Method of making a dual durometer self-locking and sealing plug

A continuous method for making a self-locking and sealing plug for filling and sealing an opening in a panel comprising:

• (1) providing progressive injection molding means having a pair of injection units,
• (2) providing in the first of said units a molten thermoplastic resin-based polyolefin material having a durometer hardness reading at ambient temperature of about 60 to about 110 Rockwell R,
• (3) providing in the second of said units a molten thermoplastic electomeric material consisting of a blend of thermoplastic crystalline polyolefin resin and cured monoolefin copolymer rubber and having a durometer reading at ambient temperature of about 65 Shore A to about 50 Shore D,
• (4) providing first and second mold means having multi-cavities respectively and relatively movable between open positions and two alternate closed molding positions,
• (5) configuring said cavities of said first mold means and at least one of said cavities of said second mold means to cooperate and provide a first complete mold cavity when said mold means are at either of said closed molding positions to form an opening-filling portion of said plug upon injection of said molten thermoplastic material from said first injection unit into said first complete mold cavity,
• (6) configuring at least one other of said cavities of said second mold means to cooperate with said cavities of said first mold means and provide a second complete mold cavity shaped when said mold means are at either of said closed molding positions and a hardened opening-filling portion of said plug is within the cooperating cavity of said first mold means to form a sealing portion of said plug having portions in intimate contact with portions of said opening-filling portion upon injection of said molten thermoplastic material from said second injection unit into said second complete mold cavity,
• (7) heating said thermoplastic material in said first unit to a temperature within a range of about 380.degree. F. to 390.degree. F., and heating said thermoplastic material in said second unit to a temperature within a range of about 375.degree. F. to 390.degree. F.,
• (8) moving said mold means to one of said closed molding positions,
• (9) injecting thermoplastic material from said first unit into said first complete mold cavity to form an opening-filling portion,
• (10) cooling said first complete mold cavity,
• (11) moving said mold means to their open positions,
• (12) while retaining the opening-filling portion within the cavity of said first mold means, simultaneously moving said mold means and said opening-filling portion within the last named cavity to the other of said closed molding positions,
• (13) simultaneously injecting said heated thermoplastic materials from said first and second units into said first and second complete mold cavities respectively to form an opening-filling portion and a molded part in said first and second complete mold cavities respectively,
• (14) cooling said mold means to partially harden said thermoplastic materials therein and to cool said opening-filling portion in said first complete mold cavity to a temperature within a range of about 325.degree. F. to about 335.degree. F.;
• (15) moving said mold means to their open positions,
• (16) ejecting the partially hardened part formed in said second complete mold cavity,
• (17) while retaining the partially hardened opening-filling portion within the cavity of said first mold means that cooperated to form said opening-filling portion, simultaneously moving said mold means and said opening-filling portion at said cooled temperature within the last named cavity to the other of said closed molding positions,
• (18) repeating steps (13)-(17), thereby in accordance with injection of said molten materials into said first and second complete mold cavities per step 13, to units and bond said opening-filling portion with a sealing portion of said plug formed in said second complete mold cavity and simultaneously to form another opening-filling portion of said plug in said first complete mold cavity.