Resin infusion processing offers several advantages over traditional open mold processing techniques. All of the reinforcements and core materials are placed in the mold without resin, so care can be taken for close fit and proper orientation. And it is a lot cleaner without the sticky resin. Resin waste is typically lower because all of the resin is added at once. VOC”s are reduced as well, and are only emitted from the
open mixing containers. There is much less worker interface with messy and stick resin on people and tools so cleanup materials and personal protection equipment expenses are reduced. The laminate itself is typically more consolidated, uniform, and visually pleasing.
One of the considerations that needs to be taken into account is that the ratios are different and the glass and resin are more compacted by the process. Using the same layup schedule would result in a thinner laminate that is lighter weight and uses less resin. One drawback to this is that the cross sectional area is less, usually resulting in a loss of stiffness. This can be regained by increasing the core thickness to compensate for that loss and to restore overall panel thickness.
Infusion processing does require specialized equipment, consumables, and materials. The resins need to have much lower viscosity(flow like water). The core and glass need to have holes and channels for the resin to flow. A bag needs to be created to cover and seal off the laminate to the mold with out ANY air leaks. The mold needs to be able to be sealed to the bag and be airtight. A high vacuum needs to be able to be drawn on the bagged mold to move the resin. The vacuum pump or venturi needs to be able to achieve a minimum of 28 inches of mercury.
The basic process is that the mold is gelcoated abd skinned with a good, low-shrink resin and chopped strand mat. Then layers of dry glass are added. Coring is placed nice and tight and glued if needed. And the final layers of glass are placed. During the process, any gaps in coring or glass will “bridge” where the vacuum doesnt pull them down, and solid resin will fill them. So good fit is very important. The the bag is placed and sealed after auxililary runner strips are added and resin feed hoses are placed. The perimeter vacuum channel is plumbed to the vacuum pump.
Air is removed from the laminate for a good amount of time before the resin lines are opened up and resin flows into the part (do not forget to catalyze it). This is part of the art of flowing resin to fill the whole laminate with resin before an area gets cutoff from the vacuum or the resin begins to harden. There are some tricks and practice is key.
Resin is stopped just before fill and hopefully resin doesnt run into the vacuum line too far, but that is what resin traps are for. The vacuum is left running as the part hardens and gets to full cure in a couple of hours.