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Closed Mold:
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Vacuum Infusion Process The vacuum infusion process is one of many closed mold processes. It distinguishes itself by being the only process that utilizes only atmospheric pressure to push the resin into the mold cavity. The mold cavity can be a one-sided mold with bagging film being utilized for the B-side, a two-sided mold, or even a soft envelope bag. The process is highly controllable, and is governed by the principles of D'Arcy's Law. This means that there are only three variables affecting the flow of the resin: (1) Permeability of the laminate, (2) Viscosity of the resin, and (3) Pressure differential in the cavity in relation to atmospheric pressure. If all three of these variables are unchanged, then the infusion process will consistently flow the same way with every injection for a given part. This also means you will enjoy an accurate bill of material for your parts since resin and fiberglass usage will remain consistent. The vacuum infusion process offers manufacturers all of the environmental advantages of a closed mold process, including reduced styrene emissions. It also provides an excellent glass-to-resin ratio with minimal-to-no voids in the finished laminate. This results in a strong composite laminate. The working environment for the vacuum infusion process is more comfortable than an open molding environment, and can result in a higher employee retention rate. Standard composite tooling can be utilized for vacuum infusion as long as it will hold a vacuum, and the flange is wide enough to seal the bag. This means that you may not have to invest as much in tooling as other closed mold processes. Utilizing core when infusing will bring a number of advantages over open molding. Most core failures in an open-molded composite structure with core material come from either "never-bonds" where the core is not bedded properly into the laminate, or when the kerfs are not fully filled. Unfilled kerfs create weaknesses in the laminate as well as allowing water to permeate through if exposed to the environment. Infusing a laminate with core material will eliminate both of these issues. When the core is grooved and perforated, it also gives a higher flow rate of the resin through the laminate by giving a better permeability.
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