SAMPE Journal - July/August 2011 - 41

Figure 7. Nevada Composite tooling progression 30cm x 20cm x 10cm (12in x 8in x 4in). ing and creating the needed molds to produce very complex mandrels. Stratasys used existing CAD data to create optimized FDM molds that were used by Nevada Composites to produce multi-part soluble mandrels for composite lay-up. Tool Design Digital master for hatch repair: The depot used reverse engineering data to capture the profile of a damaged part. CAD was used to eliminate the damaged area and create a new digital master for the repair part. Stratasys then used the CAD data to create an optimized master model to support the Nevada Composites tool-forming process. Figure 7 shows the tooling for a subscale portion of the structural-reinforcement hat-stiffener. From left to right tool progression starting with the Stratasys FDM master, followed by the Nevada Composites single-sided tool created from the FDM master, and lastly the resulting repair part cured on the single-sided tool. Molds for soluble mandrels for ducting: The existing CAD manufacturing data for the duct geometry was used to create a series of optimized molds to form Nevada Composites’ mandrel material into the desired shapes. Because of the complex duct geometry, the fabricator planned to manufacture the ducting in three sections, adhesively joining it together into a single duct after composite cure. Thus, each completed duct involved the use of three separate washout mandrels. For Nevada Composites to create these, two-part FDM molds were required for each of the three mandrels in each set. Figure 8 shows the set of three FDM molds and the resulting Nevada Composites mandrels used to create each completed duct. Note that in this design the FDM mold and the washout mandrels also provided for runout and trim areas to facilitate composite fabrication. Processing Conditions Nevada Composites’ tooling material is formed under rough vacuum pressures at ambient temperatures and is removed from the master model or mold before it is hardened at elevated temperature. In both of the applications reported here the FDM material, ABSM30, was strong enough to support the vacuum loads, handling loads and the lightweight Nevada Composites tooling material with significant margins. This allowed the FDM molds to be fabricated with a “sparse-fill” interior, reducing material consumption, cost, and build time. The “sparse-fill” is a build style that is unique to the FDM process. It enables the system to build an internal lattice like structure, rather than requiring the part to be a fully dense plastic interior. This reduces material usage and can be tailored to provide the required strength of
SAMPE Journal, Volume 47, No. 4, July/August 2011

the part. In addition, the sparse interior of the FDM molds allowed the vacuum to penetrate the mold easily, meaning that in producing Nevada Composites’ tooling, vacuum pressures were readily realized on all surfaces of the mold. This facilitated Nevada Composites’ vacuum-forming process and significantly reduced the potential of producing localized voids inside or on the surface of the mandrels. Design Value For tooling used to repair hatches on military aircraft, the ability to use a reverse-engineered FDM master model made it possible to produce Nevada Composites’ tooling rapidly and at significantly reduced cost compared to alternative methods. The repair process thus benefits from both rapid turn-around and a very significant reduction in cost over current alternatives, which typically require procuring a full hatch assembly from the aircraft manufacturer. In the case of the ducting, producing a mold for Nevada Composites’ mandrels by other methods would have been both costly and very time consuming. FDM allows a very complex mold to be created rapidly. This meshes very well with the capabilities of Nevada Composites’ tool-forming method, which places no temperature and only rough-vacuum demands upon the mold material. Together the methods can produce very complex mandrels that are available rapidly, with excellent tolerances, and at moderate cost. Advanced Composite Structures Case Study – Digitally Coordinated Tool Families Special thanks to Bruce Anning, Founder/Owner of Advanced Composite Structures (Winnipeg, Canada), for his cooperation in the development of this application and the contribution of images for this case study.

Figure 8. FDM molds & resulting Nevada Composite mandrels.

Figure 9. Two complete Nevada Composite mandrel sets.
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SAMPE Journal - July/August 2011

Table of Contents for the Digital Edition of SAMPE Journal - July/August 2011