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CADD
PRIMER
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Chapter
8: Printing and Plotting
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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
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:
Lets
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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