Sketched spline

[GrahameWard]

Can anyone explain to me what information I am leaving off this sketch?

The spline sketched below should be symmetrical, or more accurately, the ends should be as though they are rotated 180 degrees around the center, but they’re not. The little inset in the bottom right shows what it looks like when I mirror the sketch left/right then top/bottom. It should lie on top of the original but it doesn’t. The dimensions should make the thing symmetrical but don't.

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[Peter1]

I have voted for this!

We have an issue with splines where we use 2 splines with control polygons, one at each end of the part. Sometimes the splines are different shapes, but sometimes they are the same. If we dimension both splines with the same values, and then you do a mirror or output to Autocad and mirror you will see clearly they are not exactly the same geometry. PTC says there is just a lot of math behind the spline function....and the user can't control all of it. For us, the only work around is to sketch 1 spline and then mirror, but that messes up the model when you want different geometries....fun!

[TomD.inPDX]

I find splines to be very unreliable and extremely limited in sketches or as datum curves.

The fact that there is indeed a lot of math behind the spline, the control of that math should be put in the hands of the users. The current offerings are simply antiquated. Here is hoping Creo 3.0 will address this with some significant improvements.

The findings revealed in this discussion should be helpful if you have the patience to implement them and teach users the implications of those control points (nodes on the spline).

[GrahameWard]

This is totally bizarre. When I do this sketch again I cannot reproduce the same problem. It's now perfectly rotationally symmetrical like I want.

[TomD.inPDX]

Pro|Bizarre is absolutely free of charge and included in every PTC product