Problem with a helical sweep (image provided)

Hello
I have been trying to model a funky part that basically looks like cylinder that has had a helical sweep cut along its length. The pitch
of the actual helix that defines the cut path actually varies every 1/4 of a revolution getting progressively smaller. The cut profile of the helical sweep cut is defined on a plane that is coincident with one end of the helix and parallel to the axis of the cylinder. The intent is to keep that orientation throughout the sweep.
Now the curious thing is that if I start the helical swept cut at one end of the cylinder and terminate it at some distance BEFORE the end of the cylinder, the face which is created at the termination is NOT parallel to the cylinder axis (as the original cut profile sketch was), but it is at some angle to it.
Look here:
http://members.iinet.net.au/~lt.bull/Helical_sweep.JPG
How can I ensure that the profile that sweeps and cut along the helical path stays paralel to the cylinder axis throughout the length of the helix? ie. the profile plane must always remain parallel to the cylinder axis.
Cheers
Bullman
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Hi
You get that effect because the top part of the cylinder is tapered.
steve

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Aparently not. Here is a screen shot , same helix but with cut termintating on straight cylinder section, same angled plane.
http://members.iinet.net.au/~lt.bull/Helical_sweep2.JPG
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Bullman,
Have you tried tuning on "align end faces" in the sweep options ???
Your part looks like a lead screw for the component strip reel cartridges on a surface mount machine.
Mark

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Yes I have tried that but still get the error. The error actually says "The sweep can not be completed becasue it intersected itself whiel passing through segment #1 of the path. This may have been caused by: (a) the path pasing too closely to itself:Check to make sure it does not pass too closely. (b) the way the section swists as it moves along the path: Check that the Orientation/Twist Control setting is correct. If the "Align to End Faces" box is checked, the end faces may be twisting the section too much relative to the path. Note: If the sweep path is not normal to the section, the entire path is consiodered to be #1."
I have given up on using a profile that is defined on a sketch that is parallel to the cyliner axis, though this is truly the design intent I want to maintain throughout the sweep cut.
I have instead now tried to achieve an approximate result by defining the cut profile on a plane that is NORMAL to the helix (as opposed to parallel to the cylinder axis). I project the sketch that I created on teh parallel plane onto this sketch that is on a plane normal to the helix as a start. I still had to manually tweak the dimensions of that profile sketch to get the right cut on the cylinder. But the important thing is that I can now have my variable pitched helical cut continue right along the length of the cylinder. It is important to note however that again true design intent is not completely maintained throughout the helical cut as the helix changes pitch (and hence the normal plane angle) and that affects the way the profile cuts the "valley".
Here are some comaprison shots- Using parallel plane to cylinder axis for profile (note SW wouldn't let me continue the cut any further than what is show):
http://members.iinet.net.au/~lt.bull/PARALLEL.JPG
Using the normal plane for profile:
http://members.iinet.net.au/~lt.bull/NORMAL.JPG
Superimposed:
http://members.iinet.net.au/~lt.bull/SUPERIMPOSED.JPG

Not sure of what you mean, but this screw sits horizontally along a production line/conveyor along which bottles are stacked up on. Bottles enter the screw at one end, and are pushed along as the screw rotates, unifromly spacing the bottles in the process as they exit the other end of the screw. Hence the design intent was to have the same shaped "valley" (when viewed perpendicular to the cylinder axis) along the entire length of the screw despite the change in pitch. My approximate solution will do, however still interesting to know if SW could somehow be used to cut a path along the entire length of the helix exactly as per my design intent.
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Just realised I didn't answer your question in the right context. The answer is yes I have tried that but still the terminating profile is at an angle. The answer I gave above however was in the context of what i believe to be the related problem (one that I hadn't mentioned but was ultimately trying to solve) which I believe comes about becasue of this progressive angling of the profile plane despite it starting off parallel to the cylinder axis:- and that is, for some reason, if I define a helix that would extend along the full length of the cylinder (ie. beyond the 2.6 revolutions shown in PARALEL.jpg), SW will return the error I mentioned above an, effectively preventing me from making a helical cut along the entire length of the cylinder.
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