Additive manufacturing can take the place of molding in many applications. For example, in a government-funded project, composite developer IDEC set about exploring the capabilities of Resin Transfer Molding (RTM) technology. The government-funded project centered around the testing of a new composite material and its molding process for the manufacture of a curved aircraft wing.
The challenge in producing the aircraft wing centered around the preform tool. Designed to facilitate the composite lay-up process into the mold at a later stage and accelerate the curing process, preform tools are typically made of aluminum or epoxy resin. The composite fiber is laid up on top of the preform and the tool is subsequently heated to take the shape of the mold.
The challenge here was that instead of heating the preform tool, the unusual application required the composite material itself to be heated using an electric current sent through the composite fiber. Consequently, highly conductive metals like aluminum were inappropriate and would prevent the current from effectively going through the fabric.
According to Diego Calderón, Structural Analysis Manager at IDEC, standard epoxy materials available inside the company were neither resistant nor stable enough to withstand temperatures exceeding 140°C.
“This project required high temperatures of between 150°C and 180°C to heat the fabrics directly. Although there are epoxy resins resistant to such high temperatures, these are very expensive, and would not have been financially viable,” he explains. Thus, the company chose to use ULTEM 1010 and a Stratasys F900 Production System. The material’s chemical and heat-resistance enabled it to withstand the required temperatures exceeding 150° C, as well as high pressures.
IDEC and its prototyping service provider, Wehl & Partner, developed the mold.
“Stratasys additive manufacturing enabled us to produce the preform tool in just 60 hours,” said Calderón. “With CNC machining, it would have taken at least four weeks to produce this type of part. Indeed, not only did we slash the production lead-time on the preform tool, but we also expedited the whole composite molding process.
“In fact, with ULTEM 1010 resin, we reduced the composite heating stage from one hour to ten minutes by flowing the electrical current directly through composite fabrics. This would simply not have been possible without Stratasys FDM additive manufacturing,” continues Calderón.
For IDEC, its use of ULTEM 1010 resin resulted in a preform tool with perfect mechanical properties that has enabled the company to use it as part of the RTM process. According to Calderón, the preform is so solid that the team can use it for at least 25 cycles, something not possible with epoxy or other additive manufacturing technologies and similar materials. In addition, the team saved up to 67% of the costs of CNC machining using aluminum.