You do want to have a little bit of draft to help the square tubing come out
of the die. Not much is needed but you do need some.
The other thing is that you want to polish the die so that the direction of
the scoring of the sides is in the radial direction so that the scoring
won't try to hold the tubing back from coming out of the slot.

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Why do penguins walk so far to get to their nesting grounds?