Trouble with spline offset and tangent constraint

[stefanvdree]

I'm running into an issue with a spline I have offset. The sketch in the picture below is 'holte' (it's Dutch btw) and I would like a tangent constraint between the arc and the spline but it won't let me do that. I think the issue is that you need a curve and a straight line and I'm trying to do it with 2 curves.

I'm not sure how to proceed here.

I thought maybe I could make a construction line that has the same angle as the spline at that particular location (and change angle when moved) and then have a tangent constraint between that line and the arcs but I don't know if that's possible.

[g-andresen]

Hi,

I would solve it with a spline.

Screencast

günther

[jeff_strater]

Fusion, today, does not support tangent constraints to a spline (an offset is a different kind of spline) except at its endpoints.  You might have to create some construction geometry to get the effect you are looking for, and even that is going to be approximate.

[stefanvdree]

I tried to fix it with a new spline that approximates the offset. Might have to figure out an approximate calculation based on the original spline handle dimensions.
But now, in order to fully constrain the sketch, hopefully, I'd like that point in the picture below to be a certain distance from the bottom, for instance, purple projection line, but I won't let me change that and give me a bunch of errors when I try.

[KristianLaholm]

I hope I understand your design intent, (which dimensions are vital?)
I'd use an intermediate surface body of offset spline that is trimmed (Extrude3) at the desired distance (50,00mm in Sketch Holte_1) from bottom of "hoef".

This gives the possibility to add a tangent constrain to the end point of projected edge.

If the distance is changed to much there will be a geometric conflict with the dimension fx: 40,00.

[g-andresen]

Hi,

When trying to control a fit point spline by dimensioning control points or tangents, it is important to know that no definition is isolated but changes the spline as a whole.
This is better done with control point splines.
But I can only advise against developing the ambition to define splines completely. Splines are tools that can be manipulated by moving them until they meet the needs of the viewer.

günther

[stefanvdree]

The most vital dimensions overall are the length and height and also the offset from the outer edge.

Your solution works well! However, the desired distance is closer to 30 (visually, so maybe 1/5th of the length which is 150 mm right now). It won't let me change that, though. Sketch 'Holte_2' turn yellow when I do.

[KristianLaholm · Accepted solution]

I missed some double projections in the sketches, I thought there was a geometric conflict my mistake.

Redraw the sketches and file works better now, have a look.

[stefanvdree]

Thank you so much! I probably wouldn't have thought of such a solution.