LOCOG - Anodised Public Art

Embossing Tool Creates Artistic Metalwork

Renowned for its high-quality architectural metalwork throughout the United Kingdom, NES Architecture, Colchester, UK, recently was commissioned to produce the artistic metalwork cladding for an electrical substation building. Based on its long track record for high-quality niche architectural metalwork, NES set out to design a set of finely polished aluminum-panel surfaces to convey a vibrant feeling of flowing motion.

NES operations director Patrick Holt (left) and Mate Tooling Solutions’ Craig Letty take a look at the embossed/dimpled aluminum wall panels fabricated for a newly constructed electrical substation building. The sheets, embossed with holes in wavy rows, remain perfectly flat and square so they affix to the building without distortion.
NES Architecture operates out of two facilities, totaling 100,000 sq. ft. and staffed by some 60 employees. For the substation building, it fabricated 120 10-ft.-tall aluminum panels, which mount side-by-side on the building exterior walls.

The challenge for NES Architecture was to punch the aluminum sheets with rows of holes in irregular wave lines across the entire panel surface. The holes, punched in six different sizes, were unconventional in that they have a dimple around the perimeter edge to produce the required visual effects in different light conditions.

To achieve these features, NES punched the wave lines of holes in a Safan Challenger turret press using custom CNC programming, and tooling that included a special countersink embossing tool (from Mate Precision Tooling, Anoka, MN) to create the dimples. The tooling has a major diameter of 35 mm and a top-to-top of 6 mm. Run in a 3.5-in. Strippit station in the Safan press, the tooling provided consistent, accurate hole embossing to achieve the desired design, not possible with a laser or other type of machine tool.

1100 Random Holes, in the Eyes of the Artist

“To create the right visual effect, we had to punch 1100 holes on each panel utilizing six hole sizes randomly positioned, but following the design artist’s vector line on the panel surfaces,” says NES operations director Patrick Holt. The job required development of 12 CNC programs, six per side covering all six hole sizes—18, 20, 22, 24, 26 and 28 mm. Each program, used 200 times on every panel, was developed using Radan CAD/CAM software, which according to Mr. Holt, slashed programming time by a third when compared to its previous programming software.

Panels are of 3-mm-thick J57S aluminum, a Novelis alloy. According to Novelis, the material is a rolled aluminum alloy “designed to be a perfect base material for anodizing and created specifically to meet the requirements of modern architecture.” NES worked with two panel sizes, 3.6 by 2 m and 2.4 by 2 m.

Punched holes with dimpled features require additional steps when compared to the typical hole-punching process. And, the building application had additional complexity because the holes required distinctive countersunk embossed holes as well as several variations in size, appearance and position. In many cases the holes are not necessarily centered in the middle of the dimple. And hole spacing was such that some dimples overlapped.

“Overlapping the dimples put extra stress on the embossing tool,” says Holt. “But Mate’s robust tool design stood up well, without problems or maintenance concerns.”

Upforming Yields Flat, Scratch-Free Surfaces
In many cases the holes are not necessarily centered in the middle of the dimple. And hole spacing was such that some dimples overlapped, placing extra stress on the embossing tool.

To create the hole pattern, all holes were punched first into the face of a panel so slugs fell free of the panel, thanks to use of Mate’s Slug Free dies. Then an operator flipped the panel over to accommodate upforming of the dimples from the reverse side into the punched holes. This process yielded the desired visual effect for the rows of dimpled holes. It also kept the panel surface flat and scratch-free—essential to obtaining a bright and shiny finish after the aluminum panels were anodized following punching.

The waves of holes show off spectacularly. Punching time per panel averaged 11⁄2 hr., including the time required to reposition the panels on the machine to achieve the desired hole pattern and finish.

“Consistency of the embossing, not speed, was key to the success of the project,” adds Holt. “We operated the press well under top speed to ensure sheet flatness for the best visual appearance, and so the sheets align perfectly when affixed to the building.
“The finished building facade speaks for itself,” Holt continues. “The entire project went forward very smoothly without downtime or scrap. In fact, we’re anticipating an award for this design work.”