How can I convert this https://www.thingiverse.com/thing:4258694 to Rhino while reducing the file size (MeshToNURB currently bigger than 50MB), and how do I model the bottle vessel neck that it connects to?
screwcap.stl (1.4 MB)
lets talk a bit about what your trying to accomplish-
if you are going to end up back at a 3d print, there is no need to convert it. you simply need to use it as a reference for the other parts you are going to build, then export them all as stl to your printer.
if you need to create stuff that fits to this, then you have a reverse engineering job that may include projecting and rebuilding curves, and some remodeling.
you can do a quick and dirty reverse engineering job by quadremeshing this part, then convert to subd, then convert to nurbs ,but the accuracy will be a bit squishy.
I find it’s often easier to find a bottle and cap model that is already built to screw together then simply cut off and remodel the bottle itself, then merge the new bottle and the old neck together using mesh booleans or shrinkwrap.
How to create the bottle neck that fit the cap?
The shapes are simple, so I’d ToNurbs it, put a plane through it and get the intersection with the cap to give a cross-section, then use that as a guide to draw a low-density nurbs model. Result is 590 KB and accurate.
For the neck, an internet search will reveal lots of images. Here’s one example which is comprehensively dimensioned: Round bottle - order online at TheJarfactory.com 100 ml PEHD - - The Jarfactory