Inventor^® Training

Control inventor Splines with Spline Commands - Page 2

By David Melvin, PE, TEDCF Publishing

The handle can be used to change and constrain the shape of the curve near the spline point. You can change the angle of the handle by dragging one of the grips, and if you do, be sure to add an angular dimension to control the angle. To keep the spline symmetrical, add a Horizontal constraint to it.

The length of the handle defines the relative length of the curve that is tangent to the handlebar. For this example, when you add a dimension to the length of the handle, the distance is .476. This is a unitless value that describes how closely the spline hugs the handle.

Increasing this value increases the length of the tangent portion of the spline making the spline appear to hug the handlebar closer.

You can also define the radius of the spline near the spline point by changing the bowtie to a handle and curve. To do this, right click on the spline point and select Curvature.

With this option you can control the radius of the tangent portion of the spline. The radial dimension in the following example is .467 inches. So this dimension uses standard units.

The last option consists of a handle and flat curve. Before you evoke this command, delete the radial dimension. Once you’ve done that, right click on the spline point and select Flat.

If you try to add a dimension to the flat curve you’ll find that you can only add a radial dimension.

That’s because the Flat option essentially sets the radius of the curve approximately to infinity. In this case, it has the same effect as setting the radius of the Curvature option to 393.701. You can change this value back to .467 to have the same result as using the Curvature option. When you select the Flat option the Curvature option is automatically deselected. Likewise, when you select the Curvature option the Flat option is deselected.

Why is this important?
While splines are more difficult to define the exact size and shape than lines and arcs, knowing these commands give you more control over them. This will ultimately help you take more control over your solid models.