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NX Quick Tips: Control Model Parameters with Law Curve


Laws and Law Curve are two ways you can control model parameters in NX CAD.  Parameters of a model can be just about anything, but in today’s example we will focus exclusively on area.


For this NX Quick Tip, you will see some different laws, learn how to use the Law Curve function, and you will control the area of a swept surface using these various methods. Let’s get started!


You begin by editing your model. In our case, this is a simple cylinder created as a swept body.


Under Section Options there is a setting called Scaling Method, which determines the size and shape of the object. Constant is the default; the model retains the shape of the original arc. Area Law allows you to control the area by setting types of laws.


There are a few different law types you can use, each with a different result:

Area Law Constant.jpgArea Law Linear.jpgArea Law Cubic.jpg
                 Constant                                Linear                                   Cubic


Constant retains the area evenly across the model.
tapers in straight lines.

Cubic blends, so it is useful if you have to connect two parts of varying sizes.


You can also go on to more complicated options such as equations and law curves. In our case, we are going to use the Sine Curve to create a shape like a bellows. The Sine Curve determines parameters like height, length, increments (which is the distance between peaks in a cycle). All of these can be changed through Expressions.

 Law Curve Sine Curve.jpg

In Expressions, you can control the x, y, and z axis. In our case, z will remain at 0, because we are working with a 2D curve. You can use formulas to translate the x, y, and z values, thus exhibiting further control over the shape of the model.  There is a Parameter function t.


t = 0

xt = Increment*(Periods*t)

yt = 5+(Belows_Height*sin(Periods*360*t))

zt = 0


Play around with these and see how your model changes.


You can watch the video for further help.


(view in My Videos)


Note:    As many of you know, John Baker retired recently. Before that, however, we filmed a series of NX Quick Tips videos, so you’ll still be seeing him well into the next software release! Smiley Happy



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