Part Fabricated Using Resin Infusion
Fiberglass Resin Infusion
Most fiberglass parts are laid up using either a male or a female mold. The parts that are laid up in this manner have a side to them that is not as perfect as the side of the fiberglass that is against the mold during the molding process. This ‘imperfect side’ is the side where the rollers have ‘rolled’ the resin into the glass. For most parts, this method is perfectly acceptable as the resulting part has one finished side, and one ‘rough side’, at the lowest possible cost.
There is however, a class of parts that requires a ‘finish’ on both sides of the part: a part which has a uniform thickness, must conform to a specific drawing, and be consistent from part to part in production. These parts often need the strength and lightweight characteristics of fiberglass and cannot be made from either a plastic or steel. The process used to fabricate composite parts with these specific requirements is called “resin infusion” and these parts are fabricated using both a male and female mold.
Basically, the process works as follows: Cloth is laid up ‘dry’ on either the male or the female part of the mold. The mold is assembled, and any opening or joint is sealed using clay. Vacuum lines are attached to the highest point of the part (resin outflow), and a main line (resin inflow) is attached to the lowest point. The resin (mixed with catalyst) is placed in a container that is attached to the resin inflow line. A vacuum pump sucks the air out of the part at the outflow point, creating a low pressure area where the resin will be drawn towards. The resin, flowing into the mold because of the lower pressure, will flow through the cloth and towards the outflow line. Once the mold is full of resin, excess resin will flow into a resin trap to avoid resin being sucked into the vacuum pump. Once the resin has cured, the part is de-molded and trimmed. As a female/male mold was used, the resulting part thickness is uniform, and the finish is perfect on both sides of the part. Problem areas that often arise with resin infusion are incomplete areas where the resin did not flow properly, resulting in dry areas. It is also not possible to see where problem areas might arise during fabrication as the mold is closed. Furthermore, the catalyst used is often a catalyst that works at a slower rate, giving the process more time so as to avoid any dry areas.
Completed Resin Infused Part
Dry Lay-Up on Male Mold
