Chapter 10: Parametric Drawing
Using Constraints
After completing this Chapter, you will be able to use the following
features:
•Constraints
•Geometric Constraints
•Dimensional Constraints
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.
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.
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
Coincident Constraint
The Coincident constraint causes selected points on two separate
objects to maintain the same location.
Colinear Constraint
The Colinear constraint causes the second selected line to lie in
the same infinite line as the first line selected.
Concentric Constraint
The Concentric constraint constraints the second selected circle/arc
to be concentric with the first circle/arc.
Fix Constraint
The Fix constraint constrains the selected point on an object to
maintain its location.
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.
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.
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.
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.
Tangent Constraint
The Tangent constraint causes the second selected object to move
until it is tangent to the first selected object.
Smooth Constraint
The Smooth constraint forces a spline to maintain geometric
continuity with another spline, line, arc, or polyline.
Symmetric Constraint
The Symmetric constraint causes selected objects to become
symmetrically constrained about a selected line. For lines, the line’s
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).
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).
Deleting Constraint
To delete a constraint, move the cursor over a constraint icon and
choose Delete from the shortcut menu.
AutoConstrain
Choosing AUTOCONSTRAIN lets you apply geometric constraints to
a selection set of objects based on orientation of the objects relative to
each other.
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.