Failure ==> Success

Several weeks ago I saw this posting

http://www.grasshopper3d.com/forum/topics/continuous-variable-pipe-...

and thought the geometry shown there would make an interesting 3D print. Thanks to the work of GH master Hyungsoo Kim I was able to download his GH file and get a rough idea of how the geometry is generated. The part in the downloaded file looked too tall and thin for 3D printing, so I played with the various parameters in the GH file to try to get something more suitable/printable, but I didn't have much success.

After realizing I just did not understand what Hyungsoo's GH layout was doing I decided to remake it, keeping the key components but removing parts that didn't seem necessary for my purpose and also replacing the front-end with simpler GH components that I have used before. After doing this I came up with my first result that looked like it would print OK.

It didn't. What happened was the print failed almost immediately because the contact areas between the part and the print bed were far too small, and the part didn't stick to the bed. So I fixed that and tried again. The second attempt failed too, because the thickness of the part's geometry was too thin. I fixed that and got what I thought would be my first printable part. But after a few hours of printing this was my result:

What happened was the inner twisted areas of the part were not rigid enough to stay still when the printer started adding the next layer, so the area being printed either twisted or broke off. Fortunately the printer was not printing over night/unattended, so I was able to stop the print without too much waste.

I realized the fix for this was simple to do - I just needed to make a reverse-twist and combine the two. This would make a very strong structure like ones I have made before:

http://www.thingiverse.com/thing:995750

But how to make the reverse twist? I tried all sorts of ways to get the twist to reverse, but nothing worked. Clearly this was because I did not (and still do not) understand how the twist function in Hyungsoo's layout (the Bounds, ReMap, Seam components) works. What I finally discovered is that simply adding the Reverse option to the Seam function's t parameter did in fact result in a reverse twist. (I'd really like to know why/how this works.)

So with this update I was able to make this geometry:

and the final printed part looks like this:

I agree that the part would probably look nicer if it had only a single twist, but such a part can't be printed (by me at least.) I'll probably do more attempts at making the part look lighter and airy-er. If anyone wants to print this part the STL file is here:

http://www.thingiverse.com/thing:1862263

https://pinshape.com/items/27992-3d-printed-lumen2