Method of forming a container having a rolled rim

A method of forming a container having a rolled rim, comprising:

• providing a thermoformable sheet comprising a polymeric material;
• thermoforming the sheet to form a hollow body having an open first end and an opposite closed second end with a sidewall extending between the first end and the second end, and a strengthening rib on the sidewall, the strengthening rib disposed closer to the first end than the second end, the hollow body further having a rim structure formed at the first end of the hollow body, the rim structure including an inner wall portion extending upwardly from the sidewall, a flange extending outwardly from the inner wall portion, and a skirt extending downwardly from the flange;
• coining an upper section of the inner wall portion of the rim structure to form a controlled inside diameter to a depth “d” from a top surface of the flange along an inner diameter of the open first end of the hollow body;
• and
• rolling the rim structure to form a rigid rolled rim along an outer diameter of the open first end of the hollow body, wherein the skirt extends toward the sidewall after being rolled, the rolled rim and controlled inside diameter defining a lid-engaging surface;
• wherein the strengthening rib has a first concave portion extending radially outwardly from an interior of the container and a first convex portion extending radially inwardly toward the interior of the container;
• wherein the container has an overall height between the first end and the second end, and wherein the strengthening rib is disposed approximately between ½ and ¾ the overall height.