Rounded Tip on a Lofted Surface / Loft Where Sketches Share an Endpoin

[seurban]

This is an issue I've run into before and managed a work around, but I don't think it'll work this time and I'd like to find a real solution. After creating a lofted surface (or perhaps a boundary surface), basically a tube that might have a weird path or cross-section, what's the best way to put a rounded tip on the end?

A year or so ago I ran into this and tried to use a boundary surface, cutting the profile into two halves (it was symmetric) plus an intermediate section for the first curve direction, then using the curved perimeter as the other direction. Basically, it was like a revolve that morphed along its revolution. This worked ok, except showing curvature revealed some nasty things radiating the center of the “revolution” which would probably show up on this glossy part [see first row of pics in attachment].

The best I could figure out was to do a boundary surface around the perimeter, then use a filled surface to fill it in. It still wasn’t perfect, but we were cutting a hole in this part and I was able to localize the nasty curvature to the location that was being cut out (quite convenient, cutting out the parts that don’t work well is an excellent technique ) [see second row of pics in attachment]

Now I’m faced with a similar problem, only it’s a little more complicated. First, I don’t get to cut out the parts I don’t like. Second the loft is tapering as it travels in a helical path. So my tip needs to follow this helical path. First attempt (using the first technique mentioned, only without the middle section and with loft): surface quality disaster (see below). [see third row of pics in attachment]

So I tried to isolate this whole tip thing. I created the basic profile, cut in halves, made a rounded path, and lofted with perfect results. [see fourth row of pics in attachment]

Then I tried getting closer to reality and put the rounded path on a curved surface (similar to how it will be in the helix) and was back to nasty curvature radiating from the center. Using a loft or boundary surface seems like the best way to control what I want, but it seems like having the profiles share endpoints only works in perfect situations. [see fifth row of pics in attachment]

So does anyone have any ideas on how to solve this, and similar problems?

 

[SBaugh]

Looking at hte images is hard for me to tell what your doing... but it seems simple enough to just use another loft and a guild curve or 2. I made this simple example... may not be exactly what your doing but I think it gives a good idea. You might be better off attaching your file.

Regards,

Scott Baugh, CSWP

http://www.scottjbaugh.com

"If it's not broke, Don't fix it!"

faq731-376

 

[seurban]

Thanks Scott, adding the extra curve in the middle helped to ease the surface irregularity in the center, giving me a very nice, but very isolated tip (test-tip 3 attached). That's how I tried the example from a year ago, but the middle curve is going to be a pain to make, but it seems pretty vital. However, when I tried to connect this tip to a curving, tapering loft (or more accurately, add it to the end) the surface irregularity where all the curves meet in the center came back. It wasn't as bad using a loft (test-tip 4 attached) as it was with a boundary surface (test-tip 4b attached - looks obviously puckered even without curvature on), but with a loft I couldn't get the tip surface tangent with the existent loft, much less curvature continuous.

 

[rstupplebeen]

I am not currently on a computer with the appropriate version of SW however I am going to suggest what I hate most. Make a band-aide of the problematic areas.

Rob Stupplebeen

 

[ChrisDuncan]

I think you want a swept boss. The profile being your edge on the end of the existing surfaces, a straight line up the center for the path, and the guide curves (2 going to the top point) being the profile of what your trying to build

make sure the profile sketch is a child of the guide curve sketches.