Geometric Constraints When making solid models, constraints are necessary to produce parts of exact shapes and sizes. To make a part parametric it is necessary to use as many geometric constraints as possible. The next set of slides will show what that geometry is.

Geometric Constraints Parallel - Lines that are equal distance from each other at each point along their length. These two lines are parallel. The lines are also representing the symbol for parallel. Perpendicular - Lines that are 90° from one another. These two lines are perpendicular and represent the symbol for perpendicular.

Geometric Constraints Horizontal - A line is horizontal when it is parallel to the horizon. In solid modeling, the line is also parallel in the horizontal projection plane and will appear true length. Vertical - A line is vertical when it is perpendicular to the horizon. This line will be parallel to the front and profile projection planes.

Geometric Constraints Tangent - A line or arc that has one point in common with an arc. If a line is tangent with a circle(Figure A), the line will be perpendicular with a line drawn from the point of tangency through the center point of the arc. If two arcs are tangent (Figure B), a line drawn between the centers will intersect at the point of tangency. Figure A Figure B

Geometric Constraints Concentric - Circles or arcs that share the same center point. These circles and the arcs share the same center point. Coincident - Points that share the same location on the coordinate plane. Points may also be parts of arcs or curves.

Geometric Constraints Collinear - Lines that if projected at each other will become the same line. Collinear lines Coplanar - Two or more objects that sit in the same plane. Fixed Point - A point that has been forced to stay in one location in space. Equal - Two or more lines, arcs, or circles that are given the same magnitude. Back to Contents