the sheet and can apply any plotting scale to the diagram. This makes the diagram bigger or smaller according to the selected scale. It shows exactly how the diagram will be plotted on the selected sheet size. You can project multiple diagrams on the sheet and arrange them, as you like.

Another protocol used involves specifying the plotting scale when you start a drawing. You enter all the distances using 1:1 scale and the computer automatically draws the diagram to selected scale. If you draw a 100’-0"x100’-0" square using a 1:100 scale, it will automatically scale it down and draw a 1’-0" x 1’-0" square. However, when you dimension the square using the dimensioning function it will read correctly as 100’-0" x 100’-0".

Fig. 8.1 shows how you can create a drawing by arranging different diagrams on a sheet. In this layout, the engineering complex diagram is scaled at 1:100, the typical office unit diagram is scaled at 1:20 and the staircase detail is scaled at 1:10. Title block and diagram headings are added to complete the drawing.

Plotting and Printing Machines There are two distinct categories of printing machines: plotters and printers. Both are commonly used to print CADD drawings. Diagrams are generally printed at about 300-600 dpi (dots per inch) accuracy, which is considered quite high precision for engineering drawings. For special graphic applications, there are machines that can print at 1200 dpi or higher accuracy.

Plotters and printers essentially do the same task; however, there are differences the way they work. Plotters print drawings by plotting vectors. They print drawing objects one by one, just as we draw them on the screen. Printers print data in a raster format and the drawing is printed line by line from top to bottom.

The following are common machines used for printing and plotting:
 

  • Pen plotters
  • Ink-jet printers/plotters
  • Laser printers
  • Electrostatic printers/plotters
  • The above topics are described in detai in CADD PRIMER.

    Note: CADD PRIMER is illustrated with more than 100 diagrams. The above diagram is an example from CADD PRIMER illustrating the concept of plotting in CADD.

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