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# Curve curvature continuity

Pioneer

Hi all,

If draw a curve, hit the tangent button, I can choose this curve, then a line to make them tagent.

If I choose tangent + curvature continuity, I can still choose the curve, but the line can't be choosen. There is no geometrical reason why a curve could not end with zero curvature.

There should be a solution to this problem : it is to constrain the last two [edit : three] control points of the curve onto the line prolongation but in this case, in order that the curve and the line don't overlap I need to use another sketch.

Is there a simpler way of addressing this problem in ST6 or ST7 ?

TIA

7 REPLIES 7

# Re: Curve curvature continuity

Retired

I'm not sure if there's a more orthodox way, but one thing I would consider would be to eliminate the line altogether, if you can. If you constrain the last few control points of the spline to be colinear, you'll have a spline approximation of a line, and you don't have to worry about the c2 condition. Eliminating the line reduces some of the complexity of the finished part, depending on what you're doing.

Another thing you can do is to eliminate the spline and just make a Bluesurf with a c2 connection between two other entities. 3D thinking vs 2D thinking.

Or even make a sharp corner and put a c2 round over it.

If you need c2, there's a way to get it.

Retired Community Manager for Solid Edge. This account is no longer active.

# Re: Curve curvature continuity

Pioneer

Matt,

Thanks for your suggestions. I will try them.

I have just started to work with SE. At this stage, I find it far less intuitive to use than SW, though I was a complete beginner with CAD when I first used it.

As the underlying math (and moreover, the kernel) is the same, I can agree to the idea that finally it won't make any difference in the end but SE learning curve is to me far steeper.

# Re: Curve curvature continuity

Retired

Well, it depends on what you're doing. If you're doing synchronous and machine design, I think you'd find SE a lot more powerful. Surfacing in SW was a series of workarounds. Very little difference in that regard, probably. Edge definitely has a different workflow. Once you get used to that, you'll feel more at home.

Retired Community Manager for Solid Edge. This account is no longer active.

# Re: Curve curvature continuity

Community Manager

@ABM -- what kind of products do you design? What brings you to SE from SW? What's the use case you have where you want curvature continuity with a line?

Dan Staples
Director, Solid Edge Product Development

# Re: Curve curvature continuity

Pioneer

I don't design parts yet, I am learning with SE academics.

More precisely, I am in an agricultural school. In my previous school I had basic  exposure to CAD for practical purposes and liked it. Now there is no CAD in the school I am in so I switched to SE because of the avaibility of SE academics.

# Re: Curve curvature continuity

PLM World Member Legend
The only way I know how to do this is to use the 'Convert to Curve' command on the line element but you then would have to constrain the end points and breakthrough point to lie on a line or otherwise constrain it to remain straight.
What you then have is a straight line but it can be used in a Tangent with Curvature relation.
With regard to SW, I learned SE first and find SW very counter-intuitive. I also think that it much less robust when it comes to surfacing but that's just IMO.
Also, Parasolid has many options on how you can implement B-Splines so there's no guarantee that SE and SW will ultimately behave the same way because of programming/command preferences.
It would be nice to be able attach a curve to a line with a Tangent with Curvature constraint however and this should be possible (I think).

Frank
Edinburgh University

# Re: Curve curvature continuity

Pioneer

Frank,

I tried Matt's first solution (drop the line) and it works well but is a little time consuming. I will try your way too.Thanks for the tip.