Method for injection molding a large thickness flange at end of blow molding tube

A method for injection molding a large thickness flange at an end of a plurality of blow molded tubes, comprising the steps of:

• (a) providing the plurality of blow molded tubes, each of said tubes having been blow molded;
• (b) correcting the inner and outer surfaces at one end of each of said blow molded tubes;
• (c) inserting a mandrel from an injection molding die assembly into the corrected end of each of said blow molded tubes;
• (d) injecting a molten resin material into a cavity within the injection molding die assembly, said cavity being located between the outer surface of each said blow molded tube and an inner surface of the die assembly surrounding each said tube, and forming a single large thickness flange which is thermally bonded onto each said corrected end of the blow molded tubes and onto the plurality of tubes so as to couple together the plurality of blow molded tubes wherein said correcting step results in close contact between the injection die assembly and the corrected end of each of said blow molded tubes and thereby prevents leakage of said molten resin during injection;
• and
• (e) separating the resulting molded tube and flange product from the injection molding die assembly.