Layup / Molding

Whether it’s an open or closed mold, resin-infused or wrapped around a mandrel, we offer almost all manufacturing methods so we can find the optimal process for your project. Our multiple locations have centers of excellence for each process to maximize expertise in each area.

We specialize in transforming fibers (carbon, aramid, glass, flax) and resin into your finished composite parts. These are the manufacturing methods we use most often, along with some of the key benefits of each alternative.

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Open Mold/Prepreg

Open mold is the most common form of layup used. Prepreg is fabric that has been infused with resin and is in a stable state, often refrigerated to keep further curing from occurring. This fabric is layered into the mold and through vacuum bagging the layers are pressed to remove air pockets. We can use laser-assisted ply placement for critical components.

PROS

  • Less labor than wet layup since resin is already present
  • Tight control of resin content since already prepreg has a controlled amount 
  • No size limitations – can create very large parts with complex geometries

CONS

  • Material costs – prepreg is more expensive 
  • Only one fully controlled surface – not a feasible option where both sides need precision
  • Higher tooling costs

Closed Mold

Closed molds are two-piece tools or more, usually made of metal, that close around the composite material and conform it to the shape. The composite part is then cured and, when finished, removed from the tool. Other types of closed mold include bladder molding, compression molding, press molding, and modified closed mold.

PROS

  • Highest level of precision, offering exact specifications on both sides of the composite part, often used for Aerospace and Space applications
  • Tools last through many cycles making this the ideal solution for large part runs and ongoing production
  • Faster manufacturing of each part using less labor

CONS

  • Very expensive with long lead times for tool making
  • Generally limited in size based upon the curing method chosen

Resin Infusion

Resin Infusion is a composite manufacturing method that works very well for small to large flat plates as well as very large composite parts. Resin Transfer Molding (RTM) and Vacuum-Assisted Resin Transfer Molding (VARTM) combine the concept of resin infusion with either an open or closed mold. These methods are cost effective compared to operating an autoclave.

PROS

  • Can be lower cost due to materials, room temperature cure, and reduced labor
  • No size limitations – can create very large parts with complex geometries
  • Great for rapid prototyping

CONS

  • Slightly higher resin content than prepreg 
  • Only one fully controlled surface – not a feasible option where both sides need precision

Filament Winding

We use filament winding to produce medium to large diameter (1-to-24-inch diameter) in lengths from 10 – 20 feet. It is also the most automated process for producing tubing and tanks and is therefore best suited for higher quantity production runs. Filament winding can also produce composite tubes with very thick walls. Variations include wet winding, towpreg winding and tape winding. Towpreg and tape winding use prepreg materials, allowing the part to have more controlled resin content.

PROS

  • Highly automated, making it excellent for high quantity production
  • Good for longer length tubes of medium to large diameter
  • Can be tuned for specific properties

CONS

  • Expensive for short production runs
  • Not suited to small diameter parts

Roll Wrapping

Roll Wrapping is used to produce small to medium diameter composite tubes (0.250-to-12-inch diameter) in lengths up to 8 feet. It is also typically the most economical process for smaller quantity production runs. The key to roll wrapping is the mandrel, or cylindrical tube, which is the mold in this process. Rock West has thousands of mandrels in-house that can produce tubes of a wide variety of dimensions and profiles.

PROS

  • Cost effective for small quantity production
  • Ability to layer different materials within the same part, including cosmetic exteriors
  • Works well for small and medium diameter tubes

CONS

  • Labor intensive process
  • Limits in tube length and thickness

Open Mold/Wet Layup

Often referred to as hand lay up, in the open mold manufacturing method dry fabric is positioned / layered into a mold and resin is applied to it. Technicians work to ensure the resin is uniformly spread and remove air pockets, often through vacuum bagging.

PROS

  • Lowest cost with a very short lead time for tooling
  • No size limitations – can create very large parts with complex geometries

CONS

  • Labor intensive – fine for single parts or small runs but not efficient for long runs or ongoing production
  • Only one fully controlled surface – not a feasible option where both sides need precision
  • Higher resin content in the components