A mold unit in which a first mold that performs injection molding for molding an intermediate molding product molds a protrusion on an inner surface of a thick portion of the intermediate molding product, and when the intermediate molding product is fitted to a second mold in order to perform blow molding for molding a final molding product from the intermediate molding product, the second mold crushes the protrusion from an inside of the intermediate molding product.

Method for heating a preform (1) comprising: introducing the preform (1) into a heating apparatus (5) comprising an array of infrared emitters (50) arranged in multiple columns (Cj) and multiple rows (Ri), orienting angularly the preform at an input angular position by rotating the preform around the longitudinal axis; setting power levels of the infrared emitters (50) so as to divide the array of infrared emitters (50) into subsets of columns (SCn), each subset of columns (SCn) generating heat at a different power level from an adjacent subset of columns (SCn); and heating the preform (1) with the array of infrared emitters (50) while translating the preform (1) in a direction parallel to the rows (Ri) of the array at a translation speed, and simultaneously rotating said preform (1) around its longitudinal axis (A1) in front of said infrared emitters (50) at a rotation speed.

A method for heating a preform (1) comprising a body portion (4) extending along a longitudinal axis (A1). The method comprises the following steps: introducing the preform (1) into a heating apparatus (5) comprising an array of infrared emitters (50) arranged in multiple columns (Cj) and rows (Ri); setting power levels of the infrared emitters (50) so as to divide said array into subsets of columns (SCn); andheating the preform while translating it in a direction parallel to the rows (Ri), and simultaneously rotating it around its longitudinal axis, the rotation and translation speeds, and the power levels of the infrared emitters (50) being set so that the power levels of the subsets of columns (SCn) facing zones (42) of the body portion extending longitudinally are different from the power levels of the subsets of columns facing the rest of the body portion, said zones extending relative to one another in a polygonal array.