The Vacuum Infusion Process, or VIP, 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, due to it being 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 equates to a very accurate bill of material for a given part since the resin and fiberglass usage will not change.
VIP brings all of the environmental advantages of a closed mold process, where styrene emissions are minimized due to the resin curing in a closed environment. It also provides an excellent glass-to-resin ratio with minimal to no voids in the finished laminate. This allows for one of the strongest ways of building a composite laminate. The working environment for VIP is far superior to any open molding environment and usually results in a higher employee retention rate.
Standard composite tooling can be utilized for VIP as long as it will hold a vacuum and the flange is wide enough to seal the bag. This means that you don’t have to invest as much in tooling as other closed mold processes.
The two main drawbacks of VIP when compared to other closed mold processes are slower cycle times and higher consumable costs.
Benefits of VIP vs. Open Molding
|► Drastically reduced styrene emissions|
|► Stronger composite laminates|
|► Repeatability and consistency between parts (weight and dimensional properties)|
|► Superior application of core materials|
|► Accurate bill of materials|
|► Lower tooling costs than other closed mold processes|