New Developments in the Manufacture of Invar Tooling for Composite Components

When designing tooling for autoclave curing of close tolerance composite components there is always the tradeoff between the cost and durability of the tooling. Composite tooling can be easily constructed but is not very durable, whereas metal tooling made from low expansion alloy - Invar - is extremely durable but more costly to fabricate. The expense of Invar tooling is greatly affected by the complexity of the part, particularly for large components, which may have to be fabricated from welded and machined assemblies. Recent developments in the casting industry have lead to significant improvements in the design and fabrication of Invar tooling. Simulation systems for mold design and pattern-less mold preparation technologies have greatly reduced the mold design time, enhanced first-time yield and design change flexibility. It is now possible to incorporate last minute design changes shortly before the casting is poured. Thus it is possible to produce a complex near net-shape thin walled casting with all of the stiffening features that would otherwise be welded, machined and heat treated fabricated assembly. The presentation will give examples of the size and complexity of aerospace grade Invar tooling that is being used for the production of composite helicopter and aircraft components.