**Activity 5.2a Geometric Constraints**

Introduction

A CAD model can quickly display an engineer’s ideas in a realistic way. And those models can be used to generate technical drawings that can communicate the information necessary to make the idea a reality. In order to generate a 3D model, designs must start with sketches that are generated within the CAD program. These computer generated sketches will appear resemble hand drawn sketches in geometry (the combination of points, lines, and shapes), but have big advantages over hand drawn sketches. One important difference between a freehand sketch and a CAD sketch is accuracy. The lines of a CAD sketch can be drawn perfectly straight, with start and end points that occur in exact locations in space. By using numeric (dimensional) constraints a line may also be given precise length, placed a specific distance from another sketch feature, or constrained to be oriented at a specific angle from another straight line. By applying geometric constraints a line can be made perfectly horizontal or vertical. If more than one line is being sketched, they can be made perfectly parallel or perpendicular, collinear, or equal in length. Lines can be constrained to be tangent to circles or arcs, and two circles can be constrained to be concentric. In order to precisely model a part, the designer must be able to use dimensional and geometric constraints within the CAD program.

You have already used linear dimensioning in earlier activities. In this activity, you will learn about geometric constraints that are common to most CAD programs and practice applying these constraints to CAD sketches.

A CAD model can quickly display an engineer’s ideas in a realistic way. And those models can be used to generate technical drawings that can communicate the information necessary to make the idea a reality. In order to generate a 3D model, designs must start with sketches that are generated within the CAD program. These computer generated sketches will appear resemble hand drawn sketches in geometry (the combination of points, lines, and shapes), but have big advantages over hand drawn sketches. One important difference between a freehand sketch and a CAD sketch is accuracy. The lines of a CAD sketch can be drawn perfectly straight, with start and end points that occur in exact locations in space. By using numeric (dimensional) constraints a line may also be given precise length, placed a specific distance from another sketch feature, or constrained to be oriented at a specific angle from another straight line. By applying geometric constraints a line can be made perfectly horizontal or vertical. If more than one line is being sketched, they can be made perfectly parallel or perpendicular, collinear, or equal in length. Lines can be constrained to be tangent to circles or arcs, and two circles can be constrained to be concentric. In order to precisely model a part, the designer must be able to use dimensional and geometric constraints within the CAD program.

You have already used linear dimensioning in earlier activities. In this activity, you will learn about geometric constraints that are common to most CAD programs and practice applying these constraints to CAD sketches.

**Conclusion**

1. What is a geometric constraint?

A geometric constraint is something that lets you do something to improve the design

2. What are the different types of geometric constraints that are applied to sketches, and what are their functions?

There are lots of constraints that are applied to sketches one would be paralele that makes bot lines parallel and another one that make the circles the same size

3. Define “tangent”.

Tangent is any arc or circle more like any round object

a. Sketch a line tangent to two circles.

^^^^^^^^^^^^^^

b. Sketch three circles such that all circles are tangent to the other two.

^^^^^^^^^^^^^

4. How is a geometric constraint different from a numeric constraint?

A geometric constraint is different from a numeric constraint because it doesn't deal with numbers but shapes