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Sketched spline

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Sketched spline

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.

33 REPLIES 33

Re: Sketched spline

For splines, there is position and angle but also the influence drag handle. You can mirror the position and make the angles the same, but making the influence drag handle symmetric is more difficult.

One way is to make half of your spline and then use copy > paste special on the sketch entity to create a dependant copy at 180 degrees. This has the advantage of leaving the spline drag handles "dragable" in your sketch.

Another way is to select your spline in the sketch, RMB and pick "modify" and on the spline dashboard pick the icon that shows the drag handle dimensioned. This requires you to fully dimension the spline, including the drag handles, however you can then make the drag handles equal and apply constraints like symmetric to the drag handle intersections.

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Doug Schaefer | Engineering Manager
Crow Works

Re: Sketched spline

I rarely use splines, so sorry I don't have an answer, but I was trying to learn more about them. I drew this using the polygon control, but it still doesn't look 100% correct as there is a drag handle slightly off center and I'm not sure why.

spline2.JPG

Re: Sketched spline

Looks like you're missing an on entity constraint in the upper right to the line indicated.Capture.JPG

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Doug Schaefer | Engineering Manager
Crow Works

Re: Sketched spline

I thought that, too. but even changing it to this. It's still not right.

spline3.JPG

Re: Sketched spline

It's not immediately obvious to me where the problem is. It looks OK to me, have you tried rotating a copy to check symmetry?

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Doug Schaefer | Engineering Manager
Crow Works

Re: Sketched spline

yes

spline4.JPG

Re: Sketched spline

This is even drawing another spline and using the control polygon to put it in the same place.

spline5.JPG

Re: Sketched spline

I'm stumped, I assumed that locking down the control polygon would define the spline explicitly.

No time to play with it right now, I may be able later.

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Doug Schaefer | Engineering Manager
Crow Works

Re: Sketched spline

Attached file if you want to look at it.

(Creo2)