Open Mold Photo

Open Molding at MFG West

Open molding is the most commonly used molding process at MFG West and in our industry. Given the number of advantages over other processes, the reasons are clear:

  • Minimal tooling and mold costs
  • Easy mold modification
  • Design flexibility
  • Optimum for large production runs
  • Best range of large part sizes
  • Preferred for complex part
  • Mobile molding

MFG West uses open molding to produce a diverse range of products, such as:

  • Locomotive interiors
  • Military fuel cells
  • Hoods
  • Truck doors
  • Refrigerated railcar roofs
  • Rock guards for heavy trucks
  • Buildings
  • Tanks - water filteration systems
  • Troughs
  • Track pads
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How Open Molding Works

For larger parts, the simplest open molding process is hand lay-up. Using this process, precut fiber pieces are placed on the mold and resin is applied. Our team at MFG West then manually rolls all of the entrapped air out of fiberglass, leaving a finished, smooth part.

When producing more intricate parts, we use the spray-up or chopping process. The fiberglass chop and resin flow are pushed through the chopper unit and air pressure sends the resin mixture onto the mold through a spraying motion. As in hand lay-up, our MFG West team manually rolls out air bubbles to get the finished, smooth part.


At MFG West, open molding begins with a release agent which is spray coated on the mold to ensure that the part will discharge from the mold smoothly. The mold then is gel coated with a pigmented polymer to give the part the specified color finish. Next, fiberglass is added to the part, either by the hand lay-up or spray-up process. The required thickness of the part determines how many layers of the fiberglass material will be used. Once the fiberglass cures, another layer of gel coat is added, if needed, for the end product application of the part.

Our Other Molding Services
Lite Resin Transfer Molding

Lite Resin Transfer Molding, also known as Vacuum Assisted Resin Transfer Molding, is used for products that need to have two finished sides... Learn More »

Vacuum Infused Molding

Vacuum Infused Molding is a resin infusion method of molding high strength fiberglass parts like fiberglass roof supports or fiberglass ballistic panels. Learn More »