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3D-printed precast concrete molds for redeveloped NYC landmark a first

3D-printed precast concrete molds for redeveloped NYC landmark a first

It would be a shame to redevelop the Domino Sugar refinery property in Brooklyn without giving a nod to the historic building’s past. Installing concrete panels on the exterior of the 42-story tower achieved that, but manufacturing those panels from 3D-printed molds also provided a glimpse of the future. The under-development high-rise known as One South First is the first in the U.S. to incorporate concrete cast from 3D-printed molds.

Both the materials and the method can confer significant benefits over traditional time- and labor-intensive wood molds, its proponents say, yet the applicability has its limitations.

A collaborative challenge

The idea of utilizing 3D-printed molds for precast concrete exterior panels was born from a collaboration between the Oak Ridge National Laboratories (ORNL) and the Precast/Prestressed Concrete Institute. After working together on ways to improve the thermal efficiency of buildings through lightweight insulated precast panels, researchers from ORNL saw the potential for introducing 3D printing. Steve Brock, senior vice president of engineering at Gate Precast Co. and member of the PCI advisory team for the ORNL project, agreed, and used 3D-printed molds to cast about 30 samples of a 1-foot cornice piece for a client.

Just 10 days after completing this relatively low-risk trial, ORNL asked Gate Precast to go bigger: utilize Big Area Additive Manufacturing (BAAM) to produce molds for casting One South First’s 1,594 window panels, which measure up to 12 feet, 4 inches in height and 19 feet, 11 inches in length.

Although wood molds for the mock-up were already built, Gate Precastaccepted the challenge for a good portion of the balance of the project and presented the concept to the building’s designer​, CookFox Architects. ORNL developed the initial molds, then brought on Additive Engineering Solutions (AES) in Akron, Ohio, to help with production.

Efficient and economical

For this project, additive manufacturing delivered savings of both time and money. The panels CookFox designed feature varying profiles that “conceptually relate back to sugar crystals and the site’s history while providing self-shading throughout the day,” according to Arno Adkins, project architect for the New York-based firm. Those variations required more than 100 different molds, and each mold would have taken master carpenters — who are in short supply in the industry — 40 to 50 hours to produce in wood.

“We would’ve tied up carpenters in multiple plants for months,” Mo Wright, marketing director for Gate Precast, told Construction Dive.

3D printing and machining the molds, however, took just 14 to 16 hours each.

Economies of scale also made 3D printing more affordable than wood. The total cost for each 3D-printed mold, including the material, programming, numerical control machining and sanding, was $9,000. That’s compared to $1,800 for a wood and fiberglass mold.

Yet, “[When it comes to durability, 3D-printed molds have a vastly longer life than wood and fiberglass,” explained Austin Schmidt, president of AES. The acrylonitrile butadiene styrene (ABS) thermoplastic used in the molds was reinforced with carbon fibers — making the molds much more resilient. While a wood and fiberglass mold could only have been reused 10 times, each ABS mold maintained its integrity with no loss of quality for 203 uses. That yields a cost-per-pour of $44.33 for the ABS molds, compared to $180for wood.

The Article was published on constructiondive.com

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