Coincident connections between splines that are normal to each other.

[Anonymous]

I'm trying to build a lofted surface by using 3 longitudinal splines as rails, and a series of splines Drawn on planes normal to the rails as profiles. Drawing the profiles has been a challenge, because Fusion 360 does not allow drawing points by intersecting a spline with a plane, so there's nothing to attach the end of the spline to. After several aborted attempts, I built surfaces from the linear spline and trimmed them to form a solid body, then built sketch entities by intersecting the normal planes with the body, and built points where the longitudinal plane intersected these entities. I then was able to build the splines on the normal planes and use the points as the ends of the profile splines. It all worked great, except that when I build the lofted surface, it tells me that the profiles are not coincident with the rails, which seems impossible. Is there some way to let the profiles know that they are actually on the rails? I'm baffled, and if I can't solve this I guess I'll have to resort to trying to make a free form body fit my sketches, but I'd like to avoid it. 

[jeff_strater]

You should be able to do this.  Use Plane Along Path to define the normal planes for the profiles, sketch on those planes, and use Project -> Intersect to create the intersection point of the rail curve with the profile.  I'll try to throw together a quick screencast to illustrate the main idea.

Jeff

[jeff_strater]

Here is a quick screencast showing how I'd do this for one rail curve:

Jeff

[Anonymous]

I'm afraid this isn't going to work for me. I've attached the pencil drawing I used for the canvases (drawn from an actual object that I want to reproduce), and as you can see, the sections need to be normal to the center line, and in order to build a lofted surface, they need to connect with the top, bottom and center splines. I've built sketch entities in the right places by intersecting offset planes with a square section body (constructed from the "rail" splines), then made points by intersecting these entities with the planes of the linear splines, but when I draw the sections, they don't know that they are in the same location as the rail splines. So far, I haven't thought of a workaround.

[davebYYPCU]

Loft Command is just plain finicky.

Your original statement, unable to draw points from rails is not correct.  But there is only one way to get it right.  Project Commands.

My workflow for same type model, 

Either draw all rails, or all profiles first, as you have both, your choice.  I do the rails first, I found splines to work best as rails.  

Rails that would connect to a common point should be in separate sketches.

For each profile, create the sketchplane and sketch, then use Project > Intersect and project each rail into that sketch.  

Very important - hide all the rails now, and that sketch should have a purple point visible for each rail.  Snap the profile to those points, if you don't follow this, Fusion will inevitably snap the profile to somewhere close but not exact.

Repeat for each profile, or same technique, from profiles to rails, connect to purple dots that are in clean space in the viewport.

Might help...

[Anonymous]

Thanks for the great help. Since the profiles are normal to the plane of the Top rail, I was unable to project the rail onto that end, so I built a square section body from the rails, intersected it with the profile planes, intersected the vertical entity with the plane of the center rail, then drew the profiles using the points of intersection. It worked very well, and I needed the square section body anyway for blank development.
Thanks again for the great advice.

[davebYYPCU · Accepted solution]

I wasn't able to figure what you were saying,

Since the profiles are normal to the plane of the Top rail, (usually but don't have to be)

I was unable to project the rail onto that end  ??????

I have thrown together an exam[le of my methods,

Read the timeline one step at a time, use visibility light bulbs,

Did the patch loft (for thickening), then closed the profiles for the solid.

You can add a base solid or mirror from the Origin Plane from here on....

[Anonymous]

Thanks Dave, I finally get it. It finally dawned on me after stepping through your model numerous times that I could switch functions in the midst of a sketch. This is a very elegant solution. Nice model, too...and instructive in other ways. Thanks again for your help.

[davebYYPCU]

Thanks for the update,

Happy to help if / where I can....