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Two Shot Molding

IP.com Disclosure Number: IPCOM000088777D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 78K

Publishing Venue

IBM

Related People

Friery, EJ: AUTHOR [+2]

Abstract

A technique for two-shot molding of plastic parts has been developed. In a two-shot molding process, the first section of the part is molded, cooled, and removed from the mold. It is thereafter placed in a second mold where the second section is molded onto the first section, usually being of a different material than the first section. One of the problems encountered is the entrapment of air at interfaces between the two sections during the second molding operation which can reduce the effectiveness of the bond between the two sections. This technique eliminates air trapped between the sections during the second molding operation.

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Two Shot Molding

A technique for two-shot molding of plastic parts has been developed. In a two-shot molding process, the first section of the part is molded, cooled, and removed from the mold. It is thereafter placed in a second mold where the second section is molded onto the first section, usually being of a different material than the first section. One of the problems encountered is the entrapment of air at interfaces between the two sections during the second molding operation which can reduce the effectiveness of the bond between the two sections. This technique eliminates air trapped between the sections during the second molding operation.

A wheel molded by the two-shot process is shown in Fig. 1, having a hub section 10 and a rim section 12. The hub section, which may be made of glass- filled polycarbonate resin, is molded in a first operation in a first mold 14, as shown in Fig. 2, and is formed with a flange 16 having radially extending passages 18 therethrough. The hub section is cooled and removed from the mold and then placed in a second mold 20 (Fig. 3), wherein the rim section, which may be formed of polyurethane, is molded onto this hub section.

As can be seen in Fig. 3, the passages 18 allow any air trapped in the cavity during the molding of the rim portion to escape therethrough (as shown by the broken arrows), thereby preventing any air being trapped between the bonded interface 22 of the hub and rim sections, and allowing proper bonding bet...