Hi FDP,
I have modified the method to achieve the helix's to loft.
In the youtube video the helix's where created by two radii and distance between them thus creating a conic helix. The method I have used produces a helix on the surface of the hour glass shape as shown in Photo. You will need to produce 2 Outer & 2 Inner hour glass shapes to create the Cam Roller Groove.
Cheers
Barry

Anti Backlash would seem to be of benefit.

It seems to me that the worm should be cut a little bit smaller than the space between two cams, and
then the left and right halves of the worm should be separated by (half) the space difference.
(Or equivalently, be cut with the separation initially.)

The center of the worm is not doing anything. Less than half of the worm is driving the cams at any time.
So performance is much reduced...

The geometry of the Double-Roller seems to not have these drawbacks...

- Brian