projecting curves

I am trying to project a helix onto the face of a cylinder. I have done it
before but I forgot how.

Bob

 

We have to ask why?

TOP

 

To model threads on a wood screw.

Bob

 

I got it to work but the results are quite ugly. the sweep cut or bossbass
on a projected helix is quite ugly. It has to be done with helixes made from
circles to look decent.

Bob

 

If you project a helix onto the surface of a cylinder then it is no
longer a helix but just a projection. As such there is some approximation
going on because of that process. That approximation may make the result
somewhat jagged.

If you are making a thread on a wood screw a cylindrical helix or even a
tapered helix may not work. In that case you may need to make a curve by
defining points and using them to define your curve.

TOP

 

If you want to add a thread to a non-cylindrical face, try it this
way:

1. Make a helix that is larger than the largest diameter of your shank
2. Make a surface sweep of a straight line from your helix, such that
the straight line points straight toward the center of the shank. The
end result looks like an auger.
3. Use the intersection of the auger surface and the shank as a guide
for your thread section sweep.

When you make your thread section, be sure the section has positive
penetration into the shank surface. If you go line-to-line, there may
be zero-thickness issues when generating your thread.

I used a similar method for creating a barrel-shaped spring. See
spring model in "hinge.zip" at http://www.esoxrepublic.com/models/

 

I used 3 merge helixes for the path. I had to make two one for each cutter
shape.

Bob

 

Is it possible to force a sweep with a self intersecting profile? I think
Inventor will do it with a warning.

Bob

 

You might have problems with the kernel ... ?
You'd get, among other things, degenerate geometry I suspect.