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Closed Molding

Closed Molding is a process that is useful for parts with complex geometries, strict cosmetic requirements, tight outside tolerances, or a combination of all three. However, parts that are too complex for this method must be separated into multiple tools to be later bonded together.


  • Unique Custom Internal Geometry  
  • High Flexibility
  • Allows Molding Parts with a Negative Draft 


  • Limited Material Selection

Variations of Closed Molding

  • Bladder Molding
  • Compression Molding
  • Press Molding
  • Modified Closed Mold

How Does Closed Molding Work?

We use sheets of pre-impregnated fibers called “pre-preg.”

  • The sheets are wrapped around an inflatable bladder and then placed inside a mold cavity 
  • Once the mold is closed, pressure is applied to the inside of the bladder causing the bladder to expand pushing the pre-preg outward against the inside of the mold cavity 
  • Heat is then applied to the mold to solidify or “cure” the composite in the shape of the inside of the mold cavity 
  • After curing, the solid composite form is extracted from the mandrel or tool. In the case of a tank or other closed end vessel, the mandrel could be left inside the composite form or dissolved out via various methods. 

Exceptions for Variations

Bladder Molding 

  • ??? 

Compression Molding

  • ??? 

Pressure Molding

  • ???

Modified Closed Mold

  • ???


  • 5 press molding????
  • pressure ranges from x to x
  • Sizes from ____ to ____ 

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© Rock West Composites, Inc. All Rights Reserved.

© Rock West Composites, Inc. All Rights Reserved.