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Gasket Corner & Joint Designs

There are many options to produce reliable corners and joints in seals and gaskets. 
 

MOLDED CORNERS
 

Vulcanized or transfer molded corners provide a superior solution to butt joints in critical sealing applications.  The transfer molding process involves connecting two or more rubber extrusions using a moldable material from a like compound. This ensures material compatibility and avoids concerns about the breakdown of a joint over time.

Compared to butt joints and adhesives, transfer molding produces a bond with greater integrity and better appearance. Cooper Standard ISG can use this technique to create simple corners or complex frames made up of multiple dissimilar profiles.  

As an added benefit, installing a gasket as a single component not only reduces the potential for leaks, it can improve the efficiency of the assembly process.

 

SPLICING
 

When designing a spliced seal, key considerations include the physical integrity of the joint and actual sealing properties (i.e. leak resistance or load compression), cosmetics (how the seal will be fixed or attached to a substrate) and the overall cost.

There are several typical ways to splice rubber gaskets:
 

  • Hot Splicing is considered the industry standard and is the most desirable regarding cosmetics. Hot splicing uses a rubber-based adhesive (excluding products made from silicone). The splice must be cured, or vulcanized, in place. The resulting splice retains many of the properties of the original seal while maintaining its aesthetic appearance. 
     
  • Cold Splicing is simply a matter of adhering two or more pieces of a seal together using quick-setting glue, such as a cyano-acrylate. There are few, if any, tooling costs included with this technique, but the splice may become brittle and sometimes proves to be less effective than other options.
     
  • Transfer Splicing works in much the same way as transfer molding. A mold is created so that two or more pieces of a seal can be inserted into the tooling. A polymer is transferred into the mold cavity, adhering the ends of the seal and creating a continuous o-ring or multi-sided gasket. The process allows for enhanced detail work on the seal and produces a splice that is very aesthetically pleasing. 
     
  • Film Welding uses a plastic film as media to bond EPDM materials. It is typically used for parts with pre-applied adhesive or that have complex cross-sections. The benefit to this method is that it has no adverse effects on the adhesive performance at or around the joint.
     
  • Heat Welding (Plastics) uses applied pressure and heat to create a bond between thermoplastics. This process provides better strength for plastic materials than mechanical connections (such as snap fits and screws) or adhesives.