Vacuum Infusion Process
The vacuum infusion process, or VIP for short is a composite process that offers the ability to create superior products out of fiber-reinforced plastics which are light in weight yet extremely strong. Vacuum resin infusion uses a differential pressure between a closed mould system and the atmospheric pressure as the main process parameter and driving force to literally suck the resin into the laminate. This process results in less wasted resources and since epoxy allergy is still one of the evident dangers, minimal exposure to this material is desirable. In addition to that, the ratio between fiber to resin is significantly enhanced resulting in additional competitive advantages that aren’t available in the traditional hand lay-up technique for example.
The process starts with the dry reinforcement materials being placed on the mould’s surface. Specific types of flow media are then used to facilitate the resin flow. Tubing is inserted and a vacuum bag on top of the laminate is sealed on the moulds perimeter – creating a closed mould system. Then a vacuum pump is used to drive the resin into the cavity and across the laminate part under the lower than atmospheric pressure conditions. During this step the laminate is compacted, pushing the resin into the porous material until it is completely saturated.
With the ability to drive the resin into the part during the process, a better distribution and yield ratio of fiber to resin is possible. Excess resin results in products that weigh more and are brittle, drawbacks which are eliminated with the vacuum infusion process. In an industry and consumer market where lighter and stronger is better, VIP is a proven and effective advantage in composite production leading to many enhancements over traditional methods.
Vacuum Infusion Process (VIP) Benefits
There are several benefits to VIP over other traditional methods, some of which have already been mentioned above. Below is a tentative list of benefits as to why you should be using vacuum resin infusion rather than open mold techniques.
- Low initial investment to get started
- Stronger products because of better consolidation ratios and better bonding
- Reduced production costs (less wasted resin and errors)
- Lighter products (reduced resin and calculated thickness)
- Consistency (product quality can be controlled with greater certainty of perfection)
- Environmentally friendly (reduced VOCs and HAPs, and better worker conditions as well)
- Large projects (VIP aids the easy production of large structures – boat hulls and more)
- No rushing for time constraints
- Thickness control
In making the decision to switch to VIP there will be some slight downtime in order to allow for the transition to vacuum infusion, but that is quickly recouped with the benefits of the process over other techniques in the long-run. Most individuals are able to quickly learn the process as well (we also offer on-site training courses), making the conversion an even more attractive option for composite production. With the ability to reduce skin contact and odors, you’ll also increase the safety of your processes by exposing virtually no resin to the air around you. Resin is cured into the part, reducing fumes of volatile organic compounds and air pollutants. This can result in greater employee morale and better overall company recognition and image for supporting environmental preservation efforts.
Pinholes, Dry Spots, Resin Trap and Vacuum Infusion
Despite the great advantages of VIP in comparison to wet lay-up or wet lay-up and vacuum bagging there are still some wasteful areas caused by the standard VIP process materials (consumables) available on the market so far. By using a spiral wrap as the evacuation line, you run the risk of getting dry spots. When resin reaches the spiral wrap (the standard VIP evacuation line) it can easily escape the mould cavity since there is no barrier preventing that. Since the calculation of the resin flow path varies, and is dependent on certain parameters, the risk of producing dry areas which are not saturated by resin is evident and post treatment increases with more complex designed moulds.
Furthermore, the permanent existing vacuum sucks/drives the resin out of the laminate into the bleeder fabric and/or resin trap resulting in voids in the surface caused by pinholes (tiny holes on the surface which are hard to fix and require post treatment, resulting in additional labor costs). This is particularly evident with cosmetic carbon fiber parts. These parts are just covered with a clear coat and pinholes affect their processing costs tremendously.
Also, to protect the vacuum pump from resin being sucked out of the mould system, the standard VIP has to apply a resin catch pot or resin trap. Above all, the permanent existing vacuum in the system is the driving force for potential embedded air bubbles to grow to their maximum size which could cause voids in the laminate. To overcome these process uncertainties within the standard vacuum infusion process and its counterpart of costly autoclave technology, the MTI hose was developed by German engineers. The functionality of Membrane Tube Infusion (MTI®) is based on a micro-porous membrane hose which offers permeability to gas yet is impenetrable to resin. An integrated spiral hose will also ensure smooth handling and an effective airflow channel for the greatest evacuation performance even under the most extreme and adverse conditions.
The aid of MTI® in the vacuum infusion process ensures that exact calculations of resin usage on a consistent basis can be accomplished; also eliminating a resin trap completely – no matter where the resin feed line is placed. This can offer a serious competitive advantage, reducing production costs and streamlining the vacuum infusion process. The semi-permeable MTI® hose evacuates the mould offering one-shot technology. Since resin cannot escape the mould cavity, no pinholes arise and the risk of getting dry spots is tremendously reduced through MTI®‘s self-regulating pressure reduction. When the MTI® hose is completely covered with resin it shuts the door to the vacuum pump which in turn leads to the collapse of potentially embedded air bubbles. If you’re already using a vacuum infusion process, you can easily implement the MTI® hose by replacing the existing spiral hose that is present.
Recent developments in VIP technology have made it the leading choice in part production. Resin distribution is significantly enhanced and the use of flow media in the vacuum bag offers superior transport qualities. Touting faster processes and increased efficiency in saturation, vacuum resin infusion is leading the industry in terms of cutting-edge part production, quality and cost savings. The vacuum infusion process also allows for (versus traditional methods) the ability to make adjustments by stopping the vacuum and then restarting before the process has begun so you don’t have to race against initial setting times as outlined in the benefits section above.