unroll a tapered tube

[mcuser99]

I'm trying to unroll a tapered wireframe cylinder, but its not working, not creating the geometry i want. I tried different planes/axis/ etc. I can create a flat sheet and roll it, but the opposite does not work.

 

Basically its just this:

a 6" circle and a 5" circle 10" offset.

I broke the arcs, shortened the arcs a tiny bit, then drew two lines joining the 4 endpoints. Creating a "wrapped sheet". Why won't it unroll correctly?

[John Summers]

d1 6. # Diameter 1

d2 5. # Diameter 2

c1 18.849556 # Circumference 1

c2 15.707963 # Circumference 2

rcone 60.075 # Radius of cone (element of cone)

ccone 377.462357 # Circumference of cone

a 17.977528 # Angle of flattened cone

 

a/360 = c1/ccone This is the basic pro d1 6. # Diameter 1

d2 5. # Diameter 2

c1 18.849556 # Circumference 1

c2 15.707963 # Circumference 2

rcone 60.075 # Radius of cone (element of cone)

ccone 377.462357 # Circumference of cone

a 17.977528 # Angle of flattened cone

 

a/360 = c1/ccone

This is the basic proportion setup to calculate the flattened cone angle. I'll email the graphic file.

[mcuser99]

Hey thanks John, that solved the geometry.

 

However I'd still like to know how to correctly unroll wireframe geometry. If anyone knows the secret sauce, please post.

[John Summers]

You can use FlattenSurf.dll and Map.dll.

[mcuser99]

Haha, figured out how to properly use net surface on my wireframe.

 

Excellent, this flattened perfactly using FlattenSurf.dll. What is map.dll for?

[John Summers]

When you have contours (splines) that are on the surface but are not part of it, you can map them to the flattened surface, such as the edge of a windshield.