Datasheet

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CHAPTER 1 Inventor DesIgn PhIlosoPhy
shows every feature you create during the design of your part. Figure 1.5 shows the model
browser for the pivot link file.
You can see that each feature is listed in the browser in the order it was created, forming a
history tree. In order to create a part that handles changes predictably, you must create a solid
foundation on which to build the rest of the model. In most cases, when you are designing a part
model you will start off with a sketch, much like the one shown back in Figure 1.1. This base
sketch will be your foundation, and therefore you must create it to be as stable as possible.
Looking Closer at Sketch Dimensions
A large part of creating a stable sketch is understanding the way Inventor’s sketch dimensions
work. To do so you might compare Inventor dimensions with AutoCAD’s standard dimensions.
When you created a design in AutoCAD, that design process was not much different from cre-
ating the same design on a drawing board. But in AutoCAD you can draw precise lines, arcs,
circles, and other objects and place them precisely and with accurate dimensions reflecting your
design, in a way that you cannot do by hand. When a design requires modification, you erase,
move, copy, stretch, and otherwise manipulate the existing geometry more quickly than you
can by hand as well. But other than those gains in speed and accuracy, the workflow is much the
same as working on a drafting board. In short, AutoCAD automates drafting tasks but does less
to speed up and enhance the design process.
Dr i v e n Di m e n s i o n s
Standard dimensions in AutoCAD are called driven or reference dimensions. A driven dimen-
sion is controlled by the geometry, and it reflects the actual value of the geometry that is refer-
enced by the dimension. If you stretch a line, for example, the dimension attached to the line
will update to the new value. If you think about it, the only reason for a dimension on a typical
AutoCAD drawing is to convey the value of a feature or part to the person who is going to build
it. If you import that 2D file into a CAM package, no dimensions are needed because the line
work contains all the information about the part.
Parametric AutoCAD
Starting with AutoCAD 2010, you can create 2D parametric dimensions and constraints much
like Inventor.
Figure 1.5
The model browser
showing the fea-
ture tree (history)
of a part named
Pivot_Link.ipt
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