The Vacuum Infusion Process is often abbreviated as VIP for short. VIP is a process that is used in the composite industry to manufacture fiber reinforced plastic parts ()FRP). The manufacturing process consists of disposable films being applied over the laminate.
During the process setup, the dry materials are taken and stacked onto the female or male mould surface and then a vacuum bag or partially-stiff counter mould is then used around the part’s edge for a complete seal. Next, a vacuum is introduced to remove the air and apply pressure (atmospheric) to compact the dry materials and create a necessary vacuum cavity where strategically placed resin feeding lines will drive the resin into the part. In order to completely saturate the part in resin, there is a pressure differential that exists between the outside atmospheric pressure and the cavity which allows for resin to be pushed through the porous materials in a vacuum infusion process. To guarantee consolidation, the vacuum remains until the part has cured.
Elements that Determine VIP Filling Time for a Part
Viscosity – Resin viscosity will determine the time it takes to saturate a part. Ideal resin viscosity is between 100 – 300cps, with larger viscosities resulting in longer saturation times.
Permeability – The permeability or porous characteristics of the reinforcement materials affect the flow of resin. The use of flow media is an integral part for proper and timely infusion. A grooved or scored core may also be used.
Pressure Differential – The greater the pressure difference, the quicker the resin will flow during VIP. Optimal pressure is below 0.15psi absolute pressure (full vacuum).
Distance – The flow distance is also an area that will affect the filling time. If the flow distance is larger than 1.5 yards, more feeding points should be introduced.
The vacuum infusion process is the leading industry technique for the production of composite parts. This method creates stronger and lighter parts and even reduces costs. Part quality and reproducibility becomes easier to maintain versus conventional methods. Quality inspections are easily accomplished with the ability for inspection before resin is driven into the part. The process also reduces skin contact and odors of volatile organic compounds and air pollutants to the air around you. Setup time is also significantly enhanced during vacuum infusion offering unlimited time for readjustments. Resin is not catalyzed in the part until all the necessary materials are in place, leading to fewer errors under time constraints.
VIP is also known for its low transition or startup costs and ease of learning the method. With VIP, you also have the ability to easily conform to simple, larger and complex shapes because of evenly applied pressure via the vacuum bag. Finally, the use of a vacuum produces a stronger laminate because of the removal of air and volatiles during the process.
Developments During the Last Decade
Over the last decade the vacuum infusion process has received advancements in the ability to introduce resin into the vacuum bag. Using well-made resin distribution manifold systems and essential flow media in the vacuum bag has offered better management of the influx of resin into the vacuum bag; improving the process and its results. Saturation has been optimized to be faster and is more efficient because of the use of flow media on the laminate surface and the use of inflow media into the laminate. The latest technology from Germany uses the semi-permeable MTI® hose to evacuation the mould which offers a competitive advantage compared to the traditional method.
In order to implement VIP, you’ll need a few pieces of equipment. This equipment includes: the vacuum pump, leak detector, thermometer, clamps, hoses, several resin collectors, vacuum gauges, and vacuum bagging supplies. The biggest cost in introducing VIP into a larger shop is the need for a superior fail-safe vacuum system which consists of two pumps, a filter, reservoir and vacuum lines which are permanent and run throughout the shop for easy hookup.
If you’re familiar with traditional open molds, VIP tooling is almost identical in many ways. The use of an ample perimeter flange is needed to mount the vacuum bag. Building tooling will require no unique expertise except for open mold fabrication. The largest cost that you will run into in converting to VIP is the mold modification, and changes to the shops layout in order to support VIP. The use of standard open molding tooling is also sufficient to use and VIP shops often use polyester gel coat and polyester laminate molds. Another alternative would be epoxy tooling. A vacuum source will be required in VIP and a large system may be required for higher outputs and processes.
The good news is that the learning curve for VIP is manageable with limited downtime during a conversion. Vacuum infusion process courses are typically one week in length however it may take up to four weeks for the average employee to achieve quality production skills attainment.