Removing constraint from spline

[GrahameWard]

I have a sketch with 2 splines. Each is a simple 2 point spline with a 90 degree dimension at one endpoint and a tangency constraint at the other (constrained to a vertical reference). When I remove the constraint the spline stays put. Its geometry should change. The spline is still constrained at both endpoints, it's just lacking anything to drive its angle at the endpoint where I deleted the tangency constraint. If I sketched the spline from scratch with the exact same constraints and dimensions that I now have the spline would look different. Does anyone know how to get the spline to resume its proper shape based on its constraints? It's not parametric any more. See the pic below. The spline on the right is still constrained, the one on the left has had its tangency removed but hasn't changed.
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[DavidButz]

Grahame, Hmmm! Interesting. After duplicating your sketch on my own system, I'm not sure I understand fully what's happening in ProE's devious little mind, but I would first ask the following question: what do you expect to happen when you remove the constraint? If you expect the Spline to change from 90 degrees, do you expect it to get bigger or smaller? (Also, by the way, why did you constrain it tangent to vertical if you didn't want that?) In any case, what I found duplicated what you found, and I couldn't add a new controlling angle, until I slightly modified the Weak horizontal dimension. I may be wrong, but suspect that lacking other information, Sketcher makes a non visible default assumption about orthoganality. If, for some reason, you need the curve to start out tangent to vertical, try using a 90 degree angle dimension (which you can change) instead of the tangency constraint. David

[Kevin]

Check your config.pro setting for: sketcher_disp_weak_dimensions An angle dimension may be there but as a weak dimension. Couldn't tell if you're displaying weak dimensions or not. Looks like the ones in your picture are all strong ones.

[CBenner]

Almost looks like you still have a "Point on Entity" constraint at that end point.

[GrahameWard]

Why did I want to change it? Those curves bound a surface that was tangent to vertical sides originally, but the designer decided he wanted the button to look flatter. ProE is supposed allow you to modify the design. See my first "before and after" pic. Kevin, I already have weak dimensions displayed. There is no dimension at that end point. Chris, yes, I do have a "point on entity" constraint at the end of that spline. I have to locate the end point. The problem is not the constraint of the end point itself, but the constraint OR a dimension controlling the angle of the spline at the end. It is certainly possible to sketch a new spline with no constraint or dimension controlling the end point of the spline. See my second pic. This picture shows (on the left) what the spline should default to if I remove the tangency constraint. The one on the right shows it at 90 degress, which is the same as being tangent to a vertical reference. If I delete that 90 degree dimension the spline on the right should change its geometry so that it looks like the one on the left, but it doesn't.

[GrahameWard]

I meant to say, "It is certainly possible to sketch a new spline with no constraint or dimension controlling the angle of the end point of the spline." I want to emphasize the difference between constraining the end point and constraining the angle at the end point.

[DavidButz]

I understand now why you were forced to accept the original tangency; it was already there in a finished part needing redesign. I just duplicated the button using a Revolved feature to create the top dome portion. If I delete the tangency constraint in the spline sketch, I can then add an angle that allows me to control the shape. I'm puzzled, though, that you have two splines in your sketch; is this not a revolved feature? Have a feeling I'm still missing some part of your problem?

[DavidButz]

Also want to return to my original question concerning what you expect to happen. I don't agree that the system "should" return the shape to the "one on the left". The original shape of the 2-point spline, before putting the top central 90 degree dimension in place was a straight line. After adding the angle dimension the other end remains tangent to a line between the end points, but as soon as the tangency is added, any straight line reference between the end points disappears; there is no particular reason for the constrained end to move anywhere else once you remove the tangency constraint.

[GrahameWard]

"David Butz" wrote:

I understand now why you were forced to accept the original tangency; it was already there in a finished part needing redesign. I just duplicated the button using a Revolved feature to create the top dome portion. If I delete the tangency constraint in the spline sketch, I can then add an angle that allows me to control the shape. I'm puzzled, though, that you have two splines in your sketch; is this not a revolved feature? Have a feeling I'm still missing some part of your problem?

[GrahameWard]

"David Butz" wrote:

Also want to return to my original question concerning what you expect to happen. I don't agree that the system "should" return the shape to the "one on the left". The original shape of the 2-point spline, before putting the top central 90 degree dimension in place was a straight line. After adding the angle dimension the other end remains tangent to a line between the end points, but as soon as the tangency is added, any straight line reference between the end points disappears; there is no particular reason for the constrained end to move anywhere else once you remove the tangency constraint.

[GrahameWard]

So I guess this is one of those things where there's no answer. I wound up putting a 30 degree angle dimension on the end to hold the desired shape anyway - a no-angle end would have flattened it out too much.

[DavidButz]

Grahame, Don't want to beat a dead horse, but I think you answered your own question when you said "somehow "remembers"". It just doesn't. I totally agree with your logical mathematical evaluation of the situation; I think this is just one little place where the coded Sketcher logic loses track of a preceding constraint. (I figured you needed an angle anyway, since you really didn't want the shape of the "relaxed" end.) One final thought for completeness: if you want to recover the original shape you can put a centerline between the endpoints and drive the unconstrained end tangent to that centerline. You can even delete the centerline and tangency constraint afterward and it will look like it "originally" did. I certainly hope you don't think I have been trying to argue with you; I agree with your logic. Just trying to guess at what ProE is and is not doing in the situation. David

[DELETEME]

Grahame, Funny, but I wasn't able to get an angular dim on the top of the spline without ading a horizontal CL and makint it tangent to that and controlling the CL. But, anyways, I noticed what you said. If you start, say, the right spline, when you drag it up it allows you th option of making a tangent constraint. When you have the spline in there, and delete that tangent constraint, it remains tangent as David mentioned. At that point you can sketch a new spline and replace the old one (keeping your parent reference), or, what I did was put a centerline thru the bottom right point at an angle (say, 45deg CCW from vertical), and add a tangent constraint to that. That will snap it to the CL, and you can then add an anguler dim and tweak it any way you want. Is it just me, or has the boundary blend command sucked since they went to WF1? I get a ton of "curves do not form closed loop" errors. Seems to me the old surfacing in that regard was much better.

[ArisTroulis]

The sketcher treats the spline like a thin "wire" that you have originaly shaped with angular dimension or constrain and after you delete the constrain or the dimension it will stay the same. Unless you change it won't change. Be aware if it was constrained with tangency and you remove the tagency constrain the form of the spline will not change but if use the spline to create a boundary surface for example you will not be able to make the surfase tangent.