Vacuum Molding
Resin film processing includes forcing a liquid catalyzed, low-viscosity resin into a reinforced mold through low pressure. A flexible, airtight vacuum bag covers the mold and acts as a counter mold. Feed tubes placed parallel, perpendicular, in a herringbone pattern or an oblique pattern, depending on the shape of the object, distribute resin throughout the reinforcement as the vacuum is applied.
Advantages
- Closed molded for lower VOC emissions
- Moderate investment
- Large part capability
Disadvantages
- The process cannot be automated
- Preparation and positioning is time-intensive
- Risk of vacuum malfunction and sacrifice of part if system is not completely air tight
- Once the process is started, the flow cannot be modified
Production Equipment
Mold
- Usually made of resin
- High quality surface finish
- Includes an area for the resin-feed and vacuum tubes
Bag
- Single-use plastic film is used for unit molding
- Elastomer film with a seal is used for mass-production
Catchpot
- Prevents resin from being sucked out at the end of the cycle
Pressure-reducing valve
- Regulates vacuum pressure during infusion
Specific Aspects of Processing
- The mold is coated with a gelcoat layer
- Reinforcements and cores are placed
- The mold is covered with a flexible film
- Catalyzed resin is slowly injected
- Resin is sucked towards the vacuum pump and gradually fills the part
- As a function of part size, catalytic conditions and type of core, injection pressure needs to be regulated
- Resin is sucked out of an open container
- Resin is distributed throughout the mold through a resin distribution network placed on the surface before the vacuum is applied
- A grooved foam core performs the same function for sandwich materials
- A blast of compressed air between the mold and part removes the molded part from the mold
