Injection molding machine having a tie bar engagement apparatus and method of operating same

An injection molding machine, comprising:

• a) a base and an injection unit mounted to the base;
• b) a first platen for holding a first mold section and a second platen for holding a second mold section, the first and second platens supported by the base, at least one of the first and second platens coupled to a platen actuator for moving the at least one platen relative to the other along a machine axis between mold-open and mold-closed positions, the machine axis oriented horizontally and defining a longitudinal direction parallel to the machine axis;
• c) at least a first tie bar extending generally between the first and second platens for coupling together the first and second platens when in the mold-closed position, the first tie bar extending in the longitudinal direction along a first tie bar axis, the first tie bar having a fixed end secured to the second platen and a free end spaced longitudinally away from the fixed end, and the first tie bar having a first bearing surface extending longitudinally along an underside surface of the tie bar;
• and
• d) at least a first tie bar engagement apparatus associated with the first tie bar, the first tie bar engagement apparatus including:
• a first bore in the first platen for receiving the respective tie bar therethrough at least when the platens are in the mold-closed position;
• and
• a first roller mounted to the first platen proximate the first bore, the first roller comprising a first peripheral surface in rolling engagement with the first tie bar when the first tie bar is received in the first bore to support the first tie bar from beneath, the first roller rotatable about a first roller axis that is oriented horizontally and perpendicular to the machine axis, the first roller axis defining a lateral direction.