Spline Curvature Quality

[Justin_DeSilva]

I'd like to better manage the accuracy of spline curvature but am noticing a problem with my spline behavior. To diagnose the situation I've created a closed spline in the shape of a circle including these constraints:

1. Spline fit points are constrained left, bottom and right

2. Spline end point is constrained top

3. Spline handles are dimensioned equally and constrained vertically and horizontally

4. Spline fit method is Standard, and zero.

I can understand if the spline doesn't appear as a circle due to fit conditions 0-100, but if these constraints are active shouldn't the spline curvature be identical left, right, top and bottom?

[JDMather]

Your image doesn't show the Curvature radii.

[Justin_DeSilva]

Thanks JD. I'm creating an oblong shape whereas the shape needs to remain symmetrical. Does curvature radii refer to "display curvature"? Here's another screen capture of the circle and a screen capture of the oblong shape illustrating the non symmetrical placement of the control points.

[JDMather]

I wasn't referring to the Cuvature Comb display.

In addition to the Handles at each node there is also a curvature radius.

In any case, I woud avoid using splines if possible and use tangent arcs if they can be created within the realistic tolerances of your manufacturing process. (can't manufacture perfect geometry)

I would certainly use fewer points in the oblong if electing to go with the spline solution.

[Justin_DeSilva]

The curvature radius wasn't constrained, so I dimensioned the radius 50mm.

[Justin_DeSilva · Accepted solution]

I dicovered a unique strategy allowing the creation of closed uniform symmetrical spline shapes. When initially creating the oblong shape I used a continuos spline with no breaks, thinking this would result in a uniform symmetrical shape but it didn't. The continuous method works with applications like Rhinoceros but Inventor spline behaviour is different. When creating a closed uniform spline the spline must be divided into symmetrical segments. And depending on the number of reference points, the handles must be activated and aligned horizontal, vertical or per angle.

[JDMather]

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@Justin_DeSilva wrote:

.... the spline must be divided into symmetrical segments.

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Are you using the sketch Split command or mirror or symmetry constraints?

[Justin_DeSilva]

Neither, the spline command is activated multiple times using allready created reference geometry. However I'm learning that the number of reference points impacts the uniformity of the shape. The examples I'm experimenting with are using the spline fit method > standard, spline tension > 50. But now I'm experiencing multiple over-constrained errors and I'm having difficulty editing and re-creating the sketches. Here's an example of the variety of reference shapes.