Datasheet

UnDerstanDIng ParametrIc DesIgn
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Dr i v i n g Di m e n s i o n s
The workflow in Inventor sketching is substantially different from that of traditional AutoCAD,
even beyond dimensions. In Inventor, you create sketches in 2D and then add geometric con-
straints such as horizontal, vertical, parallel, and so on to further define the sketch entities. Adding
the geometric constraints allows line work to adjust in a predictable and desired manner and helps
control the overall shape of the sketch. Once geometric constraints are in place, you add paramet-
ric driving dimensions to the sketch geometry. By changing the value of the dimension, you change
or drive the size of the sketch object. As you can see, the Inventor dimension is far more powerful
than the standard AutoCAD dimension because it not only conveys the value of a feature or part
but also serves as a design parameter, allowing you to change the dimension to update the design.
Figure 1.6 shows dimensions being edited in a sketch on the left and the result of changing three
of the dimensions on the right.
Part Modeling Best Practices
A solid sketch is the foundation on which stable parts are built. Many new users do not under-
stand the importance of having fully constrained sketches, and they find it highly frustrat-
ing to have a model fail when a simple change is made, all because a sketch was not properly
constructed.
Ke e p sK e t c h e s si m p l e
The most effective way to create a healthy sketch is to keep it simple. The purpose of keeping your
base sketch simple is to get it fully defined, leaving no part of it up for interpretation. Undefined,
sketch entities (lines without defined lengths, circles without defined diameters, and so on) will
most likely not update properly and will cause your sketches to distort and break when you try
to update them. And because you will base the rest of you model on the initial sketch, your entire
feature tree comes crumbling down, requiring you to have to stop and spend time rebuilding it
again. If the idea of simple sketches seems not to fit the type of design you do, understand that
most any design will benefit from the simple sketch philosophy. More important, if you start out
employing simple sketches, you will more quickly master the sketch tools and then be ready to
create more complex sketches when a design absolutely requires it.
cr e a t e si m p l e Fe a t u r e s F r o m si m p l e sK e t c h e s
Another aspect of creating simple sketches is that it allows you to create simple features.
Parametric feature-based modeling relies on the creation of numerous simpler features
Figure 1.6
Editing Inventor
sketch dimensions
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