Sealing parts to hold water or some other liquid can sometimes be accomplished
using Insight to create water-tight surfaces on the part. This technique does not
work on every part geometry or for applications requiring high pressures; but, if
you have a relatively simple geometry, like a cup, and you would like it to hold
a liquid at atmospheric pressure, this method can seal parts without requiring a
secondary operation after the build.
It is recommended to build the part in an orientation that provides mostly vertical
walls (as opposed to horizontal surfaces and/or surfaces with a small angle of
incidence relative to horizontal). This is especially critical with curved surfaces like
those on a cylinder.
For more information, download the full best practices document here.