Combine line and spline

[c.d.pass]

Looking to confirm that a line and spline can not be joined and used as a guide rail with loft command. Task was to loft shape between three profiles. Spline A went from profile 2 and 3. Line A profile went from profile 1 and 2. After selecting all profiles and rails I get loft error for rail doesn't intersect profile occurs. Lofting is successful when spline A or line A is a single element going from profile 1 to profile 2 to profile 3. Unless one of my points are not touching a profile it means there needs to be a continuous line/spline.

[g-andresen]

Hi,

A statement about this requires an analysis of the file.

Please share the file.

File > export > save as f3d on local drive  > attach it to the next post.

günther

[TrippyLighting · Accepted solution]

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@c.d.pass wrote:

Looking to confirm that a line and spline can not be joined and used as a guide rail with loft command. 

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That cannot be confirmed. The end points of the spline and the line need to be"

1. connected AND

2. be tangent OR 

3. Curvature continuous.

Then that construct can be used as a loft rail.

[jeff_strater · Accepted solution]

There are two different things here:

1. You can use a line and a spline together as a rail, but they must be tangent at their shared endpoint.  Applying a tangent constraint will be sufficient.
2. You say that the error you get is around the rail not intersecting the profile.  This is independent of the rail continuity condition.  You must make sure that the rail intersects each profile's curve precisely.  Usually, this is done using the "Intersect" command in the sketch environment.  If you have the profiles first, and are adding rails, then, while in the rail sketch, use Intersect, selecting the profile curve.  This will create a point in your rail sketch.  Make sure you snap to this point while creating the rail curves.

[davebYYPCU · Accepted solution]

Turbine blades don’t have sharp points on the leading edges.

That pic shows other trouble to address,

line A is actually 2 lines, one black, one blue, that are not tangent connected.  Both are touching one profile.  Insert a fillet.

Line B, expect self intersection around the point second from the top, that weird bend in 2d, jumps out at me, I could be wrong, but not surprised.

Loft tool should show large red dots or big yellow patches, where your geometry is in error.

Might help.....

[c.d.pass]

Instead of replying to each person individual I am replying to all in this message.

After no success with the line and spline method I created one spline thru all three profiles and this worked. I didn't have the model with error to attach. Still posed the question to the forum to learn if Fusion didn't allow for joining a line and spline to be used as a rail. From the replies it sounds as if Fusion does allow joining under the right circumstances. In my sketch it is most likely that the two didn't make a rail due to lack of tangency. 

Thanks to all, I now have a better understanding of the requirements.