Vacuum Infusion Molding (VIP)
Vacuum Infusion Processing (VIP), RTM Light (LRTM, Resin Infusion, VARTM, SCRIMP)
VIP and RTM Light are vacuum-assisted, closed-mold resin processes. For compression on the B-side surface, VIP uses a flexible sheet or re-usable bag, and RTM Light employs a lightweight counter tool. This process yields increased laminate compression, a higher glass-to-resin ratio, and excellent strength-to-weight characteristics.
With these processes the reinforcements are placed in the mold dry, frequently combined with cores or other special inserts. Vacuum is then applied to compact the reinforcement and eliminate air. Resin is introduced and the vacuum draws it through the reinforcement.
Very large parts can be made by VIP method utilizing very low viscosity resin and an appropriate fill time with bleeder film and other venting. This resin infusion process results in very low void content and excellent mechanical properties due to the relatively high glass content. Fiber content is determined by fiber architecture and pressure.
In contrast, the RTM Light process resin is introduced via a pumping mechanism under 2psi. More flexibility in types of resins and fillers is possible, and an intermediate range of fiber contents. Benefits are better cosmetic finishes and variation in part thickness, and faster cycle times for lower cost. Tools can be aluminum, steel or composite.
- Recommended for products with high strength-to-weight requirements, or with slight design returns, edge overhangs, or high draft angles that would cause die-locks on rigid B-side mold surfaces
- Best suited for mid-volume production in the range of 200 to 5,000 parts per year*
- Environmentally-friendly – this closed mold process involves no resin exposure
- Pre-placed of reinforcement can be employed to achieve optimum strength-weight ratios
- In-mold gel coat finishes can be employed for desired cosmetic finishes
* Volume recommendations are averages and provided only as a general guideline. Actual volume efficiencies are a more complex matter requiring detailed statistics about the part to be manufactured.
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Snapshot Guide: Shapes, Uses and Considerations
VIP: High glass content, one good side, very large or small parts.
RTM-lite: Mid-volume, two good sides, 2-side gel coat, sizes up to 150 sq ft.