Chapter 10: Parametric Drawing

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Chapter 10 Parametric Drawing Using Constraints
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After completing this Chapter, you will be able
to use the followingfeatures

• Constraints
• Geometric Constraints
• Dimensional Constraints

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Constraints
The Parametric Drawing feature allows you to
apply geometric and dimensional constraints to
objects. Applying constraints makes design and
drafting easier and more accurate by assuring
that objects maintain certain specified
relationships with other objects, or with one of
the coordinate axes, during the design
process. Constraints can also be used to ensure
that sizes of objects, measured distances, or
angles between points or lines on objects can be
fixed so that they will not change when the
objects are modified.
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Geometric constraints allow you to control how
objects react when the objects they are linked to
are modified. Dimensional constraints can be
applied to two points on an object so that the
distance between those points (the length of the
object) will remain unchanged during any
modification to the object.
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Geometric Constraints
There are 12 geometric constraints available for
use in an AutoCAD drawing. They are Coincident,
Colinear, Concentric, Fix, Parallel,
Perpendicular, Horizontal, Vertical, Tangent,
Smooth, Symmetric, and Equal
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Coincident Constraint
The Coincident constraint causes selected points
on two separate objects to maintain the same
location.
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Colinear Constraint
The Colinear constraint causes the second
selected line to lie in the same infinite line as
the first line selected.
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Concentric Constraint
The Concentric constraint constraints the second
selected circle/arc to be concentric with the
first circle/arc.
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Fix Constraint
The Fix constraint constrains the selected point
on an object to maintain its location.
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Parallel Constraint
The Parallel constraint causes the second
selected line to rotate until it is parallel to
the first line selected. The procedure involves
rotating the second selected line about the
endpoint nearest to the point where the line is
selected.
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Perpendicular Constraint
The Perpendicular constraint causes the second
selected line to rotate until it is perpendicular
to the first line selected. The procedure
involves rotating the second selected line about
the endpoint nearest to the point where the line
is selected.
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Horizontal Constraint
The Horizontal constraint causes the selected
line to rotate until it is parallel to the X-axis
of the current coordinate system. The procedure
involves rotating the selected line about the
endpoint nearest to the point where the line is
selected.
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Vertical Constraint
The Vertical constraint causes the selected line
to rotate until it is parallel to the Y-axis of
the current coordinate system. The procedure
involves rotating the selected line about the
endpoint nearest to the point where the line is
selected.
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Tangent Constraint
The Tangent constraint causes the second selected
object to move until it is tangent to the first
selected object.
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Smooth Constraint
The Smooth constraint forces a spline to maintain
geometric continuity with another spline, line,
arc, or polyline.
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Symmetric Constraint
The Symmetric constraint causes selected objects
to become symmetrically constrained about a
selected line. For lines, the lines angle is
made symmetric (but not the endpoints). For arcs
and circles, the center and radius are made
symmetric (but not the endpoints of the arc).
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Equal Constraint
The Equal constraint causes the second selected
objects to become the same length for lines and
the same radius for circles and arcs as the first
selected object. For arcs and circles, the center
and radius are made symmetric (not the endpoints
of the arc).
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Deleting Constraint
To delete a constraint, move the cursor over a
constraint icon and choose Delete from the
shortcut menu.
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AutoConstrain
Choosing AUTOCONSTRAIN lets you apply geometric
constraints to a selection set of objects based
on orientation of the objects relative to each
other.
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Dimenional Constraints
There are 7 dimensional constraints available for
use in an AutoCAD drawing. They are Linear,
Horizontal, Vertical, Aligned, Angular, Radial,
and Diameter. Dimensional constraints maintain
specified distances and angles between geometric
objects or points on objects.