What are bumps?
Looks like they might be inserts that can be used to quickly change the thread, or replace the high-wear section of mold. I'm not sure why they are proud of the parting line?
at 8:05 in the video, they show the inserts being pulled out probably just for visual effect to show all the parts of the mold.
(the video is a cool shootout to compare several CAD systems)
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