Rapid prototyping helped MetroCast Corp., Westland, Mich., make aesthetically pleasing precast “polymer-concrete” building panels for an outdoor pavilion. The challenge was that the pavilion’s hyperbolic paraboloid form — somewhat similar to a ship’s prow — made it difficult to make the dense polyurethane-foam patterns for casting each panel. Each pattern or mold had different contours and dimensions, with thicknesses ranging from 13 in. at one edge to as little as 2 in. at another.
RP service bureau 3-Dimensional Service Group, Rochester Hills, Mich., created CAD files from dimensional data and structural renderings, says 3-Dimensional project liaison Jason Desotell. “A CAM program generated toolpaths to CNC-machine the patterns. The molds’ inner faces needed Class A surfaces, so finished concrete panels would have an excellent finish. High-speed cutting let us provide the surfaces directly off the CNCs, “he says.
MetroCast received all 33 molds in only three weeks. The pieces were assembled into forms, cast, and assembled on-site to build the pavilion, which measures 13-ft high at the apex and 30-ft long from corner-to-corner.