You’ve seen how the AutoConstrain and Infer Constraints features make it easy to add geometric constraints to your drawing. Although both are incredibly powerful features, sometimes you need an extra degree of control over how geometric constraints are added. For this reason, you have the option of manually adding geometric constraints to objects inside your drawing.
Even if you had been more deliberate in drawing the burners with the
proper alignment and size, the AutoConstrain feature would still have a difficult
time establishing how the four burners truly interact with one another.
Consequently, to ensure that the constraints are correctly applied, the best
approach in this case is to define the necessary geometric constraints manually.
To do so, you’ll use many of the individual constraint icons found on the
Parametric tab ➢ Geometric panel.
1. Make sure I05-14-StoveBurners.dwg (M05-14-StoveBurners.dwg)
2. Confirm that Object Snap and Object Snap Tracking are still enabled
on the status bar, and that Infer Geometric Constraints is enabled
within the Constraint Settings dialog box.
3. Click the Horizontal constraint tool from the Parametric tab ➢
4. From the Select an object or [2Points]: prompt, press the down
arrow to select 2Points, as shown in Figure 5.49.
F igu re 5 . 4 9 : Selecting the 2Points option when using Dynamic Input
5. Hover over the top-left burner, and select it when a small red circle
with an X appears in the center, as shown on the left in Figure 5.50.
F igu re 5 . 5 0 : Using the Horizontal constraint to select the center point of
6. From the Select second point: prompt, use the same method to
select the center point of the top-right burner, as shown on the right
in Figure 5.50.
The two right burners (as if you were working at the stove and facing
the rear deck) are now constrained horizontally; this means that,
although the two burners may be located anywhere along the y-axis,
they will always be aligned along the x-axis. You can try this out by
using the MOVE command to move either one of the burners. Notice
how the second burner also moves even though it was not selected.
7. Use the Horizontal constraint once again, repeating steps 5 and 6 to
constrain the two burners on the left side of the stove.
All of the burners are now constrained horizontally; however, there
is no relationship between the left and right burners. To fix this, you
will continue constraining the burners, this time applying Vertical
constraints between the right and left burners.
8. Click the Vertical constraint tool from the Parametric tab ➢
9. At the Select an object or [2Points]: prompt, click the down
arrow to select 2Points using Dynamic Input.
10. Use the Vertical 2Point constraint tool to select the center points of
the two front burners.
11. Repeat the Vertical constraint tool once again, this time selecting the
center points of the two rear burners.
Each of the burners is now fully constrained horizontally and
vertically. Notice how moving a single burner also moves the two
adjacent burners. Also note the Constraint icons under each of the
burners. Your stove should look like Figure 5.51.
Because three of the burners will be the same size, you can use the
Equal geometric constraint to build a relationship between the two
right burners and the back-left burner. It’s important to remember that
the focus here is to get the geometry correct. In the next exercise, you’ll
apply dimensional constraints to size each of the burners correctly
F igu re 5 . 5 1 : Burners fully constrained horizontally and vertically
12. Click the Equal constraint tool from the Parametric tab ➢ Geometric
13. Select the back-right burner and then the front-right burner to set
the radius of each equal to the back-right burner.
14. Repeat the process once again, this time selecting the back-right
burner and the back-left burner.
Your stove should look like Figure 5.52.
F igu re 5 . 5 2 : Stove with Equal constraints applied to three burners