Tooling Paste Reduces Wind Blade Model Production Time

When Vostermans Tooling and Prototyping BV (Venlo, The Netherlands) wanted to reduce production time for its large wind blade master models, the company turned to computer-aided designs and CNC-machinable modeling paste. Vostermans selected RenPaste 4503R/Ren 4503H seamless epoxy modeling paste from Huntsman Advanced Materials (The Woodlands, Texas). The paste enabled production of accurate 151-ft/46m long blade models with on a tight timescale.

According to Rob Luijten, location manager at Vostermans, the best time to test a wind blade is in the spring, which meant that the company had to finish the models, pull the composite tools and then mold blade test articles in time for the desired testing timeframe. To build the wind blade models, technicians at Vostermans built undersized backing structures from foam blocks, using expanded polystyrene (EPS) foam. Next, RenPaste 4503R/Ren 4503H paste was applied by machine (see photo, upper left) to the substructures in thicknesses of 0.6 inches to 0.8 inches (15 mm to 20 mm). The paste was allowed to cure for 24 hours at room temperature before the final model dimensions were CNC machined, using the blade's CAD/CAM data. The cured paste exhibited good dimensional stability and produced a smooth finish with no detectable seams, and therefore held tolerances of �0.2 inch (�5 mm) over the blade length, Vostermans reports. The paste has a Shore hardness of 60D, a compressive strength of 2,100 psi/14.5 MPa, a glass transition temperature of 159°F/71°C and a coefficient of thermal expansion (CTE) of 32×10-6, the latter a good match for the intended tooling materials.

Only light hand polishing was required to produce the fine surface desired for each model. After the polishing, technicians hand-wiped a proprietary RenShape High-performance Sealer over the model surface to fill in microporosity and enhance surface quality. A layer of a carnauba-type wax was applied as a release agent, and tools were fabricated from glass/epoxy. The tools then go through a postcure that is determined by the cure temperature required for the final wind blades.

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