User Manual

UnDerstanDIng ParametrIc DesIgn

rectangles dimensioned at an angle deﬁnes the basic shape and is much easier to sketch and

fully constrain than the ﬁnished shape would be.

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 within

the model to achieve a complex design in the end. By creating a number of features within the

model, you are able to independently change or modify a feature without rebuilding the entire

model. An example of editing a feature would be changing a hole size. If you create a base

feature ﬁrst and then create a hole feature in that base feature, you can make changes to both

independently.

pa t t e r n a n D mi r r o r a t t h e Fe a t u r e le v e l

Although there are mirror and pattern (array) tools in the sketch environment, it is generally

best to create a single instance of the item in the sketch and then create a feature from it and

create a mirror or pattern feature from that feature. The logic behind this is based on the idea of

keeping sketches simple and the anticipation of future edits. Should the mirror or pattern fea-

ture need to be updated, it is much easier to update it as a separate feature.

cr e a t e sK e t c h -Ba s e D Fe a t u r e s a n D th e n pl a c e D Fe a t u r e s

Part features can be separated into two categories: sketch-based and placed. Sketch-based features,

as you might guess, are created from sketches. Placed features are features such as ﬁllets and

chamfers that are placed by using model edges or faces and have no underlying sketch. Issues

arise when placed features are created too early in the development of the part because you

may then be required to dimension to the placed feature, which creates a weak dependency.

For instance, you might place rounded ﬁllet features along the edges of a part and then use the

tangent ﬁllet edges to deﬁne the placement of a hole. But then if you realize that machining

capabilities require a beveled chamfer edge rather than a rounded ﬁlleted one and delete the ﬁl-

let feature, the hole feature is sure to fail because the tangent ﬁllet edges used to deﬁne the hole

placement no longer exist. Keep this in mind as you create placed features such as ﬁllets and

chamfers, and reserve placed features for the end stages of the part.

un D e r s t a n D De p e n D e n t a n D in D e p e n D e n t Fe a t u r e s

Parametric model features are typically either dependent or independent of one another. A

dependent feature is dependent on the existence or position of a previously created feature. If

that previously created feature is deleted, then the dependent feature will either be deleted also

or become an independent feature. As mentioned earlier, each part ﬁle contains default origin

geometry deﬁning the x-axis, y-axis and z-axis of the part. These origin features are used to

create the ﬁrst sketch in every part by default. An independent feature is normally based on an

origin feature or is referenced off the base feature.

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