Advise on resolving cyclic dependency (constrained cone cut)

[Anonymous]

Hi everyone,

I'm stuck on a problem involving cyclic dependencies (at least I think that this is the core problem here).

Consider the attached part (Inventor 2019 Professional). I started by drawing a right triangle with the hypotenuse being parallel to the x-axis.

This triangle is then revolved about the lower side to a cone.

In a new sketch in the xz-plane I then projected the cut edges of the cone with the xz-plane. I now would like the width of the resulting hyperparabola along the z-axis to be a certain width (i.e. I want the driven constraint to be non-driven). How would I go about achieving this?

Thanks,

Max

[WHolzwarth]

Perhaps you're in search of this - perhaps not

2019 file attached

[Lewis.Young]

Hi Max,

By nature, projected edges aren't able to be modified, as they're technically reference geometry that references a parent.

In this case, the way to control the hyperbola would be to; change the distance between the triangles hypotenuse and the x-z plane or increase the width of the cone itself. If you wanted to get a specific width you'd have to determine a mathematical relationship between the dimensions.

That being said, if your aim is to create a hyperbola curve then this thread may be more useful: https://forums.autodesk.com/t5/inventor-forum/how-to-create-a-hyperbola-curve-using-equation-curve-a...

Lewis Young
Windows 7 x64 - 32GB Ram
Intel Xeon E5-1620 v2 @ 3.70GHz
nVidia Quadro M2000 - 4GB
Inventor Professional 2017.3
Vault Basic 2017
3ds Max 2018

[Anonymous]

Hi Walter,

I'd switch to german but being considerate of the other forum users, I won't 😉

I'm neither sure of whether what you did is what I need and I just don't see how nor am I sure what you are doing at all. I think what you are doing is to create a plane on the level where the chord has the desired length, but I'd rather that the cone is positioned such that the chord on the xz plane has the desired length. Nice idea nevertheless, so thanks!

[Anonymous]

Hi Lewis,

the "height" i.e. the distance of the hypotenuse to the xz plane is in the end what I wish to determine given the width of the resulting parabola at the xz crossection (along z) and I was hoping inventor could help me out with that. I want to use the upper half of the cut in the end, so just creating the parabola by formula is not serving my purpose, thanks for pointing that out however.

[Lewis.Young]

Oh right i see, bit trickier than i first thought!

If you created the hyperbola sketch on a new user workplane parallel to the x-z, you could then control the height offset of the plane by double clicking on it, and adjusting the height until the hyperbola is at the desired width (see attached part).

Again, because the hyperbola is only reference geometry, i'm not sure how you'd automatically get the plane offset at the right distance to create the desired width. If a method comes to mind i'll be sure to let you know!

Lewis Young
Windows 7 x64 - 32GB Ram
Intel Xeon E5-1620 v2 @ 3.70GHz
nVidia Quadro M2000 - 4GB
Inventor Professional 2017.3
Vault Basic 2017
3ds Max 2018

[johnsonshiue]

Hi! There are a few ways to do this. My solution is the same as Walter's (see attached part). To approach this issue, you have to think about what constitute the parabola. It is the XZ plane and the tilted cone. To alter the parabola, either the cone has to move or the XZ  plane has to move. You can move the cone up or down using Move Bodies command. But, the movement does not translate to the parabola width. XZ plane is grounded and it cannot be moved.

The solution is to create a sketch at the bottom of the cone and create a horizontal line connecting to the circular edge. The length of this line equals to the parabola width. Then create a parallel workplane to XZ passing the horizontal line. Next, create a sketch on the parallel plane and project cut edges. Now you can drive the horizontal line up and down and the projected sketch will update accordingly. Does it make sense?

Many thanks!

[Anonymous]

I see. I could use the newly created plane (parallel to XZ) as my ny XZ base plane, as I cannot ensure that that plane is on the same height as the XZ, correct?