Spline perpendicular to face or plane?

[Anonymous]

Suppose you need to do a crazy loft like this:

And you want to use a spline as a centerline (like above) or rail, you need the beginning and ending spline sections to be constrained or otherwise parametrically made to be perpendicular to face of the circle and polygon. By parametrically I mean if you reorient the circle or polygon the spline section stays perpendicular to it. How do you do that?

I think this question must have been asked before but I can't find any answer that applies.

[fritter63]

If I'm understanding you correctly, would it work if you put the circle/polygon sketch on a plane that was created with the "create plane along a path" tool? the keeps the

plan/sketch perpendicular like that, and then you'd just move the spline points to change the curve?

[rohit.bapat]

Hello @Anonymous

Thank you for posting your question.

Please correct me I am wrong. From the problem, I understand that you want the spline (guiding center line) to be perpendicular to the planes of the profiles viz circle and polygon.

I tried something at my end. Here's what I did to achieve this effect,

1) I created two construction lines through the centers of Polygon and Circle

2) Created the spline in the plane and set the tangent constraints between the spline and these construction line

3) Applied loft with this constrained (under constrained) spline as centerline

I have attached my file for demonstration.

Please let me know if I've missed something.

Thank you,

Best Regards

Rohit Bapat

[Anonymous]

@fritter63,The circle and polygon are created on planes created with the "plane along path" tool, but not with the spline as the path. The centers of those two shapes need to be a specific distance from each other and in a specific orientation relative to each other, and so I use a line (and some angled planes) to do that. As far as I can tell, you can't dimension a spline that way.

[Anonymous]

@rohit.bapat,

Thanks for the reply. What I'm missing is how the construction line is constrained to be perpendicular to, say, the circle.

If I create a circle on the XY plane at the origin and dimension it, it shows up black because it is fully constrained, like this.

If I then sketch a line along the Z axis and dimension it, the circle and the line turn blue (indicating not fully constrained?) like this:

It's probably very simple, but I'm confused. If I understood this then yes, I would draw the spline just as you show.

Thanks!

[rohit.bapat]

Hello @Anonymous

As per the requirements you mentioned, Sketch->Projection is the key (I implemented same in the file I previously attached 🙂 )

Steps are 

1. Create circle and End sketch

2. New sketch

3. Select plane perpendicular to the circle plane

4. Project circle on this plane

5. Draw a line with one point on projected circle centre

6. Constraint this line w.r.t. the projection of circle (because it has become a line after projection)

3D Line Perpendicular To Circle Plane

Please do let me know if it helps or if you have any questions.

Thank you,

Rohit Bapat

[Anonymous]

@rohit.bapat,

Thanks! That explains how to constrain the line perpendicular to the circle.

The one thing I still don't understand is how you drew the polygon at an arbitrary place and orientation in your first sketch. That sketch is on the XY plane but the polygon isn't. Also, the polygon isn't fully constrained in your sketch (it shows up blue).

[rohit.bapat · Accepted solution]

Hello @Anonymous

It is true that polygon in first sketch is on XY plane. I moved it using Move/Copy command.

But, in case you want to create a polygon which is fully constraint on an arbitrary plane I will recommend following steps

1. Create a plane (at an angle) where you want to create the polygon

2. Sketch the polygon

3. Create another plane perpendicular to the polygon plane

4. Create a perpendicular line

Create plane At AngleCreate Constrained polygon on new planeCreate a new perpendicular plane wrt the polygonCreate Perpendicular line

I hope this will be helpful. Please let me know if you have any questions.

Thank you,

Rohit Bapat

[Anonymous]

Thanks @rohit.bapat,

Actually, what I have to do is create the plane at an angle, then create a line at an angle on that plane, then create a new "plane along a path" using  that  line, then I would follow your steps.

I'll mark this answered.  Cheers!