The hand lay-up process is probably the oldest method of making molded fiberglass parts. This process is still being utilized today because on some parts, there is no other economical way to produce the part. Arrowhead has been involved in making molded fiberglass parts via the Hand Lay-Up method since 1972. The method of making fiberglass parts uses a single-sided mold where the fiber reinforcement, such as fiberglass, carbon fiber or Kevlar®, is manually placed in the mold. We then saturate the fiber reinforcement with a liquid thermoset polymer, most commonly polyester, vinyl ester, or epoxy resins. In the process of saturating the fiber, the laminate is manually formed into the shape of the mold surface using specialized laminating tools.
The term “hand lay-up” is derived from the method of manually placing the fiber reinforcement on the mold surface. The liquid resin can be applied either manually from a container, or by a spray gun (see “Spray Up” below) that dispenses the resin and curing agent mixture. The production personnel then “roll-out” the laminate to conform the materials into the mold contours, tightly consolidate the laminate, and produce the appropriate proportions of resin and fiber reinforcement. This combination of resin and glass can now be considered a laminate and once the materials fully cure, you will have a molded fiberglass part.
If a finished cosmetic surface is required, the first step in the process is to apply gel coat to the mold surface. We then build the fiberglass part up from the outside to the inside, beginning with the gel coat finish and then progressing through various layers of the structural fiberglass laminate. Depending on the requirements, many layers of fiberglass (or some other fiber) laminate can be built up to produce a specified thickness that meets the structural requirements of the application.
Hand lay-up, although one of the most basic composites/fiberglass molding processes (FRP), is widely used to produce a variety of transportation, marine, and commercial products. This process can be adapted to meet a broad range of production demands and products.