Why are standard drinking cups shaped the way the are, wider on the top and more narrow toward the bottom?

Question

Wouldn’t it make more sense to have the cup be a consistent width throughout? Or, even make the cup wider at the bottom to make it more stable when sitting on a surface?

In: Engineering

Answer 1

When molding plastic it helps to have a “draft” or an angle, so when you pull the 2 halves of the molding tool apart, they separate easily without rubbing on the part being made, like the Cup. It simplifies the tooling and reduces the amount of time per mold cycle by speeding up the release. It also helps with stackability of the items.